Hydrocephalus and Vestibular Schwannomas: Considerations about the Impact of Gamma Knife Radiosurgery

Abstract

Hydrocephalus may occur at various stages of the natural course of vestibular schwannoma and can also be diagnosed after the therapeutic procedure. The aim of the present study was to analyze the impact of Gamma Knife radiosurgery (GKR) on previously diagnosed hydrocephalus (group A patients) and to evaluate the incidence of de novo hydrocephalus after GKR (group B patients). We reviewed retrospectively our case material and the data from the literature. Among the first 1,000 vestibular schwannoma patients treated by GKR in our institution, 30 patients (3%) belonged to group A and 1% to group B. In both groups, hydrocephalus was more often associated with the following data: Elderly, large tumor, previous MS, NF2 disease and bilateral tumors. Cerebrospinal fluid (CSF) shunting system was needed in 25% of the group A and in all of the group B patients. In this latter group, CSF shunting was justified by poor clinical tolerance, and the mean interval between GKR and CSF shunting was 14.8 months (range: 4-31 months). These data suggest that GKR does not decompensate the majority of preexisting radiological hydrocephalus. De novo post-GKR hydrocephalus is of low incidence, comparable to the postoperative rate. Generally, it comes early after GKR and justifies CSF shunting. Thus, it may be postulated that in a small subgroup of patients, GKR may disturb the normal hydrodynamic pathway. Mechanisms of such event remain controversial.