A 38-year-old obese woman presents with episodic headaches that worsen when supine, brief episodes of loss of consciousness when bending forward, and progressive visual blurring. Non-contrast CT head shows a small round hyperdense lesion at the level of the foramina of Monro with mild dilation of both lateral ventricles and a normal third and fourth ventricle. The most likely diagnosis is:
- A Subependymal giant cell astrocytoma
- B Colloid cyst of the third ventricle ✓
- C Craniopharyngioma
- D Central neurocytoma
Correct answer: B. Colloid cyst of the third ventricle
Explanation
B colloid cyst arises at the roof of the third ventricle and ball-valves into the foramina of Monro, causing intermittent symmetrical obstructive hydrocephalus of both lateral ventricles with positional headache, drop attacks and sometimes sudden death. It is characteristically hyperdense on unenhanced CT. Craniopharyngioma is suprasellar and commonly calcified, while central neurocytoma arises in the lateral ventricle body near the septum pellucidum.
Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.