Anatomical variants in the floor of the third ventricle; implications for endoscopic third ventriculostomy

Longstanding hydrocephalus and raised intracranial pressure can lead to unu sual anatomical variants in the floor of the third ventricle, which may be important when performing endoscopic third ventriculostomy. Two middle aged patients with symptomatic longstanding hydrocephalus had scans that showed ventricular hydrocephalus, an empty sella, and a dilated infundibular rece ss which herniated into the sella turcica. Endoscopic third ventriculostomy confirmed that instead of the tuber cinerum and infundibular recess, the a nterior inferior floor of the third ventricle was hanging down ventral to t he pens into the sellar floor. Third ventriculostomy to the prepontine cist ern was made on the dorsal wall of the dilated infundibular recess to the a rea surrounded by the dorsum sellae, the basilar artery trunk, and the left superior cerebellar artery, with good symptomatic control. Association of the empty sella and persistence of the infundibular recess must be carefull y evaluated by MRI before attempting endoscopic third ventriculostomy. Hern iation of the anterior inferior floor of the third ventricle into the empty sella can lead to loss of anatomical landmarks that require special attent ion during third ventriculostomy.