Ventricular diverticula in obstructive hydrocephalus secondary to tumor growth

OBJECTIVE: The association of ventricular diverticula with intra- and paraventricular tumors causing obstructive hydrocephalus has rarely been reported. METHODS: Records and imaging findings for 57 patients with obstructive hydrocephalus caused by tumors who were treated at our institution were reviewed for the presence of ventricular diverticula. For the anatomic study of ventricular diverticula, data were collected from five cadaveric heads. RESULTS: Ventricular diverticula were identified on magnetic resonance imaging scans in five cases. Diverticula were similarly located in the quadrigeminal cistern but originated from the medial wall of the atrium of the lateral ventricle in three cases and from the superior portion of the fourth ventricle in two cases. Regression of diverticula occurred in all cases after either insertion of a shunt or removal of the obstructing tumor. The cadaveric study suggested that the choroidal fissure and the rostral portion of the superior medullary velum might be the origins of diverticula from the atrium and from the superior portion of the fourth ventricle, respectively. CONCLUSION: Ventricular diverticula should be distinguished from other cystic lesions in the quadrigeminal region. Detection of an ostium of a diverticulum or communication between the cyst and the ventricular system is important for diagnosis.