USMLE Answer 38
38. The correct answer is A. Tumors of the ventricular system of the brain can affect the brain tissue either directly, via pressure on or invasion into a physically close structure, or indirectly, by obstructing CSF flow and causing hydrocephalus. Choroid plexus papillomas are highly differentiated, benign tumors that can involve any ventricle but have a predilection for involving the lateral ventricles of small children, particularly boys. The caudate nucleus is a C-shaped structure that comprises part of the wall of the lateral ventricle throughout its extent. The only structure listed that is adjacent to the body of the lateral ventricle, and would therefore be directly affected by the large tumor described in the question, is the caudate nucleus.
The cerebellum (choice B) overlies the fourth ventricle.
The hippocampus (choice C) is adjacent to the inferior (temporal) horn of the lateral ventricle.
The hypothalamus (choice D) abuts the third ventricle.
The pons (choice E) forms part of the floor of the fourth ventricle.