Hydrocephalus Due to Idiopathic Fourth Ventricle Outflow Obstruction.

The fourth ventricle outlet obstruction (FVOO) is a rare but well-established cause of obstructive tetra-ventricular hydrocephalus, characterizing with dilatation or large cerebrospinal fluid collection of the foramina of Magendie and Luschka. In children, it is usually the consequence of posterior cerebral fossa malformations; while in adult, the occlusion is rather acquired than congenital, mostly linked to an inflammatory process, intraventricular hemorrhage, head trauma, brain tumors or Arnold-Chiari malformation. However, idiopathic FVOO is extremely rare, and only 6 such cases have been reported in the English literature. Hereby, we described an extraordinarily rare case of idiopathic FVOO in a 15-year-old patient successfully treated with direct microsurgical excision of the obstruction membrane. Furthermore, the clinical characteristics and treatment for this rare disease were investigated and reviewed.