Parkinson Plus Syndromes
Parkinson Plus Syndromes are a group of neurodegenerative disorders that share parkinsonian features such as bradykinesia and rigidity but are distinguished by additional neurological signs—including early autonomic failure, cerebellar ataxia, supranuclear gaze palsy, or cortical dysfunction—and typically respond poorly to levodopa.
Parkinson-Plus Syndromes
Parkinson-plus syndromes (also called atypical parkinsonian disorders or parkinsonian-plus syndromes) are a group of neurodegenerative diseases that share the core motor features of parkinsonism (tremor, rigidity, bradykinesia, postural instability) PLUS additional neurological features not seen in idiopathic Parkinson's disease (iPD) [1][2][3].
The term "plus" literally means these conditions have parkinsonism plus something extra — whether that is cerebellar ataxia, autonomic failure, vertical gaze palsy, cortical dysfunction, or early prominent dementia.
The key Parkinson-plus syndromes are:
- Multiple System Atrophy (MSA)
- Progressive Supranuclear Palsy (PSP)
- Corticobasal Degeneration (CBD)
- Dementia with Lewy Bodies (DLB)
Why does this matter clinically?
Parkinson-plus syndromes are critical to distinguish from iPD because they have a poorer prognosis (shorter survival, more rapid progression), poor response to levodopa, and different management strategies. Misdiagnosing iPD as a Parkinson-plus syndrome (or vice versa) leads to inappropriate treatment and incorrect prognostication. This is a high-yield exam topic.
Epidemiology
| Syndrome | Prevalence | Mean Age of Onset | Sex Ratio | Median Survival from Onset |
|---|---|---|---|---|
| PSP | 5–7/100,000 | 60–70 years | M > F (1.5:1) | 5–9 years |
| MSA | 2–5/100,000 | ~54 years | M:F ≈ 1:1 | 6–10 years |
| CBD | 5–7/100,000 | 61–64 years | M ≈ F | 5.5–7.9 years |
| DLB | 3.5–5% of all dementias | 65–80 years | M > F (1.5:1) | 5–8 years |
Compare with iPD: prevalence ~160/100,000 (1% of population > 65 y/o), median survival 12–20+ years with treatment [3].
Key exam point: All Parkinson-plus syndromes have shorter survival and more rapid progression than iPD [2].
- Hong Kong has an aging population (> 20% aged ≥ 65 by 2026), so the burden of all parkinsonian disorders is rising
- MSA-C (cerebellar predominant) is relatively more common in East Asian populations compared to Western populations, where MSA-P predominates
- DLB is likely underdiagnosed in Hong Kong because cognitive features may be attributed to "normal aging" or Alzheimer's disease
Most Parkinson-plus syndromes are sporadic (unlike iPD which has identifiable genetic forms in 5–10% of cases). Key risk factors:
| Factor | Details |
|---|---|
| Age | Strongest risk factor — all are diseases of middle-to-late adulthood |
| Genetics | Mostly sporadic; PSP associated with MAPT H1 haplotype (tau gene); MSA has no established strong genetic risk; CBD associated with tau; DLB associated with APOE ε4, GBA, SNCA |
| Environmental | No consistent environmental risk factors identified (unlike iPD where pesticide exposure is implicated) |
| Sex | PSP and DLB slightly more common in males |
Exam Pitfall
Students often confuse genetic associations: iPD → LRRK2, SNCA, Parkin; PSP/CBD → MAPT (tau); DLB → GBA, APOE ε4, SNCA. These are different pathways reflecting different underlying proteinopathies.
Relevant Anatomy and Physiology
The Basal Ganglia Circuit (First Principles)
To understand Parkinson-plus syndromes, you must first understand why damage to different parts of the motor system produces different clinical pictures.
Two pathways through the basal ganglia:
-
Direct pathway (facilitates movement): Cortex → Striatum → GPi/SNr (inhibition) → Thalamus released → Movement facilitated
- Dopamine from SNpc acts on D1 receptors → stimulates the direct pathway → promotes movement
-
Indirect pathway (suppresses movement): Cortex → Striatum → GPe → STN → GPi/SNr (excitation) → Thalamus inhibited → Movement suppressed
- Dopamine from SNpc acts on D2 receptors → inhibits the indirect pathway → reduces suppression of movement (net effect: promotes movement)
In iPD: Loss of dopaminergic neurons in SNpc → reduced dopamine → direct pathway underactive, indirect pathway overactive → net result is excessive inhibition of thalamus → bradykinesia, rigidity
In Parkinson-plus syndromes, neurodegeneration extends beyond the nigrostriatal system:
| Syndrome | Primary Sites of Degeneration | Why This Produces Different Features |
|---|---|---|
| MSA | Striatum, pons, cerebellum, intermediolateral column of spinal cord, Onuf's nucleus | Striatal neurons themselves are lost (the "target" of dopamine) → levodopa has nothing to act on → poor levodopa response. Cerebellar/pontine loss → ataxia. Autonomic nuclei loss → dysautonomia |
| PSP | Midbrain (superior colliculus, pretectal area, periaqueductal grey), subthalamic nucleus, globus pallidus, frontal cortex | Midbrain vertical gaze centres destroyed → vertical gaze palsy. STN/pallidal degeneration → axial rigidity. Frontal cortex → cognitive/behavioural changes |
| CBD | Asymmetric frontoparietal cortex, basal ganglia | Cortical degeneration → apraxia, alien limb, cortical sensory loss. Asymmetric BG → markedly asymmetric parkinsonism |
| DLB | Diffuse cortical and subcortical Lewy bodies (cortex > brainstem compared to iPD) | Early cortical involvement → early prominent dementia before or concurrent with parkinsonism |
The Key Insight
In iPD, the presynaptic dopaminergic neurons are lost but the postsynaptic striatal neurons are intact — so giving exogenous levodopa works because the "receptors" are still there. In MSA-P, the postsynaptic striatal neurons themselves degenerate — so even if you flood the synapse with levodopa, there's nothing left to respond. This explains the poor levodopa response in Parkinson-plus syndromes.
Vertical gaze is controlled by:
- Rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) — generates vertical saccades
- Interstitial nucleus of Cajal (INC) — maintains vertical gaze holding
- Posterior commissure — connects bilateral vertical gaze pathways
These structures are located in the dorsal midbrain/pretectal area. PSP causes tau-related neurodegeneration in this exact region → vertical supranuclear gaze palsy (especially downward gaze affected first) [2].
"Supranuclear" means the lesion is above the cranial nerve nuclei (CN III, IV) — the nuclei themselves are intact. This is why the vestibulo-ocular reflex (VOR, "doll's eye manoeuvre") is preserved initially in PSP (because the nuclear and infranuclear pathways are intact).
The intermediolateral cell column (IML) of the spinal cord (T1–L2) contains preganglionic sympathetic neurons. Onuf's nucleus in the sacral spinal cord controls urethral and anal sphincters.
In MSA, degeneration of:
- IML → severe orthostatic hypotension (loss of sympathetic vasoconstriction on standing)
- Onuf's nucleus → early urinary incontinence/retention (sphincter denervation)
- Dorsal motor nucleus of vagus → gastrointestinal dysmotility
Etiology and Pathophysiology
Molecular Classification: The Proteinopathy Framework
Modern understanding classifies Parkinson-plus syndromes by the abnormal protein that accumulates:
| Proteinopathy | Abnormal Protein | Diseases |
|---|---|---|
| Synucleinopathies | α-synuclein | iPD, MSA, DLB |
| Tauopathies | Hyperphosphorylated tau | PSP, CBD |
This classification is clinically important because it explains overlapping features within groups and guides future disease-modifying therapy targets.
α-Synuclein is a presynaptic protein normally involved in synaptic vesicle recycling and neurotransmitter release. When it misfolds and aggregates:
-
In iPD and DLB: forms intraneuronal Lewy bodies and Lewy neurites
- iPD: Lewy bodies predominantly in brainstem (SNpc) → cortex (later)
- DLB: Lewy bodies in cortex early → explains early dementia
- The difference between iPD-dementia and DLB is essentially a matter of timing (the "1-year rule" — see classification)
-
In MSA: α-synuclein forms glial cytoplasmic inclusions (GCIs) in oligodendrocytes (not neurons)
- This is unique — MSA is the only major synucleinopathy where the inclusions are glial rather than neuronal
- Oligodendrocyte dysfunction → demyelination and axonal degeneration → explains the widespread, multi-system nature of the disease
- Glial inclusion and myelin degeneration in various sites, e.g. BG, pontine nuclei, cerebellum [3]
Tau is a microtubule-associated protein that normally stabilises axonal microtubules (the "railway tracks" of intracellular transport). When hyperphosphorylated, tau dissociates from microtubules and aggregates into neurofibrillary tangles (NFTs).
- In PSP: predominantly 4-repeat (4R) tau accumulates in neurons and glia (astrocytic tufts) in midbrain, basal ganglia, and frontal cortex
- In CBD: also 4R tau but in an asymmetric frontoparietal distribution → asymmetric frontoparietal atrophy associated with tau NFT inclusions [3]
- CBD shows ballooned (achromatic) neurons and astrocytic plaques on histology (distinct from the tufted astrocytes of PSP)
High yield: PSP = tufted astrocytes; CBD = astrocytic plaques; MSA = glial cytoplasmic inclusions; DLB/iPD = Lewy bodies
Etiology by Syndrome
- Etiology: Sporadic; no established strong genetic or environmental risk factors
- Pathology: GCIs (α-synuclein in oligodendrocytes) → neuronal loss and gliosis in:
- Striatonigral system → MSA-P (parkinsonian features)
- Olivopontocerebellar system → MSA-C (cerebellar features)
- IML column and Onuf's nucleus → autonomic failure
- Pathophysiology:
- Striatal neuron loss → postsynaptic denervation → poor levodopa response
- Cerebellar/pontine loss → ataxia, dysarthria, nystagmus
- Autonomic neuron loss → orthostatic hypotension, urogenital dysfunction
- Etiology: Sporadic (rare familial cases with MAPT mutations); strong association with MAPT H1/H1 haplotype
- Pathology: 4R tauopathy → NFTs, tufted astrocytes, and coiled bodies in:
- Midbrain tegmentum (vertical gaze centres)
- Subthalamic nucleus
- Globus pallidus
- Frontal cortex
- Cerebellar dentate nucleus
- Pathophysiology:
- Midbrain degeneration → vertical gaze palsy (especially downward) → difficulty reading, eating, walking downstairs
- STN degeneration → loss of postural reflexes → early falls (typically backwards)
- Frontal cortex → executive dysfunction, apathy, pseudobulbar affect
- Axial rigidity > appendicular rigidity (neck hyperextended) [2] — the opposite of iPD where patients are flexed
- Etiology: Sporadic; 4R tauopathy
- Pathology: Asymmetric frontoparietal atrophy with ballooned neurons, astrocytic plaques, tau NFTs [3]
- Pathophysiology:
- Cortical degeneration (parietal) → limb apraxia (inability to perform learned skilled movements despite intact motor/sensory function), cortical sensory loss (astereognosis, agraphaesthesia), alien limb phenomenon
- Asymmetric basal ganglia degeneration → markedly asymmetric rigid-akinetic parkinsonism
- Frontal cortex → behavioural changes, dementia (usually late)
- Etiology: Sporadic (genetic risk factors: GBA mutations, APOE ε4, SNCA)
- Pathology: Widespread cortical and subcortical Lewy bodies; copathology with Alzheimer's disease (amyloid plaques, NFTs) present in ≥ 50% of cases [5]
- Pathophysiology:
- Cortical Lewy bodies → early cognitive impairment (attention, executive function, visuospatial — relatively preserved memory initially, unlike AD)
- Fluctuating acetylcholine levels → cognitive fluctuations (varying alertness/attention)
- Temporal/occipital cortex involvement → recurrent well-formed visual hallucinations
- Brainstem involvement → parkinsonism (usually milder and more symmetric than iPD)
- Pontine/brainstem → REM sleep behaviour disorder
Copathology in DLB — High Yield from Reference Material
Several studies have demonstrated that various copathologies are frequently observed in individuals with DLB, including amyloid beta plaques, neurofibrillary tangles, TDP-43, cerebrovascular changes, and tau. Copathology also has clinical implications in which individuals may be misdiagnosed or have an accelerated disease course. Alzheimer disease copathology is observed in at least 50% of individuals with DLB and clinically is associated with greater cognitive decline, greater risk of institutionalization, and mortality. [5]
Classification
| Old Terminology | Current Classification | Predominant Features |
|---|---|---|
| Striatonigral degeneration (SND) | MSA-P | Parkinsonian: akinesia, rigidity, poor levodopa response |
| Olivopontocerebellar atrophy (OPCA) | MSA-C | Cerebellar: gait/limb ataxia, nystagmus, ataxic dysarthria |
| Shy-Drager syndrome | MSA with predominant autonomic failure | Severe orthostatic hypotension, urogenital dysfunction |
MSA subtypes: Predominant parkinsonian (MSA-P / striatonigral degeneration) vs. Predominant cerebellar (MSA-C / olivopontocerebellar atrophy) vs. Predominant autonomic dysfunction (Shy-Drager syndrome) [2]
East Asian Epidemiology
In East Asian populations (including Hong Kong/China/Japan), MSA-C is more common than MSA-P — the reverse of Western populations. This is important for clinical suspicion in HK practice.
PSP is now recognized to have multiple phenotypic variants:
| Subtype | Key Features |
|---|---|
| PSP-Richardson syndrome (PSP-RS) | Classic form: early falls, vertical gaze palsy, axial rigidity, pseudobulbar palsy — this is what "PSP" traditionally refers to |
| PSP-Parkinsonism (PSP-P) | Asymmetric onset, tremor, moderate levodopa response initially — can mimic iPD |
| PSP-Pure akinesia with gait freezing (PSP-PAGF) | Progressive gait freezing without limb rigidity or tremor |
| PSP-Corticobasal syndrome (PSP-CBS) | Overlaps with CBD phenotype |
| PSP-Progressive non-fluent aphasia (PSP-PNFA) | Language-predominant |
| PSP-Frontal (PSP-F) | Frontal behavioural symptoms predominant |
For exams, focus on PSP-RS as the classic presentation.
This is a pragmatic clinical distinction:
- If dementia develops before or within 1 year of parkinsonism onset → classify as DLB
- If dementia develops > 1 year after established parkinsonism → classify as PD dementia (PDD)
Both DLB and PDD are Lewy body diseases on the same pathological spectrum, but the timing of cognitive vs motor symptom onset determines the clinical label. The "1-year rule" is arbitrary but clinically useful [5].
Clinical Features
Red flags of atypical Parkinsonism: [2]
- Early falls / postural instability
- Early dementia
- Bilateral symmetrical onset
- Early ANS dysfunction
- Poor response to L-DOPA
- Specific features of individual disease: e.g. autonomic dysfunction, cerebellar signs, gaze palsy
These red flags should trigger suspicion that you are NOT dealing with iPD. Let's now examine each syndrome's clinical features in detail.
