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Middle fossa vestibular nerve section in the management of Ménière's disease.

The triad of fluctuating hearing loss, tinnitus, and episodic attacks of vertigo known as Ménière's disease can be a frustrating therapeutic problem. While most patients respond to a medical regime consisting of a low salt diet, diuretics, diazepam, and propantheline bromide, there is a significant group who remain refractory to conservative management. These individuals either continue to experience their distressing symptoms or undergo some type of surgical procedure in an attempt to seek relief. There are a multitude of such techniques available to the otologic surgeon and he must make the decision as to which procedure is best for any given individual. The authors' employ three surgical approaches for the management of Ménire's disease. These are the translabyrinthine labyrinthectomy, the endolymphatic subarachnoid shunt, and the middle fossa vestibular nerve section. In this paper the indications for surgery, technique, results and complications are covered in detail. Thirty-one patients are reviewed who have been followed from one to four years postoperatively. Seventeen had total and 14 had superior vestibular nerve sections. The results were much better in the total group, as 94 percent had complete relief of vertigo and 76 percent were able to maintain their preoperative hearing level. The authors feel the middle fossa vestibular nerve section is a valuable addition to the otologist's armamentarium in the treatment of the patient who is refractory to medical management.

Adult↗

Immunohistochemistry study of human vestibular nerve schwannoma differentiation.

Differentiation of primary human vestibular nerve schwannomas (VS) caused by mutations of the NF2 gene was evaluated by examining the expression patterns of genes that are specifically expressed in different stages of Schwann cell lineage. In schwannoma cells that are not in contact with an axon, the expression levels of the major myelin sheath proteins, such as protein zero glycoprotein (P0), myelin basic protein (MBP), and peripheral myelin protein 22 (PMP22), were greatly reduced. However, high expression levels of nerve growth factor receptor (NGFR), neural cell adhesion molecule (N-CAM), and cell adhesion molecule L1 (L1) were observed. In addition, expression of transcription factors Krox20, Krox24, and SCIP/Oct6 was also detected in the tumor cells. These results suggest that loss of the NF2 gene was responsible for the transformation of the Schwann cells into a neoplastic stage that has a similar genetic profile to the pro-myelinating stage. Finally, the primary human vestibular schwannoma cells failed to be regulated and redifferentiated by a regenerating axon, when the human tumors were transplanted into sciatic nerve of nude rat. These results suggest that the NF2 gene might be involved in the differentiation of Schwann cells.

Adult↗

Air CT cisternography in the diagnosis of vascular loop causing vestibular nerve dysfunction.

Considerable interest has developed in otology concerning the relationship between the vascular loop and compression of the eighth nerve, producing vertigo. Several authors have described the radiographic findings relative to the anatomy of these vascular loops. Few previous articles have dealt with cases that have had surgical confirmation or repair of the defect. Our presentation concerns 27 patients who were studied by air CT cisternography of the cerebellopontine angle cistern and internal auditory canal followed by surgical repair. We postulate dampened pulsation as the reason for being able to visualize the vessels on the air study. The diversity of vessel-eighth nerve defects is illustrated. Compression of the vestibular nerve by a vascular loop should be considered one of the causes of intractable vertigo and motion intolerance and is a differential diagnosis in Meniere disease. Air CT cisternography is useful in diagnosing this condition in patients who do not respond to medical treatment.

Adult↗

Infrared/video ENG recording of eye movements to evaluate the inferior vestibular nerve using the minimal caloric test.

The technique was originally developed to test the inferior vestibular nerve in tumor suspects whose high-frequency hearing loss exceeded the capabilities of the auditory brainstem response tests and whose electronystagmographic results showed no significantly reduced vestibular response. The test has subsequently been found effective to demonstrate persistent singular nerve fiber function in patients with persistent vertigo after retrolabyrinthine vestibular nerve section.

Caloric Tests↗

Posterior fossa vestibular nerve section for the management of peripheral vertigo.

Patients with vertigo resistant to conservative treatment require surgical management. Between March 1991 and August 1996, vestibular nerve sections were performed in 108 patients with peripheral vertigo not responding to conservative treatment. The diagnoses were classic Ménière's disease in 96 patients and recurrent vestibulopathy in 12 patients. Combined retrosigmoid retrolabyrinthine (n = 106) and retrolabyrinthine (n = 2) approaches were used. Patients were grouped according to follow-ups of less than 2 years and more than 2 years. In the former group (n = 49), hearing preservation and vertigo control were achieved in 93.9% and 100%, respectively. In the latter group (n = 59) the rates were 89.8% and 96.6%, respectively. Overall complications were uncommon. Three patients had cerebrospinal fluid leakage and one had total hearing loss. According to our results, posterior fossa vestibular nerve section was found to be an effective treatment for the management of patients with intractable vertigo.

