• Intracranial GCTs represent ~3–5% of all paediatric CNS tumours globally, but the proportion is dramatically higher in East Asian populations.
• Much more common in Asian populations than Caucasians (6:1) ^[1][2]. This is extremely high yield for HKUMed — in Hong Kong, intracranial GCTs form a larger fraction of childhood brain tumours than in Western centres.
• In Japan and East Asia, intracranial GCTs can constitute up to 11–15% of all paediatric brain tumours (vs. ~0.5–3% in Western populations).

• Peak incidence = 10–12 years old ^[1][2][3]
• The vast majority present between 5 and 20 years; rare before age 5 and after age 30.
• There is a smaller, less well-characterised second peak in early adulthood.

• Overall male predominance (~2–3:1 M:F) for intracranial GCTs as a whole.
• Male predominance for pineal gland tumours ^[1][2]
• Female predominance in suprasellar tumours ^[1][2]
• This sex-site pattern is characteristic and frequently tested.

• Ethnicity: East Asian descent (Chinese, Japanese, Korean) — strongest epidemiological risk factor.
• Klinefelter syndrome (47,XXY): associated with mediastinal and possibly intracranial GCTs.
• Cryptorchidism: classical risk factor for gonadal GCTs, less clearly established for intracranial germinomas but part of the broader germ cell tumour diathesis.
• No consistent environmental risk factors have been identified.
• Unlike many other paediatric brain tumours, there is no association with prior irradiation or known familial cancer syndromes (cf. medulloblastoma with Gorlin syndrome, ependymoma with NF2).

• A small (~8 mm) midline structure sitting in the posterior part of the third ventricle, between the superior colliculi of the tectum (dorsal midbrain).
• Function: Produces melatonin (circadian rhythm regulation) from pinealocytes.
• Critical anatomical relationships:
  • Lies directly above the cerebral aqueduct (of Sylvius) — the narrow channel connecting the 3rd and 4th ventricles. Any mass here can obstruct CSF flow → obstructive hydrocephalus.
  • Lies directly anterior to the tectal plate (superior and inferior colliculi) — compression here causes Parinaud syndrome (dorsal midbrain syndrome).
  • The posterior commissure runs nearby — involved in vertical gaze pathways.

• "Suprasellar" = above the sella turcica (the bony cup housing the pituitary gland).
• Structures in this region:
  • Pituitary gland (anterior + posterior lobes)
  • Pituitary stalk (infundibulum) — connects hypothalamus to posterior pituitary
  • Optic chiasm — where nasal retinal fibres from each eye cross
  • Hypothalamus — master neuroendocrine regulator
• A tumour here can therefore cause:
  • Diabetes insipidus (DI) — by disrupting ADH transport down the pituitary stalk or damaging the posterior pituitary / hypothalamic nuclei
  • Anterior pituitary hormone deficiencies (hypopituitarism)
  • Visual field defects — classically bitemporal hemianopia from optic chiasm compression
  • Precocious puberty — from disruption of hypothalamic GnRH regulation

• Basal ganglia / thalamus: germinomas occasionally arise here, presenting with contralateral motor deficits, personality changes, or cognitive decline.
• Cerebral hemisphere / cerebellum: rare locations.

A pineal region mass compresses the cerebral aqueduct, which is the narrowest point in the ventricular system. This results in obstructive (non-communicating) hydrocephalus with dilatation of the lateral and third ventricles but a normal-sized fourth ventricle. This is why raised ICP symptoms dominate the pineal germinoma presentation.

This is the fundamental "why" question and is essential for understanding the entire germ cell tumour family.

During early embryogenesis (weeks 3–6), primordial germ cells (PGCs) originate in the yolk sac wall and must migrate along the dorsal mesentery of the hindgut to reach the genital ridges (future gonads). This migration pathway passes through the midline of the body.

