Gamma Knife radiosurgery for facial nerve schwannomas: a multicenter study

Abstract

F acial nerve schwannomas (FNSs) are rare tumors accounting for 1.9% of all intracranial neuromas and 0.8% of intrapetrous tumors.1 FNS can arise from any segment of the facial nerve, starting at its origin in the cerebellopontine angle and extending to its extracranial components.2 While such neuromas can mimic the radiographic features of the more common vestibular schwannoma, patients with FNS typically present with signs and symptoms of facial nerve dysfunction.The optimal management strategy for FNS patients abbreviatioNs FNS = facial nerve schwannoma; GKRS = Gamma Knife radiosurgery; NAGKC = North American Gamma Knife Consortium; SRS = sterotactic radiosurgery. obJect Facial nerve schwannomas (FNSs) are rare intracranial tumors, and the optimal management of these tumors remains unclear. Resection can be undertaken, but the tumor's intimate association with the facial nerve makes resection with neurological preservation quite challenging. Stereotactic radiosurgery (SRS) has been used to treat FNSs, and this study evaluates the outcome of this approach. methods At 8 medical centers participating in the North American Gamma Knife Consortium (NAGKC), 42 patients undergoing SRS for an FNS were identified, and clinical and radiographic data were obtained for these cases. Males outnumbered females at a ratio of 1.2:1, and the patients' median age was 48 years (range 11-76 years). Prior resection was performed in 36% of cases. The mean tumor volume was 1.8 cm 3 , and a mean margin dose of 12.5 Gy (range 11-15 Gy) was delivered to the tumor. results At a median follow-up of 28 months, tumor control was achieved in 36 (90%) of the 40 patients with reliable radiographic follow-up. Actuarial tumor control was 97%, 97%, 97%, and 90% at 1, 2, 3, and 5 years postradiosurgery. Preoperative facial nerve function was preserved in 38 of 42 patients, with 60% of evaluable patients having HouseBrackmann scores of 1 or 2 at last follow-up. Treated patients with a House-Brackmann score of 1 to 3 were more likely to demonstrate this level of facial nerve function at last evaluation (OR 6.09, p = 0.006). Avoidance of temporary or permanent neurological symptoms was more likely to be achieved in patients who received a tumor margin dose of 12.5 Gy or less (log-rank test, p = 0.024) delivered to a tumor of ≤ 1 cm 3 in volume (log-rank test, p = 0.01). coNclusioNs Stereotactic radiosurgery resulted in tumor control and neurological preservation in most FNS patients. When the tumor is smaller and the patient exhibits favorable normal facial nerve function, SRS portends a better result. The authors believe that early, upfront SRS may be the treatment of choice for small FNSs, but it is an effective salvage treatment for residual/recurrent tumor that remain or progress after resection.

Management of Facial Nerve Schwannoma: A Multicenter Study of 50 Cases

“…Several publica-tions report that Gamma Knife surgery has good results in terms of control of growth and symptoms with a small rate of radiation toxicity. [17][18][19] There are no published data about the malignant transformation of a FNS after SRS. For large or growing tumors with favorable FNF (HB < III), the choice of treatment should be discussed with the patient.…”

Schwannoma of the Greater Superficial Petrosal Nerve: An Unusual Site for a Common Tumor

“…Stereotactic radiosurgery(SRS) was described in the management of facial nerve schwannomas by various authors. [20][21][22] However, specific literature on the use of SRS in GSPN schwannoma is not available, in view of the rarity of the condition. SRS is a feasible option in small facial nerve schwannoma and should be considered.…”

“…The facial nerve tumors treated by SRS have reported excellent results with tumor control in 90 to 100% of the patients with reliable radiographic follow-up. 20,21 Sheehan et al reported that the actuarial tumor control was 97%, 97%, 97%, and 90% at 1, 2, 3, and 5 years after radiosurgery. 21 Overall, patients with smaller tumor volumes, low grade (H&B) facial weakness, and patients with < 50 db hearing loss at presentation tend to do better in terms of preservation of nerve functions after Gamma Knife radiosurgery.…”

“…20,21 Sheehan et al reported that the actuarial tumor control was 97%, 97%, 97%, and 90% at 1, 2, 3, and 5 years after radiosurgery. 21 Overall, patients with smaller tumor volumes, low grade (H&B) facial weakness, and patients with < 50 db hearing loss at presentation tend to do better in terms of preservation of nerve functions after Gamma Knife radiosurgery. 21,22 Therefore, radiosurgery could be considered as the preferred line of management in small tumors, yielding better preservation of function.…”

Image-Guided Hypofractionated Radiosurgery of Large and Complex Brain Lesions

“…A key turning point in worldwide utilization of Gamma Knife radiosurgery (GKSRS) was its first North American installation at the University of Pittsburgh in 1987 [2]. Gradually and steadily, GKSRS has been demonstrated to be a highly successful modality in managing many benign and malignant indications [3][4][5][6][7][8][9]. However, due to the finite beam collimation size (maximum beam collimator diameter of 1.6-1.8 cm) and manual setups of individual patients, majority of the targets treated are relatively small lesions (e.g., <4 or 5 cm in maximum target dimension) and are generally treated in a single fraction [6,9].…”