A 40-year-old woman has recurrent episodes of severe headache with brief loss of consciousness, provoked by straining. Non-contrast CT shows a rounded hyperdense lesion at the level of the foramen of Monro with dilated lateral ventricles. What is the diagnosis?

• A Craniopharyngioma
• B Subependymal giant cell astrocytoma
• C Central neurocytoma
• D Colloid cyst of the third ventricle ✓

Explanation

D colloid cyst arises at the anterior third ventricle near the foramen of Monro and acts as a ball valve, causing episodic obstructive hydrocephalus. Attacks are typically positional and triggered by coughing or straining, and sudden death from acute hydrocephalus is described. On non-contrast CT it appears as a well-defined hyperdense round lesion at the foramen of Monro. Subependymal giant cell astrocytoma occurs at the caudothalamic groove in tuberous sclerosis, not the foramen of Monro.

Reference: Greenberg Handbook of Neurosurgery, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.