Intracranial germinomas arise from PGCs that aberrantly migrated to — or failed to complete migration from — midline intracranial structures, particularly:

• The pineal gland (most common)
• The suprasellar region (infundibulum/hypothalamus)

This is why:

• Intracranial GCTs arise almost exclusively in midline structures ^[1][2]
• Extragonadal GCTs also occur at other midline "rest stops" along the migration path: anterior mediastinum, retroperitoneum, sacrococcygeal region

Think of it as germ cells getting "lost" during their embryonic journey and landing in the wrong place, where they later undergo malignant transformation.

• KIT/RAS pathway activation: The majority of intracranial germinomas harbour activating mutations in KIT (c-Kit, CD117) or downstream RAS/MAPK pathway genes. KIT is a receptor tyrosine kinase crucial for PGC survival and proliferation. Gain-of-function mutations drive uncontrolled proliferation.
• Isochromosome 12p — i(12p): A hallmark cytogenetic abnormality seen in many germ cell tumours (gonadal and extragonadal). It results in gain of the short arm of chromosome 12, which contains genes promoting cell survival.
• Epigenetic features: Germinomas are characterised by global DNA hypomethylation (similar to PGCs and embryonic stem cells), reflecting their primitive, undifferentiated nature.
• Immune microenvironment: Germinomas characteristically have a dense lymphocytic infiltrate (mainly T cells). This brisk immune response may contribute to their excellent sensitivity to radiation and chemotherapy. The tumour cells often express PD-L1, and this has spurred interest in immunotherapy.

• Macroscopy: Well-circumscribed, soft, grey-pink tumour. May have areas of necrosis or cystic change.
• Microscopy: Classic "two-cell pattern":
  • Large, round tumour cells with clear cytoplasm (rich in glycogen — PAS positive), large central nuclei, and prominent nucleoli — resembling seminoma cells.
  • Small reactive lymphocytes interspersed between and around nests of tumour cells — giving a characteristic appearance.
• Immunohistochemistry:
  • c-Kit (CD117): positive ^[1][2] — key marker
  • PLAP (placental alkaline phosphatase): positive or negative ^[1][2]
  • OCT4: positive (stem cell marker)
  • D2-40 (podoplanin): positive
  • AFP: NEGATIVE (this distinguishes germinoma from yolk sac tumour)
  • β-hCG: NEGATIVE in pure germinoma (but can be mildly elevated if syncytiotrophoblastic giant cells are present)

• CSF dissemination (drop metastases): Germinomas have a significant propensity for leptomeningeal / CSF seeding, particularly along the ventricular system and spinal subarachnoid space. This is why craniospinal MRI and CSF cytology are mandatory in staging.
• Local invasion: Can infiltrate surrounding brain parenchyma.
• Bifocal disease: Simultaneous pineal + suprasellar tumour is relatively common and virtually pathognomonic for germinoma. If you see synchronous pineal and suprasellar masses in a young Asian male, germinoma should be at the top of your differential.
• Systemic metastasis: Extremely rare (as with most primary brain tumours — no lymphatic drainage of the brain → extracranial metastasis rare → TNM staging not useful ^[4]).

This table is extremely high yield. The key concept: germinoma is marker-negative, while non-germinomatous GCTs (NGGCTs) secrete specific markers that guide diagnosis and monitoring.

Pure germinoma: AFP negative, β-hCG negative. Syncytiotrophoblastic variant: AFP negative, β-hCG positive. Both c-Kit positive. ^[1][2]

Intracranial GCTs arise almost exclusively in midline structures:

Peripheral GCTs (for comparison):

• Gonadal: ovaries (dysgerminoma), testes (seminoma)
• Extra-gonadal: anterior mediastinum, retroperitoneum, sacrococcygeal ^[1][2]

• Intracranial germinomas are not graded in the conventional WHO I–IV system used for gliomas.
• Staging is based on extent of disease:
  • Localised (confined to primary site)
  • Disseminated (CSF seeding, leptomeningeal disease, spinal drop metastases)
• The distinction between germinoma vs. NGGCT is the most important classification for treatment planning, as they differ dramatically in prognosis and management intensity.

