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At least 1,009 records · Page 56Linked to original sources
PubMed2005

Facial nerve function after excision of large acoustic neuromas via the suboccipital retrosigmoid approach.

We review our results for facial nerve preservation in 105 patients with large acoustic neuromas (diameter 4.0 cm or larger) undergoing excision via the suboccipital retrosigmoid approach. Microneurosurgical techniques and facial nerve monitoring were used. Complete tumor removal was achieved in 91 cases (86.7%) and subtotal removal in 14 (13.3%). There were two postoperative deaths (1.9%). The facial nerve was preserved anatomically in 83 (79.1%) patients. Using the House-Brackmann grading system, facial nerve function was assessed immediately after surgery, at the time of discharge and 1 year after surgery. Excellent function (Grades I and II) was present in 41.0%, 41.8%, and 56.7% of patients at each time interval, respectively, with acceptable function (Grade I-IV) in 78.5% (68/87 cases) at follow-up assessment at one year. The suboccipital retrosigmoid approach resulted in good anatomical and functional preservation of the facial nerve during excision of large acoustic neuromas, with minimal other morbidity and low mortality. We recommend this approach for excision of large acoustic neuromas.

Adult↗
PubMed2000

A review of facial nerve outcome in 100 consecutive cases of acoustic tumor surgery.

OBJECTIVE: To determine the facial nerve outcomes at a tertiary neurotological referral center specializing in acoustic neuroma and skull base surgery. STUDY DESIGN: Retrospective review of 100 consecutive patients in whom acoustic neuromas were removed using all of the standard surgical approaches. METHODS: Functional facial nerve outcomes were independently assessed using the House-Brackmann facial nerve grading system. RESULTS: The tumors were categorized as small, medium, large, and giant. If one excludes the three patients with preoperative facial palsies, 100% of the small tumors, 98.6% of the medium tumors, 100% of the large tumors, and 71% of the giant tumors had facial nerve function grade I-II/VI after surgery. CONCLUSION: Facial nerve results from alternative nonsurgical treatments must be compared with facial nerve outcomes from experienced surgical centers. Based on the facial nerve outcomes from our 100 consecutive patients, microsurgical resection remains the preferred treatment modality for acoustic tumors.

Facial Nerve↗
PubMed1996

Video endoscopy-assisted vestibular neurectomy: a new approach to the eighth cranial nerve.

Disequilibrium, ranging from lightheadedness to severe vertigo, is frequently of great concern to the patients with a variety of inner ear diseases, and may cause occupational and social disability. Vestibular nerve section may be considered when vestibular symptoms are resistant to medical therapy and associated with serviceable hearing in the involved ear. During the last century, numerous authors described several routes for intracranial section of the eighth nerve, such as lateral suboccipital craniotomy, middle cranial fossa approach, and retrolabyrinthine approach to the vestibular fossa. Control of vertigo by all routes to the vestibular nerve has a success rate of 80% to 90%. The potential for endoscopic approach to intracranial cavities was recognized early in this century but, due to technical limitations, was largely abandoned after a few attempts. Advances in optics, and the introduction of very fine instruments made endoscopy worth reconsideration. Since the early 1980s, rigid endoscopes have been used in otorhinolaryngology for paranasal sinus surgery and the visualization of the facial and vestibulocochlear nerves during acoustic tumor surgery. We performed endoscopic section of the vestibular nerve through a retrolabyrinthine approach in two cadavers and in two patients with the symptoms of disequilibrium. In the literature survey, we could find no reports on vestibular neurectomy performed by endoscopic technique. We describe technical details of the approach, and conclude that the technique is safe and effective.

Journal Article↗
PubMed1981

The acoustic reflex test in cochlear and eighth nerve pathology ears.

The clinical interpretation of acoustic reflex test results in ears with sensorineural impairment should be based on a consideration of three characteristics of the response: the reflex threshold hearing level, the reflex threshold sensation level, and the decay of the reflex. Examination of results in 152 ears with cochlear pathology and in 152 ears with acoustic tumor indicated that in some cases the combination of characteristics may be contradictory as to site of lesion. Regarding a contradictory response pattern as questionable -- neither confirming nor denying a specific site of lesion -- improves the predictive accuracy of the test through a reduction in the number of false identifications.

Adolescent↗
PubMed1989

[Repair of the facial nerve exclusively by fibrin glue. 56 cases].

