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

Step 1: Understanding the Question:
This child has headache, vomiting and papilloedema, which together point to raised pressure inside the skull, plus gait instability with gait ataxia, which points to a problem in the part of the brain that controls balance and coordinated movement. We need the single diagnosis that best explains all these findings together.

Step 2: Key Formula or Approach:
In a child, a mass sitting in the midline of the back of the brain, in the posterior fossa near the cerebellar vermis, is a classic cause of this exact combination. It blocks the normal flow of cerebrospinal fluid, which raises pressure inside the skull and causes headache, vomiting and papilloedema, while directly damaging the vermis, which produces truncal, gait type ataxia.

Step 3: Detailed Explanation:
Hydrocephalus by itself is a build up of fluid inside the brain's ventricles and does explain the raised pressure signs, but it is a consequence of some underlying blockage, not a standalone diagnosis that also explains the specific gait ataxia from vermis involvement. It is too generic an answer for what this case is really describing.
A brain stem tumour usually produces cranial nerve palsies and long tract signs such as limb weakness from direct pressure on brain stem pathways, more than the prominent truncal gait ataxia and papilloedema seen here, so it fits less well.
A suprasellar tumour, such as a craniopharyngioma, classically causes visual field problems and hormonal disturbances from pressing on the optic chiasm and pituitary region, not gait ataxia, so this does not match the picture either.
A midline posterior fossa tumour, such as a medulloblastoma arising from the cerebellar vermis, explains the whole picture at once. It compresses the fourth ventricle, blocking cerebrospinal fluid outflow and causing the headache, vomiting and papilloedema of raised intracranial pressure, while damaging the vermis to cause the gait instability and truncal ataxia. The diplopia fits too, since raised pressure commonly stretches the sixth cranial nerve, a well known false localising sign.

Step 4: Final Answer:
The combination of raised intracranial pressure signs with gait ataxia in a child is most probably caused by a midline posterior fossa tumour, option 4.