Spinal Stenosis

Narrowing of the spinal canal or neural foramina that compresses the spinal cord or nerve roots, resulting in pain, numbness, or weakness typically exacerbated by standing and walking.

2. Epidemiology

Category	Risk Factors	Mechanism
*Patient factors*	*Ageing, male sex, smoking* ^[3]	Ageing → disc desiccation, ligament hypertrophy, facet OA. Smoking → impaired disc nutrition via reduced vascular supply to endplates
*Mechanical factors*	*Poor posture, weak paraspinal muscles* ^[3]	Poor posture → abnormal loading → accelerated degeneration. Weak muscles → loss of dynamic stabilisation → more load on passive structures
*Occupational factors*	*Heavy lifting*, repetitive flexion/extension, whole-body vibration ^[3]	Repeated mechanical stress → cumulative disc and facet damage
Genetic/Developmental	Congenitally narrow canal (*short pedicles*), familial OPLL, Down syndrome	Smaller baseline canal diameter means less "reserve" before symptoms develop — even minor degenerative changes become symptomatic
Metabolic	Obesity, diabetes mellitus	Obesity → axial loading. DM → microvascular disease → impaired neural recovery
Comorbidities	Osteoporosis, prior spinal fractures	Vertebral body collapse → canal compromise

Developmental Stenosis — The 'Low Reserve' Concept

Patients with developmental stenosis (short pedicles) have a constitutionally narrow canal. They are prone to symptoms at any level ^[5] because even minor disc bulges or osteophytes that would be asymptomatic in a normal-sized canal become symptomatic here. Think of it as "starting with less room to spare." These patients also have higher reoperation rates: 13% of patients, 50% at adjacent levels, approximately 3.3% per year ^[5].

4. Anatomy and Function

Understanding spinal stenosis requires a solid grasp of the anatomy of the spinal canal and its contents.

Level	Canal Contents
Cervical (C1–C7)	Spinal cord (cervical enlargement C5–T1 for brachial plexus)
Thoracolumbar junction	Conus medullaris (cord termination, typically L1–L2 in adults)
Lumbar (below L2)	Cauda equina (nerve roots floating in CSF within the thecal sac)

This distinction is critical because:

Compression above L2 → upper motor neuron (UMN) signs (myelopathy)
Compression below L2 → lower motor neuron (LMN) signs (cauda equina / radiculopathy)

Ligament	Location	Role in Stenosis
Posterior Longitudinal Ligament (PLL)	Posterior surface of vertebral bodies, inside the canal	Can ossify (*OPLL*) → directly compresses cord/roots anteriorly
Ligamentum Flavum (LF)	Connects adjacent laminae, lines posterior wall of canal	Hypertrophies with degeneration → compresses cord/roots posteriorly. Can also ossify (*OLF*)
Anterior Longitudinal Ligament (ALL)	Anterior surface of vertebral bodies	Rarely causes stenosis directly, but relevant in surgical planning

5. Etiology (with Focus on Hong Kong)

The causes can be broadly classified as congenital/developmental vs. acquired.

5.2 Acquired Stenosis

This is the Kirkaldy-Willis degenerative cascade ^[7], which describes a predictable three-phase process:

Phase	Facet Joints	Disc	Result
*Phase 1: Dysfunction*	*Synovitis, hypermobility*	*Circumferential tears*	*Dysfunction*
*Phase 2: Instability*	*Continuing degeneration, capsular laxity, subluxation*	*Radial tears, internal disruption, herniation*	*Instability, lateral nerve entrapment*
*Phase 3: Stabilisation*	*Enlargement of articular processes*	*Disc resorption, osteophytes*	*One-level stenosis → multilevel spondylosis and stenosis*

The specific degenerative pathologies that narrow the canal include ^[8]:

Intervertebral disc herniation (bulging, protrusion, extrusion, sequestration)
Osteophytes (bony spurs from vertebral body endplates or uncovertebral joints)
Facet joint hypertrophy (OA of facet joints → enlargement of articular processes)
Ligamentum flavum hypertrophy (thickening and infolding, especially in extension)
Spondylolisthesis (forward slip of one vertebra on another, most commonly degenerative at L4/5, or isthmic at L5/S1)

These processes cause disc degeneration → facet joint problems → lateral canal stenosis ^[9] in a stepwise fashion.

6. Pathophysiology

7. Classification

Type	Structure Narrowed	Neural Structure Affected	Clinical Syndrome
Central stenosis	Main spinal canal	Spinal cord (cervical/thoracic) or cauda equina (lumbar)	Myelopathy or neurogenic claudication
Lateral recess stenosis	Lateral recess (subarticular zone)	Traversing nerve root	Radiculopathy
Foraminal stenosis	Intervertebral foramen	Exiting nerve root	Radiculopathy
Extraforaminal (far lateral) stenosis	Beyond the foramen	Exiting nerve root (after it exits)	Radiculopathy

Category	Examples
Congenital / Developmental	Short pedicles, achondroplasia, Down syndrome
Acquired — Degenerative	Disc herniation, facet OA, LF hypertrophy, spondylolisthesis
Acquired — Ossification	OPLL, OLF
Acquired — Inflammatory	RA, AS
Acquired — Infective	TB spine, epidural abscess
Acquired — Neoplastic	Metastases, primary tumours
Acquired — Traumatic	Fracture with retropulsed fragments
Acquired — Iatrogenic	Post-surgical, adjacent segment disease
Combined	Developmental + acquired (e.g., congenitally narrow canal + degenerative changes)

Level	Key Points
Cervical	→ Myelopathy (cord compression) ± radiculopathy. Most common at *C5/6 (most flexion & extension)* ^[2]
Thoracic	Rare. Can cause thoracic myelopathy. Consider OLF, OPLL, metastases
Lumbar	→ Neurogenic claudication ± radiculopathy ± cauda equina syndrome. Most common at L4/5

This is the standard classification/grading system for cervical myelopathy severity:

Section	Domain	Maximum Score
I	*Upper extremity function* (chopsticks/spoon use)	4
II	*Lower extremity function* (walking ability)	4
III	*Sensory* (UE, LE, trunk)	6 (2 per region)
IV	*Bladder function*	3
	*Total normal score*	*17 points*

Lower scores indicate more severe myelopathy. The recovery rate after surgery is calculated as:

Recovery rate = (postop JOA − preop JOA) / (17 − preop JOA) × 100%

8. Clinical Features

The clinical presentation depends on the level (cervical vs. lumbar) and the structure compressed (cord vs. roots vs. cauda equina).

8.1 Lumbar Spinal Stenosis

Symptom	Pathophysiological Basis
*Back pain* ^[1]	Degenerative changes in discs, facets, and ligaments → mechanical nociceptive pain. Also contributed by inflammatory mediators from degenerative tissue
*Back pain radiating to buttock and leg* ^[2]	Compression/irritation of nerve roots within the narrowed canal or foramina → referred and radicular pain along the dermatomal distribution
*Neurogenic claudication* ^[1]	The hallmark symptom. *Walking increases severity of burning/aching pain, numbness, paraesthesia, or subjective weakness* ^[1]. Mechanism: standing/walking → spinal extension → canal narrows (11%) + foramina narrow (15%) → compression of cauda equina → ischaemia of nerve roots at increased metabolic demand. *Leg and/or back pain* that is *relieved with rest and flexion (sitting, bending forward)* ^[13]. Patients characteristically adopt a flexed posture — the "shopping trolley sign"
Paraesthesia / Numbness	Compression of sensory fibres within the nerve roots → demyelination and ischaemia → abnormal sensory signalling
*Subjective weakness* in legs ^[1]	Compression of motor fibres → impaired conduction → perceived leg heaviness or giving way, especially with walking
*Bladder disturbance* ^[2]	Compression of sacral nerve roots (S2–S4) → autonomic dysfunction → initially difficulty initiating micturition, later retention with overflow incontinence (if severe / cauda equina syndrome)

The characteristic pattern of neurogenic claudication:

Pain worse with extension ^[13] (standing upright, walking downhill, lying prone)
Pain improves with rest and flexion ^[13] (sitting, bending forward, walking uphill, cycling)
"Park bench to park bench" — patients walk until symptoms become unbearable, then sit on a bench until symptoms resolve, then walk to the next bench ^[2]

Feature	*Vascular Claudication*	*Neurogenic Claudication*
Cause	Chronic limb ischaemia (PAD)	Spinal stenosis
Radiation of pain	*From distal to proximal*	*From proximal to distal*
Exacerbating factor	*Walking uphill* (increased muscle demand), exercise	*Walking downhill* (increased lordosis → extension → canal narrowing)
Relieving factor	*Rest ("shop window to shop window")*	*Bending over, sitting ("park bench to park bench")*
Pulse	*Absent* (peripheral pulses)	*Present*
Walking distance	Fixed, reproducible distance	Variable
Cycling	Provokes symptoms (exercise)	Does NOT provoke symptoms (flexed posture)
Associations	*Atherosclerotic risk factors, atrophic skin changes*	*Only 10% SLR positive, back pain* ^[15]

Why does walking downhill worsen neurogenic claudication but walking uphill worsens vascular claudication?

Walking downhill requires you to lean back (extend the spine) → narrows the canal → worse neural compression. Walking uphill requires you to lean forward (flex the spine) → opens the canal → better for stenosis patients. But uphill walking demands more muscle work → more oxygen demand → worse for ischaemic legs (PAD). This is a favourite exam question!

Sign	Pathophysiological Basis
May have relatively normal examination at rest	Stenosis is often dynamic — at rest, in a flexed sitting position, the canal is more open. Signs may only become apparent after provocative exercise (ask the patient to walk until symptoms develop, then re-examine)
Reduced lumbar lordosis / flat back	Patients adopt flexed posture to open the canal — chronic postural adaptation
*Motor deficit* ^[1]	LMN weakness in the distribution of affected nerve roots (e.g., L5 → extensor hallucis longus weakness, S1 → ankle plantarflexion weakness)
*Sensory disturbance* ^[1]	Dermatomal sensory loss corresponding to affected roots
*Reflex alterations* ^[1]	Diminished or absent reflexes at the level of the affected root (e.g., L4 → reduced knee jerk, S1 → reduced ankle jerk)
Positive stoop test	Patient walks until symptoms develop; stooping (bending forward) relieves them — confirms neurogenic claudication
SLR (Straight Leg Raise)	*Only ~10% positive* ^[15] — this is because stenosis compresses roots more centrally; SLR mainly stretches roots in lateral/foraminal locations. A positive SLR suggests concomitant disc herniation
Peripheral pulses present	Distinguishes from vascular claudication

Root	Pain / Sensory Distribution	Motor Weakness	Reflex
L4	*Pain and sensory symptoms in anterior thigh*	Knee extension (quadriceps), hip adduction	Reduced knee jerk
L5	*Pain radiates down posterior thigh, lateral calf, into great toe. Sensory symptoms affect lateral calf and great toe*	Ankle dorsiflexion (tibialis anterior), great toe extension (EHL), hip abduction	None reliably (internal hamstring reflex — unreliable)
S1	*Pain radiates down posterior leg into 4th and 5th toes. Sensory symptoms affect lateral calf, foot, and 4th/5th toes*	Ankle plantarflexion (gastrocnemius/soleus), toe flexors, hip extension	Reduced ankle jerk

Remember the L4/5 stenosis case from the lecture ^[16]: L4/5 stenosis with L4/5 spondylolisthesis can present with left anterior leg pain — this is because the L4 root exits at the L4/5 foramen and can be compressed by the spondylolisthesis causing anterior thigh pain (L4 dermatomal distribution).