1. Multiple System Atrophy (MSA)
| Symptom | Pathophysiological Basis |
|---|---|
| Dizziness/lightheadedness on standing, syncope | Loss of IML sympathetic neurons → failure of baroreceptor-mediated vasoconstriction on standing → orthostatic hypotension (defined as ≥ 20 mmHg systolic or ≥ 10 mmHg diastolic drop within 3 min of standing) |
| Urinary urgency, frequency, incontinence, or retention | Degeneration of Onuf's nucleus (sacral parasympathetic) → detrusor-sphincter dyssynergia; this is often the earliest symptom, preceding motor features by years |
| Erectile dysfunction (in males) | Autonomic denervation of pelvic plexus; may precede motor symptoms by > 5 years |
| Constipation | Loss of enteric nervous system autonomic regulation |
| Unsteadiness, staggering gait, frequent falls | Cerebellar degeneration (vermis → gait ataxia; hemispheres → limb ataxia) |
| Clumsiness of hands | Cerebellar limb ataxia (decomposition of multi-joint movements) |
| Slurred speech | Cerebellar dysarthria (scanning/staccato speech) or mixed |
| Slowness of movement, stiffness | Striatonigral degeneration → parkinsonism |
| Snoring, stridor, sleep apnoea | Laryngeal abductor paralysis (denervation of posterior cricoarytenoid muscle) — this is a distinctive and dangerous feature of MSA; can cause sudden death |
| Emotional lability (pathological crying/laughing) | Pseudobulbar affect from corticobulbar pathway involvement |
| Sign | Pathophysiological Basis |
|---|---|
| Orthostatic hypotension (≥ 30 mmHg systolic drop in MSA, more severe than iPD) | IML cell column loss; also associated with supine hypertension (loss of normal baroreceptor regulation) |
| Cerebellar signs: gait/limb ataxia, nystagmus (gaze-evoked), intention tremor, dysmetria, dysdiadochokinesia, ataxic dysarthria [2][3] | Degeneration of olivopontocerebellar system (inferior olive, pons, cerebellar cortex/peduncles) |
| Parkinsonism: akinesia, rigidity, postural instability | Striatonigral neuronal loss → postsynaptic dopamine receptor loss |
| Irregular jerky postural/action tremor (NOT classic pill-rolling resting tremor) [3] | Differs from iPD resting tremor — reflects cerebellar/irregular rather than pure nigrostriatal involvement |
| Prominent camptocormia (severe anterior flexion of spine) and anterocollis (disproportionate neck flexion) [3] | Axial muscle dystonia — MSA has disproportionate axial involvement |
| Pyramidal signs (hyperreflexia, extensor plantar responses) [2][3] | Corticospinal tract involvement — NOT seen in iPD |
| Cold, dusky, mottled hands | Peripheral autonomic vasomotor failure |
| Inspiratory stridor | Vocal cord abductor paralysis — may require tracheostomy; risk of sudden death during sleep |
| Contractures (late) | Severe rigidity and dystonia |
Stridor in MSA
Inspiratory stridor is a life-threatening feature specific to MSA (vocal cord abductor paralysis). It can cause nocturnal sudden death. Always ask about stridor/snoring in any patient with suspected MSA. This is not seen in iPD, PSP, or CBD.
2. Progressive Supranuclear Palsy (PSP)
Most common Parkinson-plus syndrome, a.k.a. "Steele-Richardson-Olzewski syndrome" [2]
| Symptom | Pathophysiological Basis |
|---|---|
| Recurrent unexplained falls, especially backwards | Early postural instability from STN and pedunculopontine nucleus degeneration → loss of postural reflexes. Falls are typically backwards (retrocollis/extension) — contrasts with iPD where patients fall forwards |
| Difficulty looking down (can't see food on plate, difficulty reading, tripping on stairs) | Vertical gaze palsy, especially downward gaze [2] — destruction of riMLF and posterior commissure in dorsal midbrain |
| Blurred vision, diplopia | Impaired convergence and vertical saccades |
| Difficulty opening eyes (apraxia of eyelid opening) [2] | Supranuclear control of levator palpebrae dysfunction |
| Dysphagia, choking on food/liquids | Pseudobulbar palsy — bilateral corticobulbar tract degeneration → UMN-type bulbar dysfunction [2] |
| Slurred speech | Pseudobulbar/spastic dysarthria (different from the hypophonic speech of iPD) |
| Personality change, apathy, irritability, poor judgment | Frontal lobe degeneration → executive dysfunction [2] |
| Slowness, stiffness (neck and trunk > limbs) | Axial rigidity > appendicular rigidity [2] — degeneration predominantly affects midline/axial structures |
| Emotional incontinence (involuntary laughing/crying) | Pseudobulbar affect from bilateral corticobulbar tract damage |
| Sign | Pathophysiological Basis |
|---|---|
| Vertical supranuclear gaze palsy (especially downward gaze) [2] | Degeneration of dorsal midbrain vertical gaze centres (riMLF, posterior commissure). "Supranuclear" = lesion above CN nuclei → VOR (doll's eye) initially preserved |
| Hyperextended neck ("proud" or "retrocollis" posture) [2] | Axial dystonia in extension — opposite to the flexed posture of iPD |
| Axial rigidity > appendicular rigidity [2] | Preferential involvement of midline structures (STN, brainstem reticular formation) |
| Square-wave jerks | Brainstem saccade generator dysfunction |
| Slow vertical saccades → complete vertical gaze palsy | Progressive midbrain degeneration |
| Pseudobulbar palsy signs: brisk jaw jerk, spastic tongue, emotional lability [2] | Bilateral corticobulbar tract degeneration |
| Frontal release signs: grasp reflex, palmomental reflex, utilisation behaviour [2] | Frontal cortex and frontal-subcortical circuit degeneration |
| Impaired cognition: executive dysfunction, reduced verbal fluency, concrete thinking [2] | Frontal-subcortical circuit degeneration |
| Procerus sign (furrowing of brow, "worried" facial expression) | Dystonic contraction of the procerus muscle — specific to PSP |
| Eyelid abnormalities: reduced blink rate, blepharospasm, apraxia of eyelid opening | Supranuclear eyelid control dysfunction |
| Wide-based gait with erect posture (NOT stooped like iPD) | Axial rigidity in extension + postural instability |
| Absent resting tremor (or minimal) | Tremor is notably LESS prominent in PSP than iPD |
PSP vs iPD — The Postural Paradox
- iPD: Stooped, flexed posture → falls forwards
- PSP: Hyperextended neck, erect posture → falls backwards
This is a classic exam discriminator. PSP patients look like they're leaning back with a "surprised" facial expression, while iPD patients are hunched forward.
Supranuclear vs Nuclear vs Infranuclear Gaze Palsy
- Supranuclear (PSP): VOR preserved (doll's eye positive), voluntary gaze impaired → the wiring above the nucleus is broken, but the nucleus itself works
- Nuclear (e.g. CN III palsy): VOR absent, pupil may be affected
- Infranuclear (e.g. myasthenia): fatigable, ptosis
If a patient with vertical gaze palsy has intact doll's eye movements, the lesion is supranuclear.
3. Corticobasal Degeneration (CBD)
| Symptom | Pathophysiological Basis |
|---|---|
| Clumsiness of one hand ("useless hand") [2] | Asymmetric frontoparietal cortical degeneration → limb apraxia (inability to perform learned motor tasks despite intact primary motor and sensory systems) |
| Feeling that one limb "doesn't belong" or "has a mind of its own" | Alien limb phenomenon — the affected limb performs purposeful-appearing movements without the patient's intention; occurs in 30–50% of CBD patients [3] |
| Difficulty performing skilled tasks (dressing, using tools) despite preserved strength | Limb apraxia — cortical motor planning disrupted |
| Inability to recognise objects by touch | Cortical sensory loss (astereognosis, agraphaesthesia) — parietal cortex degeneration |
| Stiffness, slowness (markedly worse on one side) | Marked asymmetry of parkinsonism [2] — the most distinguishing feature from other Parkinson-plus syndromes |
| Jerky involuntary movements of affected limb | Cortical myoclonus — stimulus-sensitive, reflects cortical hyperexcitability |
| Speech difficulty (non-fluent aphasia if dominant hemisphere) | Frontoparietal language area degeneration |
| Behavioural changes (late) | Frontal cortex involvement |
| Memory loss (late) | Dementia is a late feature (unlike DLB where it is early) [2] |
| Sign | Pathophysiological Basis |
|---|---|
| Marked asymmetry of examination findings [2] | Asymmetric cortical and basal ganglia degeneration — one hemisphere much more affected than the other |
| Limb apraxia (ideomotor): can't pantomime or imitate gestures | Parietal cortical degeneration disrupts motor planning (praxis network) |
| Alien limb phenomenon: involuntary grasping, levitation, or interference with the other hand [2][3] | Loss of cortical inhibition over subcortical motor programs → limb acts "autonomously" |
| Cortical sensory loss: inability to recognise shapes/textures/numbers written on skin | Parietal sensory association cortex degeneration |
| Asymmetric rigid-akinetic syndrome | Contralateral basal ganglia degeneration |
| Limb dystonia (often fixed dystonic posturing of hand/arm) [3] | Basal ganglia dysfunction → abnormal sustained muscle contraction |
| Myoclonus (cortical type: stimulus-sensitive, focal) | Cortical hyperexcitability from loss of inhibitory interneurons |
| Ocular gaze palsy (can occur but less prominent than PSP) [3] | Some midbrain/frontal eye field involvement |
| Hyperreflexia on affected side | Corticospinal tract involvement (pyramidal signs) |
| Normal or only mildly impaired cognition early | Frontal-executive dysfunction develops later (cf. DLB where dementia is early) |
CBD — The Asymmetric One
If you see a patient with markedly asymmetric parkinsonism PLUS cortical signs (apraxia, alien limb, cortical sensory loss), think CBD. Marked asymmetry (unlike other Parki-plus): clumsiness of one hand [2]. iPD can be asymmetric at onset, but it spreads contralaterally early; CBD remains strikingly unilateral for much longer.
What is Alien Limb Phenomenon?
Alien limb phenomenon occurs in 30-50% of patients with CBD and is described as a feeling that the limb does not belong to the subject or that it has a will of its own. [3]
Examples: The affected hand may involuntarily grasp objects, interfere with the other hand's actions (intermanual conflict), or levitate upward. Patients may sit on the hand to restrain it. This is a dramatic and characteristic finding.
4. Dementia with Lewy Bodies (DLB)
| Symptom | Pathophysiological Basis |
|---|---|
| Progressive cognitive decline (predominant and early: attention, executive function, visuospatial skills affected more than memory initially) | Cortical Lewy bodies → cortical cholinergic deficit. Unlike Alzheimer's where hippocampal memory loss is first, DLB affects neocortical function early |
| Fluctuating cognition and alertness ("good days and bad days," episodes of staring/confusion) [3] | Fluctuating cortical acetylcholine levels; brainstem ascending reticular activating system involvement |
| Recurrent, well-formed, detailed visual hallucinations (typically people, animals, children) [3] | Temporal and occipital (visual association) cortex Lewy body deposition; also related to cholinergic deficiency |
| Slowness, stiffness, shuffling gait | Brainstem (SNpc) Lewy bodies → parkinsonism; typically more bilaterally symmetric and milder than in PD, less tremor [3] |
| Vivid dreams, shouting/thrashing during sleep | REM sleep behaviour disorder (RBD) — loss of normal REM atonia due to pontine/brainstem Lewy bodies → patients "act out" their dreams; may precede cognitive symptoms by years |
| Depression, apathy, anxiety | Limbic system Lewy bodies, serotonergic/noradrenergic system involvement |
| Delusions (systematized, paranoid) | Cortical Lewy body deposition; may include Capgras syndrome (belief that a familiar person has been replaced by an impostor) [5] |
| Autonomic symptoms (constipation, postural dizziness, urinary symptoms) | Peripheral and central autonomic Lewy body deposition |
| Anosmia | Olfactory bulb Lewy bodies (also seen in iPD) |
| Excessive daytime sleepiness | Brainstem sleep-wake regulation disruption |
| Sign | Pathophysiological Basis |
|---|---|
| Cognitive impairment on bedside testing (deficits in attention, executive function, visuospatial tasks — draw clock, copy intersecting pentagons) | Cortical Lewy bodies especially in parieto-occipital regions |
| Fluctuating level of alertness (may appear drowsy/confused then relatively normal) | Brainstem and thalamocortical dysfunction |
| Parkinsonism: rigidity, bradykinesia, postural instability [3] | Substantia nigra Lewy bodies; typically more bilaterally symmetric and milder than in PD, less tremor [3] |
| Visual hallucinations on direct questioning (the patient may not volunteer these) | Posterior cortical cholinergic deficit |
| Severe sensitivity to neuroleptics/antipsychotics → marked worsening of parkinsonism, sedation, neuroleptic malignant syndrome [5] | DLB patients have severely depleted dopamine AND acetylcholine → dopamine blockade is extremely poorly tolerated |
| RBD documented on polysomnography | Loss of pontine REM atonia mechanisms |
| Myoclonus | Cortical Lewy body disease (can also be seen in prion diseases) |
| Postural hypotension | Autonomic nervous system Lewy body deposition |
DLB and Antipsychotic Sensitivity — CRITICAL SAFETY POINT
It is vital to recognize this prodromal syndrome given the risk of severe antipsychotic sensitivity among individuals with DLB, which is associated with increased morbidity and mortality. [5]
NEVER give typical antipsychotics (haloperidol) to a patient with suspected DLB. Even atypical antipsychotics must be used with extreme caution. Quetiapine at low doses or pimavanserin are preferred if antipsychotic treatment is absolutely necessary. Giving haloperidol to a DLB patient can cause irreversible parkinsonism, NMS, and death.