In clinical practice, the triad of:

1. Raised ICP (headache, vomiting, papilloedema)
2. Parinaud syndrome (upgaze palsy, convergence-retraction nystagmus)
3. Young Asian male, age 10–12

...should strongly suggest pineal germinoma.

1. Diabetes insipidus (often the first symptom — may precede imaging findings)
2. Visual disturbance (bitemporal hemianopia / decreased acuity)
3. Anterior pituitary hormone deficiency (growth failure, delayed puberty)

• Synchronous pineal + suprasellar tumour is virtually pathognomonic for germinoma — no other tumour commonly produces this pattern.

• Suprasellar germinomas are notorious for diagnostic delay because:
  • DI may be the only symptom for months/years
  • The tumour may be too small to see on initial imaging
  • The "absent posterior pituitary bright spot" on MRI may be the only early radiological clue
  • Growth failure is often attributed to other causes before a brain tumour is considered

Aetiology of raised ICP: SOL (tumour, abscess, haematoma), cerebral oedema (trauma, infection, post-stroke), hydrocephalus (obstructive: IVH, tumour; communicating: post-meningitis, post-SAH), idiopathic intracranial hypertension ^[5]

The key DDx for a child presenting with raised ICP + features localising to the pineal/posterior 3rd ventricle:

Obstructive hydrocephalus: ventricular enlargement proximal to block (4th ventricle normal). Communicating hydrocephalus: all ventricles dilated (4th ventricle enlarged) ^[5] — This distinction on imaging narrows the DDx significantly.

In a child (AOS Ophthalmology): CN VI palsy in a child = false localising sign of raised ICP. CN VI at risk of compression in raised ICP. Plus other signs of raised ICP: morning vomiting, cerebellar signs. Neuroimaging: usually inferior fossa lesion → MRI brain with contrast to look for intracranial tumour ^[6]

This is the first and most critical step after imaging identifies a midline mass.

Tumour markers, e.g. AFP, β-hCG (more sensitive in CSF than blood) ^[3]

Measurement of tumour markers in serum and CSF and both samples should be obtained unless contraindicated. Measurement of AFP and β-hCG is more sensitive in CSF than in serum. ^[9][10]

Why both serum AND CSF?

• The tumour sits behind the blood-brain barrier (BBB). Small germinomas may secrete markers into CSF without producing a detectable rise in serum.
• CSF is in direct contact with the tumour surface (especially pineal tumours projecting into the 3rd ventricle).
• Therefore CSF markers are more sensitive — a serum-negative, CSF-positive result is possible and diagnostically meaningful.

Why is CSF obtained?

• Via lumbar puncture (if safe — must rule out obstructive hydrocephalus / raised ICP first with imaging) or from ventricular CSF collected during an endoscopic third ventriculostomy (ETV) or EVD placement.
• Practically, in many centres, CSF is obtained at the time of ETV (which simultaneously treats the hydrocephalus).

Caveats:

• AFP is physiologically elevated in infants (< 6–8 months). In young children, interpret AFP against age-specific reference ranges.
• β-hCG cross-reacts with LH in some assays — in pubertal patients, verify with a specific β-hCG assay.

MRI with contrast: generally preferred over CT ^[4]. Contrast MRI for pituitary → soft tissue differentiation ^[17]

Imaging serves three purposes:

1. Localisation and characterisation of the primary tumour
2. Assessment of CSF dissemination (craniospinal MRI)
3. Evaluation for obstructive hydrocephalus and its complications

Details of findings are in Section 3 below.

Histological diagnosis by surgical biopsy is mandatory if serum and CSF tumour markers are normal — to differentiate pure germinoma and mature teratoma from other intracranial tumours such as PNETs, ependymoma, craniopharyngioma, Langerhans cell histiocytosis or metastatic disease ^[9][10]

Methods of obtaining tissue:

• Endoscopic biopsy (during ETV for hydrocephalus) — allows simultaneous CSF sampling, tumour biopsy, and treatment of hydrocephalus. This is the preferred approach in many centres.
• Stereotactic biopsy — CT- or MRI-guided needle biopsy, used when endoscopic access is not feasible.
• Open biopsy / craniotomy — less commonly needed for diagnosis alone; reserved for debulking if indicated.