8.2 Cervical Spinal Stenosis

Cervical stenosis causes myelopathy (cord compression) ± radiculopathy (root compression), depending on the location and severity.

Symptom	Pathophysiological Basis
*Neck pain and stiffness* ^[2]	Degenerative changes in discs and facet joints → mechanical pain. Loss of cervical lordosis → altered biomechanics
*Upper limb weakness and numbness*	Compression of the spinal cord at the cervical level → corticospinal tract (motor) and spinothalamic/dorsal column (sensory) involvement. Cervical radiculopathy adds dermatomal symptoms
*Lower limb weakness and numbness with UMN signs* ^[2]	The corticospinal tracts for the legs travel medially in the cervical cord — central compression affects them. Results in spastic paraparesis
Clumsiness in hands / loss of fine motor control	Compression of the corticospinal tracts and dorsal columns → impaired proprioception and motor control → difficulty with buttons, writing, chopstick use
*Lhermitte's sign* ^[2]	Electric shock-like sensation radiating down the spine/limbs on neck flexion. Mechanism: demyelinated dorsal columns are mechanically irritated by stretching during flexion
Gait unsteadiness	Posterior column (proprioception) + lateral corticospinal tract (motor) damage → sensory ataxia + spastic gait

Neck Signs:

Loss of lordosis ^[2] — chronic muscular splinting and degenerative changes
Lhermitte's sign — neck flexion produces electric shock down spine/limbs
Reversed Lhermitte's sign ^[2] — same sensation on neck extension (suggests posterior compression, e.g., LF hypertrophy)
Reduced range of motion

Upper Limb (Myelopathic Hand Signs) ^[2]: These are UMN signs in the hands that indicate cervical cord compression:

Sign	Test	Mechanism
*Inverted supinator reflex*	Tap brachioradialis → finger flexion instead of forearm supination	Loss of supinator reflex arc (C5/6) + hyperactive finger flexors (C8) due to UMN disinhibition below the lesion
*Inverted biceps reflex*	Tap biceps tendon → finger flexion instead of elbow flexion	Same principle — loss of biceps arc (C5/6) + hyperactive finger flexors
*Finger escape sign*	Ask patient to hold fingers extended and adducted → the ulnar fingers drift into abduction and flexion	Disruption of cortical hand control pathways → loss of fine motor inhibition → intrinsic muscle dysfunction
*10-second grip and release test*	Ask patient to rapidly open and close fist for 10 seconds → < 20 cycles is abnormal	Impaired corticospinal tract conduction → reduced speed of hand movements
*Hoffmann sign*	Flick the terminal phalanx of the middle finger → involuntary flexion of thumb and index finger	UMN sign — hyperreflexia of finger flexors due to loss of cortical inhibition (analogous to Babinski in the foot)

Lower Limb Signs ^[2]:

Gait instability with positive Romberg test — dorsal column dysfunction → sensory ataxia (worse with eyes closed)
Difficulty with toe-to-heel (tandem) walking — combined posterior column and corticospinal tract dysfunction
Hyperreflexia (knee, ankle jerks)
Clonus (sustained rhythmic involuntary muscular contractions)
Upgoing plantars (Babinski sign) — UMN sign
Spastic gait (circumduction, scissoring)

Mixed UMN and LMN Picture in Cervical Stenosis

At the level of compression, you get LMN signs (the anterior horn cells and nerve roots at that level are directly damaged → weakness, wasting, hyporeflexia in the myotome of that segment). Below the level of compression, you get UMN signs (the corticospinal tracts are interrupted → hyperreflexia, spasticity, upgoing plantars in the limbs below). This mixed picture is characteristic and helps localise the lesion. For example, C5/6 stenosis → LMN signs at C5/6 (weak/wasted biceps, reduced biceps jerk) + UMN signs below (hyperreflexic triceps, finger flexors; spastic legs).

Investigation	Purpose
*XR spine* ^[2]	First-line. Cervical: loss of lordosis, Pavlov ratio < 0.8, OPLL. Lumbar: loss of lordosis, reduced disc height, spondylolisthesis, calcification of PLL/LF ^[2]
*MRI spine* ^[2]	Gold standard. Shows *disc* (signal intensity, height, herniation), *neural tissues* (*"Mickey Mouse" sign* = cauda equina + traversing nerve roots in cross-section), *cord oedema, degree of canal compromise ^[2]. Disc height normally L4/5 > L5/S1 > L3/4* ^[2]. Look for *high-intensity zone (oedema)* ^[2]
CT spine / CT myelography	Better for bony detail (osteophytes, OPLL, facet OA). CT myelography when MRI contraindicated
Flexion-extension XR	Assess dynamic instability / spondylolisthesis
Electrodiagnostics (NCS/EMG)	Differentiate radiculopathy from peripheral neuropathy; confirm nerve root involvement
Bloods	If infection (WCC, CRP, ESR) or malignancy suspected

10. Key Anatomical and Pathological Correlations — Summary

Spondylolysis (lysis = dissolution/break): defect in the pars interarticularis with no movement of the vertebral body
Spondylolisthesis (olisthesis = slipping): defect causing forward slip of one vertebra on another, most commonly L5/S1 ^[3]
This can contribute to stenosis through both the forward slip (narrowing the canal) and the associated facet/ligament hypertrophy

High Yield Summary

Definition: Abnormal narrowing of the spinal canal or IV foramina → neural compression. Most common in the lumbar spine.

Epidemiology: Most common cause of spinal surgery in over 65s. OPLL up to 2–4% in Asian populations. Male predominance.

Risk Factors: Ageing, male sex, smoking, heavy lifting, poor posture, congenitally narrow canal (short pedicles).

Key Pathophysiology:

Kirkaldy-Willis cascade: Dysfunction → Instability → Stabilisation (= stenosis)
Extension narrows the canal by 11% and foramina by 15%; flexion opens them by the same amount — this explains neurogenic claudication
Neural compression causes ischaemia + venous congestion + mechanical injury + inflammation

Clinical Features — Lumbar:

Neurogenic claudication: walking-induced pain/numbness/weakness in legs, relieved by flexion/sitting ("park bench to park bench"), worsened by extension/standing/walking downhill
Neurogenic vs. vascular claudication: Neurogenic = proximal→distal pain, pulses present, worse downhill, better with flexion. Vascular = distal→proximal, pulses absent, worse uphill, better with rest only
Cauda equina syndrome: bilateral sciatica, saddle anaesthesia, urinary retention, faecal incontinence — surgical emergency

Clinical Features — Cervical:

Myelopathy: UMN signs (hyperreflexia, spasticity, Babinski, clonus) ± LMN signs at level of compression
Myelopathic hand signs: Hoffmann's, finger escape, inverted reflexes, grip-and-release < 20/10s
JOA score: Gold standard grading (total 17 points)

Nerve Root Levels: L4 = anterior thigh / knee jerk; L5 = lateral calf / great toe / EHL; S1 = posterior calf / lateral foot / ankle jerk

Cervical vs. Lumbar Root Mismatch: In the cervical spine, both central and foraminal discs at the same level affect the same root. In the lumbar spine, posterolateral disc affects the traversing root (one below), far lateral affects the exiting root (same level).

Active Recall - Spinal Stenosis (Definition to Clinical Features)

Differential Diagnosis of Spinal Stenosis

The differential diagnosis of spinal stenosis is really about unpacking the clinical presentation. A patient doesn't walk in and say "I have spinal stenosis" — they present with back pain, leg pain, claudication, weakness, or myelopathic symptoms. Your job is to figure out which of many possible diagnoses is responsible. Let's work through this systematically.

A. Differential Diagnosis of Back Pain (The Lumbar Stenosis Presentation)

This is the broadest DDx. The lecture slide ^[17] lays out the framework beautifully:

These are by far the most common causes. "Mechanical" means the pain relates to the structural/biomechanical elements of the spine and is typically affected by posture and movement.

Condition	Why it mimics stenosis	How to differentiate
Back sprain / muscle strain ( > 70%) ^[17]^[2]	Commonest cause of back pain overall. Paraspinal muscle injury → localised back pain, may radiate to buttock. Can be mistaken for early stenosis	No neurological deficit. Pain is muscular (tender paraspinal muscles), worsened by specific movements, improves in days–weeks. No claudication pattern. No imaging abnormality
Lumbar disc degeneration ^[17]	Chronic discogenic pain from degenerative disc → axial back pain, sometimes referred to buttock/thigh. Part of the same degenerative cascade as stenosis (Kirkaldy-Willis)	Pain is predominantly axial (midline), aggravated by sitting/flexion (loads the disc), NOT positional in the extension-flexion pattern of stenosis. MRI shows disc desiccation (dark disc) but canal remains adequate
Lumbar disc herniation ^[17]	Acute posterolateral disc protrusion → nerve root compression → radiculopathy (sharp, shooting leg pain in a dermatomal pattern). Can coexist with stenosis	Typically acute onset, often precipitated by lifting/bending. SLR strongly positive (vs. only ~10% in stenosis ^[15]). Pain follows a specific dermatome. Younger patients. MRI shows focal disc protrusion compressing a single root
Spondylolisthesis ^[17]	Forward slip of one vertebra → can narrow the canal (actually causes stenosis) or the foramen. Presents with back pain ± radiculopathy ± claudication	XR shows the slip (lateral view). Often at L4/5 (degenerative) or L5/S1 (isthmic). Can coexist with stenosis — in fact, spondylolisthesis with stenosis changes the surgical approach (decompression + fusion needed ^[3])
Fracture — vertebral body ^[17]	Compression fracture (osteoporotic or pathological) → acute back pain. If retropulsed fragments enter canal → stenosis/cord compression	Acute onset, often with minimal trauma in elderly/osteoporotic patients. Point tenderness over spinous process. XR/CT shows fracture. Red flag: chronic steroid use, osteoporosis ^[2]
Spondylolysis ^[17]	Pars interarticularis defect → back pain, especially in young athletes with repetitive extension (e.g., gymnasts, fast bowlers). No slip = no stenosis, but can progress to spondylolisthesis	Young patient. Pain with extension. Oblique XR shows "Scotty dog" fracture. CT confirms pars defect. No neurological signs unless progressed to listhesis

These are the "red flag" causes — less common but more dangerous. Always screen for these.

