γ-knife therapy in acoustic neuroma

Summary

During 1992–95 79 patients suffering from acoustic neuromas were treated by radiosurgery at the Department of Neurosurgery of the University Medical School at Graz. Fifty-one patients underwent γ-knife treatment as primary therapy, 28 patients after neurosurgical operation because of remaining or recurrent tumour. The tumour diameter ranged from 5.3 to 37.7 mm and patient follow-up was 3–6 years. In all patients contrast-enhanced CT (until 1993) or MRI was performed, with the stereotactic head-frame applied to determine the target. The total central tumour dose varied from 14 to 50 Gy, the total peripheral dose ranged from 9 to 18 Gy, respective to the 30–70% isodose. Tumour shrinkage was seen in 10.1% of the neuromas and 57.0% showed variable changes in morphology, due to a partial necrosis. There was no increase in tumour size during the study. The overall hearing preservation rate was approximately 85%. Seven patients became deaf after radiosurgery, six patients (7.6%) developed facial neuropathies after stereotactic treatment and two patients (2.5%) trigeminal symptoms. Three patients developed a post-therapeutic perifocal oedema, two of them asymptomatic, the other one with neurological signs, including vertigo, nausea and dizziness. All patients returned to their preoperative function level within a couple of days. Stereotactic radiosurgery using the Leksell γ-knife is a safe, non-invasive therapy for acoustic neuromas and is a good alternative to microsurgery in cases of inoperable patients and those who refused surgery. For recurrent or partially removed tumours, radiosurgery seems to be the therapy of choice.

Key Words:

• stereotactic radiosurgery
• gamma knife
• acoustic neuroma
• vestibular schwannoma