A 45-year-old woman has recurrent brief episodes of severe headache with vomiting that occur on bending forward. On one occasion she lost consciousness for 20 seconds. MRI shows a small spherical well-defined lesion at the anterior third ventricle attached to the roof just behind the foramen of Monro, with dilated lateral ventricles. What is the most likely diagnosis?
- A Colloid cyst of the third ventricle ✓
- B Craniopharyngioma
- C Subependymoma
- D Germinoma
Correct answer: A. Colloid cyst of the third ventricle
Explanation
A colloid cyst sits at the foramen of Monro and acts as a ball valve, causing intermittent acute obstructive hydrocephalus. This produces positional headaches and can cause sudden drop attacks or even death from acute ventricular obstruction. Craniopharyngioma is suprasellar, calcified, and causes bitemporal field loss rather than episodic positional symptoms. Subependymoma arises in the ventricular wall of the lateral or fourth ventricle. Germinoma occurs in the pineal or suprasellar region in young patients and enhances densely.
Reference: Greenberg's Handbook of Neurosurgery, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.