Lateral ventricular diverticulum extending into supracerebellar cistern from unilateral obstruction of the foramen of monro in a neonate.

A ventricular diverticulum is usually found in patients with long-standing severe obstructive hydrocephalus that may extend into the supracerebellar cistern. The route involved in the supracerebellar extension of the ventricular diverticulum is believed to originate through the tela choroidea of the temporal choroid plexus or of the antral choroid plexus. The authors report a 4-week-old girl with hydrocephalus as a result of unilateral obstruction of the foramen of Monro, which dilated the right ventricle and displaced the midline to the left side, collapsing the contralateral lateral ventricle. The dilated lateral ventricular diverticulum herniated to the supracerebellar cistern in the posterior fossa that compressed the cerebellum inferiorly. She was treated successfully by a ventriculoperitoneal shunt, resulting in a marked reduction of the ventricle and diverticulum on the follow-up computed tomography and magnetic resonance imaging. We reviewed the literature for the supracerebellar extension route of ventricular diverticulum and suggest that the medial choroidal fissure in the antrum and the velum interpositum may be important anatomical structures for the extension of the lateral ventricular diverticulum into the supracerebellar cistern.