Clinical long-term observation of the keyhole microvascular decompression with local anesthesia on diagnosis and treatment of vestibular paroxysmia.

Background: The pathophysiology and etiology of vestibular paroxysmia (VP) remains unclear, moreover, due to the lack of reliable diagnostic features for VP, the clinical diagnosis will be made mainly by exclusion.Aims/objectives: To evaluate the diagnostic value and curative effect of keyhole microvascular decompression with local anesthesia for VP.Material and methods: 54 patients with trigeminal neuralgia, hemifacial spasm and glossopharyngeal neuralgia underwent keyhole microvascular decompression with local anesthesia, twelve of whom were coexistent with VP. The evaluation of the vertigo after operation was performed with symptom report card for 12 patients with VP and the mean follow-up period was 116 months (range 114-118 months).Results: The cochleovestibular neurovascular compression at the root zone of vestibular nerve was found in 12 patients with VP, of whom 11 patients had the neurovascular compressive vertigo induced intra-operatively and the vertigo disappeared postoperatively, moreover, one patient had no neurovascular compressive vertigo induced intra-operatively and the vertigo was not improved significantly after operation. Of 12 patients with VP during the mean 116-month follow-up, 11 patients had no recurrence of neurovascular compressive vertigo and the effective control rate of vertigo was 91.7%.Conclusions and significance: Keyhole microvascular decompression with local anesthesia is not only an effective method for treating VP and controlling neurovascular compressive vertigo, but also has definite clinical significance in the diagnosis of VP.

[Functional assessment of cochlear nerve and hearing]. / Exploration fonctionnelle du nerf cochléaire et de l'audition.

BACKGROUND/PURPOSE: Since otoneurosurgical pathologies are being diagnosed increasingly early, the functional prognosis of surgery is gaining in importance. Hearing and cochlear nerve exploration can be carried out using three principal methods: pure-tone and speech audiometry, evoked otoacoustic emissions (EOAEs), and brainstem auditory evoked potentials (BAEPs). The aim of this paper is to present the current knowledge on auditory functional assessment. MATERIALS AND METHODS: The medical and scientific literature from the Pubmed-Medline database was reviewed. Recently published related books were also included. RESULTS/DATA SYNTHESIS: Preoperative audiological evaluation makes it possible to assess pathology consequences on hearing. Depending on auditory status, conservative surgery, including intraoperative auditory monitoring, can be planned. From this perspective, prognostic factors for hearing preservation - such as the speech intelligibility score, the presence of transient EOAEs, and the presence of the BAEPs wave III - were identified. However, several surgical teams argue for a systematic conservative procedure, particularly when EOAEs are present, whatever the patient's preoperative hearing status. Postoperative audiological evaluation provides the opportunity for monitoring: in the short term, to detect complications early, through BAEPs recorded in the nonoperated ear; in the long term, to detect recurrence of the pathology. Moreover, the consequences of surgery on hearing can be assessed and long-term follow-up of auditory function can be carried out. Finally, the comparison of pre- and postoperative audiological status provides inductive feedback on surgery and electrophysiological monitoring, giving the otoneurosurgeon and neurophysiologist the opportunity to improve the entire procedure. CONCLUSION: Auditory functional assessment is essential for optimal care of tumor or functional pathologies involving the cochlear nerve and/or the cerebellopontine angle.

The influence of prophylactic vasoactive treatment on cochlear and facial nerve functions after vestibular schwannoma surgery: a prospective and open-label randomized pilot study.

OBJECTIVE: Facial nerve paresis and hearing loss are common complications after vestibular schwannoma surgery. Experiments with facial nerves of the rat and retrospectively analyzed clinical studies showed a beneficial effect of vasoactive treatment on the preservation of facial and cochlear nerve functions. This prospective and open-label randomized pilot study is the first study of a prophylactic vasoactive treatment in vestibular schwannoma surgery. METHODS: Thirty patients were randomized before surgery. One group (n = 14) received a vasoactive prophylaxis consisting of nimodipine and hydroxyethylstarch which was started the day before surgery and was continued until the seventh postoperative day. The other group (n = 16) did not receive preoperative medication. Intraoperative monitoring, including acoustic evoked potentials and continuous facial electromyelograms, was applied to all patients. However, when electrophysiological signs of a deterioration of facial or cochlear nerve function were detected in the group of patients without medication, vasoactive treatment was started immediately. Cochlear and facial nerve function were documented preoperatively, during the first 7 days postoperatively, and again after long-term observation. RESULTS: Despite the limited number of patients, our results were significant using the Fisher's exact test (small no. of patients) for a better outcome after vestibular schwannoma surgery for both hearing (P = 0.041) and facial nerve (P = 0.045) preservation in the group of patients who received a prophylactic vasoactive treatment. CONCLUSION: Prophylactic vasoactive treatment consisting of nimodipine and hydroxyethylstarch shows significantly better results concerning preservation of the facial and cochlear nerve function in vestibular schwannoma surgery. The prophylactic use is also superior to intraoperative vasoactive treatment.

Effects of olivocochlear bundle section on otoacoustic emissions in humans: efferent effects in comparison with control subjects.

The effects of contralateral acoustic stimulation on evoked otoacoustic emissions (OAE) were examined in three subject groups in order that the impact of efferent olivocochlear bundle section (as a consequence of vestibular neurectomy) could be compared with normal findings, and with a control surgical population. Results demonstrated that the inhibitory effect of contralateral noise on OAE amplitude was absent from the cochlea with severed efferent fibers. These findings appear to be independent of acoustic reflex activity, as suppression was absent despite normal reflexes. Inter-aural suppression of emissions recorded from the patients' intact cochleae act as a control and show a clear reduction in amplitude during contralateral stimulation in a frequency specific pattern consistent with normal findings. Patients who had undergone a similar surgical approach for vascular decompression of the VIIIth nerve without vestibular nerve section, were studied in order to assess the impact of retrolabyrinthine surgery on inter-aural suppression. Inhibition of OAE amplitude was maintained in all control cases in both the operated and intact sides, and was consistent with suppression observed in normal subjects, suggesting that the surgical procedures had not disturbed inter-aural suppression of otoacoustic emissions. It is concluded that the olivocochlear efferent system, when activated by low level contralateral acoustic stimulation, has an inhibitory role in controlling the cellular mechanisms responsible for the generation of otoacoustic emissions in humans. OAE techniques in conjunction with contralateral acoustic stimulation may thus prove to be of value in providing a rapid and non-invasive clinical test of efferent function and offer a means of investigating the functional significance of the efferent auditory system in humans.

Multichannel extracochlear implant.

The transcutaneous eight-channel extracochlear implant has undergone continuous revision to simplify the surgical technique, to minimize patient morbidity, and to improve performance. The extracochlear electrode array has been miniaturized so that it can be inserted through the facial recess without disturbing the external auditory canal, tympanic membrane, or malleus. The use of the remote antenna placed around the external auditory canal has greatly increased battery life and patient comfort. With its simplified incisions, the surgical procedure can be performed as out-patient surgery. Preoperative cochlear nerve testing and use of evoked response cochlear nerve testing allow preadjustment of the speech processor. Current features and performance of the implant are discussed.

Electrical stimulation of cochlear nucleus in man.

Auditory percepts can be produced by electrical stimulation of the cochlear nucleus in man. The ability to locate accurately and stimulate selectively the cochlear nucleus after removal of an acoustic schwannoma was confirmed in this patient. The surgical approach, electrode design, and a discussion of the results and concerns of electrical stimulation are reviewed.