Brain and spinal tumours: Viva

This is a branching oral built to probe the reasoning that holds the location and the molecular classification at the centre, and to expose the candidate who has memorised the headline without the corners. The questions escalate from the framing to the stabilisation, the imaging, and the definitive management, with deliberate probes into the pitfalls. [3]

Opening question: framing the problem

The examiner opens with the history and the examination and asks: how do you frame this problem in a single sentence, and what is your first priority? [2]

A strong answer names the syndrome of raised intracranial pressure with a posterior fossa sign, the ataxia, and states that the progressive early morning headache and vomiting with the papilloedema is a tumour until imaging proves otherwise. The first priority is the relief of the raised pressure, because the obstructive hydrocephalus from a posterior fossa mass can progress to the herniation within hours. [11]

Model answer. This child has raised intracranial pressure from a posterior fossa tumour with obstructive hydrocephalus, almost certainly a medulloblastoma until imaging proves otherwise. My first priority is to relieve the pressure with the dexamethasone and the neurosurgical management of the hydrocephalus, and to reach the urgent magnetic resonance imaging of the brain and the whole neuraxis. [3]

Probe one: the resuscitation

The examiner presses: tell me exactly what you do in the first four hours, and why you choose the dexamethasone. [11]

A strong answer reproduces the dexamethasone at zero point one to zero point two milligrams per kilogram per dose every six hours for the vasogenic oedema, tapered after the surgery, with the head elevation and the isotonic fluids. The hydrocephalus is managed with the external ventricular drain at the surgery or before it, and the endoscopic third ventriculostomy is the alternative. The falling consciousness or the Cushing response triggers the emergency measures. [11]

Pitfall probe. Why is the dexamethasone tapered after the surgery and not continued? Because the long course carries the hyperglycaemia, the gastritis, the mood change and the infection risk, and the definitive therapy relieves the mass effect that made the steroid necessary. [11]

Probe two: the imaging and the staging

The examiner asks: what imaging do you arrange, and why do you image the whole neuraxis before the treatment plan is set? [3]

A strong answer describes the magnetic resonance imaging of the brain with and without contrast, and the whole neuraxis imaging because the medulloblastoma disseminates through the cerebrospinal fluid. The spinal magnetic resonance and the cerebrospinal fluid cytology, once the pressure is relieved, stage the disease, and the metastatic disease moves the child from the average-risk to the high-risk category and intensifies the craniospinal irradiation. The residual tumour on the postoperative scan, measured against the one point five square centimetre threshold, and the molecular subgroup together define the risk group. [3]

Pitfall probe. Why would the whole-neuraxis imaging be a waste for a cerebellar pilocytic astrocytoma but essential for a medulloblastoma? Because the pilocytic astrocytoma is a grade one lesion that does not disseminate, while the medulloblastoma is an embryonal tumour that seeds the cerebrospinal fluid pathway. [8]

Branch one: the diffuse intrinsic pontine glioma

The examiner pivots: imagine instead a six-year-old with a short history of a right sixth and seventh palsy, the hyperreflexia and the upgoing plantar, and the ataxia, and the magnetic resonance shows a diffusely enlarged pons that encases the basilar artery. What is this, and how is it managed? [7]

A strong answer names the diffuse intrinsic pontine glioma, reclassified as the diffuse midline glioma, H3 K27-altered, WHO grade four. The diagnosis is radiographic, the biopsy is increasingly performed for the molecular profiling, and the standard treatment is the focal radiotherapy to the pons at fifty four to fifty nine gray. The prognosis is near uniformly fatal within the year, the chemotherapy and the targeted agents have failed, and the contemporary research is built around the ONC201, the dordaviprone. The family is counselled honestly, and the palliative care is involved early. [7]

Branch two: the curable lesion

The examiner pivots again: imagine instead a child with the ipsilateral dysmetria and the magnetic resonance shows a cerebellar cyst with a mural nodule. What is this, and how is it managed? [8]

A strong answer names the cerebellar pilocytic astrocytoma, the WHO grade one lesion with the BRAF fusion, cured by the gross total resection with no further therapy. The subtotal resection is followed with the surveillance imaging, and the chemotherapy or the targeted BRAF inhibitor is reserved for the progressive or the unresectable disease. The survival exceeds ninety five percent for the completely resected lesion, which is the opposite end of the spectrum from the diffuse intrinsic pontine glioma. [8]

Branch three: the under-three child

The examiner pivots once more: imagine the same medulloblastoma in a two-year-old. What changes about the management, and why? [3]

A strong answer states that the craniospinal irradiation is avoided under three years of age because of the devastating neurocognitive injury to the developing brain, and a chemotherapy-first strategy is used to defer or to replace the radiotherapy. The infant protocols are tailored to the very young child, and the fellow must know that the age of three years is the threshold that reshapes the entire treatment. [3]

Closing question: counselling the family

The examiner closes: the diagnosis of a non-metastatic, molecularly average-risk medulloblastoma is confirmed. How do you counsel the family? [3]

A strong answer describes the honest and hopeful conversation that names the diagnosis, explains that it is the commonest malignant brain tumour of childhood, that the contemporary survival sits around seventy to eighty percent for the average-risk disease, and that the treatment runs over roughly a year with the surgery, the craniospinal irradiation and the chemotherapy. The family is introduced to the multidisciplinary team, taught the late effects, the recurrence signs and the school support, and the survivorship plan is begun from the day of diagnosis, with the surveillance for the neurocognitive decline, the endocrinopathy, the hearing loss and the second malignancy. [12]