Hearing preservation after gamma knife radiosurgery for vestibular schwannomas presenting with high-level hearing.

OBJECTIVE: The aim of this study was to evaluate long-term hearing preservation after gamma knife radiosurgery (GKS) for vestibular schwannomas in patients with initially normal or subnormal hearing (Gardner-Robertson Class 1) and to determine the predictive factors for functional hearing preservation. METHODS: Since July 1992, more than 2053 vestibular schwannomas have been treated by GKS and followed at the Timone University Hospital, Marseille. A minimum of 3 years of follow-up (range, 3-11 years; median, 48 months) is available for 74 patients (without neurofibromatosis Type 2 or previous surgery) with Gardner-Robertson Class 1 hearing. RESULTS: The average age of the patients was 47.5 years (range, 17-76 years). The number of tumors in Koos Stage I was 8, the average number in Stage II was 21, the average number in Stage III was 43, and the average number in Stage IV was 2. The median number of isocenters was 8 (range, 2-45), and the median marginal dose was 12 Gy (range, 9-13 Gy). At the time of the last follow-up evaluation, 78.4% of the patients had preserved functional hearing. Tumor control was achieved in 93% of the cases. The probability of preserving functional hearing was higher in patients who had an initial symptom other than hearing decrease (91.1%), in patients younger than 50 years (83.7%), and in those treated with a dose to the cochlea of less than 4 Gy (90.9%). CONCLUSION: This study shows that the probability of preserving functional hearing in the long term after GKS for patients presenting with unilateral vestibular schwannomas is very high. The positive predictive factors appear to be young age, an initial symptom other than hearing decrease, and a low dose to the cochlea.

Gamma knife surgery for facial nerve schwannomas.

OBJECTIVE: Radical resection of facial nerve schwannomas classically implies a high risk of severe facial palsy. Owing to the rarity of facial palsy after gamma knife surgery (GKS) of vestibular schwannomas, functional evaluation after GKS seems rational in this specific group of patients. To our knowledge, no previous similar evaluation exists in the literature. METHODS: Of 1783 schwannomas of the cerebellopontine angles treated by GKS at 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 (n = 9) and/or preoperative observation of a facial nerve deficit that had occurred during previous microsurgery (two patients). The rare occurrence of facial palsy after vestibular schwannoma radiosurgery, usually within 18 months of treatment, has been considered only in the patients with more than 2 years of follow-up (n = 9). RESULTS: Six of these patients experienced a previous spontaneous facial palsy on one (n = 4) or several occasions (n = 2). A normal motor facial function was observed in only three patients before GKS (House-Brackmann Grade II in six patients, Grade III in one patient, Grade IV in one patient). The median follow-up period was 39 months (range, 18-84 mo). At the time of the last follow-up examination, no patients had developed a new facial palsy or experienced deterioration of a preexisting facial palsy and three patients had improvement of a preoperative facial palsy. Ten out of the 11 tumors are stable or decreased in size; in the other, a microsurgical resection of the tumor had been recommended owing to the development of a cyst. Clinical management owing to the specificity and heterogeneity of this group of patients has required the development of an original classification of four anatomic subtypes presenting different clinical and surgical difficulties. CONCLUSION: 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 medium-size facial nerve schwannomas.