Condition	Why it mimics stenosis	How to differentiate
Neoplasia ^[17]	Spinal metastases or primary tumours → progressive back pain ± cord/root compression. Can actually cause stenosis by space-occupying effect	Red flags: unrelenting pain (worse at night, not relieved by rest), weight loss, history of primary malignancy (lung, breast, prostate, kidney, thyroid). No mechanical pattern. Raised inflammatory markers. MRI shows bony/soft tissue mass
Inflammatory arthritis — AS/spondyloarthropathy ^[17]	Inflammatory back pain → morning stiffness > 30 min, improves with exercise, worsens with rest. Late: bamboo spine → rigid → prone to fracture → stenosis	Young male ( < 40), insidious onset, HLA-B27+, sacroiliitis on XR/MRI, raised CRP/ESR. Pain pattern is opposite to mechanical (better with activity, worse at rest)
Infection ^[17]	TB spine (Pott's disease), pyogenic discitis/osteomyelitis, epidural abscess → back pain ± cord/root compression ± constitutional symptoms	Fever, night sweats, weight loss, immunosuppression (HIV, DM, IVDU). Raised WCC/CRP/ESR. MRI shows disc/endplate destruction, paravertebral or epidural collection. Red flag: fever + immunosuppression ^[2]

These are extra-spinal pathologies that can refer pain to the back, mimicking spinal disease:

Condition	Mechanism of Referred Pain
Pelvic inflammatory disease ^[17]	Pelvic visceral afferents share spinal segments (T10–L1) with somatic innervation of lower back
Endometriosis ^[17]	Cyclical pain, may involve uterosacral ligaments → referred lumbosacral pain
Nephrolithiasis / Pyelonephritis ^[17]	Renal capsule distension and ureteric spasm → referred flank/back pain via T10–L1 afferents. Costovertebral angle tenderness, haematuria, dysuria distinguish these
Aortic aneurysm ^[17]	Expanding or leaking AAA → deep, boring back pain. Can compress lumbar vertebral bodies. Life-threatening — always consider in elderly patient with acute back pain + haemodynamic instability

The 'Surgical Sieve' for Back Pain DDx

A useful mnemonic to remember the categories: VITAMIN CD — Vascular (AAA), Infection (TB, abscess), Trauma (fracture), Autoimmune/inflammatory (AS, RA), Metabolic (osteoporotic fracture), Idiopathic, Neoplastic (mets), Congenital, Degenerative (spondylosis, disc, stenosis). The lecture categorises them as mechanical (97%) vs. non-mechanical (3%) — but always actively screen for the 3%.

This is one of the highest-yield comparisons in the entire orthopaedic and vascular surgery curriculum. Both cause exercise-induced leg symptoms, but the pathophysiology is completely different.

Claudication vs. radiculopathy — the lecture slide ^[1] emphasises that you must distinguish these two patterns. Neurogenic claudication is bilateral and positional; radiculopathy is typically unilateral and dermatomal.

Feature	Vascular Claudication	Neurogenic Claudication
Underlying cause	Chronic limb ischaemia (PAD) ^[2]^[15]	Spinal stenosis ^[2]^[15]
Radiation of pain	From distal to proximal (starts in calf, moves up) — because distal muscles are furthest from blood supply and become ischaemic first ^[2]^[15]	From proximal to distal (starts in buttock/thigh, moves down) — because proximal nerve roots in the narrowed central canal are compressed first ^[2]^[15]
Exacerbating factor	Walking uphill, exercise ^[2]^[15] — uphill demands more calf muscle work → more O₂ demand → ischaemia	Walking downhill, increased lordosis ^[2]^[15] — downhill requires leaning back (extension) → canal narrows by 11%, foramina by 15% ^[1]
Relieving factor	Rest alone ("shop window to shop window") ^[2]^[15] — stopping reduces O₂ demand → supply catches up	Bending over, sitting ("park bench to park bench") ^[2]^[15] — flexion opens the canal → decompresses neural elements. Just stopping is not enough — posture must change
Peripheral pulses	Absent ^[2]^[15] — atherosclerotic occlusion	Present ^[2]^[15] — no vascular pathology
Claudication distance	Fixed and reproducible (same distance each time)	Variable (depends on spinal position, terrain) ^[15]
Cycling	Provokes symptoms (exercise = more O₂ demand)	Does NOT provoke symptoms (seated position = flexion = canal open)
Associations	Atherosclerotic risk factors, atrophic skin changes ^[15]	Only 10% SLR positive, back pain ^[15]
Examination	Absent pulses, bruits, trophic changes (hair loss, thin skin, nail changes), reduced ABPI	Normal vascular exam. May have subtle neurological signs. Stoop test positive

Additional vascular DDx of leg pain with walking (from senior notes ^[18]):

Sciatica ^[18]: radiculopathy (L5–S1 from herniated disc) → sharp/burning pain radiating down posterior/lateral leg. Not truly exercise-dependent; aggravated by sitting/coughing/straining (increased intrathecal pressure)
Arthritis of hip or foot ^[18]: joint-based pain, worsened by weight-bearing, localised to joint, limited ROM on examination
Chronic compartment syndrome ^[18]: typically young athletes with heavy musculature. Reversible increased pressure within a muscle compartment during exercise → pain/tightness. Subsides with rest. Diagnosed by intracompartmental pressure measurement
Baker's cyst ^[18]: popliteal synovial cyst → posterior knee pain/swelling. Can compress popliteal vein or tibial nerve → mimics vascular or neurogenic symptoms

When a patient presents with UMN signs in the limbs, gait disturbance, and myelopathic hand signs, the DDx extends beyond just cervical stenosis ^[19]:

Condition	Why it mimics cervical stenosis	Key differentiating features
Cervical myelopathy (from stenosis) ^[19]	This IS the diagnosis — but the point is that myelopathy symptoms can overlap with other conditions	Progressive, insidious. UMN signs. Myelopathic hand signs. MRI shows cord compression
Peripheral nerve compression ^[19]	e.g., carpal tunnel syndrome (median nerve), cubital tunnel syndrome (ulnar nerve). Hand weakness/numbness can be mistaken for myelopathy	Symptoms restricted to a single peripheral nerve distribution (not UMN pattern). No LL signs. NCS/EMG localises the lesion to peripheral nerve. Double crush syndrome ^[20]: peripheral entrapment can coexist with cervical spondylosis — proximal compression renders the nerve more susceptible to distal compression
Shoulder pathology ^[19]	Shoulder impingement, rotator cuff tear, frozen shoulder → arm pain/weakness that can mimic cervical radiculopathy	Pain localised to shoulder, specific provocative tests positive (Neer's, Hawkins, empty can), ROM limitation. No dermatomal sensory loss. No UMN signs
Motor neuron disease (ALS)	Progressive UMN + LMN signs → weakness, fasciculations, spasticity. Can affect upper and lower limbs	No sensory involvement (pure motor). Fasciculations prominent. Bulbar symptoms (dysarthria, dysphagia) develop. EMG shows widespread denervation. No pain
Multiple sclerosis	Demyelinating disease → UMN signs, sensory disturbance, Lhermitte's sign. Can cause myelopathy	Younger patient (20–40). Relapsing-remitting course. Visual symptoms (optic neuritis). MRI brain shows periventricular white matter lesions. CSF shows oligoclonal bands
Subacute combined degeneration (B12 deficiency)	Dorsal column + corticospinal tract degeneration → sensory ataxia + UMN signs. Mimics posterior cord compression	Peripheral neuropathy (glove-and-stocking), macrocytic anaemia, low B12, psychiatric symptoms. No structural compression on MRI
Syringomyelia	Central cavity in the cord → "cape-like" dissociated sensory loss (loss of pain/temperature, preserved light touch). Can cause hand weakness	MRI shows syrinx. Chiari malformation often associated. Dissociated sensory loss is the hallmark
Spinal cord tumour	Intradural or extradural mass → progressive myelopathy	Progressive course, night pain, weight loss if malignant. MRI shows mass lesion with cord compression
Compressive myelopathy from other causes ^[21]	Epidural haematoma, abscess, OPLL	Each has distinct clinical context: haematoma (post-procedural/anticoagulated), abscess (fever, immunocompromised), OPLL (Asian patient, younger age)

Exam Pitfall: Myelopathy vs. Peripheral Neuropathy

A common mistake is attributing myelopathic hand signs to peripheral nerve compression. The key distinguishing feature is the presence of UMN signs (hyperreflexia, Hoffmann's, upgoing plantars, clonus) in myelopathy, which are never present in peripheral nerve compression (which only gives LMN signs). If a patient has hand clumsiness AND hyperreflexia in the legs — that's myelopathy until proven otherwise.

Since severe stenosis or large central disc herniation can cause cauda equina syndrome ^[1], you should also know the DDx of CES itself:

Cause	Mechanism
Massive central disc herniation (most common)	Large NP fragment compresses the entire cauda equina at L4/5 or L5/S1
Chronic deterioration of spinal stenosis ^[1]	Progressive narrowing → eventually critical compression of cauda equina
Spinal fracture (traumatic/pathological)	Retropulsed bone fragments into the canal
Malignancy (metastasis)	Space-occupying lesion within the spinal canal — paired organs: thyroid, breast, lung, kidney, prostate ^[2]
Infection (discitis, TB spine, epidural abscess)	Expanding inflammatory mass/collection within the canal
Inflammatory (AS)	Rarely, but fracture through a fused bamboo spine can cause CES
Iatrogenic (haematoma post-spinal anaesthesia) ^[2]	Epidural haematoma compresses cauda equina — more common in anticoagulated patients

Feature	Spinal Stenosis	Disc Herniation	Vascular Claudication	Inflammatory (AS)	Infection	Malignancy
Age	> 50	30–50	> 50	< 40	Any	Any (but > 50)
Onset	Insidious	Acute/subacute	Insidious	Insidious	Subacute	Progressive
Pain character	Claudication, bilateral	Radicular, unilateral	Calf cramping	Stiffness, ache	Constant, boring	Unrelenting, nocturnal
Positional	Worse extension, better flexion	Worse sitting/flexion	Worse exercise, better rest	Worse rest, better activity	No positional relief	No positional relief
SLR	10% positive	Strongly positive	Negative	Negative	May be positive	May be positive
Pulses	Present	Present	Absent	Present	Present	Present
Neurological signs	Variable, often subtle	Dermatomal deficit	None	Late: rigid spine	If abscess: rapid deficit	Progressive deficit
Red flags	CES features	CES if central	Gangrene, tissue loss	Uveitis, enthesitis	Fever, immunosuppression	Weight loss, night pain

High Yield Summary

The DDx of spinal stenosis is structured by presentation:

Back pain DDx — Mechanical (97%): muscle strain ( > 70%), disc degeneration, disc herniation, spondylolisthesis, fracture, spondylolysis. Non-mechanical (3%): neoplasia, inflammatory arthritis (AS), infection. Non-spinal: AAA, renal, gynaecological ^[17].
Claudication DDx — The must-know comparison is neurogenic vs. vascular claudication: neurogenic = proximal→distal, pulses present, worse downhill/extension, better flexion/sitting ("park bench to park bench"); vascular = distal→proximal, pulses absent, worse uphill/exercise, better rest ("shop window to shop window") ^[2]^[15].
Cervical stenosis/myelopathy DDx — Peripheral nerve compression, shoulder pathology ^[19] are the main mimics. Also consider MS, MND, B12 deficiency, syringomyelia, cord tumour. Key: UMN signs = myelopathy, not peripheral.
Always screen for red flags: CES (saddle anaesthesia, urinary retention, bilateral weakness), infection (fever, immunosuppression), fracture (steroid use, osteoporosis), malignancy (weight loss, night pain) ^[2].
Double crush syndrome ^[20]: peripheral entrapment often coexists with cervical spondylosis — proximal compression makes the nerve more susceptible to distal injury.