Three recognised prodromal presentations:
- Mild cognitive impairment (MCI-LB): mild cognitive decline with Lewy body features but preserved function
- RBD-onset: isolated REM sleep behaviour disorder years before cognitive/motor symptoms (> 80% of isolated RBD eventually converts to a synucleinopathy)
- Psychiatric-onset DLB: late-onset depression, psychosis, visual hallucinations, systematized delusions including Capgras syndrome, apathy, anxiety [5]
| Feature | iPD | MSA | PSP | CBD | DLB |
|---|---|---|---|---|---|
| Onset symmetry | Asymmetric | Symmetric/mild asymmetry | Symmetric (axial) | Markedly asymmetric | Symmetric |
| Tremor | Resting (pill-rolling) | Jerky postural/action | Minimal/absent | Minimal | Less prominent |
| Rigidity | Limb > axial | Limb + axial | Axial > limb | Asymmetric limb | Limb = axial |
| Posture | Flexed/stooped | Camptocormia, anterocollis | Hyperextended neck | N/A | Stooped |
| Falls | Late | Early | Very early (backwards) | Variable | Early |
| Gaze abnormality | Impaired upgaze | No specific | Vertical (downgaze) palsy | Possible | No specific |
| Cerebellar signs | No | Yes (MSA-C) | No | No | No |
| Pyramidal signs | No | Yes | Possible | Possible | No |
| Autonomic failure | Mild/late | Severe/early | Mild | No | Moderate |
| Dementia | Late (PDD) | No/mild | Frontal | Late | Early, prominent |
| Alien limb | No | No | No | Yes (30-50%) | No |
| Hallucinations | Late (drug-induced) | No | No | No | Early, visual |
| RBD | Common | Common | Uncommon | Uncommon | Very common |
| Levodopa response | Good | Poor | Poor | Poor | Partial |
| Pathology | Lewy bodies (neuronal) | GCIs (glial) | 4R tau (tufted astrocytes) | 4R tau (astrocytic plaques) | Lewy bodies (cortical) |
| Median survival | 12–20+ years | 6–10 years | 5–9 years | 5.5–7.9 years | 5–8 years |
| Syndrome | MRI Finding | Significance |
|---|---|---|
| MSA | Hot cross bun sign (cruciform hyperintensity in pons on T2/FLAIR) [2] | Selective loss of pontine neurons and myelinated fibres with preservation of tegmentum and pontine raphe |
| MSA | Putaminal slit sign (hyperintense lateral putaminal rim on T2) | Gliosis at lateral putaminal border from neuronal loss |
| MSA | Cerebellar atrophy (MSA-C), putaminal atrophy (MSA-P) | Reflects respective system degeneration |
| PSP | Hummingbird sign (on sagittal MRI) — midbrain atrophy with relative preservation of pons [2] | Midbrain tegmentum atrophy |
| PSP | Mickey Mouse sign (on axial MRI) — concavity of lateral midbrain [2] | Same — cross-sectional view of midbrain atrophy |
| PSP | Midbrain-to-pons ratio < 0.52 | Quantitative marker of midbrain atrophy |
| CBD | Asymmetric frontoparietal cortical atrophy with dilatation of lateral ventricles [3] | Correlates with clinical asymmetry |
| DLB | Relative preservation of medial temporal lobe (hippocampi) | Distinguishes from AD (where hippocampal atrophy is prominent) |
| DLB | Occipital hypoperfusion on SPECT/FDG-PET | Visual association cortex dysfunction → hallucinations |
High Yield Summary
Parkinson-Plus Syndromes — Key Discriminating Features:
-
MSA: Parkinsonism + severe early autonomic failure + cerebellar ataxia + pyramidal signs; hot cross bun sign; stridor is life-threatening; GCIs (glial α-synuclein)
-
PSP: Most common Parkinson-plus syndrome; early falls backwards + vertical downgaze palsy + axial rigidity (hyperextended neck) + pseudobulbar palsy + frontal cognitive dysfunction; hummingbird/Mickey Mouse sign; 4R tauopathy
-
CBD: Markedly asymmetric parkinsonism + cortical signs (limb apraxia, alien limb phenomenon, cortical sensory loss); asymmetric frontoparietal atrophy; 4R tauopathy
-
DLB: Early dementia (attention/visuospatial > memory) + fluctuating cognition + visual hallucinations + RBD + mild symmetric parkinsonism; severe antipsychotic sensitivity; cortical Lewy bodies; "1-year rule" distinguishes from PDD
Red flags for Parkinson-plus (vs iPD):
- Early falls/postural instability
- Early dementia
- Bilateral symmetric onset
- Early autonomic failure
- Poor levodopa response
- Additional neurological features (cerebellar, pyramidal, gaze palsy, cortical signs)
All Parkinson-plus syndromes have shorter survival and poorer prognosis than iPD.
Active Recall - Parkinson-Plus Syndromes
[1] Lecture slides: GC 091. Unsteady gait cerebellar lesions; movement disorders; Parkinsonism.pdf [2] Senior notes: Maksim Medicine Notes.pdf (Neurology - Parkinson-plus syndromes, pp.248–253) [3] Senior notes: Ryan Ho Neurology.pdf (Section 5.2.3 Parkinson plus syndromes, pp.118–126) [4] Lecture slides: Neurology - Two cases of movement disorders.pdf (p.5) [5] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf (Copathology in DLB, Psychiatric-onset DLB)
Differential Diagnosis of Parkinson-Plus Syndromes
When a patient presents with parkinsonism (bradykinesia + at least one of rigidity or resting tremor), the clinical question is: Is this idiopathic Parkinson's disease (iPD), or something else? The "something else" includes the Parkinson-plus syndromes themselves, secondary/symptomatic causes, and mimics. This section addresses the differential diagnosis from two angles:
- Differentiating Parkinson-plus syndromes from iPD and other causes of parkinsonism (the broad DDx of parkinsonism)
- Differentiating the individual Parkinson-plus syndromes from each other (once you suspect "atypical," which one is it?)
A. Broad Differential Diagnosis of Parkinsonism
Parkinson's disease (PD): idiopathic degeneration of substantia nigra with intraneuronal Lewy bodies. A clinicopathological entity, major (80%) cause of parkinsonism. Cf parkinsonism = syndrome of clinical features seen in PD. Cf Parkinsonian syndromes including other diseases with similar S/S. [3]
The causes of parkinsonism can be systematically categorised. The lecture slides framework is essential here:
Causes of Parkinsonism: Tremor, rigidity, bradykinesia, stooped posture, and/or shuffling gait [4]
- Parkinson's disease (familial cases uncommon, α-synuclein [Park1/4, AD], Parkin [Park2, AR]…Park24)
- Progressive supranuclear palsy (Steele-Richardson-Olzewski syndrome)
- Multiple system atrophy (striatonigral degeneration, sporadic olivopontocerebellar atrophy, and Shy-Drager syndrome)
Let's work through each category, explaining why each condition mimics parkinsonism and how to differentiate it:
This is the most important differential to distinguish Parkinson-plus syndromes FROM.
MDS Clinical Diagnostic Criteria for PD: Parkinsonism = bradykinesia plus at least 1 of rest tremor or rigidity. Clinically established PD vs clinically probable PD. Supportive and absolute exclusion criteria. Red flags: rapid progression of gait impairment, recurrent falls within 3 years, absence of common nonmotor features despite 5 years duration, complete absence of motor progression over 5 or more years, other signs which could suggest atypical parkinsonism. [1]
Key features favouring iPD over Parkinson-plus:
| Feature | iPD | Parkinson-Plus |
|---|---|---|
| Onset | Unilateral, asymmetric | Bilateral/symmetric (except CBD which is markedly asymmetric) |
| Tremor | Classic resting pill-rolling tremor (4–6 Hz) | Absent/minimal (PSP), jerky postural/action (MSA), or minimal (DLB) |
| Levodopa response | Excellent, sustained | Poor or absent [2] |
| Progression | Slow (years–decades) | Rapid (years) |
| Falls | Late feature (> 3 years) | Early (especially PSP: within first year) |
| Autonomic failure | Mild, late | Severe, early (especially MSA) |
| Dementia | Late (PD-dementia after years) | Early (DLB: before/within 1 year of motor onset) |
| Additional neurological features | None (pure extrapyramidal) | Cerebellar signs, pyramidal signs, gaze palsy, cortical signs |
The MDS Red Flags — High Yield from GC Lecture Slides
Red flags that suggest atypical parkinsonism (i.e. NOT iPD): [1]
- Rapid progression of gait impairment
- Recurrent falls within 3 years
- Absence of common nonmotor features despite 5 years duration
- Complete absence of motor progression over 5 or more years
- Other signs which could suggest atypical parkinsonism
These are MDS absolute exclusion criteria and red flags from the GC 091 lecture — expect direct exam questions on these.
Covered in detail in the comparison table below (Section B).
3. Secondary (Symptomatic) Parkinsonism
These are acquired, often reversible causes where the parkinsonism results from an identifiable external insult rather than primary neurodegeneration.
Drug-induced parkinsonism, e.g. neuroleptics, dopamine-depleting/anti-dopaminergic drugs, lithium, antihistamines [3]
I learned that drug-induced parkinsonism from metoclopramide, antipsychotics, or antihistamines is particularly important to identify as it is reversible. [8]
Why it mimics PD: These drugs block D2 dopamine receptors in the striatum (antipsychotics, metoclopramide) or deplete dopamine stores (reserpine, tetrabenazine), creating an iatrogenic dopamine-deficient state identical in mechanism to iPD.
How to differentiate:
- Temporal relationship: Parkinsonism develops within weeks–months of starting the offending drug
- Bilateral and symmetric from onset (iPD is asymmetric)
- Tardive dyskinesia may coexist (stereotypical orofacial movements — chewing, tongue protrusion) [6]
- Resolves upon withdrawal of offending agent (may take weeks–months)
- No response to levodopa (because the receptors are blocked, not the presynaptic neuron lost)
Type C adverse drug reaction → long term use. Tardive dyskinesia → parkinson's-like symptoms. E.g. long term use of Chlorpromazine → you develop stereotypical repetitive movements (chewing, facial tics, uncontrollable) [6]
Common Drug Culprits in Hong Kong
In HK clinical practice, the most common causes of drug-induced parkinsonism are:
- Antipsychotics: haloperidol, chlorpromazine, risperidone (typical > atypical)
- Antiemetics: metoclopramide (widely prescribed in HK), domperidone (crosses BBB less, so lower risk)
- Others: valproate, lithium, methyldopa, calcium channel blockers (flunarizine, cinnarizine)
Always take a thorough drug history in any new presentation of parkinsonism!
Signs to r/o other d/dx: Tardive dyskinesia for drug-induced parkinsonism [3]
Toxic: MPTP, manganese, CO poisoning, rotenone [3]
| Toxin | Mechanism | Clinical Clue |
|---|---|---|
| MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) | Metabolised by MAO-B to MPP+, which selectively destroys dopaminergic neurons in SNpc | History of illicit drug use (contaminated synthetic heroin); produces rapid-onset, severe, levodopa-responsive parkinsonism |
| Manganese | Accumulates in globus pallidus (NOT SNpc) → pallidal degeneration | Occupational exposure (welding, mining); "cock-walk" gait; poor levodopa response (because the lesion is pallidal, not nigral) |
| Carbon monoxide | Causes bilateral globus pallidus necrosis from hypoxic-ischaemic damage | History of CO exposure; delayed-onset parkinsonism weeks after exposure; may have pallidal calcification on CT |
| Rotenone | Mitochondrial complex I inhibitor → nigrostriatal degeneration | Pesticide exposure |
Post-encephalitic, e.g. encephalitis lethargica (not present anymore) [3]
Historical importance (epidemic of encephalitis lethargica in 1917–1928); modern relevance includes parkinsonism following viral encephalitis (e.g. Japanese encephalitis — relevant in HK/Asia), autoimmune encephalitis, or HIV.
Parkinsonism can result from any structural lesion affecting basal ganglia circuits:
- Tumours: parasagittal meningioma compressing motor cortex/basal ganglia
- Head trauma: chronic traumatic encephalopathy ("punch-drunk" syndrome / pugilist encephalopathy) — repetitive head trauma → tau accumulation
- Normal pressure hydrocephalus (see pseudoparkinsonism below)
4. Hereditary Neurodegenerative Diseases
Wilson's disease: Can mimic Parkinson's, extrapyramidal deposition of the copper [7]
Why it matters: Wilson's disease is a treatable cause of parkinsonism. It should be excluded in any patient < 40 years presenting with parkinsonism or other movement disorders.
How it mimics PD: Copper deposits in the basal ganglia (especially putamen and caudate) → neuronal damage → parkinsonism, dystonia, tremor, dysarthria
How to differentiate:
- Young age of onset (typically 5–35 years, average 13 years) [9]
- Neurological features rarely isolated parkinsonism — usually mixed with dystonia, ataxia, tremor, choreoathetosis, cognitive impairment, psychiatric symptoms [9]
- Kayser-Fleischer rings (corneal copper deposits) present in 98% with neurological disease [9]
- Liver disease (hepatitis, cirrhosis) often coexists or precedes neurological onset
- Coombs-negative haemolytic anaemia — unique clue [9]
- Investigations: low serum ceruloplasmin, high 24h urinary copper, KF rings on slit lamp
Genetic test does not have to be positive to reach a diagnosis → with compatible clinical and history still can diagnose, since hereditary pathway of Wilson's is very heterogeneous → not just ATP7B [7]
Huntington's disease: autosomal dominant condition caused by CAG trinucleotide repeats on chromosome 4p16.3, leading to atrophy of the caudate and putamen. The triad of chorea, psychiatric manifestations including depression and psychosis, and progressive dementia. [8]
- Classic HD: chorea (hyperkinetic) rather than parkinsonism (hypokinetic)
- Westphal variant / juvenile-onset HD: can present with akinetic-rigid syndrome (bradykinesia, rigidity) mimicking parkinsonism — the "akinetic form of Huntington's chorea" [3]
- Family history of autosomal dominant transmission with anticipation (earlier onset in successive generations, especially paternal transmission)
- Caudate atrophy on imaging → "box car" ventricles
Hallervorden-Spatz syndrome: neurodegeneration with brain iron accumulation [3]
- Rare; presents in childhood/early adulthood with dystonia, parkinsonism, cognitive decline
- "Eye of the tiger" sign on T2 MRI (bilateral pallidal hyperintensity within hypointensity)
- PANK2 gene mutation (pantothenate kinase 2)
5. Pseudoparkinsonism
These conditions mimic parkinsonism clinically but arise from non-basal-ganglia pathology.
Cerebral arteriosclerotic disease: stepwise deterioration, LL > UL involvement, more symmetrical, with poor response to levodopa [3]
Why it looks like PD: Multiple lacunar infarcts in the basal ganglia or white matter disrupt the same circuits that degenerate in iPD.
How to differentiate:
- "Lower body parkinsonism": gait disorder disproportionate to upper limb involvement (shuffling magnetic gait, postural instability)
- Stepwise rather than insidiously progressive course
- Vascular risk factors (hypertension, diabetes, smoking, AF)
- Poor response to levodopa
- Imaging shows multiple lacunar infarcts or extensive white matter disease
Normal pressure hydrocephalus: classical triad of frontal dementia, apraxic gait and urinary incontinence. ALL ventricles enlarged disproportionate to sulcal effacement. [10]
Why it mimics PD: The gait in NPH is a wide-based, magnetic, shuffling "apraxic" gait that superficially resembles parkinsonian gait. Cognitive slowing and frontal features overlap.
How to differentiate (the triad: "Wet, Wacky, Wobbly"):
- Urinary incontinence (wet) — not typically early in iPD
- Dementia (wacky) — frontal subcortical type
- Gait apraxia (wobbly) — wide-based, magnetic (feet "glued to floor"), NOT festinating
- Imaging: all ventricles enlarged disproportionate to sulcal effacement + periventricular lucency [10]
- Treatable: Large-volume LP (30–50 mL) → temporary gait improvement → predicts shunt response
- No tremor or rigidity (differentiates from true parkinsonism)
Parkinsonism should be differentiated from: Essential tremor, Cerebellar tremor, Akinetic form of Huntington's chorea [3]
| Condition | Key Differentiating Feature |
|---|---|
| Essential tremor | Tremor only present on posture and movement (cf PD resting tremor); bilateral; improves with alcohol; no rigidity or bradykinesia; family history |
| Cerebellar tremor | Tremor only present on intention (worse approaching target); associated cerebellar signs (nystagmus, dysmetria, ataxia) |
| Depression | Psychomotor retardation can mimic bradykinesia; but no rigidity, no tremor, responds to antidepressants |
| Hypothyroidism | Slowness, constipation, reduced facial expression can mimic PD; check TFT |
B. Differentiating the Parkinson-Plus Syndromes from Each Other
This is the crux of the exam question: given a patient with atypical parkinsonism, which Parkinson-plus syndrome is it?
| Discriminating Feature | MSA | PSP | CBD | DLB |
|---|---|---|---|---|
| Onset symmetry | Symmetric | Symmetric (axial) | Markedly asymmetric [2] | Symmetric |
| Dominant motor feature | Parkinsonism (MSA-P) or cerebellar ataxia (MSA-C) | Axial rigidity, early falls backwards [2] | Limb apraxia, alien limb [2] | Mild symmetric parkinsonism |
| Falls | Early (orthostatic) | Very early, backwards [2] | Variable | Moderate |
| Gaze abnormality | None specific | Vertical downgaze palsy (supranuclear) [2] | Possible | None |
| Cerebellar signs | Yes (MSA-C) [2] | No | No | No |
| Pyramidal signs | Yes [2] | Possible | Possible | No |
| Autonomic failure | Severe, early, prominent [2] | Mild | None | Moderate |
| Cognitive features | None/minimal | Frontal (apathy, executive) [2] | Cortical (apraxia, alien limb) — dementia late [2] | Early prominent dementia (attention, visuospatial, executive) [2] |
| Hallucinations | None | None | None | Recurrent visual hallucinations (well-formed) [2] |
| Fluctuating cognition | No | No | No | Yes [2] |
| RBD | Common | Uncommon | Uncommon | Very common [2] |
| Postural abnormality | Camptocormia, anterocollis [3] | Hyperextended neck (retrocollis) [2] | N/A | Stooped |
| Stridor | Yes (life-threatening) | No | No | No |
| Pathology | α-synuclein GCIs (glial) | 4R tau (tufted astrocytes) | 4R tau (astrocytic plaques, ballooned neurons) | α-synuclein Lewy bodies (cortical) |
| Characteristic imaging | Hot cross bun sign [2] | Hummingbird sign, Mickey Mouse sign [2] | Asymmetric frontoparietal atrophy [3] | Preserved hippocampi; occipital hypoperfusion |
| Proteinopathy | Synucleinopathy | Tauopathy | Tauopathy | Synucleinopathy |
C. Special Considerations in Differential Diagnosis
This is a common clinical dilemma because both present with progressive dementia in the elderly.
