Facial nerve preservation in stereotactic radiosurgery of tumors of the cerebellopontine cistern

Abstract

Introduction. Surgery has traditionally remained the main treatment for tumors of the cerebellopontine cistern but is associated with high risks of dysfunction of the cranial nerves. Radiosurgery is usually performed both as an adjuvant treatment and as an independent option.The study objective is to assess the safety of routine use of radiosurgery to preserve facial nerve function in the treatment of tumors of different origins located in the cerebellopontine cistern.Materials and methods. Since March 2018 to March 2020 there were 145 patients with tumors of cerebellopontine cistern (CPC) at the Center for High-Precision Radiology. Vestibilar schwannomas were detected in 116 (80 %) patients, in 37 cases - relapses or remains after surgery. The 22 patients had meningiomas, 6 after open surgery (WHO I). Trigeminal schwannomas - in 3 patients, facial schwannomas - in 2, jugular schwannomas - in 1 and metastasis of prostate cancer - in 1. 31 patients had facial paresis of different degrees after previous surgery. Among non-operated patients, facial paresis before radiosurgery was observed in only 1 patient. Radiosurgery was performed using the Leksell Gamma Knife Perfexion, the mean marginal dose was 12.2 Gy (11-15 Gy), the mean tumor volume was 3.98 cm3 (0.06-17.47 cm3).Results. Follow-up was performed in 85 patients. The mean follow-up was 359.3 days (91-776), the median follow-up was 367 days. Reduction of the tumor volume was detected in 27 patients, stabilization of the process in 15. The average decrease was 23.9 % (95 % CI 16.8-31.0 %). Transient postirradiation increase was observed in 30 patients only in the group of schwannomas and mean tumor volume increase was 53.7 % (95 % CI 38.5-68.9 %). In patients with previous surgery there were not cases of decline or regression facial paresis. Among patients who had not been operated on before radiosurgery, only in 1 case was the development of facial paresis (House-Brackman III) 5 months after irradiation, which amounted to 1.8 %. It should be especially noted that facial nerve function remained unchanged (House-Brackman I) in both patients with facial schwannomas. Also, not a single case of hemifacial spasm was identified.Conclusion. Radiosurgery of CPC tumors with a marginal dose from 12 to 15 Gy has a high degree of safety in relation to the facial nerve. This makes it possible to justify radiosurgery as alternative to traditional neurosurgical interventions.