Active Recall - Differential Diagnosis of Spinal Stenosis

References

^[1] Lecture slides: GC 226. Lumbar Spine Pathology_Part F (2).pdf, p2–3 ^[2] Senior notes: maxim.md (sections 2.3, 2.5 — approach to spine diseases, spinal stenosis, cauda equina syndrome) ^[3] Senior notes: maxim.md (section 2.6 — spondylolisthesis, PID) ^[15] Senior notes: maxim.md (vascular vs neurogenic claudication comparison table, section on chronic limb ischaemia) ^[17] Lecture slides: GC 226. Lumbar Spine Pathology_Part E (2).pdf, p2 ^[18] Senior notes: felixlai.md (section on differential diagnosis of intermittent claudication) ^[19] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p44 ^[20] Senior notes: maxim.md (section 5.2 — compression neuropathy, double crush syndrome) ^[21] Senior notes: maxim.md (section 2.4 — cervical myelopathy etiology)

Diagnostic Criteria, Algorithm, and Investigations for Spinal Stenosis

Diagnostic Framework — What Constitutes the "Diagnosis"

The diagnosis rests on three pillars:

Pillar	Detail
1. Clinical syndrome	Neurogenic claudication: walking increases severity of burning/aching pain, numbness, paraesthesia, or subjective weakness ^[1]. Pain worse with extension, improves with rest and flexion ^[1]. ± Leg and/or back pain, motor deficit, sensory disturbance, reflex alterations ^[1].
2. Imaging correlation	MRI showing canal, lateral recess, or foraminal narrowing at a level consistent with the clinical picture (correct dermatome/myotome)
3. Exclusion of mimics	Vascular claudication excluded (pulses present), peripheral neuropathy excluded, hip/knee OA excluded

Pillar	Detail
1. Clinical syndrome	Myelopathic signs (UMN signs in limbs, myelopathic hand signs, gait disturbance) ± radiculopathy
2. Imaging correlation	MRI showing cord compression ± intramedullary signal change (myelomalacia) ^[22] at a level consistent with clinical findings
3. Severity grading	JOA score (total 17 points) ^[2] — quantifies functional impairment and guides surgical decision-making

These are quantitative imaging criteria that help define stenosis objectively:

Measurement	Definition	Threshold
a = Midsagittal diameter of spinal canal	AP diameter of the bony canal on lateral XR or CT	Relative stenosis if < 12 mm; absolute if < 10 mm ^[6]
b = Dynamic stenosis	Distance from posteroinferior corner of cranial vertebra to anterosuperior edge of caudal lamina	Dynamic stenosis if < 12 mm ^[6]
c = Olisthesis	Slip distance between adjacent vertebral bodies	Measured in mm — any slip suggests instability
Pavlov ratio	Ratio of AP diameter of canal to diameter of vertebral body at same level	< 0.8 suggests stenosis ^[2]

Measurement	Threshold	Notes
AP diameter of canal	< 12 mm relative; < 10 mm absolute	Measured on axial CT or MRI
Dural sac cross-sectional area	< 100 mm² moderate; < 75 mm² severe	On axial MRI — this is the most clinically relevant measure
Lateral recess height	< 4 mm	Suggests lateral recess stenosis compressing traversing root
Foraminal height	< 15 mm	Suggests foraminal stenosis compressing exiting root

The Imaging-Clinical Disconnect

A critical concept: up to 20–30% of asymptomatic people over 60 have imaging evidence of lumbar stenosis. Conversely, some patients with classic neurogenic claudication have only modest narrowing on MRI. Never diagnose stenosis on imaging alone — always correlate with the clinical presentation. The question on the exam is not "Is the canal narrow?" but "Does the narrowing explain this patient's symptoms?"

Investigation Modalities — Detailed Interpretation

1. Plain Radiographs (XR Spine) — First-Line

XR is the starting point because it is cheap, widely available, and gives you critical structural information. However, it cannot directly visualise soft tissues (discs, ligaments, neural structures).

Views: AP, lateral ^[23], oblique views for foraminal narrowing ^[23]

Finding	What It Means	Mechanism/Significance
Loss of cervical lordosis ^[2]	Normal cervical spine has a lordotic curve; loss suggests muscular splinting, degenerative disc disease, or chronic myelopathy	Paraspinal muscles go into spasm to protect the cord → straightening of the spine
Pavlov ratio < 0.8 ^[2]	Ratio of canal AP diameter to vertebral body AP diameter. A ratio < 0.8 means the canal is disproportionately narrow	Suggests either developmental or acquired stenosis. Quick bedside calculation on lateral XR
Osteophytes	Bony spurs at vertebral body margins or uncovertebral joints	Degenerative — can encroach on the canal or foramina
Reduced disc height	Loss of disc space height	Disc degeneration → loss of NP height → secondary canal narrowing
OPLL visible as calcification along PLL	Radiopaque line posterior to vertebral bodies	Ossified PLL compressing the cord anteriorly. Better delineated on CT ^[25]
Dynamic instability	Assessed on flexion-extension views — abnormal translation or angulation between adjacent vertebrae	Suggests spondylolisthesis or ligamentous instability contributing to dynamic stenosis

Soft tissue assessment (C-spine specific) ^[2]:

3×7=21 rule: prevertebral soft tissue width: C1 ≤ 10 mm, C3 ≤ 7 mm, C7 ≤ 21 mm
Widened prevertebral soft tissue suggests retropharyngeal haematoma/abscess or fracture

Views: AP, lateral, ± oblique (for pars defects)

The lecture slide ^[24] emphasises three key things to assess on lumbar XR:

Finding	What It Means
Disc space ^[24]	Reduced disc height indicates degeneration. Normal disc height: L4/5 > L5/S1 > L3/4 ^[3]. Asymmetric loss suggests focal pathology
Deformity ^[24]	Loss of lumbar lordosis ^[2], scoliosis (degenerative), kyphosis (compression fracture). Loss of lordosis is the body's attempt to open the canal (flexion posture adopted chronically)
Spondylolisthesis ^[24]	Forward slip visible on lateral view. Graded by Meyerding classification (I–V based on % slip). L4/5 (degenerative) or L5/S1 (isthmic) most common
Calcification of PLL/LF ^[2]	Indicates OPLL or OLF — potential compressive pathology
Spondylolysis	Pars interarticularis defect — best seen on oblique view ("Scotty dog" with collar = pars fracture). May be precursor to spondylolisthesis

X-ray: correlation with symptoms is essential [22a]. The lecture emphasises that XR should be interpreted with positive history and used to screen for malignancy and infection — but beware false assurance as normal XR does NOT exclude stenosis [22a].

When to Get XR vs. Going Straight to MRI

In the acute setting (trauma, suspected fracture), get XR first (or CT if high-energy). For chronic neurogenic claudication with no red flags, you can start with XR to assess alignment, disc height, and listhesis, then proceed to MRI if surgery is being considered. For suspected cauda equina syndrome or myelopathy, go straight to urgent MRI — do not wait for XR.

2. MRI Spine — The Gold Standard

MRI is the definitive investigation because it directly visualises soft tissues: discs, ligaments, neural structures, cord, and CSF. It is the only modality that can confirm neural compression and cord signal change.

The lecture slide ^[22] specifies a systematic MRI interpretation framework:

Feature	What to Assess	Significance
Level of lesion, location ^[22]	Which disc level? Central, lateral, foraminal?	Determines which neural structure is compressed and guides surgical approach
Pathoanatomy ^[22]	Disc, osteophyte, OPLL, flavum — what is causing the compression?	Each has different surgical implications (anterior vs. posterior approach [see Management section])
Obliteration of the CSF space ^[22]	On T2-weighted images, CSF appears bright (white). If the bright CSF signal is obliterated around the cord → significant compression	The "CSF buffer" is gone — the cord is being squeezed. Loss of CSF space even without cord signal change indicates at-risk cord
Cord shape / cross-sectional area ^[22]	Flattened or banana-shaped cord on axial views indicates external compression	Normal cord is round/oval. Flattening means mechanical deformation
Intramedullary signal change (myelomalacia) ^[22]	T2 hyperintensity within the cord substance	Indicates irreversible cord damage — gliosis and oedema within the cord. This is a poor prognostic sign for recovery after surgery. T1 hypointensity = even worse (cavitation/necrosis)

Feature	What to Assess	Significance
Disc: signal intensity ^[3]	T2-weighted: normal disc is bright (hydrated NP). Dark disc = desiccated, degenerated	Dark disc on T2 = loss of aggrecan and water content — the starting point of the degenerative cascade
Disc height ^[3]	Normal: L4/5 > L5/S1 > L3/4 ^[3]	Reduced height indicates degeneration at that level
PID — high-intensity zone ^[3]	Bright spot within the posterior annulus on T2	Indicates annular tear with oedema/inflammation — clinically significant, often a pain generator
Neural tissues: "Mickey Mouse" sign ^[3]	On axial T2 images at the lumbar level, the thecal sac in cross-section looks like Mickey Mouse's head (the dural sac) with two ears (the traversing nerve roots in the lateral recesses)	If the "Mickey Mouse" is compressed/distorted — the nerve roots are being squeezed. If you can't see it at all, you have severe central stenosis
Degree of canal compromise	Schizas classification (Grade A–D based on CSF visibility and rootlet aggregation)	Grades severity of compression — useful for surgical decision-making
Foraminal compromise	Exiting root surrounded by fat (white on T1) vs. no fat visible	Loss of perineural fat = foraminal stenosis compressing the exiting root
Cord oedema ^[3]	T2 hyperintensity in the cord (if conus involvement at thoracolumbar junction)	Same significance as myelomalacia in cervical cord

MRI sequences and what they show:

Sequence	What It's Best For	Key Interpretation
T1-weighted	Anatomy, fat (bright), marrow	Fat around nerve roots appears white — loss of fat signal = compression. Bone marrow replacement (tumour/infection) appears dark
T2-weighted	Fluid (CSF bright), pathology, cord signal	CSF is white → can see compression by loss of white signal around cord/roots. Disc degeneration = dark disc. Cord myelomalacia = bright within cord
STIR	Oedema, inflammation (fat suppressed)	Bone marrow oedema (fracture, infection, tumour). Soft tissue inflammation
T1 + gadolinium	Enhancement (tumour, infection, inflammation)	Enhancing mass = tumour or abscess wall. Post-surgical scar vs. recurrent disc (scar enhances, disc doesn't)

3. CT Spine

CT provides excellent bony detail and is superior to MRI for certain indications.

Modality	Best For
CT ^[26]	Fracture configuration — precise bony anatomy, retropulsed fragments, facet joint morphology
CT myelogram ^[26]	When MRI is contraindicated (pacemaker, severe claustrophobia). Intrathecal contrast outlines the thecal sac and nerve roots → shows compression indirectly
MRI ^[26]	Nerve compression, sinister pathologies, confirmation of lesions ^[26]

Finding	Significance
Facet joint hypertrophy	Bony overgrowth of superior/inferior articular processes → lateral recess and foraminal narrowing
Osteophytes	Bony spurs from vertebral endplates or uncovertebral joints → canal or foraminal encroachment
OPLL — plain CT to delineate ossification of posterior longitudinal ligament ^[25]	CT is superior to MRI for characterising OPLL because ossified tissue appears as dense bone on CT. MRI may underestimate the extent of ossification (bone and ligament both appear dark on MRI). CT shows the exact morphology: continuous, segmental, mixed, or localised type
Ligamentum flavum ossification	Dense calcification along the posterior canal wall
Pars defect	Spondylolysis — CT is more sensitive than XR for detecting pars fractures

Dynamic X-rays to diagnose atlantoaxial subluxation in rheumatoid arthritis ^[25] — and more generally to assess instability.