Dopamine transporter imaging is most helpful in distinguishing DLB from Alzheimer disease. [5]
| Feature | DLB | AD |
|---|---|---|
| Early cognitive profile | Attention, executive, visuospatial (memory relatively preserved) | Memory (hippocampal) predominant |
| Fluctuations | Present | Absent |
| Visual hallucinations | Early, well-formed | Late, if at all |
| Parkinsonism | Present | Absent (until very late) |
| RBD | Present | Absent |
| Antipsychotic sensitivity | Severe | Not typically |
| Imaging | Preserved medial temporal lobes; reduced DAT uptake | Hippocampal/temporal atrophy; normal DAT |
| EEG | Posterior slow-wave activity < 8 Hz [5] | Normal or diffuse slowing |
A 2020 systematic review of the application of EEG in the diagnosis of DLB revealed that slowing of the posterior dominant EEG rhythm was observed in approximately 90% of patients with DLB and approximately 10% of patients with Alzheimer disease. [5]
The 1-year rule remains in effect to clinically differentiate DLB from PDD: if dementia occurs before or within 1 year of motor symptoms of bradykinesia, rigidity, or resting tremor, a diagnosis of DLB is established. If dementia develops after 1 year of the onset of motor symptoms or an established diagnosis of PD then the diagnosis of PDD is given. [5]
Pathologically these are on the same Lewy body spectrum — the distinction is clinical and prognostic.
Both are 4R tauopathies with overlapping features (indeed PSP-CBS phenotype exists):
| Feature | PSP-RS | CBD |
|---|---|---|
| Symmetry | Symmetric/axial | Markedly asymmetric |
| Falls | Very early, backwards | Variable |
| Gaze | Vertical downgaze palsy | Possible but less prominent |
| Cortical signs | Frontal (executive) | Parietal (apraxia, alien limb, cortical sensory loss) |
| Neck posture | Hyperextended | Not specific |
| Myoclonus | Uncommon | Common (cortical type) |
| Imaging | Midbrain atrophy | Asymmetric frontoparietal atrophy |
Early MSA-P can closely mimic iPD. Key discriminators:
| Feature | MSA-P | iPD |
|---|---|---|
| Tremor | Jerky, postural/action, irregular | Classic resting pill-rolling |
| Levodopa response | Poor or transient (< 30% benefit) | Excellent (> 30% benefit) |
| Autonomic failure | Severe, early (orthostatic hypotension, urinary dysfunction, erectile dysfunction) | Mild, late |
| Cerebellar signs | May be present | Never present |
| Pyramidal signs | May be present | Never present |
| Stridor | Present (potentially fatal) | Never present |
| Camptocormia / anterocollis | Prominent [3] | Can occur but less severe |
| Imaging | Hot cross bun sign, putaminal changes | Normal or non-specific |
Clinical Exam Approach — Bedside Signs to R/O Other DDx
Signs to r/o other d/dx: [3]
- UMN and cerebellar signs for MSA
- Vertical gaze palsy for PSP
- Tardive dyskinesia for drug-induced parkinsonism
At the bedside, always specifically examine for these three features in any patient presenting with parkinsonism.
The neurology clinical skills lecture reminds us to systematically consider pathological categories [11]:
What is the lesion (pathological differentials)?
- Vascular (stroke)
- Infection (encephalitis, myelitis)
- Neoplasm (brain tumour)
- Degenerative (Parkinson's disease)
- Inflammatory (multiple sclerosis)
- Congenital (cerebral palsy)
- Autoimmune (encephalitis)
- Trauma / Toxins
- Endocrine (B12 deficiency)
Applied to parkinsonism DDx:
| Category | Examples |
|---|---|
| Vascular | Vascular parkinsonism (lacunar infarcts), cerebral arteriosclerotic disease |
| Infection | Post-encephalitic (viral, Japanese encephalitis), HIV, neurosyphilis |
| Neoplasm | Parasagittal meningioma, basal ganglia tumours |
| Degenerative | iPD, MSA, PSP, CBD, DLB, Huntington's, NBIA |
| Inflammatory | Autoimmune encephalitis (anti-NMDA, anti-LGI1 — can cause movement disorders) |
| Congenital | Dopa-responsive dystonia (DRD/Segawa disease) — mimics juvenile parkinsonism |
| Autoimmune | Anti-IgLON5 disease (tauopathy with sleep disorder and bulbar dysfunction — rare) |
| Trauma/Toxins | CTE (punch-drunk), MPTP, Mn, CO |
| Endocrine/Metabolic | Wilson's disease, hypothyroidism, hypoparathyroidism (basal ganglia calcification) |
| Drug-induced | Antipsychotics, metoclopramide, valproate |
| Structural | NPH, subdural haematoma |
When you see a patient with parkinsonism on the ward or in an exam:
Step 1: Confirm parkinsonism is present (bradykinesia + rest tremor and/or rigidity)
Step 2: Take a thorough drug history → rule out drug-induced parkinsonism first (most common reversible cause)
Step 3: Assess for red flags of atypical parkinsonism:
- Early falls? → PSP
- Early autonomic failure? → MSA
- Early dementia? → DLB
- Marked asymmetry with cortical signs? → CBD
- Poor levodopa response? → All Parkinson-plus
Step 4: Consider age:
- < 40 years: Wilson's disease (must exclude), juvenile PD (Parkin mutation), NBIA, dopa-responsive dystonia
- 40–70 years: iPD, Parkinson-plus syndromes
-
70 years: iPD, vascular parkinsonism, DLB, NPH
Step 5: Neuroimaging (MRI brain) for characteristic signs and to exclude structural causes
Step 6: Specific investigations based on clinical suspicion (DAT scan, autonomic function tests, copper studies, genetic testing)
High Yield Summary — DDx
The DDx of Parkinson-Plus syndromes is really the DDx of parkinsonism:
Must-know categories (from lecture slides [1][3][4]):
- iPD (80%) — good levodopa response, asymmetric, classic resting tremor
- Parkinson-plus: MSA, PSP, CBD, DLB — poor levodopa response + additional neurological features
- Drug-induced — always take drug history; reversible; symmetric; tardive dyskinesia
- Wilson's disease — must exclude in young patients (< 40); treatable
- Vascular parkinsonism — stepwise, lower body, vascular risk factors
- NPH — triad of wet-wacky-wobbly; treatable with shunt
- Toxic — MPTP, Mn, CO; occupational/exposure history
Key bedside discriminators [3]:
- UMN + cerebellar signs → MSA
- Vertical gaze palsy → PSP
- Tardive dyskinesia → drug-induced
- Alien limb + apraxia → CBD
- Visual hallucinations + fluctuating cognition → DLB
- KF rings + liver disease → Wilson's
Active Recall - Parkinson-Plus Syndromes DDx
References
[1] Lecture slides: GC 091. Unsteady gait cerebellar lesions; movement disorders; Parkinsonism.pdf (pp.21, 24) [2] Senior notes: Maksim Medicine Notes.pdf (Neurology - Parkinson-plus syndromes, pp.248–253) [3] Senior notes: Ryan Ho Neurology.pdf (Section 5.2, pp.118–126) [4] Lecture slides: Neurology - Two cases of movement disorders.pdf (p.5) [5] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf (pp.3, 6, 7) [6] Senior notes: Block A - Introduction to Clinical pharmacology (II) (Drug Interactions, adverse drug reactions).pdf (p.1) [7] Senior notes: Block A - Patients with non-viral chronic liver diseases.pdf (p.2 - Wilson's) [8] Senior notes: learning_points_output.txt (Neurology - Two Cases of Movement Disorders) [9] Senior notes: Ryan Ho GI.pdf (p.297 - Wilson's disease) [10] Senior notes: Ryan Ho Psychiatry.pdf (pp.77, 82, 88, 95) [11] Lecture slides: CFB_Neuro clinical skills demonstration_01.08.22_file to students.pdf (p.8)
Diagnostic Criteria, Diagnostic Algorithm, and Investigations for Parkinson-Plus Syndromes
Parkinson-plus syndromes remain primarily clinical diagnoses. There is no single blood test or scan that definitively confirms MSA, PSP, CBD, or DLB during life — definitive diagnosis requires neuropathological confirmation at autopsy. However, consensus diagnostic criteria have been developed for each syndrome to improve clinical accuracy, and investigations serve to support the clinical impression, exclude mimics, and rule out treatable causes.
Neuroimaging: considered for atypical cases. CT/MRI: usually normal for age → r/o alternative cause. Dopaminergic SPECT/PET: ↓dopamine activity in basal ganglia → Does not differentiate between different forms of Parkinsonism (only from non-Parkinsonism, e.g. ET) [3]
The key teaching point: investigations in Parkinson-plus syndromes are used to:
- Support a clinical diagnosis (e.g. hot cross bun sign for MSA)
- Exclude secondary/treatable causes (Wilson's, NPH, structural lesions)
- Differentiate from iPD and from each other when clinical features overlap
A. Diagnostic Criteria for Each Parkinson-Plus Syndrome
The 2022 MDS criteria introduced a three-tier diagnostic certainty framework:
| Certainty Level | Requirements |
|---|---|
| Neuropathologically established MSA | Autopsy: widespread α-synuclein-positive glial cytoplasmic inclusions (GCIs) + neurodegenerative changes in striatonigral or olivopontocerebellar structures |
| Clinically established MSA | (1) Sporadic, progressive, adult-onset (> 30 years) disease; (2) Autonomic failure (orthostatic hypotension within 10 min of standing: ≥ 20/10 mmHg or neurogenic bladder with post-void residual > 100 mL); (3) Parkinsonism with poor levodopa response OR cerebellar syndrome; (4) MRI showing hot cross bun sign, putaminal atrophy/slit sign, or middle cerebellar peduncle hyperintensity |
| Clinically probable MSA | Core autonomic + motor features (less stringent imaging requirement) |
Clinical subtypes are designated based on predominant motor features:
- MSA-P (parkinsonian predominant): akinesia, rigidity, postural instability, jerky tremor
- MSA-C (cerebellar predominant): gait ataxia, limb ataxia, ataxic dysarthria, gaze-evoked nystagmus
MSA Diagnostic Red Lines
Features that exclude MSA:
- Onset before age 30
- Family history of a similar disorder
- Established alternative diagnosis (e.g. drug-induced, structural)
- Classic pill-rolling resting tremor (suggests iPD)
- Sustained, excellent levodopa response (> 30% improvement)
The 2017 MDS criteria use a clinical predominance type framework. For the classic PSP-Richardson syndrome (PSP-RS) — the most testable form:
| Certainty Level | Requirements |
|---|---|
| Definite PSP | Neuropathological: 4R tau NFTs + tufted astrocytes in characteristic distribution (midbrain, STN, GP, frontal cortex) |
| Probable PSP-RS | Vertical supranuclear gaze palsy (especially downward) OR slowing of vertical saccades PLUS repeated unprovoked falls within 3 years of onset PLUS progressive course + onset > 40 years + sporadic |
| Possible PSP-RS | Slowing of vertical saccades PLUS postural instability with tendency to fall within 3 years |
Mandatory inclusion criteria for any PSP phenotype:
- Gradually progressive course
- Onset ≥ 40 years
- Sporadic occurrence
PSP: Most common Parki-plus syndrome, a.k.a. "Steele-Richardson-Olzewski syndrome." Vertical gaze palsy: especially downward gaze, difficulty in opening eyes. Axial rigidity > appendicular rigidity: hyperextended neck, tend to fall backwards. [2]
Mandatory exclusion criteria:
- Predominant, sustained levodopa-responsive parkinsonism
- Prominent cerebellar signs (→ think MSA-C instead)
- Evidence of relevant structural brain lesion or Whipple's disease
CBD is diagnosed clinically as corticobasal syndrome (CBS) because the same clinical picture can be produced by different pathologies (tau, AD, TDP-43). The Armstrong criteria define CBS:
| Feature Category | Requirements |
|---|---|
| Probable CBS | Asymmetric presentation + ≥ 2 of: (a) limb rigidity or akinesia, (b) limb dystonia, (c) limb myoclonus PLUS ≥ 2 of: (a) orobuccal or limb apraxia, (b) cortical sensory deficit, (c) alien limb phenomenon |
| Possible CBS | May be symmetric; ≥ 1 motor feature + ≥ 1 cortical feature |
CBD Clinical features: Marked asymmetry (unlike other Parki-plus): clumsiness of one hand. Cortical signs: limb apraxia, agnosia, alien limb phenomenon. Dementia (late). [2]
Dx: clinically by compatible clinical features with poor response to LD. Neuroimaging: focal atrophy involving posterior frontal and parietal regions with dilatation of lateral ventricles. [3]
CBD vs CBS — An Important Distinction
CBD = a pathological diagnosis (4R tauopathy with specific histological findings). CBS = a clinical syndrome (the clinical picture we see at the bedside). Not all CBS is caused by CBD pathology — up to 50% of patients with CBS at autopsy have Alzheimer's disease, PSP, or other pathologies. The Armstrong criteria are for CBS, not CBD per se.