Key histological findings for germinoma:

• Large, round tumour cells with clear cytoplasm (glycogen-rich, PAS+), large central nuclei, prominent nucleoli
• Dense lymphocytic infiltrate — the hallmark "two-cell pattern"
• ± Syncytiotrophoblastic giant cells (produce small amounts of β-hCG)

Immunohistochemistry (IHC):

Once germinoma is confirmed (or strongly suspected), staging determines the extent of disease:

• Craniospinal MRI with gadolinium — to detect leptomeningeal / drop metastases along the spinal cord
• CSF cytology — to detect malignant cells in the CSF (evidence of microscopic dissemination)
• Complete endocrine evaluation — baseline pituitary function (even pineal germinomas can have endocrine effects after treatment)

Disease is classified as:

• Localised: confined to primary site
• Disseminated / Metastatic: CSF-positive cytology, leptomeningeal enhancement on MRI, or spinal drop metastases

Role: Usually the first-line investigation in a child presenting with acute raised ICP symptoms. CT is fast, widely available, and excellent at detecting hydrocephalus and calcification.

CT brain: site and multiplicity, mass effect, contrast enhancement. Normal brain tissue does not enhance (due to BBB). Enhancement indicates: outside BBB (e.g. meningioma — homogeneously enhancing) or disruption of BBB (e.g. high-grade tumours, inflammation) ^[4]

Limitations of CT:

• Poor soft tissue contrast compared to MRI — cannot characterise the tumour as well
• Cannot reliably detect leptomeningeal disease or small suprasellar lesions
• Radiation exposure — a concern in paediatric patients

MRI with contrast: generally preferred over CT. Advantages: allow better soft tissue delineation, especially useful at skull base, craniocervical junction, brainstem ^[3]

MRI is the definitive imaging modality for intracranial germinoma. Every patient with a suspected intracranial GCT should have a complete craniospinal MRI.

MRI appearance: high-grade glioma: ↓T1W, heterogenous enhancement with surrounding vasogenic edema (↑T2W) ± central necrosis. Low-grade glioma: ↑T2W, non-enhancing expansile lesion without surrounding vasogenic edema. Primary CNS lymphoma: solitary/multifocal T2W-iso/hypointense, contrast-enhancing lesions in subcortical regions, classically a/w prominent diffusion restriction on DWI ^[3]

Key imaging patterns to distinguish midline tumours:

Contraindications to LP: raised ICP — suspect if immunocompromised, seizure, GCS < 15, FND → CT brain first ^[18]

Purpose: Obtain CSF for tumour markers, cytology, and biochemistry.

Practical considerations:

• In patients with pineal germinoma, there is usually obstructive hydrocephalus → LP may be contraindicated due to raised ICP (risk of tonsillar herniation).
• In these cases, CSF is obtained from ventricular sampling during ETV or EVD placement — this is both diagnostically superior (closer to tumour) and safer.

If a suprasellar germinoma presents with polyuria/polydipsia, confirm DI:

• Water deprivation test: Patient is water-deprived under close monitoring (hourly weight, serum osmolality, urine osmolality).
  • In central DI (vasopressin deficiency): urine remains dilute despite rising serum osmolality → administration of DDAVP causes urine osmolality to rise (concentrating ability restored).
  • This distinguishes central DI from nephrogenic DI (where DDAVP has no effect).
• Modern approach: copeptin — a surrogate marker for AVP (more stable than AVP itself, which has a very short half-life). Can separate nephrogenic and central DI ^[21].

Indication: Obstructive hydrocephalus causing raised ICP — the most common acute presentation of pineal germinoma.

Why emergency management comes first: A child presenting with progressive headache, vomiting, drowsiness, and papilloedema from pineal germinoma has acute obstructive hydrocephalus. Without CSF diversion, this can progress to brainstem herniation and death. Definitive tumour treatment (RT/chemo) takes weeks to plan and deliver — the patient needs immediate decompression.