Purpose	What to Look For
Lumbar instability	> 4 mm translation or > 10° angulation between adjacent vertebrae on flexion vs. extension views → unstable spondylolisthesis
Cervical instability	Increased atlantodental interval (ADI) on flexion (normal < 3 mm in adults). ADI > 3 mm suggests C1/2 instability (RA, Down syndrome, trauma)
Dynamic stenosis	Canal narrows in extension, opens in flexion — quantifies the dynamic component

Why this matters: if spondylolisthesis is present AND dynamic (increases with movement), surgery requires fusion in addition to decompression ^[3]. A fixed slip may only need decompression.

NCV / EMG ^[23] — these are ancillary tests that help:

Test	What It Does	When to Use
Nerve Conduction Studies (NCS)	Measures speed and amplitude of electrical conduction along peripheral nerves	Differentiates radiculopathy (normal distal conduction, abnormal proximal) from peripheral neuropathy (abnormal distally). Helps exclude diabetic neuropathy or carpal tunnel as the cause of symptoms
Electromyography (EMG)	Needle electrode inserted into muscles; detects denervation potentials (fibrillations, positive sharp waves)	Confirms which specific nerve root is affected (e.g., denervation in L5-innervated muscles confirms L5 radiculopathy). Also helps determine chronicity (acute vs. chronic denervation)
Somatosensory Evoked Potentials (SSEP) ^[27]	Stimulate peripheral nerve → record cortical response. Measures entire sensory pathway from periphery to cortex	Helps confirm myelopathy (prolonged central conduction time). Used intraoperatively to monitor cord function during cervical decompression

When NCS/EMG Is Most Useful

NCS/EMG is most valuable when: (1) clinical and MRI findings don't match (e.g., multilevel disease on MRI but symptoms suggest single root), (2) distinguishing radiculopathy from peripheral neuropathy (e.g., diabetic patient with foot drop — is it L5 radiculopathy or peroneal neuropathy?), (3) suspected double crush syndrome (cervical stenosis + carpal tunnel). Remember: normal NCS does not rule out the diagnosis — it's a supportive, not definitive test.

Bloods are not for diagnosing stenosis itself but for excluding red-flag pathologies (infection, malignancy, metabolic bone disease).

The lecture slide [22a] lists the following as relevant investigations:

Test	Purpose	When to Order
WCC [22a]	Elevated in infection (pyogenic spondylodiscitis, epidural abscess)	Fever, immunosuppression, acute deterioration
ESR [22a]	High blood fibrinogen causes RBC to stick to each other [22a] → elevated in infection, inflammation, malignancy. Non-specific but sensitive screening test	Suspected infection (TB, pyogenic), malignancy, inflammatory arthritis
CRP [22a]	6–8 hours after onset of infection [22a] → more acute-phase marker than ESR. Rises and falls faster	Same as ESR — helps monitor treatment response
Alkaline phosphatase (ALP) [22a]	Elevated in bony metastases (osteoblastic activity), Paget's disease, healing fractures	Suspected malignancy or metabolic bone disease
Globulin level [22a]	Elevated in multiple myeloma (monoclonal gammopathy)	Suspected myeloma — an important cause of pathological vertebral fracture
Ca/PO4 [22a]	Hypercalcaemia in bony metastases (osteolytic), hyperparathyroidism. Helps identify metabolic bone disease	Suspected malignancy or metabolic bone disease
Serum protein electrophoresis [22a]	Detects M-band (monoclonal spike) in multiple myeloma	Suspected myeloma
Tumour markers [22a]	PSA (prostate), CA 15-3 (breast), CEA (colorectal), AFP (liver) — help identify primary if metastatic disease suspected	Known primary malignancy or suspicion of metastatic spine disease

Investigation	Purpose	Specific Indications
Advanced imaging: evaluation of compression and deformity of spinal cord, evaluation of intramedullary lesion, detection of pathological spinal factors, surgical planning ^[28]	MRI is the mainstay, but CT myelography, 3D CT reconstruction, and dynamic MRI add further detail	Complex cases, surgical planning, MRI-contraindicated patients
CT myelography	Intrathecal contrast + CT → outlines the thecal sac and roots with bony detail	MRI contraindicated (pacemaker); dynamic assessment (standing/flexion/extension CT myelogram)
Bone scan (Tc-99m)	Detects areas of increased bone turnover	Screening for metastases, infection, or occult fracture when MRI is equivocal
DEXA scan	Bone mineral density	If osteoporotic fracture suspected as contributor to stenosis
Diagnostic selective nerve root block	Local anaesthetic ± steroid injected around a specific nerve root under fluoroscopic guidance	When multilevel disease makes it unclear which level is the pain generator — if the block relieves symptoms, that root is the culprit

Clinical Scenario	Investigation Sequence	Rationale
Chronic neurogenic claudication, no red flags	XR lumbar spine → MRI lumbar spine → ± NCS/EMG	XR for alignment and listhesis; MRI for neural compression; NCS/EMG if DDx unclear
Suspected cervical myelopathy	XR C-spine (AP, lateral, oblique) → MRI C-spine → ± CT if OPLL suspected → ± SSEP	XR for Pavlov ratio and alignment; MRI for cord compression and myelomalacia; CT for OPLL characterisation
Suspected cauda equina syndrome	Urgent MRI whole spine — do NOT delay	This is an emergency. Every hour of delay worsens prognosis. MRI confirms diagnosis and identifies cause
Suspected infection	Bloods (WCC, CRP, ESR, blood cultures) + MRI with gadolinium	Gadolinium enhances abscess wall and infected tissue
Suspected malignancy	Bloods (ALP, Ca/PO4, globulin, SPEP, tumour markers) + MRI + ± bone scan + CT chest/abdo/pelvis	Identify primary, assess extent of spinal involvement
RA patient with neck symptoms	Dynamic X-rays ^[25] (flexion/extension lateral C-spine) → MRI if instability confirmed	Assess for C1/2 subluxation which may not be evident on neutral films
Asian patient with myelopathy	XR → CT to delineate OPLL ^[25] → MRI	CT characterises the ossification morphology better than MRI

High Yield Summary

Diagnosis of spinal stenosis is clinico-radiological — compatible clinical syndrome + imaging evidence of narrowing that correlates with symptoms. There are no formal diagnostic criteria.

Cervical stenosis measurements ^[6]: Midsagittal diameter < 12 mm = relative stenosis, < 10 mm = absolute. Dynamic stenosis < 12 mm. Pavlov ratio < 0.8 ^[2].

XR spine (first-line): Lumbar — assess disc space, deformity, spondylolisthesis ^[24]. Cervical — assess lordosis, Pavlov ratio, OPLL, soft tissue width ^[2].

MRI spine (gold standard): Lumbar — disc signal/height, Mickey Mouse sign, nerve root compression, high-intensity zone ^[3]. Cervical — level, pathoanatomy (disc/osteophyte/OPLL/flavum), CSF obliteration, cord shape, intramedullary signal change (myelomalacia) ^[22].

CT spine: Superior for bony detail. CT to delineate OPLL ^[25]. CT for fracture configuration; CT myelogram and MRI for nerve compression ^[26].

NCS/EMG ^[23]: Ancillary — differentiates radiculopathy from peripheral neuropathy. Most useful when clinical and MRI findings are discordant.

Bloods [22a]: Not for diagnosing stenosis; for excluding red flags. WCC, ESR, CRP for infection; ALP, Ca/PO4, globulin, SPEP, tumour markers for malignancy.

Always rule out other pathological processes ^[25] — infection, malignancy, inflammatory disease (RA → dynamic XR), OPLL (CT).

Active Recall - Diagnosis and Investigations for Spinal Stenosis

References

^[1] Lecture slides: GC 226. Lumbar Spine Pathology_Part F (2).pdf, p2–3 ^[2] Senior notes: maxim.md (sections 2.4, 2.5 — cervical myelopathy, spinal stenosis, XR findings, Pavlov ratio) ^[3] Senior notes: maxim.md (section 2.6 — PID, MRI disc assessment; section 2.5 — MRI neural tissues) ^[6] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p11 ^[22] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p29 [22a] Lecture slides: GC 226. Lumbar Spine Pathology_Part C (2).pdf, p2 ^[23] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p45 ^[24] Lecture slides: GC 226. Lumbar Spine Pathology_Part F (2).pdf, p7 ^[25] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p31 ^[26] Lecture slides: GC 226. Lumbar Spine Pathology_Part C (2).pdf, p6 ^[27] Senior notes: maxim.md (section 5.6 — spine investigations, NCS, SSEP) ^[28] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p28

Management of Spinal Stenosis

A. Conservative (Non-Operative) Management

Conservative management is the first-line approach for both cervical and lumbar stenosis in the absence of emergency indications. The rationale is that many patients have stable symptoms that can be adequately controlled, and surgery carries inherent risks (especially in the elderly, comorbid population who typically presents with this condition).

Drug Class	Mechanism	Role in Stenosis
NSAIDs ^[2]^[3]^[30]	Inhibit COX-1/2 → reduce prostaglandin synthesis → anti-inflammatory and analgesic	First-line pain relief. Reduce inflammatory mediators around compressed nerve roots. Use with caution in elderly (GI bleeding, renal impairment, CV risk)
Neuroleptics / Neuropathic agents ^[30]	Gabapentin, pregabalin — bind α2δ subunit of voltage-gated calcium channels → reduce excitatory neurotransmitter release at dorsal horn	Useful for neuropathic pain component (burning, shooting, tingling). Not truly "neuroleptics" in the psychiatric sense — the lecture uses this term for anti-neuropathic medications
Steroids (oral) ^[30]	Potent anti-inflammatory → reduce oedema and inflammation around compressed neural structures	Short courses for acute flares. Not for long-term use (side effects: osteoporosis, hyperglycaemia, immunosuppression)
Epidural steroid injection ^[3]^[30]	Targeted delivery of corticosteroid into the epidural space (interlaminar or transforaminal approach under fluoroscopic guidance) → reduces perineural inflammation and oedema	Useful when oral medications insufficient. Provides temporary relief (weeks to months). Can be diagnostic (if relief confirms the pain source) and therapeutic. Up to 90% of patients with cervical radiculopathy have good response to conservative treatment measures ^[30]
Selective nerve root steroid injection ^[3]	Steroid injected around a specific nerve root	Both diagnostic and therapeutic — confirms which root is the pain generator
Simple analgesics	Paracetamol — central COX inhibition, mechanism not fully understood	First-step, safe in elderly. Limited anti-inflammatory effect
Muscle relaxants	e.g., baclofen, tizanidine — reduce muscle spasm via GABA or α2-adrenergic agonism	For associated paraspinal muscle spasm component

B. Surgical Management

Indications for Surgery

The indications differ slightly between cervical and lumbar, and between stenosis, myelopathy, and radiculopathy. Let me lay them out systematically.