Criteria for Diagnosis of Possible and Probable Dementia With Lewy Bodies [5]:
Essential / Required feature:
- Progressive cognitive decline interfering with normal social or occupational function
- Prominent and early deficits in attention, executive function, and visuoperceptual processing [5]
Core clinical features (must have ≥ 2 for probable, ≥ 1 for possible):
| Core Feature | Description |
|---|---|
| Fluctuating cognition | Pronounced variations in attention and alertness [5] |
| Recurrent visual hallucinations | Well formed and detailed, often of people, children, and animals. Passage hallucinations, sense of presence, and visual illusions may also occur concurrently. [5] |
| REM sleep behaviour disorder (RBD) | May precede other symptoms [5] |
| Parkinsonism | One or more cardinal features: bradykinesia, rest tremor, or rigidity [5] |
Indicative biomarkers (count as core features for diagnostic certainty):
- Reduced dopamine transporter uptake in basal ganglia by SPECT or PET [5]
- REM sleep without atonia confirmed on polysomnography [5]
- Abnormal (low uptake) iodine-123 MIBG myocardial scintigraphy [5]
Supportive clinical features:
- Severe sensitivity to antipsychotics [5]
- Hypersomnia, postural instability, hyposmia, repeated falls [5]
- Other hallucinations, systematised delusions, apathy/anxiety/depression
Diagnostic certainty:
- Probable DLB = Dementia + ≥ 2 core clinical features OR 1 core + ≥ 1 indicative biomarker
- Possible DLB = Dementia + 1 core clinical feature with no indicative biomarkers OR ≥ 1 indicative biomarker with no core features
The 1-year rule: if dementia occurs before or within 1 year of motor symptoms of bradykinesia, rigidity, or resting tremor, a diagnosis of DLB is established. If dementia develops after 1 year of the onset of motor symptoms then the diagnosis of PDD is given. [5]
Dopamine transporter imaging is most helpful in distinguishing DLB from Alzheimer disease. [5]
DLB Diagnostic Criteria — GC High Yield
This is directly from GC 241 reference material [5] and is high yield for the in-house exam. Know:
- The 4 core features: fluctuations, visual hallucinations, RBD, parkinsonism
- The 3 indicative biomarkers: reduced DAT uptake, PSG-confirmed RBD, reduced MIBG uptake
- The 1-year rule for DLB vs PDD
- Probable = 2 core or 1 core + 1 biomarker
- Antipsychotic sensitivity as a supportive (not core) feature
The following algorithm outlines the systematic clinical approach when a patient presents with parkinsonism and atypical features suggesting a Parkinson-plus syndrome:
Consider alternative diagnosis when: Onset/course — sudden onset, rapid progression, young onset with strong FHx of other disease. Clinical pattern — early and prominent dementia, early frequent falls, early incontinence, no tremor in presence of significant bradykinesia. S/S of other causes — pyramidal/cerebellar signs/autonomic dysfunction (MSA), gaze palsy (PSP), cortical signs/alien hand syndrome (CBD). Retrospective — poor treatment response to levodopa (PD usually excellent response). [3]
C. Investigation Modalities with Key Findings and Interpretations
MRI is the first-line imaging modality for any patient with atypical parkinsonism. It serves two purposes: (a) exclude structural/secondary causes, and (b) identify syndrome-specific patterns.
| Syndrome | Sequence | Key Finding | Interpretation / Why |
|---|---|---|---|
| MSA-C | T2/FLAIR | Hot cross bun sign: cruciform hyperintensity in pons [2] | Selective loss of myelinated transverse pontocerebellar fibres + pontine neurons, with preservation of pontine tegmentum and median raphe → produces a cross-shaped pattern |
| MSA-P | T2 | Putaminal slit sign: hyperintense lateral putaminal rim | Gliosis and iron deposition at the lateral margin of the putamen from neuronal loss |
| MSA-P | T2 | Putaminal atrophy + hypointensity | Iron deposition in degenerated putamen (iron appears dark on T2) |
| MSA-C | T1/T2 | Cerebellar atrophy (vermis + hemispheres), pontine atrophy | Loss of Purkinje cells and pontine neurons |
| MSA-C | T2 | Middle cerebellar peduncle hyperintensity | Wallerian degeneration of pontocerebellar fibres |
| PSP | T1 sagittal | Hummingbird sign (penguin sign): midbrain atrophy with preserved pons [2] | Selective degeneration of midbrain tegmentum (vertical gaze centres, SNpc) → the thin midbrain looks like the head/beak of a hummingbird sitting on the pons body |
| PSP | T2 axial | Mickey Mouse sign: concavity of lateral midbrain [2] | Cross-sectional view of the same midbrain atrophy → the cerebral peduncles resemble Mickey Mouse ears |
| PSP | Quantitative | Midbrain-to-pons area ratio < 0.52 | Objective measure; normal ratio ≈ 0.55–0.65 |
| PSP | T2/FLAIR | Superior cerebellar peduncle atrophy | Degeneration of dentato-thalamic outflow |
| CBD | T1/T2 | Asymmetric frontoparietal cortical atrophy with ex-vacuo dilatation of lateral ventricles [3] | Reflects the asymmetric cortical neurodegeneration; the atrophy is contralateral to the clinically more affected side |
| DLB | T1 | Relative preservation of medial temporal lobe / hippocampi | Key differentiator from AD (which shows hippocampal atrophy). DLB has cortical Lewy bodies diffusely but hippocampus is relatively spared |
| DLB | T1 | Generalised atrophy without specific pattern | Cortical Lewy body deposition is diffuse; no focal signature atrophy like PSP or CBD |
| NPH | T1/T2 | All ventricles enlarged disproportionate to sulcal effacement + periventricular lucency [12] | Communicating hydrocephalus; if sulci are also widened → ex-vacuo hydrocephalus from atrophy, NOT NPH |
| Vascular | T2/FLAIR | Multiple lacunar infarcts, extensive white matter hyperintensities | Small vessel disease affecting basal ganglia circuits |
| Wilson's | T2 | Bilateral putaminal hyperintensity, "face of the giant panda" sign in midbrain | Copper deposition and oedema in basal ganglia and brainstem |
MRI Pattern Recognition — Exam Favourite
These are classic "spot diagnosis" imaging findings in exams:
- Hot cross bun → MSA-C
- Hummingbird / penguin → PSP
- Mickey Mouse → PSP (axial view)
- Asymmetric frontoparietal atrophy → CBD
- Preserved hippocampi + clinical DLB features → DLB (vs AD)
- Eye of the tiger → NBIA (Hallervorden-Spatz)
2. Functional / Nuclear Medicine Imaging
- Radiopharmaceutical: ¹²³I-FP-CIT (DaTSCAN) for SPECT; ¹⁸F-DOPA for PET
- What it measures: Presynaptic dopamine transporter density in the striatum (reflects the integrity of nigrostriatal dopaminergic terminals)
- Principle: In any parkinsonian syndrome with nigrostriatal degeneration, DAT uptake is reduced in the striatum (comma-shaped normal → dot-shaped abnormal)
| Condition | DAT Scan Result | Explanation |
|---|---|---|
| iPD | Reduced (asymmetric, putamen > caudate) | SNpc neuronal loss → fewer presynaptic dopamine transporters |
| MSA | Reduced | Nigrostriatal degeneration present |
| PSP | Reduced | Nigrostriatal degeneration present |
| CBD | Reduced (asymmetric, contralateral to affected side) | Asymmetric basal ganglia degeneration |
| DLB | Reduced | Nigrostriatal Lewy body pathology |
| Essential tremor | Normal | No nigrostriatal degeneration |
| Alzheimer's disease | Normal | No nigrostriatal degeneration |
| Drug-induced parkinsonism | Normal | Receptors blocked but presynaptic neurons intact |
| Psychogenic parkinsonism | Normal | No organic nigrostriatal pathology |
Dopaminergic SPECT/PET: ↓dopamine activity in basal ganglia → Does not differentiate between different forms of Parkinsonism (only from non-Parkinsonism, e.g. ET) [3]
Dopamine transporter imaging is most helpful in distinguishing DLB from Alzheimer disease. [5]
What DAT Scan Can and Cannot Do
CAN: Distinguish parkinsonism (reduced DAT) from essential tremor, drug-induced parkinsonism, and Alzheimer's disease (normal DAT). This is its main clinical use.
CANNOT: Distinguish iPD from MSA, PSP, CBD, or DLB — all show reduced DAT uptake because all involve nigrostriatal degeneration to some degree.
Clinical pearl: The most common clinical scenario where DAT scan is ordered is differentiating DLB from AD (both present with dementia in elderly; DAT scan is reduced in DLB but normal in AD).
Measures regional cerebral glucose metabolism (a proxy for neuronal activity).
| Syndrome | FDG-PET Pattern |
|---|---|
| MSA-P | Hypometabolism in putamen and cerebellum |
| MSA-C | Hypometabolism in cerebellum, pons, middle cerebellar peduncles |
| PSP | Hypometabolism in frontal cortex and midbrain |
| CBD | Asymmetric hypometabolism in frontoparietal cortex (contralateral to affected side) + thalamus + basal ganglia |
| DLB | Occipital hypometabolism (posterior cortical involvement → visual hallucinations); also parietal; relative preservation of posterior cingulate ("cingulate island sign") |
| AD | Temporoparietal hypometabolism (bilateral), posterior cingulate affected |
The cingulate island sign (preserved metabolism of the posterior cingulate gyrus) is relatively specific for DLB vs AD (where posterior cingulate is affected early).
Cerebral Perfusion Study — Clinical indications: evaluation of cerebrovascular disease, aid diagnosis of dementia. Demonstrates perfusion to specific brain areas. Different types of dementia typically present with different patterns of perfusion changes. [13]
Perfusion patterns largely mirror FDG-PET patterns (reduced perfusion correlates with reduced metabolism):
- What it measures: Postganglionic sympathetic cardiac innervation
- Principle: ¹²³I-MIBG is a norepinephrine analogue taken up by cardiac sympathetic nerve terminals
- In Lewy body diseases (iPD, DLB): Cardiac sympathetic denervation occurs (Lewy body deposition in cardiac sympathetic ganglia) → reduced MIBG uptake (low heart-to-mediastinum ratio)
- In MSA: Cardiac sympathetic innervation is relatively preserved (the autonomic failure in MSA is predominantly preganglionic) → normal or mildly reduced MIBG uptake
Abnormal (low uptake) iodine-123 MIBG myocardial scintigraphy is an indicative biomarker for DLB [5]
| Condition | MIBG Uptake | Why |
|---|---|---|
| iPD | Reduced | Postganglionic sympathetic Lewy body deposition |
| DLB | Reduced | Same mechanism |
| MSA | Normal or mildly reduced | Preganglionic (IML cell column) degeneration; postganglionic neurons relatively intact |
| PSP | Normal | No significant cardiac sympathetic involvement |
| Essential tremor | Normal | No sympathetic denervation |
MIBG — Differentiating DLB/iPD from MSA
This is one of the few tests that can help distinguish between synucleinopathies: DLB/iPD (reduced MIBG) vs MSA (normal MIBG). The key is understanding where in the autonomic chain the pathology lies: DLB/iPD = postganglionic (Lewy bodies in ganglia), MSA = preganglionic (IML column degeneration).
3. Electrophysiology
- Purpose: Confirm REM sleep behaviour disorder (RBD)
- Finding: REM sleep without atonia — EMG shows sustained or excessive phasic muscle activity during REM sleep [5]
- Clinical significance: RBD is a core feature of DLB and a prodromal feature of all synucleinopathies (> 80% of isolated RBD converts to a synucleinopathy within 10–15 years)
- Polysomnographic confirmation of REM sleep without atonia is an indicative biomarker for DLB [5]
- In DLB: Posterior slow-wave EEG activity with frequencies slower than 8 Hz [5]
- This reflects cortical dysfunction in posterior regions (temporal-parietal-occipital), consistent with Lewy body deposition
-
A 2020 systematic review revealed that slowing of the posterior dominant EEG rhythm was observed in approximately 90% of patients with DLB and approximately 10% of patients with Alzheimer disease [5]
- Supportive biomarker for DLB (high sensitivity)
- In MSA: Shows denervation of the external urethral and anal sphincters (motor unit potentials are large, polyphasic, with prolonged duration)
- Why: Degeneration of Onuf's nucleus (sacral motor neurons innervating external sphincters) is relatively specific to MSA among parkinsonian disorders
- Caveat: Abnormal sphincter EMG can also occur in cauda equina/conus lesions; clinical context is essential
Particularly important for suspected MSA (which has the most severe autonomic failure among Parkinson-plus syndromes):
| Test | What It Assesses | Expected in MSA |
|---|---|---|
| Head-up tilt table test | Orthostatic BP and HR response | Sustained systolic drop ≥ 20–30 mmHg without compensatory tachycardia (neurogenic OH) |
| Thermoregulatory sweat test | Sympathetic sudomotor function | Widespread anhidrosis |
| Urodynamic studies | Bladder function | Detrusor-sphincter dyssynergia, atonic bladder, high post-void residual |
| Cardiovascular autonomic reflex tests | Heart rate variability (Valsalva, deep breathing) | Abnormal HR responses (reduced variability) |
5. Cerebrospinal Fluid (CSF) and Biomarkers
This is a relatively new and increasingly important test:
The α-synuclein-based seed amplification assay performed in CSF can detect α-synuclein across the spectrum of Lewy body-related disorders, which includes DLB, PD, isolated RBD, and primary autonomic failure with sensitivity from 59% to 95% and specificity from 83% to 98%. [5]
- Principle: Misfolded α-synuclein in CSF acts as a "seed" that can recruit normal α-synuclein to misfold and aggregate in vitro. The assay amplifies this process and detects it fluorometrically.
