MANAGEMENT OF 1000 VESTIBULAR SCHWANNOMAS (ACOUSTIC NEUROMAS) - HEARING FUNCTION IN 1000 TUMOR RESECTIONS

OBJECTIVE: The realistic chances of hearing preservation and the compa rability of international results on hearing preservation in complete microsurgical vestibular schwannoma resections were the focus of this study in a large patient population treated by uniform principles. MET HODS: One thousand vestibular schwannomas were operated on at Nordstad t Neurosurgical Department, from 1978 to 1993, by the senior surgeon ( MS). There were 1000 tumors in 962 patients, i.e., 880 patients with u nilateral tumors and 82 patients operated on for bilateral tumors in n eurofibromatosis-2 (120 cases). Preservation of the cochlear nerve was attempted whenever possible. The audiometric data were analyzed by th e Nordstadt classification system and graded in steps of 30 dB by audi ometry and in steps of 10 to 30% by speech discrimination; for compara bility, the data were also evaluated by the criteria of Gardner, Shelt on, and House, and they were assessed in relation to the Hannover tumo r extension grading system. RESULTS: Anatomic cochlear nerve preservat ion was achieved in 682 of 1000 cases (68%), as well as in some preope ratively deaf patients, a very few of whom regained some hearing. Of a total of 732 cases with some preoperative hearing, anatomic cochlear nerve preservation was achieved in 580 cases (79%) and functional coch lear nerve preservation in 289 (39.5%); analysis over time revealed an actual preservation rate of 47% in the most recent 200 cases. Specifi c factors, such as gender, tumor extension, preoperative hearing quali ty, and symptom duration, were investigated for their predictive value for hearing preservation. Male gender, small to medium tumor size (ma inly extending within the cerebellopontine cistern; Classes T2 and T3) , good to moderate hearing (up to 40-dB loss), and short duration of h ypoacusis (<1.5 yr) or of vestibular disturbances (<0.7 yr) were advan tageous factors, with chances of hearing preservation between 47 and 8 8%. CONCLUSION: Functional cochlear nerve preservation in complete mic rosurgical resection should belong to the contemporary standard of tre atment goals.