Choice of Surgical Approach

Factor	Favours Anterior	Favours Posterior
1. Sagittal alignment ^[34]	Fixed kyphotic deformities favour anterior approach — you need to address the kyphosis from the front (corpectomy and reconstruction with cage/graft to restore lordosis). A posterior approach on a kyphotic spine leaves the cord draped over the anterior compression	Maintained lordosis — posterior approach is safe because the cord falls away from the anterior structures once posterior decompression is performed
2. Pathoanatomy ^[34]	Disc protrusions into the spinal cord — better treated with anterior technique ^[34] — the compression is coming from the front (disc/osteophyte), so approach from the front to directly remove it	Infolding/thickening of ligamentum flavum — better treated with posterior technique ^[34] — the compression is coming from behind, so approach from behind. Also for OPLL that extends over many segments
3. Number of levels involved ^[34]	1–2 levels: anterior approach works well (ACDF, corpectomy)	3-level pathology or more favours posterior approach ^[34] — multilevel anterior surgery has higher complication rates (dysphagia, adjacent segment disease). Posterior laminoplasty or laminectomy + fusion is more efficient for long-segment disease
4. Subluxation or instability ^[36]	Fusion is indicated ^[36] — whether anterior or posterior, if there is instability, you must add fusion. Anterior plate + cage or posterior lateral mass screws	Same principle — instability demands stabilisation
5. Neck pain ^[36]	Generally less post-op axial neck pain with anterior approach	Laminoplasty patients may experience more post-op axial neck pain ^[36] — because the posterior musculature is disrupted during the approach. Muscle-sparing techniques help but don't eliminate this problem

Procedure	What It Involves	When to Use
Anterior Cervical Discectomy and Fusion (ACDF) [32a]	Anterior approach → remove the disc (and any osteophytes/PLL) at the offending level → place interbody cage/bone graft → anterior plate fixation → the two vertebrae fuse into one solid block	1–2 level disease, disc protrusion, kyphosis ^[34]. The workhorse anterior cervical operation. Directly removes the compressive pathology. Fusion sacrifices motion at that segment but provides stability
Artificial Disc Replacement [32a]	Same anterior approach → remove disc → insert mobile prosthesis instead of fusing	1–2 level disease in younger patients with preserved motion. Preserves segmental motion → theoretically reduces adjacent segment disease. Contraindicated in instability, significant facet OA, osteoporosis, OPLL
Anterior Corpectomy ^[37]	Remove entire vertebral body (or bodies) + adjacent discs → reconstruct with cage/strut graft + anterior plate	Multi-level anterior compression, OPLL (if resectable), burst fracture with retropulsed fragments. More morbid than ACDF but allows wider decompression
Laminoplasty ^[2]	Posterior approach → hinge open the laminae (one side cut, other side hinged) → expand the canal → plate to keep it open. Does NOT fuse the spine	Multi-level posterior compression (3+ levels), preserved lordosis, no instability ^[34]. Preserves motion (no fusion). Contraindication: kyphosis (cord won't drift posteriorly), instability
Laminectomy + Posterior Fusion ^[2]	Remove laminae completely → fuse with lateral mass/pedicle screws and rods	Multi-level disease WITH instability. Definitive decompression + stabilisation but sacrifices all motion at fused segments
Posterior Cervical Foraminotomy [32a]	Posterior approach → keyhole removal of bone/ligament from the foramen → decompress the exiting root	Isolated foraminal stenosis / lateral disc herniation causing radiculopathy [32a]. Preserves motion (no fusion needed if spine is stable). Does not address central stenosis

Procedure	What It Involves	When to Use
Decompressive Laminectomy ^[3]	Remove lamina(e) and thickened ligamentum flavum at the stenotic level(s) → opens the central canal	Lumbar stenosis WITHOUT spondylolisthesis ^[3]. Performed at every relevant level ^[3]. The standard open decompression. Risk: post-laminectomy instability if too much bone is removed
Laminoplasty ^[3]	Expand the canal without complete removal of the lamina	Similar indications to laminectomy; may preserve more posterior structural integrity
Interspinous Process Spacer (MIS) ^[3]	A device placed between adjacent spinous processes → holds them apart → maintains the spine in slight flexion → opens the canal and foramina	Mild to moderate stenosis, without instability ^[3]. Minimally invasive — can be done percutaneously. Mimics the flexion posture that relieves symptoms. Lower morbidity than open laminectomy. Limitation: does not address severe stenosis or instability. Not suitable if spondylolisthesis present
Decompressive Laminectomy + Spinal Fusion ^[3]	Laminectomy PLUS instrumented fusion (pedicle screws + rods ± interbody cage)	Lumbar stenosis WITH spondylolisthesis ^[3]. The spondylolisthesis means the segment is unstable — decompression alone would worsen instability. Fusion stabilises the segment
TLIF (Transforaminal Lumbar Interbody Fusion) [3a]	Posterior approach → laminectomy + unilateral facetectomy → insert interbody cage via transforaminal route → pedicle screw fixation	Spondylolisthesis with stenosis. Provides both decompression and 360-degree fusion (anterior column support via cage + posterior fixation). Specifically mentioned for spondylolisthesis management [3a]
Microdiscectomy ^[3]	Hemi-laminotomy + partial disc removal through a small incision with microscope/loupe magnification	Focal disc herniation causing radiculopathy ^[3] rather than generalised stenosis. Targeted decompression of the specific root involved

The Key Surgical Decision in Lumbar Stenosis

The critical decision point is: is there spondylolisthesis? ^[3]

No spondylolisthesis → Decompression alone (laminectomy/laminoplasty) or interspinous spacer (MIS)
With spondylolisthesis → Decompression + spinal fusion (laminectomy + TLIF)

Why? Because if you decompress (remove laminae) in a spine that is already slipping forward, you remove the posterior restraints and the slip worsens → catastrophic instability. Fusion locks the vertebrae together, preventing further slip.

C. Management of Specific Scenarios

The senior notes provide a useful decision matrix [3b]:

	Neurology Stable	Neurology Unstable
Mechanically Stable	Routine management (conservative)	Investigate for other causes — e.g., epidural haematoma, incomplete cord lesion, stroke. Also consider: wrong diagnosis of mechanical stability
Mechanically Unstable	Early stabilisation of spine (surgical)	Emergency: early stabilisation of spine + neurological management

This framework applies broadly to all spinal pathology. The key teaching point is: neurological deterioration in a "mechanically stable" spine should prompt you to look for other causes — don't just assume it's progressive stenosis.

Scenario	First-Line Treatment	Surgical Option	Key Considerations
Mild lumbar stenosis, no neuro deficit	PT (flexion exercises) + NSAIDs + lifestyle modification	Not indicated unless conservative fails	Most patients improve or stabilise
Moderate lumbar stenosis, neurogenic claudication	PT + NSAIDs + epidural steroid injection	If fails after 3–6 months: laminectomy (no listhesis) or laminectomy + fusion (with listhesis)	Interspinous spacer is a MIS option for select patients
Lumbar stenosis with spondylolisthesis	Conservative trial	Decompressive laminectomy + spinal fusion ^[3]	Must fuse if decompressing — otherwise slip worsens
Cauda equina syndrome	High-dose steroid	Emergency laminectomy +/- discectomy within 48h ^[2]	Time-critical — delays worsen outcome
Cervical radiculopathy	PT (traction, ROM, strengthening) + NSAIDs/neuroleptics/steroids + epidural injection ^[29]^[30]	ACDF, artificial disc, or posterior foraminotomy [32a]	Up to 90% respond to conservative Mx ^[30]
Cervical myelopathy	Close monitoring if mild/stable. PT for conditioning	Surgical decompression + stabilisation ^[2] when progressive deficit, impaired ADL, compatible imaging ^[33]	Low threshold for surgery — cord damage is irreversible. Choose anterior vs. posterior based on alignment, pathoanatomy, levels ^[34]^[36]
Disc herniation with radiculopathy	Encourage mobility, PT, NSAID, selective nerve root injection ^[3]	Microdiscectomy ^[3] if failed conservative, progressive deficit, or CES	Most disc herniations resolve with conservative Mx (60–90% improve in 6–12 weeks)

High Yield Summary

Conservative management is first-line for most patients:

Lumbar: PT (flexion exercises, stretching), NSAIDs, epidural steroid injection, encourage mobility ^[3]
Cervical radiculopathy: PT (traction, ROM, strengthening), NSAIDs, neuroleptics, steroids, epidural injection — up to 90% respond to conservative measures ^[29]^[30]
Cervical myelopathy: Low threshold for surgery; conservative only if mild and stable ^[33]

Surgical indications: Progressive neurological deficit, failed conservative management, myelopathy/radiculopathy with compatible imaging, intractable pain, CES ^[31]^[33]^[37]

Lumbar surgery decision: Without spondylolisthesis → decompressive laminectomy/laminoplasty or interspinous spacer. With spondylolisthesis → decompressive laminectomy + spinal fusion ^[3]

Cervical surgery — anterior vs. posterior ^[34]^[36]:

Anterior favoured for: kyphosis, disc protrusion, 1–2 levels
Posterior favoured for: LF thickening, 3+ levels, preserved lordosis
Instability → fusion indicated
Laminoplasty → more post-op axial neck pain

CES: High-dose steroid + surgical decompression within 48 hours ^[2]

Developmental stenosis: Counsel about high reoperation rates — 13% of patients, 50% at adjacent levels, 3.3% per year ^[5]

Active Recall - Management of Spinal Stenosis

References

^[1] Lecture slides: GC 226. Lumbar Spine Pathology_Part F (2).pdf, p2–3 ^[2] Senior notes: maxim.md (sections 2.4, 2.5 — cervical myelopathy management, spinal stenosis management, cauda equina syndrome management) ^[3] Senior notes: maxim.md (section 2.5 — lumbar stenosis management; section 2.6 — PID management) [3a] Senior notes: maxim.md (section on spondylolisthesis management — TLIF, surgical indications) [3b] Senior notes: maxim.md (mechanically stable vs unstable decision matrix) ^[5] Lecture slides: GC 226. Lumbar Spine Pathology_Part F (2).pdf, p9 ^[29] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p47 ^[30] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p48 ^[31] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p87 [32a] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p49 ^[33] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p36 ^[34] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p37 ^[35] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p88 ^[36] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p38 ^[37] Lecture slides: GC 110. Paraplegia Spinal cord compression Transverse myelitis Spinal dysraphism Neuroimaging III Spinal Cord.pdf, p22

Complications of Spinal Stenosis

Complications of spinal stenosis can be divided into two broad categories: complications of the disease itself (what happens if stenosis is left untreated or progresses) and complications of treatment (both conservative and surgical). Both are high-yield and both need to be understood from first principles.

A. Complications of the Disease (Natural History of Untreated/Progressive Stenosis)

Spinal stenosis is fundamentally a progressive degenerative condition. Left untreated, the Kirkaldy-Willis cascade continues: dysfunction → instability → stabilisation → one-level stenosis → multilevel spondylosis and stenosis ^[7]. The neural structures tolerate a certain degree of compression, but once a critical threshold is crossed, complications arise.

B. Complications of Surgical Treatment

Surgical complications are especially important to know because they form part of the informed consent discussion and are frequently examined.