CSF shunting for hydrocephalus (e.g., in posterior fossa lesions, leptomeningeal meningitis, CSF mets) ^[23]

High-dose glucocorticoids: reduction of cerebral oedema. Use: PO (or IV if severe) dexamethasone 10mg then 4mg Q4h or 8mg BD ^[23]

• Indication: Symptomatic raised ICP / cerebral oedema before or after surgery/radiation
• Mechanism: Reduces vasogenic oedema by restoring BBB integrity, decreasing capillary permeability, and inhibiting prostaglandin-mediated inflammation
• Important caution: Contraindication: suspect CNS lymphoma → steroid causes acute lysis of lymphocytes → decreased diagnostic yield on biopsy ^[23]. Germinomas can also partially respond to steroids (due to the brisk lymphocytic infiltrate being steroid-sensitive), potentially confusing the diagnostic picture. Ideally, obtain tissue diagnosis before starting steroids.
• Practical approach: If steroids are absolutely needed for life-threatening raised ICP before biopsy, use the minimum effective dose and proceed to biopsy as soon as clinically feasible.

Radiation therapy (RT) is the single most effective treatment for intracranial germinoma. Germinomas are exquisitely radiosensitive — their primitive germ cell origin, high mitotic rate, and limited DNA repair capacity make them highly vulnerable to ionising radiation.

This is analogous to how testicular seminoma (the gonadal counterpart) is also exquisitely radiosensitive ^[15].

Evolution of RT approach:

• Historically, germinomas were treated with craniospinal irradiation (CSI) at high doses (> 36 Gy), yielding > 95% cure rates but at the cost of severe long-term toxicity (neurocognitive impairment, growth failure, endocrinopathy, secondary malignancies).
• The modern approach uses reduced-dose, reduced-field RT combined with chemotherapy to maintain excellent cure rates while minimising late effects.

Why whole-ventricular and not just focal RT?

• Germinomas have a propensity for ventricular surface seeding — even "localised" tumours may have microscopic disease along the ventricular lining. Whole-ventricular irradiation covers this risk while avoiding the toxicity of whole-brain or craniospinal RT.
• Studies (SIOP CNS GCT 96, ACNS 0232) showed that focal-field-only RT had unacceptable ventricular relapse rates (~20–30%) in localised germinoma, supporting WVI as the minimum field.

RT modalities:

External beam radiotherapy (ERT): standard radiotherapy with parallel rays. Stereotactic radiosurgery (SRS): multiple converging beams to focus on a selected target. Modalities: X-knife with linear accelerator, Gamma knife with gamma source ^[24]

• Intensity-modulated RT (IMRT) and proton beam therapy (PBT) are increasingly preferred for intracranial germinoma:
  • Proton beam therapy: Protons deposit energy at a defined depth (the Bragg peak) and do not exit through the tissue → dramatically reduces dose to surrounding normal brain → lower neurocognitive toxicity, fewer secondary malignancies. This is particularly important in children.
  • Proton beam therapy is now considered the standard of care for paediatric CNS tumours in many leading centres worldwide (although availability remains limited).

Chemotherapy is used in combination with RT (not as monotherapy) for intracranial germinoma. The rationale:

• Allows reduction of RT dose and field → fewer long-term side effects
• Germinomas are chemosensitive (though not as dramatically as with RT)
• Chemotherapy alone (without RT) has shown unacceptable relapse rates (~50% at 5 years) — therefore chemotherapy alone is NOT adequate for definitive treatment

Standard regimens:

Chemotherapy toxicities:

Surgical resection: principle: maximal removal within safety limit. Aim: cytoreduction + functional preservation ^[23]

Maximal safe resection without causing serious neurological sequelae is the key component of treatment ^[16] — However, this principle applies primarily to other brain tumours (gliomas, medulloblastoma). For germinoma, the approach is fundamentally different:

This is the most common scenario and carries the best prognosis.

