Complications of fourth-ventricular shunts.

Fourth-ventricular shunting is commonly used to treat symptomatic posterior fossa cysts of the Dandy-Walker malformation and trapped fourth ventricle. Although the benefits of this procedure have been widely reported, there is a paucity of data on the pitfalls of posterior fossa shunting in the neurosurgical literature. During the 4-year period from July 1989 to June 1993, we placed fourth-ventricular shunts in 12 patients. Remarkably, 5 patients suffered complications related to posterior fossa catheter placement (42% rate). Three of these patients developed new cranial nerve dysfunction caused by direct injury to the floor of the fourth ventricle, 1 patient suffered an intracystic hemorrhage and acute shunt malfunction, and 1 patient had the catheter tip in the brainstem on postoperative studies without new neurological deficit. We conclude that placement of fourth-ventricular shunts can be fraught with complications which we believe is related to technique. We propose that altering the trajectory of the ventricular catheter from our usual midline technique to a more lateral position will lessen the chances for injury to the floor of the fourth ventricle. In this manner we hope to decrease our incidence of complications for this procedure.