1. Complications of Cervical Spine Surgery

The lecture slide ^[39] provides an explicit list for counselling patients:

Complication	Mechanism / Explanation
Oesophageal injury (intra-op or late due to implant) ^[39]	The anterior cervical approach requires retraction of the oesophagus and trachea to the opposite side to access the vertebral bodies. Excessive retraction can cause direct injury, or late perforation can occur from implant migration/erosion. Presents with dysphagia, fever, mediastinitis (late). Rare but devastating
Vertebral artery injury ^[39]	The vertebral arteries run through the transverse foramina of C1–C6. Lateral dissection or drilling too far laterally during corpectomy/discectomy can lacerate the artery → massive haemorrhage, posterior circulation stroke. Highest risk at C3–C6 and when anatomy is distorted by osteophytes
Airway compromise ^[39]	Post-operative retropharyngeal haematoma or soft tissue swelling can compress the airway → stridor, respiratory distress. Risk increases with multi-level surgery, longer operative time, and revision procedures. This is a surgical emergency — may require urgent intubation or tracheostomy
Pseudoarthrosis (failed fusion) ^[39]	After ACDF, the bone graft or cage must fuse with the adjacent vertebrae. If fusion fails → persistent motion at the operated segment → ongoing pain, hardware loosening or failure. Smoking is the strongest modifiable risk factor for pseudoarthrosis (nicotine inhibits osteoblast activity and reduces bone blood supply)
Adjacent level degeneration ^[39]	After fusion, the fused segment is rigid → the levels above and below must compensate with increased motion → accelerated degenerative changes at adjacent segments → new stenosis/disc herniation at a different level → may require further surgery. This is the most important long-term complication of spinal fusion

Complication	Mechanism / Explanation
Post-operative kyphosis ^[39]	Posterior surgery (especially laminectomy without fusion) disrupts the posterior tension band (laminae, spinous processes, supraspinous/interspinous ligaments, ligamentum flavum, paraspinal muscles). Loss of this posterior restraint → progressive forward angulation of the cervical spine → kyphotic deformity → the cord drapes over the vertebral bodies anteriorly → myelopathy recurs from a different mechanism. This is why cervical laminectomy without fusion is generally avoided in patients at risk of kyphosis
Axial symptoms (shoulder and neck pain) ^[39]	Posterior approach requires extensive paraspinal muscle dissection and detachment from the spinous processes → muscle denervation, atrophy, and chronic pain. Laminoplasty patients may experience more post-op axial neck pain ^[36] — the hinged laminae heal in an expanded position but the muscle disruption contributes to chronic axial symptoms in up to 30–40% of patients
C5 nerve root paresis ^[39]	A unique and somewhat mysterious complication seen after both laminoplasty and laminectomy. The C5 root has the shortest intradural course of the cervical roots → when the cord drifts posteriorly after posterior decompression, the C5 root is stretched like a guitar string over the remaining anterior structures → traction palsy → deltoid weakness (C5 myotome). Typically presents 1–14 days post-op. Most recover over weeks to months but some have persistent weakness

Complication	Mechanism
Dural tear / CSF leak	The dura is thin and adherent to surrounding structures, especially in revision surgery or severe stenosis. Inadvertent durotomy during laminectomy → CSF leak → postural headache, wound leak, risk of meningitis. Repaired with primary suture ± fibrin sealant ± lumbar drain
Nerve root injury	Direct injury during root retraction, thermal injury from electrocautery, or compression from haematoma. Presents as new or worsened radiculopathy post-operatively
Epidural haematoma	Post-operative bleeding into the epidural space → mass effect on cauda equina or cord → acute neurological deterioration. Risk increased with anticoagulation, coagulopathy. Emergency surgical evacuation required
Surgical site infection	Superficial (wound) or deep (discitis, epidural abscess). Risk factors: diabetes, obesity, smoking, immunosuppression, prolonged surgery. Deep infection may require return to theatre for debridement + IV antibiotics
Recurrent stenosis / recurrent disc herniation	Scar tissue formation (epidural fibrosis) → re-narrowing of the canal. Recurrent disc herniation at the same level (5–15% after microdiscectomy). Distinguished from scar tissue on gadolinium-enhanced MRI (scar enhances, disc does not)
Post-laminectomy instability	Excessive removal of posterior elements → loss of structural support → segmental instability → progressive spondylolisthesis → recurrent stenosis. This is why fusion is added when decompression is extensive or spondylolisthesis coexists ^[3]
Adjacent segment disease	Same concept as cervical: fusion at one level → increased stress at adjacent levels → accelerated degeneration → new stenosis. Particularly relevant in patients with developmental stenosis: reoperation in 13% of patients, 50% at adjacent levels, 3.3% per year ^[5]
Failed back surgery syndrome	Persistent or recurrent pain after spinal surgery despite technically adequate decompression. Multifactorial: epidural fibrosis, foraminal stenosis missed at surgery, sacroiliac joint pain, myofascial pain, central sensitisation, psychosocial factors

Complication	Mechanism
NSAID gastropathy	COX-1 inhibition → reduced protective prostaglandin production in the gastric mucosa → erosions, ulcers, GI bleeding. Particular risk in elderly patients who are the main stenosis population. Mitigate with PPI co-prescription
NSAID nephrotoxicity	Prostaglandins maintain afferent arteriolar vasodilation; NSAIDs reduce renal perfusion → AKI. Risk in elderly, CKD, dehydration, concurrent ACEi/ARB use
Steroid complications (if prolonged oral steroids or repeated injections)	Osteoporosis (accelerates the degenerative process), hyperglycaemia (problematic in diabetics), adrenal suppression, immunosuppression, avascular necrosis
Epidural steroid injection complications	Rare: infection (epidural abscess), bleeding (epidural haematoma — risk with anticoagulants), dural puncture → headache, transient worsening of radiculopathy, very rare spinal cord infarction
Progression of disease	Conservative management treats symptoms but does not halt the underlying degenerative process. Stenosis may progress, and delayed surgery may be less effective if irreversible neural damage has occurred (myelomalacia in cervical, denervation atrophy in lumbar)

If spinal stenosis culminates in spinal cord injury (e.g., central cord syndrome after a fall, or progressive myelopathy), the systemic complications of SCI are extensive. The lecture slide ^[40] provides a comprehensive organ-system-based table:

Organ System	Complications ^[40]	Explanation
Cardiovascular	Bradycardia/dysrhythmia, cardiac arrest, cardiogenic pulmonary oedema ^[40]	Loss of sympathetic outflow (T1–L2) with unopposed vagal tone → bradycardia. Fluid overload + neurogenic cardiac stunning → pulmonary oedema
Pulmonary	Hypoventilation/respiratory failure, poor secretion control, ARDS, aspiration, pneumonia ^[40]	Cervical SCI → diaphragm (C3–5) and intercostal muscle (T1–T12) weakness → reduced tidal volume, ineffective cough → secretion retention → atelectasis → pneumonia. Pneumonia is the leading cause of death in chronic SCI
Gastrointestinal	Gastric dysmotility, adynamic ileus, gastritis and ulceration, pancreatitis ^[40]	Loss of autonomic regulation → GI stasis. Stress response + steroid use → Cushing's ulcers. Paralytic ileus common in acute phase
Haematologic	Venous thromboembolism ^[40]	Immobility + loss of muscle pump in paralysed limbs → venous stasis → DVT → PE. PE is a major cause of mortality in SCI. Prophylaxis: LMWH, compression stockings, early mobilisation
Neurologic	Neurogenic shock, depression, PTSD, anxiety, autonomic dysreflexia ^[40]	Neurogenic shock (distinct from spinal shock): loss of sympathetic vasomotor tone → vasodilation → hypotension with bradycardia. Autonomic dysreflexia (in injuries above T6): noxious stimulus below injury level → massive unregulated sympathetic response → hypertensive crisis, bradycardia, headache, flushing. Long-term issues with dysreflexia, spasticity, contracture ^[38]
Genitourinary	Bladder dysfunction, UTI, priapism ^[40]	Long-term issues with neurogenic bladder ^[38]. Loss of voluntary bladder control → retention → intermittent catheterisation required → recurrent UTIs → potential long-term renal damage. Priapism indicates sacral parasympathetic disruption (S2–4)
Integument	Pressure ulceration ^[40]	Loss of sensation + immobility → prolonged pressure on bony prominences (sacrum, ischial tuberosities, heels, occiput) → tissue ischaemia → skin breakdown. Long-term issues with skin problems ^[38]. Prevention: regular repositioning, pressure-relieving mattresses, skin inspection

Key Conclusions from the Lectures on Spinal Cord Complications

The neurosurgical lecture concludes with critical teaching points ^[38]:

The spinal cord is very unforgiving
Acute paraplegia is an EMERGENCY
Sphincter dysfunction — a point of no return
Early detection and investigation
Complete injury — prognosis is generally poor
Incomplete injury — prognosis highly variable
Long-term issues with dysreflexia, neurogenic bladder, spasticity, contracture, and skin problems

These are the phrases you must know for exams. They encapsulate the urgency and gravity of spinal cord disease.

Category	Key Complications	Key Teaching Point
Disease progression (lumbar)	CES, progressive radiculopathy, chronic pain, deconditioning	CES is the most important — always screen for red flags
Disease progression (cervical)	Progressive myelopathy, central cord syndrome after minor trauma, irreversible cord damage	Pre-existing stenosis + minor trauma can cause devastating SCI
Anterior cervical surgery	Oesophageal injury, vertebral artery injury, airway compromise, pseudoarthrosis, adjacent level degeneration ^[39]	Adjacent level degeneration is the most important long-term issue
Posterior cervical surgery	Post-op kyphosis, axial neck pain, C5 nerve root paresis ^[39]	C5 palsy is unique to posterior decompression — traction mechanism
Lumbar surgery	Dural tear, nerve injury, haematoma, infection, recurrence, instability, adjacent segment disease	Post-laminectomy instability → why fusion is added with spondylolisthesis
Conservative treatment	NSAID GI/renal toxicity, steroid side effects, disease progression	Conservative treats symptoms, not the underlying pathology
SCI (if stenosis → cord injury)	Multi-system: cardiovascular, pulmonary, GI, VTE, neurogenic bladder, pressure sores, autonomic dysreflexia ^[40]	Pneumonia and PE are leading causes of death in chronic SCI

High Yield Summary

Disease complications:

Lumbar: Cauda equina syndrome (severe stenosis or large central disc herniation ^[1]) — sphincter dysfunction is a point of no return ^[38]. Progressive radiculopathy with irreversible denervation.
Cervical: Progressive myelopathy → the spinal cord is very unforgiving ^[38]. Central cord syndrome in old adults with pre-existing spinal stenosis after low-energy trauma ^[11][38a]. Myelomalacia on MRI = irreversible damage.

Surgical complications ^[39]:

Anterior cervical: oesophageal injury, vertebral artery injury, airway compromise, pseudoarthrosis, adjacent level degeneration
Posterior cervical: post-op kyphosis, axial symptoms, C5 nerve root paresis
Lumbar: dural tear, nerve root injury, epidural haematoma, infection, post-laminectomy instability, adjacent segment disease
Adjacent level degeneration is the most important long-term complication of any spinal fusion — and patients with developmental stenosis have reoperation rates of 13%, 50% at adjacent levels, 3.3% per year ^[5]

SCI complications ^[40]: Multi-system — cardiovascular (bradycardia), pulmonary (pneumonia — leading cause of death), GI (ileus, ulcers), VTE, neurogenic bladder, autonomic dysreflexia, pressure ulcers.