Facial nerve was repaired with fibrin glue in 56 cases using end to end (20 cases), cable graft (28 cases) or hypoglosso-facial anastomosis (8 cases). 33 patients were evaluated one year after surgery: clinical testing was higher than 70% in 42% cases, and between 50% and 70% in 36% cases. No result was observed in only 5 cases after immediate repair of the facial nerve during acoustic neuroma surgery. Fibrin glue provides a safe technique for facial nerve repair.

Anastomosis, Surgical↗
PubMed1997

Changes in the tonotopic map of the dorsal cochlear nucleus in hamsters with hair cell loss and radial nerve bundle degeneration.

Hamsters were exposed to an intense tone (10 kHz) at levels and durations sufficient to cause hair cell loss and radial nerve bundle degeneration. A previous study reported changes in the tonotopic map of the dorsal cochlear nucleus (DCN) in hamsters with tone-induced stereocilia loss. Such changes appear similar to those observed by others in the auditory nerve following acoustic trauma, and suggest that the map alterations have a peripheral origin. However, the potential for tonotopic map reorganization after more severe lesions involving cellular degeneration in the cochlea has not yet been determined. The purpose of the present study was to determine how the tonotopic map of the DCN appears in animals with severe cochlear injury involving hair cell loss and radial nerve bundle degeneration. Neural population thresholds and tonotopic organization were mapped over the surface of the DCN in normal unexposed animals and those showing tone-induced lesions. The results indicate that cochlear lesions characterized mainly by radial bundle degeneration in a restricted portion of the organ of Corti cause changes in a corresponding region of the tonotopic map which reflect primarily changes in the shape and thresholds of neural tuning curves. In many cases the center of the lesion was represented in the DCN as a distinct characteristic frequency (CF) gap in the tonotopic map in which responses were either extremely weak or absent. In almost all cases the map area representing the center of the lesion was bordered by an expanded region of near-constant CF, a feature superficially suggestive of map reorganization (i.e., plasticity). However, these expanded map areas had abnormal tip thresholds and showed other features suggesting that their CFs had been shifted downward by distortion and deterioration of their original tips. Such changes in neural tuning following tone-induced loss of anatomical input to the central auditory pathway are similar to those observed in our previous study and by others in the auditory nerve following less severe acoustic trauma, and thus would seem to have a peripheral origin. Thus, changes in the DCN tonotopic map can be explained by peripheral modifications and do not seem to involve plastic changes (i.e., reorganization).

Acoustic Stimulation↗
PubMed1983

Electron microscopical studies on the nerve endings of the outer hair cells in acoustically exposed rabbits.

The afferent and efferent nerve endings of the outer hair cells of the rabbit after acoustic exposure were investigated under the electron microscope. After acoustic stimulation, the afferent and efferent nerve endings of normal range were respectively 57 per cent and 64 per cent. This result suggests that half of the afferent and efferent nerve endings maintain their function under the conditions of this experiment. An abnormal inclusion body forming an oblong dense body and cistern in addition to the postsynaptic cisterna was observed. The active zone and the vesicular gap-structure of the synapse are discussed.

Acoustic Stimulation↗
PubMed2003

Predicting the threshold of single-pulse electrical stimuli using a stochastic auditory nerve model: the effects of noise.

An important factor that may play a role in speech recognition by individuals with cochlear implants is that electrically stimulated nerves respond with a much higher level of synchrony than is normally observed in acoustically stimulated nerves. Recent work has indicated that the addition of noise to an electrical stimulus may result in neural responses whose statistical characteristics are more similar to those observed in acoustically driven neurons. Psychophysical data have indicated that performance on some tasks might also be enhanced by the addition of noise. However, little theoretical work has been done toward predicting the effect of noise on psychoacoustic measurements. In this paper, theoretical predictions of these effects are developed through the use of a stochastic computational model. The effect of additive noise on the input and output characteristics and aggregate threshold behavior of modeled auditory nerves (ANs) is specifically studied. This paper derives the stochastic properties of the model input and output when using adaptive threshold procedures. A closed form solution for the input, or amplitude, probability distribution is obtained via Markov models for both one-down one-up (1D1U) and two-down one-up (2D1U) experimental paradigms. The output statistics are derived by integrating over the noise-free probability mass function (PMF). All theoretical PMFs are verified by simulations with the model. Theoretical threshold is predicted as a function of noise level based on these PMFs and the predictions match simulated performance. The results indicate that threshold may be adversely affected by the presence of high levels of noise.

Action Potentials↗