Gamma Knife Radiosurgery for Facial nerve schwannomasNoriko Tamura1, Mothiro Hayashi2, Yoshikazu Okada21Tokyo, Japan 2Department of Neurosurgery, Tokyo Womenâ€™s Medical University, Tokyo, Japan Keywords: facial nerve function, schwannoma, cranial nerve, gamma knife, outcome
Surgical resection of facial nerve schwannomas (FNS) results a high risk of severe facial nerve palsy.
Our purpose was to evaluate functional preservation and tumor control after Gamma knife radiosurgery (GKRS) .
Between January 2002 and May 2011, 6 patients with FNS were treated by GKRS and followed in our institute.
Diagnosis of facial nerve schwannoma was based on MRI. Clinical evaluation on House-Brackmann grade. Classified of two types tumor location for evaluate facial and chocleovestibular function after GKRS.(Type I: tumor develops in geniculate ganglion to tympanic, vertical ,mastoid segment of the facila canal, Type II; tumor develops in the middle fossa or internal auditory canal, cerebello pontine angle cistern.) Three patients were type I and 3 patients were type II .
Mean follow up periods were 37 months ( 6-72 months).No patients had a previous resection. The radiosurgery dose was 11 or 12 Gy at 50% isodose. Three tumors had regressed and 3 were unchanged in size at latest MRI. Transient facial nerve worsening were observed 2 patients in type I tumor. All patients maintained their hearing after GKRS.
This was a retrospective study.
Although longer follow up period is necessary, GKRS is shown to be a safe and effective treatment of FNS.
Treatment decisions should be based on initial facial function, tumor volume growth
rate, and informed patient consent especially for type I schwannomas. Project Roles:
N. Tamura (), M. Hayashi (), Y. Okada ()