third ventriculostomy /ventrik′yəlos″təmē/ [L, tertius, three, ventriculus, little belly; Gk, stoma, mouth] , a surgical procedure for draining cerebrospinal fluid into the cisterna chiasmatis of the subarachnoid space in hydrocephalus, usually in the newborn. The procedure is not commonly performed and is used chiefly when the cisterna magna is not available for ventriculocisternostomy. The third ventriculostomy makes an opening on the anterior wall of the floor of the third ventricle into the interpeduncular cistern and is performed to correct an obstructive type of hydrocephalus.
