Treatment of acoustic schwannomas associated with neurofibromatosis type 2

Abstract

Seventy-four patients with bilateral acoustic schwannomas (AS) registered in a nationwide study from 1986 to 1987 were studied. Kaplan-Meier analysis indicated that overall 10- and 20-year survival rates following diagnosis of NF2 patients were 67% and 38%, respectively. Early onset of the initial symptom significantly compromised survival. The AS volume was measured on CT or MRI and retrospectively studied in 27 patients (54 AS). In natural course, it was difficult to predict tumor growth. After treatments, clinical factors that significantly contributed to the tumor growth were younger symptom onset, association of intracranial meningioma, and larger tumor volume before the treatment. Regrowth rate was low after gamma-knife treatment and no recurrence after total tumor removal. Large AS in patients with earlier symptom onset or intracranial meningioma require total removal. During the past 5 years, 243 NF2 patients were followed in 78 institutes: 49 without treatment, 125 with surgical resection, 47 with radiosurgery, and 22 with resection and radiosurgery. Opinions about treatment of NF2 patients from 67 institutions were analyzed. Strategies for AS were divergent. Large AS or AS showing tumor growth on serial MRI require treatment. Total removal is desirable. Gamma-knife radiosurgery is effective for small AS. The first side of bilateral AS need early treatment. The second side of AS should be treated after hearing deterioration occurs in this side. With brainstem or cerebellar signs present, however, the second side requires early resection as well.