Endoscopic Treatment Strategy for a Disproportionately Large Communicating Fourth Ventricle: Case Series and Literature Review.

An isolated fourth ventricle (IFV) is characterized by fourth ventricular dilation due to obstruction of its inlet and outlet. A disproportionately large communicating fourth ventricle (DLCFV) is a rare subtype of IFV, characterized by dilation of the fourth ventricle, regardless of the size of the lateral ventricles, with no apparent obstruction of the cerebral aqueduct. To our knowledge, this is the first case series describing endoscopic diagnosis and treatment strategy for DLCFV. We retrospectively reviewed six cases of DLCFV in which endoscopic surgery was performed at our institution and affiliated facilities between June 2013 and March 2017. DLCFV was diagnosed using radiographic imaging and intraoperative endoscopy. We also conducted a PubMed search and included only original studies related to DLCFV treatment written in English in our review of the literature. Endoscopic third ventriculostomy (ETV) was performed in all patients. Additional endoscope-assisted placement of a fourth ventriculoperitoneal (VP) shunt was performed in two patients who could not be managed with ETV alone because of severe adhesion of the interpeduncular cistern due to subarachnoid hemorrhage (SAH). The patients' symptoms and the size of the fourth ventricle improved with surgical treatment, without complications. Endoscopic surgery for DLCFV appears to be a safe and effective treatment. Based on our treatment strategy, ETV is the first-line treatment for DLCFV. Endoscope-assisted placement of the fourth VP shunt can be treatment for severe adhesion of the interpeduncular cistern.