The Collapsing Child with a Posterior Fossa Tumour
A 6-year-old boy presents with 3 weeks of morning vomiting, ataxia and lethargy. He is drowsy but rousable, GCS 13 (E3 V4 M5). Fundoscopy shows bilateral papilloedema. CT shows a 4 cm midline cerebellar mass with hydrocephalus (temporal horns dilated, effaced fourth ventricle) and early tonsillar herniation. He has no prior imaging and no known comorbidity. The on-call registrar asks whether to insert an external ventricular drain (EVD) now, give steroids, or take him straight to theatre.
1. What is your immediate management priority and how do you sequence the interventions?
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Priority: control raised ICP and prevent herniation - this child has obstructive hydrocephalus with early tonsillar herniation and declining consciousness. This is a neurosurgical emergency.
Sequencing. (1) Immediate medical measures: head-up 30°, avoid hypoxia/hypercapnia, controlled ventilation if intubated, osmotherapy (hypertonic saline or mannitol) for acute deterioration, and dexamethasone - steroids are controversial in paediatric posterior fossa tumours (they may reduce peritumoural oedema and improve symptoms pre-operatively, but can complicate histology and are not a substitute for CSF diversion). (2) CSF diversion: an EVD is a reasonable bridge to relieve hydrocephalus and allow safe transfer/imaging, but carries infection and haemorrhage risk and may not be needed if definitive surgery is imminent. (3) Definitive surgery: posterior fossa craniotomy and tumour resection is the definitive treatment and also relieves the hydrocephalus in many cases.
Judgement call. If theatre and a neurosurgical team are immediately available, proceeding to definitive resection with intra-operative CSF release may be preferable to a separate EVD. If there will be delay (transfer, theatre availability), place an EVD. Do not perform a shunt as a first step in a child with an untreated posterior fossa tumour - it commits the child to a shunt and does not address the tumour.
Danger. Do not perform lumbar puncture in this setting - it risks tonsillar herniation.
2. Post-operatively he develops mutism and ataxia despite good resection. What is the likely cause, how do you counsel the family, and what does it teach about consent?
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Likely cause: cerebellar mutism syndrome (posterior fossa syndrome). It occurs in a significant minority of children after resection of midline posterior fossa tumours (especially medulloblastoma), typically presenting 1–2 days post-operatively with mutism, emotional lability, and worsening ataxia/hypotonia. It is usually transient but recovery can take weeks to months and some children have residual language or motor deficits. It is thought to relate to disruption of the dentate nucleus / superior cerebellar peduncle pathways.
Counselling. Explain that this is a recognised post-operative phenomenon, not a surgical error, that it usually improves, and that rehabilitation (speech and language therapy, physiotherapy) is the mainstay. Avoid over-promising a timeline. Involve the multidisciplinary team and school liaison.
Consent lesson. This is precisely the kind of specific, foreseeable risk that must be discussed pre-operatively: parents consented to 'tumour removal' but may not have been warned about mutism. Good consent names the specific syndrome, the likelihood, and the recovery trajectory. It also reinforces the need to document the discussion. The exam is testing whether you recognise that consent is about specific material risks, not generic statements.
Follow-up. Ensure histology is discussed at MDT; adjuvant therapy depends on tumour type (e.g., medulloblastoma requires craniospinal irradiation and chemotherapy). Address hydrocephalus - some children need a permanent shunt or ETV.