Management of seventh and eighth nerve involvement by cerebellopontine angle tumors.
Microsurgical techniques have made a significant contribution in the advancement of surgery. Since then, the field of neurosurgery has made great and rapid strides. Neurosurgeons now venture through the deep and delicate regions of the brain where they dared not venture only a few years ago. In particular, the morbidity and mortality of surgery in the CPA has seen a progressive decrease. This presentation deals with 200 consecutive tumors in the CPA operated on using microsurgical techniques during the last 6 years. One hundred sixty-seven (83.5%) of them were acoustic neuromas (which included 12 patients with bilateral tumors). Of the remaining 33, there were 21 meningiomas, 10 epidermoids, and 2 angioblastomas. Preoperative investigation has been aimed at arriving at a diagnosis which is as exact as possible in order to plan the operative strategy. All patients, ranging in age from 16 to 84, have been operated upon in the lounging position (with the necessary precautions) through a unilateral suboccipital craniectomy. The basic surgical technique, irrespective of the tumor, is to decompress it from within in order to relieve its tension and pressure on surrounding nerves, vessels, and the brain stem. The structures which are only compressed are spontaneously relieved of compression. This helps define their full anatomic course. Having been identified, they are protected from damage. The most adherent points between tumor and nerves are recognized and handled last under direct vision when there is sufficient space to allow manipulation of the tumor. In the rare event of the facial nerve being interrupted, nerve graft procedures are attempted during the same operation. Our experience with the technique of intracranial-intratemporal facial nerve grafting has yielded excellent results. The cochlear nerve lacks a Schwann cell cover in the CPA and is more prone to being affected, either by tumor processes or surgical manipulation. Of our 167 acoustic nerve tumors, 60% were larger than 3 cm in diameter. The two important factors with regard to predicting the preservation of the seventh and eighth cranial nerves are tumor size (less than 3 cm) and preoperative hearing loss (less than 40 dB). The preservation of facial nerve function after tumor removal was achieved in 87.8% of patients. The facial nerve was preserved in all patients with other tumors. With regard to hearing ability the overall result of preservation of function was achieved in 27.6%. However, when a low hearing loss (less than 40 dB) and small tumor size (less than 3 cm) are taken into account, the preservation was as high as 58%.(ABSTRACT TRUNCATED AT 400 WORDS)