A 32-year-old woman presents with episodic headaches worse in the morning and transient blurring of vision on standing. Non-contrast CT head shows a well-defined round hyperdense lesion at the foramen of Monro causing symmetric dilatation of both lateral ventricles with normal fourth ventricle. The most likely diagnosis is:
- A Central neurocytoma
- B Subependymoma
- C Colloid cyst ✓
- D Ependymoma
Correct answer: C. Colloid cyst
Explanation
C rounded hyperdense lesion at the foramen of Monro producing bilateral lateral ventricular dilatation with an intact fourth ventricle is the classic appearance of a colloid cyst, which causes intermittent obstructive hydrocephalus and positional headache. Central neurocytoma arises from the septum pellucidum or ventricular walls as a larger heterogeneous intraventricular mass, not a small discrete lesion wedged at the foramen of Monro.
Reference: Osborn's Brain, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.