Hearing preservation in cerebellopontine angle tumor surgery: the NYU experience 1974-1991

Between 1974 and 1991, hearing preservation surgery was attempted on 161 of 476 patients with a variety of cerebellopontine (CPA) tumors, at New York University School of Medicine. This included 146 unilateral acoustic neuromas, seven meningiomas, and six cases of neurofibromatosis. The suboccipital/retrosigmoid approach was used almost exclusively. The cochlear nerve was anatomically preserved in 131 cases, 32 percent of whom had successful hearing preservation. In the most successful group, hearing was preserved in 9 of 12 patients (75%). Success was defined as a postoperative pure-tone average (PTA) or speech reception threshold (SRT) of no more than 50 dB, and a speech discrimination score (SDS) of at least 50 percent. In those patients whose preoperative hearing was worse that this, success was based on a loss of no more than 10 dB in PTA or SRT, and 10 percent in SDS. Success was dependent mostly on extracanalicular (EC) tumor size, with the smallest tumors yielding the best results. When controlled for EC size, intracanalicular size and preoperative hearing were statistically significant variables. Origin from the superior vestibular nerve was also a favorable prognostic indicator. The character and duration of hearing loss, the patient's age, and the histology of the tumor did not have prognostic value. Auditory monitoring with either auditory brainstem response (ABR) or direct eighth nerve electrodes did not have a significant impact on success. Complications were somewhat increased by attempted hearing preservation. Facial nerve function was type I or II in 93 percent of patients. Cerebrospinal fluid leaks occurred in 15 percent of cases, but only 4 percent required surgical repair. There was one death, a patient with a 2.5-cm tumor. Early in the series, when a classic long vertical nuchal incision was used, headache and neck pain were common.