Safety and Efficacy of Gamma Knife Radiosurgery for the Management of Koos Grade 4 Vestibular Schwannomas

Iorio-Morin C1, AlSubaie F, Mathieu D.

*Neurosurgery Division, Université de Sherbrooke, Centre Hospitalier Universitaire de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Quebec, Canada; ‡Saudi National Neuroscience Institute, Riyadh, Saudi Arabia.


Gamma Knife radiosurgery (GKRS) is commonly used in treating small vestibular schwannomas; however, its use for larger vestibular schwannomas is still controversial.


To assess the long-term safety and efficacy of treating eligible Koos grade 4 vestibular schwannomas with GKRS.


We conducted a single-center, retrospective evaluation of patient undergoing GKRS for Koos grade 4 vestibular schwannomas. We evaluated clinical, imaging, and treatment characteristics and assessed treatment outcome. Inclusion criteria were tumour size of ≥4 cm and follow-up of at least 6 months. Patients with neurofibromatosis type 2 were excluded. Primary outcomes measured were tumour control rate, hearing and facial function preservation rate, and complications. All possible factors were analyzed to assess clinical significance.


Sixty-eight patients met inclusion criteria. Median follow-up was 47 months (range, 6 to 125 months). Baseline hearing was serviceable in 60. Actuarial tumour control rates were 95% and 92% at 2 and 10 years, respectively. Actuarial serviceable hearing preservation rates were 89% and 49% at 2 and 5 years, respectively. Facial nerve preservation was 100%. Clinical complications included balance disturbance (11%), facial pain (10%), facial numbness (5%), and tinnitus (10%). Most complications were mild and transient. Hydrocephalus occurred in 3 patients, requiring ventriculoperitoneal shunt insertion. Larger tumour size was significantly associated with persisting symptoms post-treatment.


Patients with Koos grade 4 vestibular schwannomas and minimal symptoms can be treated safely and effectively with GKRS.

U.S. National Library of Medicine, National Institutes of Health