Unusual intraventricular herniation of the suprasellar arachnoid cyst and its successful endoscopic management.

A child with a benign intrinsic tectal tumor and obstructive hydrocephalus developed a huge intraventricular cystic lesion following insertion of a shunt, which was complicated by a subdural-subarachnoid bleeding. The lesion was identified to be an entrapped chiasmatic cistern, which disrupted the septum pellucidum in front of the third ventricle and filled gradually the anterior horn of the lateral ventricle. The condition was successfully treated endoscopically by fenestration of the cyst and a third ventriculostomy. Probable mechanisms of such unusual cyst formation and general management strategies in patients with obstructive hydrocephalus are discussed.