Acoustic Neurinoma and Its Treatment Using the Leksell γ-Knife as a Primary or Secondary Treatment


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Abstract

Over 4 years (1992–1996) we have treated 122 patients with unilateral acoustic neurinoma using the Leksell γ-knife; 121 patients had a follow-up of 2–48 months (median 24 months). Tumor volume was 0.1–17.8 cm3 (median 2.9 cm3); dose to the tumor margin was 10–17.5 Gy (median 12 Gy) delivered on 40–80% isodose (median 50%). A decrease in the tumor volume was observed in 41.3% of patients, the tumor volume was unchanged in 54.6%, and an increase in the tumor despite radio-surgery was observed in 4.1%. Hearing loss was detected in 17.4% of patients, and 3% of patients gained useful hearing after radiosurgery. The overall risk of the method is 4.3% of hearing loss. Weakness of the facial nerve was observed in 1.9% of patients; normalization of the weakness, which was present before radiosurgery, was observed in 6.3% of patients. The overall risk of facial weakness is 1% for γ-knife radiosurgery. Impairment of trigeminal neuropathy was observed in 5% of patients and improvement in 31%. Impairment of vertigo was observed in 5.8% of patients and improvement in 46%. Leksell γ-knife radiosurgery was the primary treatment in 97 patients (80.7%); microsurgical resection preceded radiosurgery in 24 patients (19.8%). Hearing loss and neuropathy of facial and trigeminal nerves before γ-knife radiosurgery were significantly more frequent in the group of patients with previous microsurgical resection than in the group with γ-knife radiosurgery as the primary treatment. After radiosurgery there was no significant difference in impairment or improvement of hearing, facial and trigeminal nerve neuropathy, and vertigo and imbalance for the groups of patients with previous microsurgery or primary γ-knife treatment. After γ-knife radio-surgery neuropathy of facial and trigeminal nerves in the group of patients with previous microsurgery was significantly worse.

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