Gamma Knife as an Alternative Treatment for Large Acoustic Neuromas

Purpose: For patients with large vestibular schwannomas (VS) three major treatment options are available: microsurgery, stereotactic radiation, and combined treatment. For the present, microsurgery represents the standard treatment method for large VS, but high-risk patients facing additional cardiopulmonary problems are alternatively offered stereotactic radiation. Combination of microsurgery and stereotactic radiation is suggested mostly for tumors that can be only partly removed. The goal of this investigation was to look upon the neurological development of 100 patients that had been treated for large VS.

Patients and Methods: Seventeen patients were excluded or lost to follow-up. We reviewed and compared the remaining 83 patients that had been treated for large VS, the tumors having a diameter of ≥ 2.5 cm. Twenty-six of them underwent microsurgery, 35 patients were treated solely by gamma knife radiosurgery, and 22 patients received both open surgery and gamma knife. The mean age of all patients was 54 years, while the mean age of the patients treated by gamma knife was found to be higher than in the other two groups (60.34 yrs). Gender distribution did not differ in the three groups. All gamma knife procedures were performed under local anesthesia. The mean duration of follow-up was 30 months, ranging from 6 to 84 months.

Results: Development of facial palsy with clinical relevance (House-Brackmann ≥ III) was significantly higher in the microsurgical (23%) group than after radiosurgical procedure (0%) or in the combined group (0%), respectively. Reduction of tumor size was evident in all three groups but more impressive after microsurgery and combined therapy than after gamma knife. Imbalance and mild trigeminal pain that appeared after gamma knife were transitory or showed continuous improvement during follow-up.

Conclusion: Microsurgery of large VS, compared to gamma knife radiosurgery, is associated with a higher rate of facial nerve palsy and other complications, like CSF leakage or infection. Treatment of large VS solely using the gamma knife alternative provides the possibility of controlling tumor growth and achieving decompression of the region with low risk for severe complications. Combined treatment of open surgery for tumor reduction, followed by gamma knife radiosurgery of tumor remnants, is found to be a successful strategy in reducing complications when dealing with large VS.