- Clinical use: Supports diagnosis of synucleinopathies (iPD, DLB, MSA) vs non-synucleinopathies (PSP, CBD, AD)
-
Studies have demonstrated high specificity and sensitivity when Lewy body pathology affects the neocortex (97% to 100%) and limbic regions (96%), and the sensitivity was lower in amygdala-predominant LBD (43% to 50%) and brainstem-predominant LBD (17% to 50%) [5]
The α-synuclein skin biopsy test identifies phosphorylated α-synuclein in cutaneous nerve fibres with a sensitivity greater than 92% for synucleinopathies. [5]
- Procedure: Punch biopsies from three sites (posterior cervical, posterior thigh, posterior distal leg)
- Rationale: α-synuclein deposits in autonomic nerve fibres in the skin, making this a less invasive alternative to CSF-based assays
- Useful for differentiating DLB from AD (both can present with dementia)
- AD pattern: Low Aβ42, elevated phospho-tau and total tau
- DLB pattern: Aβ42 may be low (copathology in ~50%), but phospho-tau is typically normal or only mildly elevated
- Purpose: Assess dopaminergic responsiveness
- Method: Give levodopa (titrated up to 600–1000 mg/day for ≥ 1 month, or acute challenge with 200–250 mg after domperidone pretreatment)
- Interpretation:
- Caveat: This is a supportive, not definitive, test. Some iPD patients respond poorly early on, and some MSA patients have initial partial response
Specific Ix to r/o secondary/alternative causes in young patients [3]
| Investigation | Purpose | Expected Finding if Positive |
|---|---|---|
| Serum ceruloplasmin | Wilson's disease | Low (< 20 mg/dL) |
| 24-hour urinary copper | Wilson's disease | Elevated (> 100 μg/day) |
| Slit lamp examination | Wilson's disease | Kayser-Fleischer rings (copper in Descemet's membrane) |
| TFT | Hypothyroidism (can cause slowness, constipation mimicking PD) | Elevated TSH, low T4 |
| Serum B12, folate | B12 deficiency (can cause cognitive impairment) | Low |
| RFT, Ca, glucose | Metabolic causes | Abnormal |
| LFT | Wilson's disease, hepatic encephalopathy | Deranged transaminases |
| HIV serology | HIV-associated parkinsonism | Positive |
| CT/MRI brain | Structural lesion (NPH, tumour, SDH, vascular disease) | Lesion identified |
| Genetic testing | Hereditary PD (LRRK2, SNCA, Parkin, PINK1), Wilson's (ATP7B), Huntington's (HTT CAG expansion) | Pathogenic variant |
| Investigation | MSA | PSP | CBD | DLB |
|---|---|---|---|---|
| MRI brain | Hot cross bun, putaminal changes, cerebellar atrophy | Hummingbird, Mickey Mouse, midbrain atrophy | Asymmetric frontoparietal atrophy | Preserved hippocampi, generalised atrophy |
| DAT scan | Reduced (non-specific) | Reduced (non-specific) | Reduced (asymmetric) | Reduced (key to differentiate from AD) |
| FDG-PET | Putamen/cerebellar hypometabolism | Frontal/midbrain hypometabolism | Asymmetric frontoparietal | Occipital hypometabolism, cingulate island sign |
| MIBG | Normal/mildly reduced | Normal | N/A | Reduced |
| PSG | RBD may be present | Usually normal | Usually normal | RBD — indicative biomarker |
| EEG | Non-specific | Non-specific | Non-specific | Posterior slowing < 8 Hz |
| Sphincter EMG | Denervation (Onuf's nucleus) | Normal | Normal | Normal |
| Autonomic function tests | Severely abnormal | Mildly abnormal | Normal | Mildly–moderately abnormal |
| CSF α-synuclein SAA | Positive (synucleinopathy) | Negative | Negative | Positive |
| Levodopa trial | Poor/transient response | Poor response | Poor response | Partial response |
High Yield Summary — Diagnostic Criteria and Investigations
Diagnostic Criteria — Know These Core Points:
- MSA: Sporadic adult-onset + autonomic failure (OH or neurogenic bladder) + poorly levodopa-responsive parkinsonism OR cerebellar syndrome + MRI changes
- PSP-RS: Vertical supranuclear downgaze palsy (or slow vertical saccades) + early unprovoked falls within 3 years + progressive, sporadic, onset > 40
- CBD/CBS: Asymmetric rigidity/akinesia/dystonia/myoclonus + cortical signs (apraxia, alien limb, cortical sensory loss)
- DLB: Progressive dementia (attention/executive/visuospatial early) + ≥ 2 core features (fluctuations, visual hallucinations, RBD, parkinsonism) OR 1 core + 1 indicative biomarker
Key Investigations:
- MRI brain: First-line for all — pattern recognition is essential (hot cross bun, hummingbird, asymmetric atrophy)
- DAT scan: Differentiates parkinsonism from non-parkinsonism (ET, AD) but does NOT differentiate between parkinsonian disorders
- MIBG: Differentiates Lewy body diseases (reduced) from MSA (normal) — postganglionic vs preganglionic autonomic failure
- PSG: Confirms RBD — indicative biomarker for DLB
- CSF α-synuclein SAA: Emerging test to confirm synucleinopathies (iPD, DLB, MSA)
- Levodopa trial: Good response → iPD; poor response → Parkinson-plus
Active Recall - Parkinson-Plus Dx Criteria and Investigations
References
[1] Lecture slides: GC 091. Unsteady gait cerebellar lesions; movement disorders; Parkinsonism.pdf (pp.21, 24) [2] Senior notes: Maksim Medicine Notes.pdf (Neurology - Parkinson-plus syndromes, pp.248–253) [3] Senior notes: Ryan Ho Neurology.pdf (Section 5.2, pp.119–128) [5] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf (pp.3, 6, 7) [12] Senior notes: Ryan Ho Psychiatry.pdf (pp.77, 82, 93, 95) [13] Senior notes: Ryan Ho Diagnostic Radiology.pdf (p.69)
Management of Parkinson-Plus Syndromes
Before diving into syndrome-specific management, there are several fundamental principles that apply across all Parkinson-plus syndromes:
- There is NO cure and NO disease-modifying therapy for any Parkinson-plus syndrome as of 2026. All treatment is symptomatic and supportive.
- Levodopa response is poor or absent — unlike iPD where levodopa is the mainstay. A trial of levodopa is still warranted (some patients, especially early MSA-P, may have a partial transient response), but expectations must be set appropriately.
- Multidisciplinary team (MDT) care is the cornerstone — involving neurology, physiotherapy, occupational therapy, speech and language therapy, palliative care, nursing, social work, and psychology/psychiatry.
- Management focuses on treating individual symptoms (autonomic failure, dysphagia, falls, cognitive decline, psychiatric symptoms, sleep disturbance) rather than the underlying disease.
- Prognosis is poorer than iPD — median survival 5–10 years from onset. Early palliative care planning and advance directives should be discussed.
Mx: supportive [3] (for CBD)
Parkinsonism: generally NOT responsive to dopaminergic agents [12] (for FTD-associated parkinsonism, equally applicable to tauopathies PSP/CBD)
DBS is CONTRAINDICATED in Parkinson-Plus Syndromes
Deep brain stimulation — Contraindications: Parkinson-plus syndrome [2]
This is a critical exam point. DBS works in iPD because the postsynaptic basal ganglia circuitry is relatively intact and modifiable. In Parkinson-plus syndromes, degeneration is multi-system and extends beyond the nigrostriatal pathway, so electrical stimulation of the STN or GPi cannot compensate.
A. Pharmacological Management by Symptom
1. Motor Symptoms (Parkinsonism)
Despite the poor overall response, a structured levodopa trial is recommended in all Parkinson-plus syndromes because:
- A small subset of patients (especially early MSA-P and some DLB) may have a partial, transient benefit
- Confirming poor levodopa response supports the diagnosis of Parkinson-plus over iPD
| Aspect | Detail |
|---|---|
| Regimen | Titrate levodopa/carbidopa (e.g. Madopar or Sinemet) up to 600–1000 mg/day levodopa over 1–3 months |
| Assessment | Standardised motor assessment (UPDRS Part III) before and after |
| Good response | > 30% improvement in UPDRS-III → suggests iPD or partial DLB response |
| Poor response | < 30% improvement → consistent with Parkinson-plus |
| Considerations in DLB | Levodopa can be tried cautiously — may worsen hallucinations and psychosis; start low and go slow |
| When to stop | If no meaningful motor improvement and patient develops side effects (nausea, hallucinations, orthostatic hypotension worsening), discontinue |
Why Does Levodopa Fail in Parkinson-Plus?
- MSA-P: The postsynaptic striatal neurons are lost (striatonigral degeneration) → no target for exogenous dopamine
- PSP: Degeneration extends beyond the nigrostriatal system to STN, GP, and frontal cortex → motor circuit disruption is too widespread for dopamine replacement alone
- CBD: Cortical and asymmetric basal ganglia degeneration → the motor deficit is partly cortical (apraxia), not purely dopaminergic
- DLB: Some nigrostriatal Lewy bodies present → partial response possible, but cortical Lewy body pathology dominates the clinical picture
- Generally less effective than in iPD and more likely to cause side effects (hallucinations, confusion, impulse control disorders)
- May be tried cautiously in MSA-P or PSP-P if levodopa has partial benefit and motor fluctuations develop
- Contraindicated in DLB (risk of worsening psychosis and hallucinations)
- Mechanism: NMDA receptor antagonist → anti-dyskinetic properties [3]
- In Parkinson-plus syndromes: occasionally tried for rigidity/akinesia in PSP or MSA but evidence is limited
- May help with fatigue in some patients
- Caution: Can cause confusion, hallucinations, livedo reticularis, ankle oedema; avoid in cognitively impaired patients
- Indication: Focal dystonia (e.g. blepharospasm in PSP, limb dystonia in CBD, anterocollis in MSA)
- Mechanism: Blocks presynaptic acetylcholine release at the neuromuscular junction → localised muscle relaxation
- Particularly useful for:
- PSP: Apraxia of eyelid opening, blepharospasm (injection into pretarsal orbicularis oculi)
- CBD: Fixed dystonic posturing of the affected limb
- MSA: Anterocollis (but use with caution — may worsen dysphagia if injected into neck flexors near swallowing muscles)
2. Autonomic Dysfunction (Primarily MSA)
Autonomic failure is the most disabling non-motor feature, especially in MSA. Each symptom requires targeted management:
This is often the most functionally limiting symptom. Management follows a stepwise approach:
| Level | Intervention | Mechanism / Rationale |
|---|---|---|
| Non-pharmacological (first) | Head-up tilt of bed by 10–30° at night | Reduces nocturnal supine hypertension and reduces renal sodium/water loss; avoids sudden BP drop on morning rising |
| Increase fluid intake (2–2.5 L/day) + liberal salt intake (6–10 g NaCl/day) | Expands intravascular volume → raises BP | |
| Compression stockings (waist-high, 30–40 mmHg) + abdominal binder | Reduces venous pooling in lower limbs and splanchnic bed | |
| Small frequent meals; avoid large carbohydrate-heavy meals | Reduces postprandial hypotension (carbohydrate loads cause splanchnic vasodilation) | |
| Avoid standing still; cross legs when standing; physical counter-manoeuvres | Activates skeletal muscle pump to maintain venous return | |
| Review medications: stop/reduce antihypertensives, diuretics, nitrates, α-blockers | Remove iatrogenic contributors | |
| Pharmacological | Fludrocortisone (0.1–0.3 mg/day) | Mineralocorticoid → promotes renal sodium and water retention → expands plasma volume. Side effects: supine hypertension, hypokalaemia, ankle oedema, heart failure |
| Midodrine (2.5–10 mg TDS, taken during daytime only) | α1-adrenergic agonist → direct peripheral vasoconstriction → raises BP. Contraindicated in supine hypertension, urinary retention, severe IHD. Avoid evening dosing (worsens supine hypertension). | |
| Droxidopa (norepinephrine prodrug) | Converted to norepinephrine → restores sympathetic tone. Used in neurogenic OH in some centres | |
| Pyridostigmine (30–60 mg TDS) | Cholinesterase inhibitor → enhances ganglionic neurotransmission at sympathetic ganglia → modest BP rise without worsening supine hypertension |
Supine Hypertension — The Management Paradox
MSA patients often have both severe orthostatic hypotension AND supine hypertension (due to loss of normal baroreceptor buffering). This is a therapeutic challenge because treating one worsens the other. Key strategies:
- Head-up tilt at night (reduces supine hypertension AND attenuates morning OH)
- Give midodrine only during daytime (last dose by 4 PM)
- Short-acting antihypertensives at bedtime if supine hypertension is severe (e.g. nitroglycerin patch, applied at night and removed before rising)
| Symptom | Management |
|---|---|
| Urinary urgency/frequency (detrusor overactivity) | Anticholinergics (oxybutynin, solifenacin) — but use cautiously as may worsen cognitive function and cause urinary retention |
| Urinary retention (atonic detrusor, Onuf's nucleus degeneration) | Clean intermittent self-catheterisation (CISC); suprapubic catheter if CISC not feasible |
| Erectile dysfunction | PDE5 inhibitors (sildenafil) — but caution: can worsen orthostatic hypotension |
| Nocturnal polyuria | Desmopressin intranasal at bedtime (reduces nocturnal urine production); monitor for hyponatraemia |
- Increase dietary fibre + adequate fluid
- Osmotic laxatives (macrogol/PEG), stimulant laxatives (senna, bisacodyl)
- Prokinetics (prucalopride — 5-HT4 agonist) if refractory
This is a medical emergency — vocal cord abductor paralysis can cause sudden death during sleep.
| Intervention | Detail |
|---|---|
| CPAP (Continuous Positive Airway Pressure) | First-line; splints the airway open during sleep |
| Tracheostomy | Considered for severe, life-threatening stridor unresponsive to CPAP |
| Botulinum toxin to vocal cords | Rarely used; may worsen swallowing |
3. Cognitive and Psychiatric Symptoms
Treatment of DLB — Cognition and neuropsychiatric S/S: Cholinesterase inhibitor often 1st line due to C/I to antipsychotics [12]
| Treatment | Indication | Mechanism | Evidence |
|---|---|---|---|
| Cholinesterase inhibitors (donepezil, rivastigmine, galantamine) | DLB — first-line for cognitive and neuropsychiatric symptoms [12] | Inhibit acetylcholinesterase → increase synaptic ACh → compensate for cholinergic deficit in DLB. DLB has even greater cholinergic loss than AD, so cholinesterase inhibitors may be MORE effective in DLB than AD | Rivastigmine has the strongest evidence base in DLB; improves attention, visual hallucinations, and behavioural symptoms |
| Memantine | Adjunct or alternative if cholinesterase inhibitors not tolerated | NMDA receptor antagonist → reduces glutamate excitotoxicity | Mixed evidence, minimal effect [12]; some evidence for apathy and cognitive fluctuations in DLB |
| Anticholinergics | STOP in any patient with cognitive impairment | Worsen cognition by further reducing cholinergic transmission | > Consider cholinesterase inhibitor and stop anticholinergics (worsens cognitive function) [3] |
PD drug-induced psychosis: Levodopa is least likely. Mx: ↓amantadine / selegiline → ↓DA agonist → ↓levodopa → start atypical antipsychotics (clozapine) / ECT [2]
This stepwise approach from iPD-related psychosis is adapted for Parkinson-plus syndromes:
Step 1: Identify and treat precipitants (infection, dehydration, metabolic derangement, constipation)
Step 2: Review and reduce/stop offending medications in order:
- Stop anticholinergics first (highest risk of confusion)
- Reduce/stop amantadine
- Reduce/stop dopamine agonists
- Reduce levodopa (if being used)
Step 3: If psychosis persists despite medication reduction:
| Drug | Role | Key Points |
|---|---|---|
| Quetiapine (low dose: 12.5–50 mg) | Most commonly used in practice for DLB/PDD psychosis | Atypical antipsychotic with low D2 affinity and high 5-HT2A/H1 affinity → less likely to worsen parkinsonism. Still must use with extreme caution in DLB. |
| Clozapine (6.25–50 mg) | Gold standard for PD/DLB psychosis (best evidence) | Minimal D2 blockade → least likely to worsen parkinsonism. Requires mandatory regular blood monitoring (risk of agranulocytosis ~1%). |
| Pimavanserin | Selective 5-HT2A inverse agonist approved for PD psychosis | No dopamine receptor activity → does not worsen motor symptoms. Available in some centres. |
NEVER Use Typical Antipsychotics in DLB
Atypical antipsychotics: low dose only, only when BPSD is very severe [12]
Severe sensitivity to antipsychotics is a supportive diagnostic feature of DLB. Typical antipsychotics (haloperidol, chlorpromazine) and even higher doses of atypical agents can cause catastrophic worsening — irreversible rigidity, obtundation, NMS, and death. If antipsychotics are absolutely necessary, use only quetiapine or clozapine at the lowest possible doses.
| Treatment | Notes |
|---|---|
| SSRIs (citalopram, sertraline) | First-line for depression in Parkinson-plus syndromes [3]. Avoid combination with MAO-B inhibitors (serotonin syndrome risk) |
| SNRIs (venlafaxine, duloxetine) | Alternative if SSRIs ineffective |
| Mirtazapine | Useful if insomnia and poor appetite coexist |
| TCAs (desipramine, nortriptyline) | Can be effective but anticholinergic side effects limit use in cognitively impaired patients |
| Pramipexole | Dopamine agonist with some antidepressant properties — limited role in Parkinson-plus due to poor motor response and hallucination risk |
Depression: recommend desipramine and citalopram [3]
| Drug | Mechanism | Notes |
|---|---|---|
| Melatonin (3–12 mg at bedtime) | Restores normal REM sleep architecture | First-line; fewer side effects; preferred in elderly and cognitively impaired patients |
| Clonazepam (0.25–1 mg at bedtime) | Benzodiazepine → suppresses phasic muscle activity in REM | Effective but risk of daytime sedation, falls, and worsening of obstructive sleep apnoea. Avoid in patients with gait instability or concomitant OSA |
- Involuntary laughing/crying (common in PSP, MSA)
- Dextromethorphan/quinidine combination (Nuedexta): approved for pseudobulbar affect
- SSRIs or TCAs may also help
4. Syndrome-Specific Management Summary
| Problem | Treatment |
|---|---|
| Parkinsonism | Levodopa trial (partial response in ~30% MSA-P, usually transient 1–3 years) |
| Orthostatic hypotension | Non-pharmacological measures → fludrocortisone / midodrine |
| Urinary dysfunction | Anticholinergics for urgency; CISC for retention |
| Stridor | CPAP; tracheostomy if severe |
| Cerebellar ataxia | No effective drug treatment; physiotherapy for balance and gait |
| Constipation | Dietary measures, laxatives, prokinetics |
| Depression | SSRIs |
| Problem | Treatment |
|---|---|
| Parkinsonism / axial rigidity | Levodopa trial (usually ineffective); physiotherapy is more important |
| Falls (backward) | Fall prevention: physiotherapy, environmental modifications, weighted walker, hip protectors |
| Dysphagia | Early SALT assessment; modified diet texture; PEG if aspiration risk high |
| Blepharospasm / apraxia of eyelid opening | Botulinum toxin injection to orbicularis oculi |
| Frontal cognitive dysfunction | No proven pharmacological treatment; supportive strategies |
| Pseudobulbar affect | Dextromethorphan/quinidine; SSRIs |
| Depression | SSRIs, SNRIs |
Falls management is arguably the most important intervention in PSP — aspiration pneumonia and fall-related injuries (hip fractures, subdural haematomas) are leading causes of death.
