We treated recurrent hydrocephalus in a previously shunted patient by neuroendoscopic third ventriculostomy. A tear was noted in the septum pellucidum. As the foramen of Monro was found to be occluded, we first fenestrated the floor of the lateral ventricle and then performed third ventriculostomy through the fenestration. A tough membrane believed to be Liliequist's membrane isolated the space immediately beneath floor of the third ventricle from the cistern below. Cerebrospinal fluid pulsation appeared after fenestration of this membrane. These obstructions presumably resulted from congenital and/or inflammatory causes. In cases such as this, successful neuroendoscopic third ventriculostomy presents a challenge to surgical judgment.
Foramen of Monro - Liliequist's Membrane - Neuroendoscopic Third Ventriculostomy - Occlusion
