Gamma knife surgery for facial nerve schwannomas

Abstract

Radical resection of facial nerve schwannomas classically implies a high risk of severe facial palsy. Due to the rarity of facial palsy following Gamma Knife surgery (GKS) of vestibular schwannomas, functional evaluation after GKS in this specific group of patient appears rational. Clinical management due to the specificity and heterogeneity of this group of patients has required the development of an original classification of 4 anatomical subtypes presenting different clinical and surgical difficulties. Among 1,783 schwannomas of the cerebellopontine angle treated by GKS in Timone University Hospital between July 1992 and May 2003, 11 were diagnosed as originating from the facial nerve. Criteria for this diagnosis were: the involvement of the tympanic or mastoid segment of the facial nerve (9 patients); and/or preoperative observation of a facial nerve deficit that had occurred during previous microsurgery (2 patients). The rare occurrence of facial palsy after vestibular schwannoma radiosurgery, usually occurring within 18 months of treatment, has been considered only in the patients with more than 2 years of follow-up (9 patients). At last follow-up examination, no patients had developed a new facial palsy or experienced deterioration of a pre-existing facial palsy; 3 patients had improvement of a preoperative facial palsy. Ten of 11 tumors were stable, or decreased in size; in the remaining case, microsurgical resection of the tumor had been recommended due to the development of a cyst. This first study demonstrates that radiosurgery allows treatment of these patients while preserving normal motor facial function. Such an advantage should lead to the consideration of GKS as a first treatment option for small- to middle-sized facial nerve schwannomas.