Mx: supportive [3]
| Problem | Treatment |
|---|---|
| Asymmetric rigidity / akinesia | Levodopa trial (usually poor response); physiotherapy |
| Limb dystonia | Botulinum toxin |
| Myoclonus | Clonazepam, levetiracetam, valproate |
| Limb apraxia / alien limb | No effective treatment; OT for adaptive strategies; restraining techniques (e.g. wearing a mitt) |
| Cognitive decline (late) | No proven treatment; cholinesterase inhibitors have not been shown to help in CBD |
| Pain (from dystonia) | Analgesics; botulinum toxin; physiotherapy |
Treatment: symptomatic (no disease-modifying Tx available) [12]
| Problem | Treatment |
|---|---|
| Cognitive decline | Cholinesterase inhibitors (first-line) [12]; memantine as adjunct |
| Visual hallucinations | Cholinesterase inhibitors may reduce; if severe → low-dose quetiapine or clozapine |
| Fluctuating cognition | Cholinesterase inhibitors may help; no specific treatment |
| Parkinsonism | Similar to Tx in PD [12] — cautious levodopa trial; avoid dopamine agonists (worsen psychosis) |
| RBD | Melatonin, clonazepam [12] |
| Depression | SSRIs |
| Autonomic dysfunction | Manage as per MSA autonomic management principles |
| Psychosis (severe) | Low-dose atypical antipsychotics only [12] — quetiapine or clozapine; NEVER typical antipsychotics |
Non-pharmacological measures are often more impactful than medications in Parkinson-plus syndromes because drug treatments have limited efficacy.
| Discipline | Interventions |
|---|---|
| Physiotherapy | Gait training, balance exercises, postural re-education, fall prevention strategies, stretching to prevent contractures; weighted walking aids for PSP (reduce backward falls) |
| Occupational therapy | Home environment assessment and modification (grab rails, raised toilet seat, shower chair); adaptive equipment for dressing, eating, writing; wheelchair assessment when gait becomes unsafe |
| Speech and language therapy (SALT) | Voice volume training (Lee Silverman Voice Treatment — LSVT); swallowing assessment (videofluoroscopy, FEES); dietary texture modification; communication aids if speech becomes unintelligible |
| Dietetics | Nutritional optimisation; PEG tube discussion if unsafe oral intake; management of weight loss |
| Psychology / Psychiatry | Cognitive assessment; behavioural strategies for BPSD; caregiver support and counselling |
| Social work | Financial and legal planning (power of attorney, advance directives); respite care; community support services |
| Palliative care | Early integration (not just end-of-life); symptom management; goals-of-care discussions; advance care planning |
Palliative Care — Start Early, Not Just at the End
Given the poor prognosis and limited disease-modifying treatment, palliative care should be introduced early in Parkinson-plus syndromes — ideally at diagnosis. This is a shift from the traditional view of palliative care as "end-of-life care." Early palliative involvement improves quality of life, reduces caregiver burden, and facilitates advance care planning while the patient still has capacity to participate in decisions.
While no disease-modifying therapies are currently approved, several approaches are under active investigation (2024–2026):
| Approach | Target | Status |
|---|---|---|
| Anti-α-synuclein immunotherapy (prasinezumab, cinpanemab) | Monoclonal antibodies targeting extracellular α-synuclein aggregates | Phase II–III trials in iPD/MSA; results mixed so far |
| Anti-tau immunotherapy (tilavonemab, bepranemab) | Monoclonal antibodies targeting tau aggregates | Phase II trials in PSP; tilavonemab did not meet primary endpoint in PSP-RS |
| ASO (antisense oligonucleotides) targeting SNCA | Reduce α-synuclein production at the mRNA level | Early-phase trials in MSA |
| LMTM (TRx0237) | Tau aggregation inhibitor | Investigated in PSP; inconclusive results |
| GBA-targeted therapy (ambroxol, venglustat) | Enhance glucocerebrosidase activity in GBA-mutation carriers | Phase II in DLB/PD-GBA |
| Stem cell therapy | Replace lost dopaminergic or other neurons | Very early stage; not yet applicable to Parkinson-plus |
| Intervention | Contraindication / Caution | Reason |
|---|---|---|
| Deep brain stimulation | Contraindicated in all Parkinson-plus syndromes [2] | Multi-system degeneration beyond nigrostriatal pathway; does not address cortical, cerebellar, autonomic, or bulbar pathology |
| Typical antipsychotics (haloperidol, chlorpromazine) | Contraindicated in DLB (and use with extreme caution in all Parkinson-plus) | Severe antipsychotic sensitivity → catastrophic motor deterioration, NMS, death |
| Anticholinergics | Avoid in cognitively impaired patients (DLB, PSP with frontal dysfunction) [3] | Worsen cognitive function, cause delirium, urinary retention, constipation |
| Dopamine agonists | Avoid in DLB | High risk of worsening hallucinations and psychosis |
| Sildenafil (for erectile dysfunction) | Caution in patients with severe orthostatic hypotension | Can further lower BP → syncope |
| Clonazepam (for RBD) | Caution in patients with falls, OSA, or cognitive impairment | Sedation, falls, respiratory depression |
| MAO-B inhibitors + SSRIs | Risk of serotonin syndrome | MAO-B inhibition + serotonin reuptake inhibition → excess serotonergic activity |
High Yield Summary — Management
Key Management Principles for Parkinson-Plus Syndromes:
- No cure, no disease-modifying treatment — all management is symptomatic and supportive
- DBS is contraindicated in Parkinson-plus syndromes [2]
- Levodopa trial should be attempted but expect poor/transient response (especially MSA, PSP, CBD)
- DLB management cornerstones: cholinesterase inhibitors (first-line for cognition and neuropsychiatric symptoms), melatonin/clonazepam for RBD, NEVER typical antipsychotics
- MSA autonomic management: head-up tilt, fluids/salt, compression, fludrocortisone/midodrine; CPAP/tracheostomy for stridor
- PSP: falls prevention is the priority; botulinum toxin for blepharospasm; SALT for dysphagia
- CBD: supportive only; botulinum toxin for dystonia; clonazepam for myoclonus
- MDT approach is more important than any single drug
- Early palliative care integration
- Avoid: anticholinergics in cognitively impaired, typical antipsychotics in DLB, dopamine agonists in DLB
Active Recall - Parkinson-Plus Management
References
[2] Senior notes: Maksim Medicine Notes.pdf (Neurology - DBS, Parkinson-plus syndromes, pp.250–253) [3] Senior notes: Ryan Ho Neurology.pdf (Section 5.2.2–5.2.3, pp.124–126) [12] Senior notes: Ryan Ho Psychiatry.pdf (pp.94–95 — DLB treatment, FTD management)
Complications of Parkinson-Plus Syndromes
Complications in Parkinson-plus syndromes arise from three interrelated sources:
- Disease progression itself — the relentless multi-system neurodegeneration causes worsening motor, autonomic, bulbar, and cognitive dysfunction
- Secondary consequences of the disease features — e.g. falls causing fractures, immobility causing pressure sores, dysphagia causing aspiration pneumonia
- Treatment-related complications — iatrogenic problems from medications used to manage symptoms
Prognosis compared to iPD: shorter survival, rapid progression, more frequent complications [2]
The complications are often what kills these patients. Understanding the chain from pathology → symptom → complication → cause of death is essential for clinical reasoning and exam answers.
A. Complications Common to All Parkinson-Plus Syndromes
Why falls occur:
- Postural instability (loss of postural reflexes from brainstem/basal ganglia degeneration)
- Orthostatic hypotension (autonomic failure, especially MSA)
- Gait impairment (freezing, festination, cerebellar ataxia)
- Rigidity and bradykinesia (impaired protective reflexes)
- Cognitive impairment (poor judgment, impaired spatial awareness)
- Visual impairment (vertical gaze palsy in PSP → can't see ground/obstacles)
Axial rigidity > appendicular rigidity: hyperextended neck, tend to fall backwards [2] (PSP)
Gait disturbance resulting in falls is a typical initial feature in the most classic phenotype of PSP [14]
Consequences of falls:
| Injury | Mechanism | Clinical Significance |
|---|---|---|
| Hip fracture | Fall onto greater trochanter; osteoporosis common in elderly immobilised patients | Major morbidity and mortality; surgical repair often complicated by post-operative delirium and immobility |
| Subdural haematoma (SDH) | Fall with head strike; brain atrophy (common in neurodegeneration) creates bridging vein tension | Chronic SDH may mimic or accelerate cognitive decline; may be overlooked if attributed to the underlying disease |
| Other fractures (Colles', vertebral compression) | FOOSH or axial loading | Pain, further immobility |
| Soft tissue injuries | Contusions, lacerations | Infection risk, reduced mobility |
| Loss of confidence | Fear of falling → reduced activity → deconditioning → more falls | Vicious cycle of immobility |
PSP Falls — The Leading Killer
In PSP specifically, early falls (especially backwards) are the hallmark feature. The inability to look down (vertical downgaze palsy) means patients cannot see steps, kerbs, or objects on the ground. Combined with axial rigidity and loss of postural reflexes, PSP patients fall frequently and unpredictably. Fall-related injuries (hip fractures, head trauma) are a leading direct cause of death in PSP.
Why dysphagia develops:
- Pseudobulbar palsy (PSP, MSA): bilateral corticobulbar tract degeneration → spastic tongue, impaired pharyngeal coordination
- Cerebellar involvement (MSA-C): impaired coordination of swallowing muscles
- Oropharyngeal rigidity and bradykinesia: slow oral preparatory phase, delayed swallowing reflex
- Cognitive decline (DLB, PSP frontal): poor awareness of food bolus, impaired swallowing initiation
Pathophysiology of aspiration pneumonia: Dysphagia → silent aspiration (food/liquid/saliva enters the airway without triggering an adequate cough reflex) → bacterial colonisation of aspirated material in the lungs → pneumonia. The impaired cough reflex (itself a consequence of bulbar dysfunction) compounds the problem.
DLB progresses faster than Alzheimer disease, with the most common cause of death being failure to thrive, followed by pneumonia and swallowing difficulties, other medical conditions, and complications from a fall. [5]
Pseudobulbar palsy e.g. dysarthria, dysphagia [2] (PSP)
Clinical progression:
- Early: occasional coughing during meals, prolonged mealtimes
- Moderate: recurrent chest infections, weight loss, need for modified diet textures
- Late: unsafe oral intake → PEG/RIG tube feeding or palliative approach
Aspiration Pneumonia — The Final Common Pathway
Aspiration pneumonia is the most common direct cause of death across all Parkinson-plus syndromes. This makes early SALT assessment and proactive dysphagia management critical. Always ask about coughing during meals, recurrent chest infections, and weight loss.
