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]