Standard approach (current practice, most international protocols 2024–2026):

1. CSF diversion if obstructive hydrocephalus (ETV preferred)
2. Biopsy for tissue confirmation (during ETV or stereotactically)
3. Neoadjuvant chemotherapy: 2–4 cycles of carboplatin/etoposide
   • Assess response with MRI after 2 cycles
   • Most germinomas show excellent partial or complete response
4. Reduced-dose, reduced-field RT: Whole-ventricular irradiation (WVI) 21–24 Gy + tumour bed boost to 30–40 Gy total
5. Long-term follow-up

Alternative (if chemotherapy is contraindicated or refused):

• RT alone: WVI 24 Gy + tumour boost to 40–45 Gy
• Cure rates remain excellent (> 90%) but with higher RT doses and therefore more long-term toxicity

Expected outcomes:

• 5-year overall survival: > 95%
• 5-year progression-free survival: > 90%

1. CSF diversion if needed
2. Chemotherapy: 4 cycles of carboplatin/etoposide or cisplatin/etoposide
3. Craniospinal irradiation (CSI): 24–30 Gy to the entire craniospinal axis + tumour bed boost to 40 Gy
   • CSI is necessary because disease has spread throughout the CSF pathways
4. Long-term follow-up

Expected outcomes:

• 5-year overall survival: ~85–90% (slightly lower than localised disease but still excellent)

• Treated as localised disease (not "disseminated") in most protocols, because bifocal presentation is considered a characteristic pattern of germinoma rather than true metastatic spread
• Treatment: Chemotherapy + WVI with boosts to both sites
• Prognosis: Similar to localised disease

• Treated with the same protocol as pure germinoma (not as NGGCT)
• β-hCG < 50–100 IU/L from syncytiotrophoblastic cells does not worsen prognosis
• Some protocols add one extra cycle of chemotherapy

• Mechanism: Pineal germinoma compresses the cerebral aqueduct → obstruction of CSF flow from 3rd to 4th ventricle → progressive dilatation of lateral and 3rd ventricles → raised ICP
• Why it matters: This is the most immediately life-threatening complication. Without treatment, progressive hydrocephalus leads to:
  • Brain herniation:
    • Uncal herniation: "blown pupil" (fixed dilated pupil due to CN3 palsy), contralateral hemiplegia (cerebral peduncle), reduced consciousness (reticular formation) ^[5]
    • Tonsillar herniation: Cushing's triad (systemic HT, bradycardia, respiratory depression) ^[5] → cardiorespiratory arrest and death
  • Chronic cognitive decline from sustained ventricular enlargement damaging periventricular white matter
• Management: Emergency CSF diversion (ETV preferred, or VP shunt / EVD)

• Mechanism: Direct compression of the pretectal area and posterior commissure by a pineal region mass
• Components: Upgaze palsy, convergence-retraction nystagmus, light-near dissociation, lid retraction
• Prognosis: Often partially or fully reversible after successful treatment (tumour shrinkage with chemo/RT relieves compression). However, some patients have persistent upgaze limitation, especially if treatment was delayed.

• Diabetes insipidus: From destruction of ADH-producing hypothalamic neurons or disruption of the pituitary stalk. Usually irreversible — even after successful tumour treatment, the damaged neurons do not regenerate. Most patients require lifelong DDAVP replacement.
• Anterior pituitary deficiency: GH deficiency (growth failure), central hypothyroidism, central adrenal insufficiency (potentially life-threatening), hypogonadotropic hypogonadism (delayed puberty). These may be partially reversible after tumour treatment in some cases, but more commonly persist or even worsen after irradiation.
• Hypothalamic obesity: Damage to ventromedial hypothalamic satiety centres → intractable weight gain that is notoriously resistant to dietary and lifestyle interventions. This significantly impacts quality of life and long-term cardiovascular risk.

• Mechanism: Suprasellar tumour compressing the optic chiasm → bitemporal hemianopia; or chronic papilloedema from raised ICP → optic atrophy
• Prognosis: If the visual loss is from chiasmal compression alone, it may partially recover after tumour shrinkage. However, if chronic papilloedema has led to optic atrophy (axonal death), the visual loss is irreversible.
• CN VI palsy in a child = false localising sign of raised ICP ^[6] — This typically resolves once hydrocephalus is treated.

