The treatment of acoustic neuroma and Menière's disease in the same patient.

Although total excision is accepted as the standard of care in the treatment of acoustic neuromas, for the elderly patient this approach is modified. Small tumors which cause only eighth nerve symptoms of hearing loss and tinnitus can be followed radiologically while larger tumors with brain stem compression may be subtotally excised through the translabyrinthine route. Our standard treatment for Menière's disease--that is refractory to medical management--has been vestibular nerve section through a retrolabyrinthine approach. In the event of bilateral Menière's disease or Menière's disease in an only hearing ear, treatment with low-dose intramuscular injections of streptomycin sulfate is preferred. Two elderly patients are discussed, each of whom has an acoustic neuroma in one ear and Menière's disease in the other. These patients' histories, diagnostic evaluations, treatment rationale, and follow-up data are presented to illustrate the decision-making process and the management of complicated and unusual cases.

The unrecognized rotation of the vestibular and cochlear nerves from the labyrinth to the brain stem: its implications to surgery of the eighth cranial nerve.

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.

A comparison of PORP, TORP, and incus homograft for ossicular reconstruction in chronic ear surgery.

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.

Retrolabyrinthine vestibular neurectomy with and without monitoring of eighth nerve potentials.

Retrolabyrinthine vestibular neurectomy is a safe and effective treatment for Meniere's disease and inner ear vertigo. Hearing was maintained within 20 dB of the preoperative level in 83% of our patients and speech discrimination scores were preserved within 20% in 80%. Intraoperative monitoring of audiometric evoked potentials, employed to study the possible causes of hearing loss, provided rapid, sensitive detection of trauma to the auditory system. Our patients benefited from this technique--those who underwent retrolabyrinthine vestibular nerve section, as well as those who experienced acoustic neuroma surgery, where hearing preservation is a goal. Direct intraoperative monitoring of eighth nerve function continues to be a standard part of our surgical practice.

Evoked serial electromyography in the evaluation of the paralyzed face.

Serial evoked electromyography (EEMG) is a reliable, objective, repeatable test of facial nerve function. It is very important in the initial patient evaluation in determining percent degeneration of the facial nerve. A response of 0-20% will usually result in incomplete return of facial function while responses of 60% or better will usually result in normal function. With viral facial paralysis (Bell's palsy, herpes zoster oticus), serial EEMG after several weeks has little value in predicting the final percent recovery of facial function. If there is no EEMG response, the diagnosis of viral facial paralysis is questionable and serial tests should be done until facial function begins to return. If there is no return of facial function or EEMG responses, the diagnosis is probably a tumor and the nerve should be explored. When surgical manipulation of the facial nerve has resulted in partial facial weakness, EEMG helps predict the degree of recovery of facial function. EEMG results of 60% or better will result in normal facial function while EEMG results of 25% or less will result in incomplete return of facial function. Serial testing is not necessary in this group of patients. After transection and repair of the facial nerve, serial EEMG is of value in showing continuity of the repair. Lack of improvement in EEMG over 5-12 months and no return of facial function indicates poor prognosis.

Hearing preservation after acoustic neuroma surgery using intraoperative direct eighth cranial nerve monitoring.

Since the advent of brainstem auditory evoked response audiometry and computerized tomography, small acoustic neuromas are found more frequently. The patients often have serviceable hearing and wish to preserve it during complete tumor removal. Since 1978, we operated on thirteen patients with acoustic neuromas using the retrosigmoid suboccipital approach. Our goal in these cases was to preserve hearing. We began using intraoperative direct eighth nerve monitoring in 1983. This allowed us to rapidly assess cochlear nerve function during excision of small acoustic neuromas. Intraoperative monitoring was used in 5 of 13 cases, and in three patients, hearing was preserved. In the 8 cases where intraoperative monitoring was not used, hearing was preserved in only two patients. Our overall success rate of simultaneous total tumor removal hearing preservation was 38%. Tumor size varied from intracanalicular to one with a 3.0 cm protrusion medial to the porus acousticus. Hearing was preserved in 54% of cases where tumor size was less than 1.5 cm. We find continuous monitoring of direct eighth nerve evoked action potentials to be extremely valuable and a rapid indication of reversible cochlear nerve trauma.