Progressive motor impairment (rigidity, akinesia, postural instability, ataxia) leads to increasing immobility. The complications of immobility are extensive and interconnected:
| Complication | Mechanism | Prevention/Management |
|---|---|---|
| Pressure ulcers | Sustained pressure on bony prominences (sacrum, heels, trochanters) → tissue ischaemia → necrosis | Regular repositioning (every 2 hours); pressure-relieving mattress; skin inspection; nutrition optimisation |
| Deep vein thrombosis / pulmonary embolism | Venous stasis from immobility → Virchow's triad (stasis + hypercoagulability + endothelial injury) | Mobilisation where possible; compression stockings; pharmacological prophylaxis if hospitalised |
| Contractures | Prolonged joint immobilisation in flexion (rigidity, dystonia) → periarticular soft tissue shortening | Physiotherapy, passive range-of-motion exercises, splinting |
| Deconditioning | Loss of muscle mass and cardiovascular fitness from disuse | Exercise programmes (adapted physiotherapy) |
| Constipation | Reduced physical activity + autonomic dysfunction + anticholinergic medications | Dietary fibre, fluids, laxatives, prokinetics |
| Urinary tract infections | Urinary retention/stasis (autonomic dysfunction) + catheter use | Intermittent catheterisation rather than indwelling; bladder management |
| Hospital-acquired pneumonia | Reduced respiratory effort (chest wall rigidity, reduced cough), immobility, aspiration | Chest physiotherapy, early mobilisation, aspiration precautions |
| Syndrome | Cognitive Pattern | Timing | Significance |
|---|---|---|---|
| DLB | Early dementia — attention, executive, visuospatial | Presents with or before parkinsonism | Defining feature; progresses faster than AD |
| PSP | Frontal subcortical — executive dysfunction, apathy, reduced verbal fluency, personality change [2] | Develops over years | May impair capacity for decision-making; complicates care |
| CBD | Cortical — apraxia, aphasia, visuospatial dysfunction; dementia (late) [2] | Late feature | Eventually severe; may overlap with bvFTD |
| MSA | Minimal/mild; relatively preserved cognition compared to iPD [3] | Usually preserved until late | Not a prominent feature |
Consequences of cognitive decline:
- Loss of capacity (legal and medical decision-making)
- Behavioural and psychological symptoms of dementia (BPSD): agitation, aggression, wandering, apathy
- Increased caregiver burden
- Need for institutional care
- Increased risk of delirium on top of baseline cognitive impairment (any intercurrent illness can precipitate delirium)
| Complication | Syndromes Most Affected | Mechanism | Management |
|---|---|---|---|
| Depression | All (PSP > others) | Frontal cortex degeneration (serotonergic/noradrenergic pathways); psychological reaction to diagnosis and disability | SSRIs, SNRIs, psychological support |
| Psychosis (hallucinations and delusions) | DLB (visual hallucinations early); iPD/MSA (drug-induced) | Cortical Lewy bodies (DLB); dopaminergic medication side effects; cholinergic deficit | Reduce dopaminergic drugs; low-dose quetiapine/clozapine (NEVER typical antipsychotics in DLB) |
| Apathy | PSP, DLB | Frontal-subcortical circuit disruption (medial frontal/anterior cingulate degeneration) | Cholinesterase inhibitors (DLB); no proven treatment for PSP apathy; exclude depression |
| Anxiety | All | Disease uncertainty; autonomic dysfunction (sympathetic dysregulation) | SSRIs, benzodiazepines (cautiously), psychological support |
| Impulse control disorders | Rare in Parkinson-plus (more common in iPD on dopamine agonists) | Dopamine agonist stimulation of mesolimbic reward pathway | Rare in Parkinson-plus since dopamine agonists are less used |
B. Syndrome-Specific Complications
| Complication | Pathophysiological Basis | Clinical Impact |
|---|---|---|
| Sudden death (nocturnal) | Inspiratory stridor from vocal cord abductor paralysis (nucleus ambiguus degeneration) → airway obstruction during sleep | Leading cause of sudden death in MSA; occurs in up to 30% of patients; requires CPAP/tracheostomy |
| Severe orthostatic hypotension with syncope | Intermediolateral cell column degeneration → failure of sympathetic vasoconstriction | Recurrent syncope → falls → injuries; limits upright activity and independence |
| Supine hypertension | Loss of baroreceptor buffering → unopposed supine vasoconstriction | Co-exists with orthostatic hypotension; management paradox; can cause cardiac/cerebrovascular complications |
| Urinary retention and recurrent UTIs | Onuf's nucleus degeneration → detrusor underactivity / sphincter denervation | Incomplete bladder emptying → residual urine → bacterial colonisation → UTIs → urosepsis |
| Gastroparesis | Autonomic denervation of GI tract | Nausea, vomiting, early satiety, malnutrition, erratic drug absorption |
Causes of gastroparesis: Neurological disease (e.g. Parkinsonism, amyloidosis, paraneoplastic disease) [15]
Prognosis: Dysautonomia in 2.5 years, wheelchair-bound in 3.5–5 years, bedridden in 5–8 years, death in 6–10 years [3]
MSA Prognosis Timeline — High Yield
The natural history of MSA follows a predictable trajectory:
- 2.5 years: Significant autonomic dysfunction
- 3.5–5 years: Wheelchair-dependent
- 5–8 years: Bedridden
- 6–10 years: Death (most commonly from aspiration pneumonia, sudden nocturnal death from stridor, or cardiovascular complications of autonomic failure)
| Complication | Pathophysiological Basis | Clinical Impact |
|---|---|---|
| Recurrent backward falls | Early postural instability + hyperextended neck + impaired downgaze | Hip fractures, head injuries, subdural haematomas — leading cause of morbidity/mortality |
| Severe dysphagia | Pseudobulbar palsy (bilateral corticobulbar degeneration) | Aspiration pneumonia (leading cause of death); early PEG consideration |
| Aspiration pneumonia | Dysphagia + impaired cough reflex + bulbar dysfunction | Most common cause of death in PSP |
| Communication breakdown | Progressive dysarthria (spastic/hypokinetic) + apraxia of eyelid opening | Social isolation; inability to express needs; reduced quality of life |
| Visual impairment (functional) | Supranuclear vertical gaze palsy (especially downgaze) | Cannot read, watch television, see food on plate, navigate stairs; increases fall risk |
| Complication | Pathophysiological Basis | Clinical Impact |
|---|---|---|
| Fixed dystonic limb | Progressive basal ganglia + cortical degeneration → sustained dystonic posturing | Pain, skin breakdown in clenched hand, inability to use the limb, difficulty with hygiene |
| Complete limb apraxia | Frontoparietal cortical degeneration | Total loss of function of the affected limb; requires one-handed adaptive strategies |
| Alien limb interference | Loss of cortical inhibition → involuntary movements of affected limb | Functional impairment (alien hand may grab objects, interfere with the other hand's actions); psychological distress |
| Language deterioration | Progressive non-fluent aphasia (if dominant hemisphere) | Complete loss of speech; may need alternative communication devices |
| Late-stage dementia | Spread of tau pathology to involve broader cortical regions | Loss of independence, capacity, personality |
| Complication | Pathophysiological Basis | Clinical Impact |
|---|---|---|
| Severe antipsychotic sensitivity | Severe dopaminergic + cholinergic depletion → extreme vulnerability to D2 blockade | Irreversible parkinsonism, obtundation, NMS, death if given typical antipsychotics |
| Rapid cognitive decline | Cortical Lewy bodies + frequent Alzheimer copathology (> 50%) | Faster functional decline than AD; early institutionalisation |
| Recurrent falls and syncope | Autonomic dysfunction + parkinsonism + fluctuating alertness | Fall-related injuries |
| Failure to thrive | Multifactorial: dysphagia, apathy, depression, cognitive decline, reduced oral intake | Weight loss, sarcopenia, increased infection susceptibility |
| Caregiver burnout | Fluctuating cognition (unpredictable good/bad days), hallucinations, behavioural disturbance, sleep disruption (RBD) | High caregiver distress; need for respite and support services |
DLB progresses faster than Alzheimer disease, with the most common cause of death being failure to thrive, followed by pneumonia and swallowing difficulties, other medical conditions, and complications from a fall. [5]
| Treatment | Complication | Mechanism |
|---|---|---|
| Levodopa | Nausea, vomiting | Peripheral dopamine stimulation of area postrema (reduced by carbidopa/benserazide) |
| Orthostatic hypotension (worsening) | Peripheral vasodilation from dopamine | |
| Hallucinations/psychosis | Central dopaminergic stimulation of mesolimbic pathway | |
| Dyskinesia (rare in Parkinson-plus) | Less common because these patients have poor levodopa response and rarely reach the doses/duration needed for dyskinesia | |
| Fludrocortisone | Supine hypertension, heart failure, hypokalaemia | Mineralocorticoid effects — sodium/water retention, potassium loss |
| Midodrine | Supine hypertension, urinary retention, piloerection | α1-agonist → vasoconstriction (systemic); detrusor inhibition |
| Anticholinergics (oxybutynin for bladder) | Cognitive worsening, delirium, constipation, urinary retention | Central and peripheral muscarinic blockade |
| Cholinesterase inhibitors (for DLB) | Nausea, diarrhoea, bradycardia, worsened parkinsonism | Increased cholinergic activity — GI (vagal), cardiac (vagal), and striatal (relative cholinergic excess in basal ganglia may worsen rigidity) |
| Clonazepam (for RBD) | Excessive sedation, falls, worsened sleep apnoea | GABAergic CNS depression; respiratory depression |
| Atypical antipsychotics (low-dose quetiapine) | Even at low doses in DLB: sedation, worsened parkinsonism | Residual D2 blockade; histamine/muscarinic effects |
The leading causes of death are largely shared across Parkinson-plus syndromes, though the relative contribution varies:
| Cause of Death | Mechanism | Most Common In |
|---|---|---|
| Aspiration pneumonia | Dysphagia → silent aspiration → pneumonia → sepsis → multiorgan failure | All (PSP and MSA most common) |
| Failure to thrive | Progressive dysphagia + apathy + reduced intake → cachexia → immune compromise | DLB [5] |
| Sudden death (stridor) | Nocturnal laryngeal obstruction from vocal cord abductor paralysis | MSA |
| Fall-related injuries | Fractures (especially hip) → immobility → pneumonia/PE/decline | PSP (backward falls) [5] |
| Cardiovascular complications | Autonomic failure → BP instability → MI/stroke | MSA |
| Urosepsis | Urinary retention → UTI → septicaemia | MSA |
| Pulmonary embolism | Immobility → DVT → PE | All (late stages) |
| Syndrome | Median Survival from Onset | Key Prognostic Factors |
|---|---|---|
| MSA | 6–10 years [3] | Early severe autonomic failure and stridor predict shorter survival |
| PSP | 5–9 years | Early dysphagia and frequent falls predict poorer outcome |
| CBD | 5.5–7.9 years [3] | Variable; cognitive decline accelerates functional deterioration |
| DLB | Average 7.7 years [12]; some sources 5–8 years | DLB progresses faster than AD [5]; Alzheimer copathology worsens prognosis |
| iPD (comparison) | 12–20+ years with treatment | Much better prognosis |
High Yield Summary — Complications
Top Complications to Know for Exams:
- Aspiration pneumonia — the most common cause of death across all Parkinson-plus syndromes; arises from progressive dysphagia and pseudobulbar palsy
- Falls and fall-related injuries — especially PSP (backward falls → hip fractures, SDH); also MSA (orthostatic syncope) and DLB (fluctuating alertness)
- Sudden nocturnal death from stridor — MSA-specific; vocal cord abductor paralysis → airway obstruction
- Failure to thrive — leading cause of death in DLB (multifactorial: dysphagia, apathy, cognitive decline)
- Antipsychotic sensitivity — DLB-specific; typical antipsychotics cause catastrophic worsening; this is both a diagnostic feature and a lethal complication
- Autonomic crises — MSA: severe orthostatic hypotension causing syncope and injuries; supine hypertension causing cardiovascular complications
- Cognitive decline → loss of capacity — affects decision-making, safety, and independence
- Immobility complications — pressure ulcers, DVT/PE, contractures, deconditioning, UTIs
All Parkinson-plus syndromes have shorter survival (5–10 years) than iPD (12–20+ years).
Active Recall - Parkinson-Plus Complications
References
[2] Senior notes: Maksim Medicine Notes.pdf (Neurology - Parkinson-plus syndromes, pp.251–253) [3] Senior notes: Ryan Ho Neurology.pdf (Section 5.2.3, pp.124–126) [5] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf (pp.1, 20) [12] Senior notes: Ryan Ho Psychiatry.pdf (pp.94–95) [14] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p.1298) [15] Senior notes: Block A - Indigestion and 'heartburn'_ nausea and vomiting; gastric motility problems; benign esophageal lesions.pdf (p.26)
High Yield Summary
Parkinson-Plus Syndromes — Key Discriminating Features:
-
MSA: Parkinsonism + severe early autonomic failure + cerebellar ataxia + pyramidal signs; hot cross bun sign; stridor is life-threatening; GCIs (glial α-synuclein)
-
PSP: Most common Parkinson-plus syndrome; early falls backwards + vertical downgaze palsy + axial rigidity (hyperextended neck) + pseudobulbar palsy + frontal cognitive dysfunction; hummingbird/Mickey Mouse sign; 4R tauopathy
-
CBD: Markedly asymmetric parkinsonism + cortical signs (limb apraxia, alien limb phenomenon, cortical sensory loss); asymmetric frontoparietal atrophy; 4R tauopathy
-
DLB: Early dementia (attention/visuospatial > memory) + fluctuating cognition + visual hallucinations + RBD + mild symmetric parkinsonism; severe antipsychotic sensitivity; cortical Lewy bodies; "1-year rule" distinguishes from PDD
Red flags for Parkinson-plus (vs iPD):
- Early falls/postural instability
- Early dementia
- Bilateral symmetric onset
- Early autonomic failure
- Poor levodopa response
- Additional neurological features (cerebellar, pyramidal, gaze palsy, cortical signs)
All Parkinson-plus syndromes have shorter survival and poorer prognosis than iPD.
High Yield Summary — DDx
The DDx of Parkinson-Plus syndromes is really the DDx of parkinsonism:
Must-know categories (from lecture slides [1][3][4]):
- iPD (80%) — good levodopa response, asymmetric, classic resting tremor
- Parkinson-plus: MSA, PSP, CBD, DLB — poor levodopa response + additional neurological features
- Drug-induced — always take drug history; reversible; symmetric; tardive dyskinesia
- Wilson's disease — must exclude in young patients (< 40); treatable
- Vascular parkinsonism — stepwise, lower body, vascular risk factors
- NPH — triad of wet-wacky-wobbly; treatable with shunt
- Toxic — MPTP, Mn, CO; occupational/exposure history
Key bedside discriminators [3]:
- UMN + cerebellar signs → MSA
- Vertical gaze palsy → PSP
- Tardive dyskinesia → drug-induced
- Alien limb + apraxia → CBD
- Visual hallucinations + fluctuating cognition → DLB
- KF rings + liver disease → Wilson's
High Yield Summary — Diagnostic Criteria and Investigations
Diagnostic Criteria — Know These Core Points:
- MSA: Sporadic adult-onset + autonomic failure (OH or neurogenic bladder) + poorly levodopa-responsive parkinsonism OR cerebellar syndrome + MRI changes
- PSP-RS: Vertical supranuclear downgaze palsy (or slow vertical saccades) + early unprovoked falls within 3 years + progressive, sporadic, onset > 40
- CBD/CBS: Asymmetric rigidity/akinesia/dystonia/myoclonus + cortical signs (apraxia, alien limb, cortical sensory loss)
- DLB: Progressive dementia (attention/executive/visuospatial early) + ≥ 2 core features (fluctuations, visual hallucinations, RBD, parkinsonism) OR 1 core + 1 indicative biomarker
Key Investigations:
- MRI brain: First-line for all — pattern recognition is essential (hot cross bun, hummingbird, asymmetric atrophy)
- DAT scan: Differentiates parkinsonism from non-parkinsonism (ET, AD) but does NOT differentiate between parkinsonian disorders
- MIBG: Differentiates Lewy body diseases (reduced) from MSA (normal) — postganglionic vs preganglionic autonomic failure
- PSG: Confirms RBD — indicative biomarker for DLB
- CSF α-synuclein SAA: Emerging test to confirm synucleinopathies (iPD, DLB, MSA)
- Levodopa trial: Good response → iPD; poor response → Parkinson-plus
High Yield Summary — Management
Key Management Principles for Parkinson-Plus Syndromes:
- No cure, no disease-modifying treatment — all management is symptomatic and supportive
- DBS is contraindicated in Parkinson-plus syndromes [2]
- Levodopa trial should be attempted but expect poor/transient response (especially MSA, PSP, CBD)
- DLB management cornerstones: cholinesterase inhibitors (first-line for cognition and neuropsychiatric symptoms), melatonin/clonazepam for RBD, NEVER typical antipsychotics
- MSA autonomic management: head-up tilt, fluids/salt, compression, fludrocortisone/midodrine; CPAP/tracheostomy for stridor
- PSP: falls prevention is the priority; botulinum toxin for blepharospasm; SALT for dysphagia
- CBD: supportive only; botulinum toxin for dystonia; clonazepam for myoclonus
- MDT approach is more important than any single drug
- Early palliative care integration
- Avoid: anticholinergics in cognitively impaired, typical antipsychotics in DLB, dopamine agonists in DLB
High Yield Summary — Complications
Top Complications to Know for Exams:
- Aspiration pneumonia — the most common cause of death across all Parkinson-plus syndromes; arises from progressive dysphagia and pseudobulbar palsy
- Falls and fall-related injuries — especially PSP (backward falls → hip fractures, SDH); also MSA (orthostatic syncope) and DLB (fluctuating alertness)
- Sudden nocturnal death from stridor — MSA-specific; vocal cord abductor paralysis → airway obstruction
- Failure to thrive — leading cause of death in DLB (multifactorial: dysphagia, apathy, cognitive decline)
- Antipsychotic sensitivity — DLB-specific; typical antipsychotics cause catastrophic worsening; this is both a diagnostic feature and a lethal complication
- Autonomic crises — MSA: severe orthostatic hypotension causing syncope and injuries; supine hypertension causing cardiovascular complications
- Cognitive decline → loss of capacity — affects decision-making, safety, and independence
- Immobility complications — pressure ulcers, DVT/PE, contractures, deconditioning, UTIs
All Parkinson-plus syndromes have shorter survival (5–10 years) than iPD (12–20+ years).