P03.07 Radiosurgical managementof trigeminal schwannomas: A single center experience

Abstract BACKGROUND Trigeminal schwannomas are a rare form of intracranial schwannomas. They can occur anywhere along the track of the trigeminal nerve, including the middle, posterior fossa or both. It can even extend extracranially. The variability of its location and extent, in addition to its close proximity to critical neurovascular structures makes surgical intervention challenging. Taking from the success of treating vestibular schwannomas with stereotactic radiosurgery, it has been used as an alternative to surgery for the treatment of trigeminal schwannomas. Because these tumors are rare more clinical evidence is required to assess the response of these tumors to stereotactic radiosurgery.The aim of this study was to evaluate the efficacy and complications associated with treatment of the trigeminal schwannomas by gamma knife radiosurgery. MATERIAL AND METHODS The study included 51 patients with trigeminal schwannomas not associated with NF2, treated by Leksell gamma knife. There were 25 males and 26 females. The mean age at presentation was 43 years. The patients underwent a total of 58 gamma knife sessions (44 single and 7 volume-staged sessions). Eight patients had previous surgery. The tumor nature was solid in 46, cystic in 3 and mixed in 2 patients. The mean target volume was 8.5 cc (0.6–30.7 cc) with the mean overall tumor volume being 9.6 cc (0.6–31.1 cc). The mean prescription dose was 12 Gy. RESULTS The mean follow up was 57 months (12–152 months). The tumor shrank in 23 (45%) patients and remained stable in 25 (49%). Tumor progressions occurred in 3 (6%) patients. The tumor control rate was 92%. The progression-free survival at 5,7 and 10 years was 95%, 88% and 79%, respectively. Clinical improvement occurred in 27 (53%) patients and was significantly associated with tumor shrinkage (p 0.03). Twenty patients (39%) remained clinically unchanged. Adverse radiation events occurred in 7 patients and were significantly associated with target and overall tumor volume (p 0.028 and 0.004). CONCLUSION Gamma knife radiosurgery appears to be an effective and safe adjuvant and primary treatment modality for trigeminal schwannomas. Large tumors should be debulked first before radiosurgery, when feasible.