AIM: To evaluate clinical and radiological outcome in surgically treated Koos 4 vestibular schwannomas.

MATERIAL and METHODS: Volumetric analysis of the tumour volumes before surgery, after surgery (before radiation), and at follow-up time-points after radiation was performed. Clinical data on facial nerve function and complications were collected. Approximately 6 months after surgery, all patients were treated with a single fraction of stereotactic radiosurgery using the gamma knife radiosurgery with a mean marginal dose of 12.9 Gy to the residual tumour volume.

RESULTS: Mean tumour volume was 11.64 cm3 which was reduced to a mean volume of 4.17 cm3 after partial resection. After a mean follow-up of 100 months, residual tumour showed a decrease in volume in 20 patients, stable disease in one patient and two patients showed progressive tumour volume requiring a second operation in one patient. Facial nerve function was preserved in all patients. One patient suffered from a trigeminal neuralgia after radiation.

CONCLUSION: Planned partial resection followed by radiation for patients with Koos 4 vestibular schwannoma is an effective strategy to preserve facial nerve function and achieve tumour control. Residual tumours after planned partial resection showed a mean decrease in volume of 50% at the last follow-up time point.