✓ The authors describe an acute facial and acoustic neuropathy following gamma knife surgery (GKS) for vestibular schwannoma (VS). This 39-year-old woman presenting with tinnitus underwent GKS for a small right-sided intracanalicular VS, receiving a maximal dose of 26 Gy and a tumor margin dose of 13 Gy to the 50% isodose line. Thirty-six hours following treatment she presented with nausea, vomiting, vertigo, diminished hearing, and a House—Brackmann Grade III facial palsy. She was started on intravenous glucocorticosteroid agents, and over the course of 2 weeks her facial function returned to House—Brackmann Grade I. Unfortunately, her hearing loss persisted. A magnetic resonance (MR) image obtained at the time of initial deterioration demonstrated a significant decrease in tumor enhancement but no change in tumor size or peritumoral edema. Subsequently, the patient experienced severe hemifacial spasms, which persisted for a period of 3 weeks and then progressed to a House—Brackmann Grade V facial palsy. During the next 3 months, the patient was treated with steroids and in time her facial function and hearing returned to baseline levels. Results of MR imaging revealed transient enlargement (3 mm) of the tumor, which subsequently returned to its baseline size. This change corresponded to the tumor volume increase from 270 to 336 mm3. The patient remains radiologically and neurologically stable at 10 months posttreatment.
This is the first detailed report of acute facial and vestibulocochlear neurotoxicity following GKS for VS that improved with time. In addition, MR imaging findings were indicative of early neurotoxic changes. A review of possible risk factors and explanations of causative mechanisms is provided.