Outlet fenestration for isolated fourth ventricle with and without an internal shunt

Conventional shunting of isolated fourth ventricle is notorious for leading to frequent and severe complications. We present four patients with isolat ed fourth ventricle who have been treated with open posterior fossa surgery together with either outlet fenestration alone or outlet fenestration and a fourth ventricle-spinal subarachnoid space (SSS) shunt. A survey of the r elevant literature did not yield any other case reports of fourth ventricle shunting to the SSS under such circumstances. This paper discusses the rea sons for choosing this mode of treatment. The main advantage of this techni que is that the catheter is inserted along the anatomical long axis of the fourth ventricle. This positioning lessens the possibility of irritating or penetrating the brain stem. Moreover, as a more physiological solution, th e shunt does not require a valve system. Because of these advantages, inter nal fourth ventricle-SSS shunting is proposed as a valid alternative to the "classic" fourth ventriculo-peritoneal shunt.