A subtotal resection through the translabyrinthine approach should be used in the treatment of large symptomatic acoustic neuromas in patients over the age of 65. This approach will consistently relieve the patient's symptoms of brain stem compression, reduce postoperative morbidity and complications, and preserve facial nerve function. In the elderly, after subtotal resection, the remaining tumor in 80% of cases appears to remain dormant during the average six year follow‐up (1‐16 year range). Eighty percent of acoustic neuromas not operated upon, appear to grow at a slow rate (0.2 cm/yr) while 20% grow at a fast rate (1 cm/yr). Patients over the age of 65 with small acoustic neuromas do not need surgical intervention. Yearly CT scanning is recommended to determine the growth rate of the acoustic neuroma. A conservative approach should be used in the treatment of all acoustic neuromas in the elderly.

Since the advent of brainstem auditory evoked response audiometry and computerized tomography, small acoustic neuromas are more frequently found. Often the patient has serviceable hearing, which we would like to preserve during complete tumor removal. Since 1978, sixteen patients with acoustic neuromas have been operated upon through the retrosigmoid suboccipital approach, with the goal of hearing preservation. In 1983, we began using intraoperative direct eighth nerve monitoring, which produced a rapid assessment of cochlear nerve function during the excision of small acoustic neuromas. The tumors varied in size from intracanalicular lesions to one lesion with a 3.0 cm protrusion medial to the porus acousticus. In eight of sixteen cases, intraoperative monitoring was used, and in four of the patients hearing was preserved. In eight cases, intraoperative monitoring was not used, and hearing was preserved in only two patients. The overall success rate--in total tumor removal with hearing preservation--was 37%. Hearing was preserved in six of eight patients who had tumors which measured less than 1.5 cm. In this group of cases, two of the patients had a Class I good hearing result (PTA 0 to 30 dB and 70 to 100% discrimination), one patient had Class III nonserviceable hearing, (PTA 65 to 75 dB and 25 to 45% discrimination), and three patients had Class IV poor hearing, (PTA 80 to 100 dB and 0 to 20% discrimination). We found that continuous monitoring of direct eighth-nerve-evoked action potentials were extremely valuable and rapidly indicated reversible cochlear nerve trauma.

This report presents the results of 210 cases over a 10-year period using PORPs, TORPs, and notched incus homografts (NIH), for ossicular reconstruction in chronic ear surgery. There were 192 adults and 18 children. The surgical technique utilized temporalis fascia in an underlay technique with canal skin covering the outer surface of the fascia. Intact canal wall mastoid-tympanoplasty, as a one-stage procedure, was used for most cases. Homograft nasal cartilage was placed between the Plasti-Pore prosthesis and the graft. Notched incus homografts were prepared prior to surgery and stored in 4% formalin. There were 149 mastoid-tympanoplasties and 61 tympanoplasties performed. Revision of our cases was performed in 16.6%. Within 3 months of surgery, 86% of adults, and 44% (8/18) of children had dry, healed ears free of disease. The graft take rate was 96%. In adults, a total of 99 NIH, 50 TORPs, and 43 PORPs were implanted. In adults, the closure of the air-bone gap to 20 dB or less occurred in 58% using TORPs, 67% using PORPs, 76% using NIH-Partial replacement, and 20% using NIH-Total replacement. Excluding the cases that failed for reasons other than conductive hearing loss, the results improved to 69% for TORPs, 77% for PORPs, 77% for NIH-P, and 27% for NIH-T. In adults, the extrusion rate was 5.5% for Plasti-Pore and 3% for NIH. In children, the extrusion rate was 17% for Plasti-Pore prostheses. From this study, it appears that PORPs and TORPs with homograft nasal cartilage are satisfactory prostheses for chronic ear surgery in adults. In children, Plasti-Pore prostheses should be avoided unless the ear is healed, aerated, and stable. NIHs are good prostheses when the stapes is intact, but they are inferior to the TORP when placed on the footplate. Also, the NIH requires preparation prior to surgery and may be difficult to obtain. We plan to continue using PORPs and TORPs in chronic ear surgery until a better technique is found, or the complication rate becomes unacceptable.

The cochlear and vestibular nerves rotate 90 degrees from the inner ear to the brain stem. Most of the rotation occurs within the internal auditory canal (IAC); only minimal rotation occurs in the cerebellopontine (CP) angle. At the labyrinthine end of the IAC, the cochlear nerve--which at first lies anterior to the inferior vestibular nerve (saccular nerve)--rapidly fuses with the inferior vestibular nerve. It then rotates to become inferior as the nerves leave the porus acousticus. The cochleovestibular (C-V) cleavage plane lies in a superior-inferior direction in the lateral IAC and rotates to become anterior-posterior in the CP angle. In 25% of patients in whom no C-V cleavage plane can be seen, it is not possible to completely transect all vestibular fibers. The surgical implications are that the most complete vestibular neurectomy can be done only in the lateral IAC, the cochlear and inferior vestibular nerves, because of their intimate association, should not be separated in the mid-IAC, in order to prevent damage to the cochlear nerve, and to create a complete denervation of the vestibular labyrinth, only the posterior ampullary nerve along with the superior vestibular nerve should be transected.

We have used retrolabyrinthine vestibular neurectomy in 36 of 49 cases as the primary surgical procedure to relieve vertigo. Most of the patients (46 of 49) had Meniere's disease. Results indicate that 71% (35 of 49) of the patients had no vertigo after the operation, while 22% (11 of 49) had much improvement. Hearing was maintained within 20 dB of the preoperative level in 78% (38 of 49) of the patients. During surgery in the last 23 patients, direct nerve potentials were recorded from the middle ear promontory and the intracranial cochlear nerve. Brain stem auditory evoked responses were simultaneously recorded in the last 10 patients. It appears that the intraoperative direct cochlear nerve potentials can be used as a sensitive monitor of trauma to the cochlear nerve during and after vestibular neurectomy. If the latency of the eighth nerve action potential changes less than 0.3 msec and the waveform does not change after vestibular neurectomy, there is an excellent chance that hearing at 1 month after surgery will be within 15 dB of the level before surgery. The retrolabyrinthine vestibular neurectomy has replaced the middle fossa vestibular neurectomy and the endolymphatic subarachnoid shunt procedure in our clinic.