Question

A 10 year old child presented with headache, vomiting, gait instability and diplopia. On examination he had papilloedema and gait ataxia. The most probable diagnosis is:

• A. Hydrocephalus
• B. Brain stem Tumour
• C. Suprasellar tumour
• D. Midline posterior fossa tumour

Hint:

Raised ICP signs plus truncal gait ataxia in a child point to a midline posterior fossa mass like medulloblastoma.

Answer 1

The Correct Option is D

This 10 year old has two groups of findings: headache, vomiting and papilloedema, which signal raised pressure inside the skull, and gait instability with gait ataxia, which signals trouble in the balance centre of the brain. The diagnosis has to explain both groups at once.

1. Hydrocephalus: this is fluid build up inside the brain and does explain the raised pressure findings, but it is really the downstream effect of something blocking cerebrospinal fluid flow. On its own it does not account for the specific gait ataxia, so it is too broad an answer.
2. Brain stem tumour: this usually shows up with cranial nerve palsies and weakness from pressure on the long nerve tracts running through the brain stem, rather than the prominent truncal ataxia seen in this child, so it is a weaker fit.
3. Suprasellar tumour: tumours in this location, like craniopharyngioma, typically cause visual field loss and hormone problems from pressing on the optic chiasm and pituitary gland, not gait ataxia, so this does not match either.
4. Midline posterior fossa tumour: a tumour such as medulloblastoma growing from the cerebellar vermis presses on the fourth ventricle, blocking cerebrospinal fluid drainage and producing the headache, vomiting and papilloedema of raised pressure. At the same time it damages the vermis directly, producing truncal gait ataxia. The diplopia also fits, since raised pressure commonly stretches the sixth cranial nerve as a false localising sign.

Only a midline posterior fossa tumour ties every finding, the raised pressure signs and the gait ataxia, into one single lesion.

Let's summarize:

• Headache, vomiting and papilloedema point to raised intracranial pressure.
• Gait, truncal ataxia points to the cerebellar vermis, which sits in the midline posterior fossa.

The most probable diagnosis is a midline posterior fossa tumour.