Long-term issues ^[38]: Dysreflexia, neurogenic bladder, spasticity, contracture, skin problems.

Active Recall - Complications of Spinal Stenosis

References

^[1] Lecture slides: GC 226. Lumbar Spine Pathology_Part F (2).pdf, p2 ^[2] Senior notes: maxim.md (section 2.5 — spinal stenosis clinical features, bladder disturbance) ^[3] Senior notes: maxim.md (section 2.5 — lumbar stenosis management, decompression + fusion rationale) ^[5] Lecture slides: GC 226. Lumbar Spine Pathology_Part F (2).pdf, p9 ^[7] Lecture slides: GC 226. Lumbar Spine Pathology_Part D (2).pdf, p7 ^[11] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p55 ^[36] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p38 ^[38] Lecture slides: GC 110. Paraplegia Spinal cord compression Transverse myelitis Spinal dysraphism Neuroimaging III Spinal Cord.pdf, p27 [38a] Lecture slides: GC 110. Paraplegia Spinal cord compression Transverse myelitis Spinal dysraphism Neuroimaging III Spinal Cord.pdf, p21 ^[39] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p40 ^[40] Lecture slides: GC 227. Cervical Spine Pathology.pdf, p89

High Yield Summary

Definition: Abnormal narrowing of the spinal canal or IV foramina → neural compression. Most common in the lumbar spine.

Epidemiology: Most common cause of spinal surgery in over 65s. OPLL up to 2–4% in Asian populations. Male predominance.

Risk Factors: Ageing, male sex, smoking, heavy lifting, poor posture, congenitally narrow canal (short pedicles).

Key Pathophysiology:

Kirkaldy-Willis cascade: Dysfunction → Instability → Stabilisation (= stenosis)
Extension narrows the canal by 11% and foramina by 15%; flexion opens them by the same amount — this explains neurogenic claudication
Neural compression causes ischaemia + venous congestion + mechanical injury + inflammation

Clinical Features — Lumbar:

Neurogenic claudication: walking-induced pain/numbness/weakness in legs, relieved by flexion/sitting ("park bench to park bench"), worsened by extension/standing/walking downhill
Neurogenic vs. vascular claudication: Neurogenic = proximal→distal pain, pulses present, worse downhill, better with flexion. Vascular = distal→proximal, pulses absent, worse uphill, better with rest only
Cauda equina syndrome: bilateral sciatica, saddle anaesthesia, urinary retention, faecal incontinence — surgical emergency

Clinical Features — Cervical:

Myelopathy: UMN signs (hyperreflexia, spasticity, Babinski, clonus) ± LMN signs at level of compression
Myelopathic hand signs: Hoffmann's, finger escape, inverted reflexes, grip-and-release < 20/10s
JOA score: Gold standard grading (total 17 points)

Nerve Root Levels: L4 = anterior thigh / knee jerk; L5 = lateral calf / great toe / EHL; S1 = posterior calf / lateral foot / ankle jerk

High Yield Summary

The DDx of spinal stenosis is structured by presentation:

Back pain DDx — Mechanical (97%): muscle strain ( > 70%), disc degeneration, disc herniation, spondylolisthesis, fracture, spondylolysis. Non-mechanical (3%): neoplasia, inflammatory arthritis (AS), infection. Non-spinal: AAA, renal, gynaecological ^[17].
Claudication DDx — The must-know comparison is neurogenic vs. vascular claudication: neurogenic = proximal→distal, pulses present, worse downhill/extension, better flexion/sitting ("park bench to park bench"); vascular = distal→proximal, pulses absent, worse uphill/exercise, better rest ("shop window to shop window") ^[2]^[15].
Cervical stenosis/myelopathy DDx — Peripheral nerve compression, shoulder pathology ^[19] are the main mimics. Also consider MS, MND, B12 deficiency, syringomyelia, cord tumour. Key: UMN signs = myelopathy, not peripheral.
Always screen for red flags: CES (saddle anaesthesia, urinary retention, bilateral weakness), infection (fever, immunosuppression), fracture (steroid use, osteoporosis), malignancy (weight loss, night pain) ^[2].
Double crush syndrome ^[20]: peripheral entrapment often coexists with cervical spondylosis — proximal compression makes the nerve more susceptible to distal injury.

High Yield Summary

Diagnosis of spinal stenosis is clinico-radiological — compatible clinical syndrome + imaging evidence of narrowing that correlates with symptoms. There are no formal diagnostic criteria.

Cervical stenosis measurements ^[6]: Midsagittal diameter < 12 mm = relative stenosis, < 10 mm = absolute. Dynamic stenosis < 12 mm. Pavlov ratio < 0.8 ^[2].

XR spine (first-line): Lumbar — assess disc space, deformity, spondylolisthesis ^[24]. Cervical — assess lordosis, Pavlov ratio, OPLL, soft tissue width ^[2].

CT spine: Superior for bony detail. CT to delineate OPLL ^[25]. CT for fracture configuration; CT myelogram and MRI for nerve compression ^[26].

NCS/EMG ^[23]: Ancillary — differentiates radiculopathy from peripheral neuropathy. Most useful when clinical and MRI findings are discordant.

Bloods [22a]: Not for diagnosing stenosis; for excluding red flags. WCC, ESR, CRP for infection; ALP, Ca/PO4, globulin, SPEP, tumour markers for malignancy.

Always rule out other pathological processes ^[25] — infection, malignancy, inflammatory disease (RA → dynamic XR), OPLL (CT).

High Yield Summary

Conservative management is first-line for most patients:

Lumbar: PT (flexion exercises, stretching), NSAIDs, epidural steroid injection, encourage mobility ^[3]
Cervical radiculopathy: PT (traction, ROM, strengthening), NSAIDs, neuroleptics, steroids, epidural injection — up to 90% respond to conservative measures ^[29]^[30]
Cervical myelopathy: Low threshold for surgery; conservative only if mild and stable ^[33]

Surgical indications: Progressive neurological deficit, failed conservative management, myelopathy/radiculopathy with compatible imaging, intractable pain, CES ^[31]^[33]^[37]

Lumbar surgery decision: Without spondylolisthesis → decompressive laminectomy/laminoplasty or interspinous spacer. With spondylolisthesis → decompressive laminectomy + spinal fusion ^[3]

Cervical surgery — anterior vs. posterior ^[34]^[36]:

Anterior favoured for: kyphosis, disc protrusion, 1–2 levels
Posterior favoured for: LF thickening, 3+ levels, preserved lordosis
Instability → fusion indicated
Laminoplasty → more post-op axial neck pain

CES: High-dose steroid + surgical decompression within 48 hours ^[2]

Developmental stenosis: Counsel about high reoperation rates — 13% of patients, 50% at adjacent levels, 3.3% per year ^[5]

High Yield Summary

Disease complications:

Lumbar: Cauda equina syndrome (severe stenosis or large central disc herniation ^[1]) — sphincter dysfunction is a point of no return ^[38]. Progressive radiculopathy with irreversible denervation.
Cervical: Progressive myelopathy → the spinal cord is very unforgiving ^[38]. Central cord syndrome in old adults with pre-existing spinal stenosis after low-energy trauma ^[11][38a]. Myelomalacia on MRI = irreversible damage.

Surgical complications ^[39]:

Anterior cervical: oesophageal injury, vertebral artery injury, airway compromise, pseudoarthrosis, adjacent level degeneration
Posterior cervical: post-op kyphosis, axial symptoms, C5 nerve root paresis
Lumbar: dural tear, nerve root injury, epidural haematoma, infection, post-laminectomy instability, adjacent segment disease
Adjacent level degeneration is the most important long-term complication of any spinal fusion — and patients with developmental stenosis have reoperation rates of 13%, 50% at adjacent levels, 3.3% per year ^[5]

Long-term issues ^[38]: Dysreflexia, neurogenic bladder, spasticity, contracture, skin problems.

Spinal Stenosis

1. Definition

2. Epidemiology

Prevalence

Demographics

Hong Kong Context

3. Risk Factors

4. Anatomy and Function

4.1 The Spinal Canal

4.2 Contents

4.3 Canal Dimensions

4.4 The Intervertebral Disc

4.5 Ligaments Relevant to Stenosis

4.6 Nerve Root Anatomy — The Mismatch Concept

5. Etiology (with Focus on Hong Kong)

5.1 Congenital / Developmental Stenosis

5.2 Acquired Stenosis

A. Degenerative (by far the most common cause)

B. Ossification [4]

C. Inflammatory [10]

D. Infection (Important in HK)

E. Neoplastic

F. Traumatic

G. Iatrogenic

5.3 Pathological Causes of Canal and Foraminal Compression — Summary Diagram [12]

6. Pathophysiology

6.1 The Static vs. Dynamic Model

6.2 Neural Compression Mechanisms

6.3 Why Neurogenic Claudication Occurs

7. Classification

7.1 By Anatomy / Location of Narrowing

7.2 By Etiology

7.3 By Level

7.4 Japanese Orthopaedic Association (JOA) Score — Cervical Myelopathy [2]

7.5 Severity Classification of Lumbar Stenosis (Imaging-Based)

8. Clinical Features

8.1 Lumbar Spinal Stenosis

Symptoms

Neurogenic vs. Vascular Claudication — A Critical Comparison [2][15]

Signs

Root-Specific Clinical Features [3]

Cauda Equina Syndrome (CES) [1][2]

8.2 Cervical Spinal Stenosis

Symptoms

Signs

9. Investigations (Brief Overview — Expanded in Diagnosis Section)

10. Key Anatomical and Pathological Correlations — Summary

Prolapsed Intervertebral Disc (PID) — As a Cause of Stenosis [3]

Spondylolysis & Spondylolisthesis [3]

Active Recall - Spinal Stenosis (Definition to Clinical Features)

References

Framing the Problem

A. Differential Diagnosis of Back Pain (The Lumbar Stenosis Presentation)

Mechanical pain (97%) [17]

Non-mechanical pain (3%) [17]

Non-spinal diseases (referred pain) [17]

B. Differential Diagnosis of Claudication — Neurogenic vs. Vascular

C. Differential Diagnosis of Cervical Myelopathy (The Cervical Stenosis Presentation)

D. Differential Diagnosis of Cauda Equina Syndrome

E. Clinical Approach — Decision Framework

F. Summary Table — Key Differentiating Features

Active Recall - Differential Diagnosis of Spinal Stenosis

Why There Are No "Formal Diagnostic Criteria" — and What We Use Instead

Diagnostic Framework — What Constitutes the "Diagnosis"

Lumbar Spinal Stenosis

Cervical Spinal Stenosis (Cervical Myelopathy)

Cervical Stenosis Measurement Thresholds [6]

Lumbar Stenosis Imaging Criteria

Diagnostic Algorithm

Investigation Modalities — Detailed Interpretation

1. Plain Radiographs (XR Spine) — First-Line

Cervical Spine XR [2][23]

Lumbar Spine XR [2][24]

2. MRI Spine — The Gold Standard

Cervical Spine MRI — What to Look For [22]

Lumbar Spine MRI — What to Look For [3]

3. CT Spine

For nerve tissues [26]:

Specific CT Findings in Stenosis:

4. Dynamic (Flexion-Extension) Radiographs [25]