Review Question - QID 217698

This patient who presents with a cerebral mass and has dilated lateral ventricles but a compressed 3rd ventricle most likely has obstruction at the junction between these structures. This connection is known as the foramen of Monro.

The ventricular system forms a set of chambers that allows cerebrospinal fluid (CSF) to circulate in the brain. CSF is produced by the choroid plexus epithelial cells within the lateral, 3rd, and 4th ventricles. It then moves from the lateral ventricles to the 3rd ventricle through the foramen of Monro. From there, it proceeds to the 4th ventricle through the cerebral aqueduct (also known as the aqueduct of Sylvius). Finally, it circulates to the subarachnoid space through the foramina of Luschka (located laterally) and the foramen of Magendie (located medially). From there, the CSF is reabsorbed into the circulation by arachnoid granulations.

Alarifi et al. present a case report of an adult gangliocytoma arising within the ventricular system and causing hydrocephalus.

Incorrect Answers:
Answer 1: A tumor that caused dysfunction of the arachnoid granulations would result in diffuse hydrocephalus throughout all the ventricles because it would inhibit the resorption of CSF from the entire system.

Answer 2: A tumor obstructing the cerebral aqueduct would result in dilation of the lateral and 3rd ventricles but compression of the 4th ventricle.

Answers 3 & 4: A tumor obstructing the foramina of Lucschka and Magendie would result in dilation of the lateral, 3rd, and 4th ventricles.

Bullet Summary:
Obstruction of the foramen of Monro would result in dilation of the lateral ventricles but compression of the 3rd and 4th ventricles.