• Mechanism: Germinoma cells seed into the CSF via the ventricular system and spread along the leptomeninges to the spinal cord
• Consequences: Spinal cord compression, nerve root involvement (radiculopathy, cauda equina syndrome with sphincter dysfunction), cranial neuropathies
• Impact on prognosis: Disseminated disease requires more intensive treatment (craniospinal irradiation instead of whole-ventricular RT) and has a slightly lower survival (~85–90% vs. > 95% for localised disease)

• Occurs in approximately 5–10% of treated germinoma patients, usually within the first 3 years
• Patterns: Local recurrence at the primary site, ventricular relapse (if RT field was too limited), or distant CSF/spinal relapse
• Salvage: Re-irradiation, high-dose chemotherapy + autologous HSCT. Salvage cure rates are reasonable (~50–60%) because germinoma retains its chemo/radiosensitivity.

Since radical resection is NOT performed for germinoma, surgical complications are limited to those of diagnostic/CSF diversion procedures:

Complications of transsphenoidal surgery (if suprasellar approach needed): mortality (very rare), endocrine — diabetes insipidus, hypopituitarism; vision loss; CSF leakage and meningitis; vascular injury and CVA; ENT symptoms; intracranial haemorrhage ^[26]

• Prevalence: Affects the majority of survivors who received whole-brain or craniospinal RT, especially those treated at younger ages
• Pattern: Progressive decline in processing speed, working memory, attention, and executive function. IQ may decline by 2–4 points per year in the years following RT.
• Mechanism: Radiation damages oligodendrocyte precursors (→ demyelination), hippocampal neurogenesis (→ memory deficits), and cerebral microvasculature (→ chronic ischaemia)
• Craniospinal radiation is avoided or delayed in children due to severe toxicity to the rapidly developing CNS such as neurocognitive impairment ^[16]
• Mitigation: Modern protocols use reduced-field RT (whole-ventricular instead of whole-brain), lower doses, proton beam therapy (spares more normal tissue), and chemotherapy to allow dose reduction. Neurocognitive rehabilitation and educational support should be offered.

• Moyamoya syndrome: Progressive stenosis/occlusion of the distal internal carotid arteries and their branches, with development of fragile collateral vessels (the "puff of smoke" appearance on angiography)
  • Particularly well-described after cranial RT in children
  • Presents with TIAs, ischaemic stroke, or haemorrhagic stroke (from rupture of fragile collaterals)
  • Management: revascularisation surgery (e.g., EDAS — encephaloduroarteriosynangiosis)
• Accelerated atherosclerosis: Radiation damages the vascular endothelium → premature large-vessel atherosclerosis → increased risk of stroke and cardiovascular disease decades later
• Cerebrovascular abnormalities (stroke / intracranial haemorrhage) ^[16]

• Radiation-associated 2nd malignancy — the lifetime risk is about 1 in 1000 ^[27]
• Most common types: meningioma (most frequent radiation-induced intracranial tumour), high-grade glioma, thyroid carcinoma (if RT field included the neck, as in CSI)
• Latency: Typically > 10–20 years for meningiomas, > 5–10 years for gliomas
• Etoposide-related therapy-related AML: 2–3 years post-treatment
• Screening: Long-term MRI surveillance; thyroid examination and ultrasound in those who received CSI

• Depression, anxiety, PTSD: Common in childhood cancer survivors
• Social isolation, academic difficulties: Related to neurocognitive deficits and long absences from school during treatment
• Body image concerns: Alopecia during treatment (usually temporary), growth failure, obesity, delayed puberty
• Fertility concerns: Significant source of distress for adolescent and young adult survivors
• Transition to adult care: Many paediatric germinoma survivors "age out" of paediatric services but still require ongoing endocrine, neurocognitive, and oncological surveillance — the transition must be carefully managed