Brain and spinal tumours: SAQ

This boy has the classic presentation of a posterior fossa tumour with obstructive hydrocephalus: the progressive early morning headache and vomiting of raised intracranial pressure, the papilloedema, the false-localising sixth palsy, and the truncal ataxia of a cerebellar vermis lesion. This is a medical emergency, and the task is to recognise the pattern, to image urgently, to resuscitate the pressure, and to move to the risk-adapted definitive therapy in a specialist paediatric neuro-oncology centre. [3]

Question 1 (10 marks)

Outline your immediate assessment and the urgent diagnostic pathway for this six-year-old boy. [2]

A full-mark answer covers the recognition of the emergency, the resuscitation of the raised pressure, the magnetic resonance imaging of the brain and the whole neuraxis, and the surgical and the molecular diagnostic pathway that delivers the named diagnosis. [3]

Recognition and the first decision (1 mark). The progressive early morning headache and vomiting with the papilloedema, the abducens palsy and the ataxia together declare a posterior fossa tumour with obstructive hydrocephalus, and the child is moved from an elective workup to an emergency. The first priority is the relief of the raised pressure and the urgent imaging, because the unrelieved hydrocephalus can progress to the herniation within hours. [2]

Resuscitation (3 marks). The dexamethasone is started at the first sign of the pressure or the deficit, at zero point one to zero point two milligrams per kilogram per dose every six hours, to control the vasogenic tumour oedema, and it is tapered after the surgery. The head is elevated, the isotonic fluids are maintained, and the child is monitored for the falling consciousness that signals the herniation. The hydrocephalus is managed with the external ventricular drain at the surgery or before it, and the endoscopic third ventriculostomy is an alternative where the anatomy allows. The neurosurgical and the oncology teams are alerted at once. [11]

Diagnostic imaging (3 marks). The magnetic resonance imaging of the brain with and without contrast is the standard, and it shows the tumour, the oedema, the hydrocephalus and the relationship to the critical structures. The whole neuraxis is imaged at the diagnosis because the medulloblastoma disseminates through the cerebrospinal fluid, and the spinal magnetic resonance and the cerebrospinal fluid cytology (once the pressure is relieved) stage the disease. The computed tomography is reserved for the emergency setting where the magnetic resonance is unavailable, and it misses the posterior fossa detail. [3]

Surgical and molecular diagnosis (3 marks). The maximal safe resection is performed, and the residual tumour is measured on the postoperative scan, because the residual under one point five square centimetres with no metastatic disease defines the average risk. The histology grades the tumour, and the molecular studies add the defining alteration, with the methylation profiling and the subgroup markers defining the WNT, the SHH, the Group 3 and the Group 4 medulloblastoma. The residual and the molecular subgroup together drive the risk group and the intensity of the craniospinal irradiation. [3][4]

Question 2 (10 marks)

Discuss the risk-adapted definitive management once the diagnosis of a non-metastatic, molecularly average-risk medulloblastoma is confirmed, and contrast it with the management of the diffuse intrinsic pontine glioma and of the cerebellar pilocytic astrocytoma. [3]

A full-mark answer reproduces the risk-adapted therapy for the medulloblastoma, and contrasts the fatal brainstem glioma and the curable pilocytic astrocytoma. [7]

Average-risk medulloblastoma (4 marks). The treatment is the maximal safe resection with the residual under one point five square centimetres, the craniospinal irradiation at twenty three point four gray to the neuraxis with a boost to the posterior fossa, and the concomitant and the maintenance chemotherapy. The molecular subgroup refines the risk, with the WNT carrying the best and the Group 3 the worst prognosis. The craniospinal irradiation is avoided under three years of age, and a chemotherapy-first strategy is used. The contemporary survival of the average-risk medulloblastoma sits around seventy to eighty percent, and the proton therapy is increasingly used to reduce the late effects. [3][4]

Diffuse intrinsic pontine glioma (3 marks). In contrast, the diffuse intrinsic pontine glioma carries the H3 K27M mutation and the diffuse midline glioma, WHO grade four, designation, and it has no curative therapy. The standard treatment is the focal radiotherapy to the pons at fifty four to fifty nine gray, delivered over six weeks, which improves the symptoms and the quality of life and extends the median survival to the nine to eleven months, but which does not cure. The chemotherapy, the targeted agents and the immunotherapies have failed in the trials, and the contemporary research is built around the ONC201, the dordaviprone. The family is counselled honestly, and the palliative care is involved early. [7]

Cerebellar pilocytic astrocytoma (2 marks). The third contrast is the cerebellar pilocytic astrocytoma, the WHO grade one lesion with the classic cyst and mural nodule and the BRAF fusion, which is cured by the gross total resection with no further therapy. The subtotal resection is followed with the surveillance imaging, and the chemotherapy with the carboplatin and vincristine 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. [3]

Synthesis (1 mark). The fellow who can hold these three tumours together, the curable pilocytic astrocytoma, the treatable medulloblastoma, and the fatal diffuse intrinsic pontine glioma, has the framework that organises the whole topic of the paediatric brain tumour, and the late-effects surveillance that follows each. [12]