Adolescent↗

Retrolabyrinthine vestibular nerve section: a viable alternative to the middle fossa approach.

Vestibular nerve section, whether by the middle fossa or retrolabyrinthine approach, is effective in relieving intractable vertigo while preserving hearing. However, the potential morbidity and technical difficulty of the middle fossa approach have limited its usefulness. In an attempt to determine if the two approaches produce comparable results, we evaluated 52 patients who underwent retrolabyrinthine vestibular neurectomy between April 1981 and March 1983 at the Otologic Medical Group. We compared their audiometric data and questionnaire responses with published data on patients who had a middle fossa vestibular neurectomy. Although differences between the two procedures do exist, the retrolabyrinthine method, with its 93% success rate in improving or resolving vertigo and its zero incidence of total sensorineural hearing loss, offers the surgeon a strong alternative to the middle fossa approach.

Adult↗

Long-term results of vestibular nerve section.

Records are available on 27 patients who had vestibular nerve section between 1975 and 1987 giving a follow-up time of 10 to 22 years with a mean of 16 years. Episodic vertigo was fully controlled in 26 patients, one needing a labyrinthectomy 18 months later. In addition to the patient who had labyrinthectomy, one patient had immediate post-operative profound hearing loss so that long-term follow-up of hearing was possible in 25 patients. After six months there was an overall average improvement in hearing of 1 dB. Thereafter there were average deterioration of 7 dB at two years, 15 dB at 10 years, 23 dB at 15 years and 29 dB at 20 years. This deterioration was more marked in those who had better hearing at the time of surgery, with all 10 whose hearing was classified as good deteriorating to poor by 15 years. At 10 years hearing deteriorated by 25 dB in those with good hearing and by 7 dB in those with poor hearing. In 20 per cent of patients there was audiological evidence of eventual involvement of the other ear. Tinnitus became worse in five patients but was a major problem in only one patient. One patient suffered a facial paralysis with partial recovery and, in addition, in one the frontal branch was divided in the incision.

Adult↗

Fine structure of the medial and descending vestibular nuclei in normal rats and after unilateral transection of the vestibular nerve.

Cells and neuropil are of similar structure in the descending and medial vestibular nuclei. Two cell types were found: small neurons and larger cells. Three types of axon terminals have been defined: small and large terminals containing spherical vesicles (SV) and terminals with elongated vesicles (EV). Small SV terminals contact perikarya and dendrites, whereas large SV terminals contact fine dendritic branches. EV terminals contact neurons at perikarya and large as well as small dendritic profiles. SV terminals can be presynaptic to EV terminals. Vestibular nerve transection resulted in degeneration of small SV terminals which were found from the first to fifth postoperative day in the ipsilateral nuclei. Glycogen granules were found in various types of axon terminals bilaterally in the vestibular nuclei 3-5 days after right vestibular transection. They were not observed in normal animals or in degenerating vestibular afferent terminals.

Animals↗

[A case of Tolosa-Hunt syndrome accompanied by facial and vestibular nerve damage].

A 37-year old man, who had repeatedly suffered from transient ophthalmoplegia in his left eye at the age of 29 and 36, developed left painful ophthalmoplegia accompanied by ipsilateral facial nerve palsy in August, 1991. Neurological examination revealed involvement of the left oculomotor, trochlear, ophthalmic division of the trigeminal, abducens, facial and vestibular nerves. Gadolinium-enhanced MRI which was taken at the acute phase of the illness demonstrated markedly enhanced left cavernous sinus and adjacent thickened dura mater in the middle cranial fossa. At the remission phase after starting corticosteroid therapy, these enhanced lesions were no longer observed even in enhanced MRI studies. We diagnosed him as suffering from Tolosa-Hunt syndrome presently accompanied by facial and vestibular nerve damage because of his history of illness, confined lesion in the left cavernous sinus and steroid-induced remission. We concluded that Tolosa-Hunt syndrome may be accompanied by damage of other cranial nerves in its course and that repeated gadolinium-enhanced MRIs are necessary for diagnosis and observation of the patients.

Adult↗

Arrangement of vestibular nerve fibers in the semicircular canal crista of the chinchilla.

The topographic arrangement of vestibular nerve fibers innervating semicircular canal cristae of the chinchilla was studied using computer-aided video-microscopy and three-dimensional reconstruction. At the level 20 microns proximal to the base of the crista, bundles consisting of 30-50 nerve fibers each were identified. Nerve fibers in bundles were classified into seven categories depending on the diameter. We confirmed that large nerve fibers were more frequently found in the central bundles and small nerve fibers were more frequently found in the peripheral bundles. The central bundle might function as a physiological unit coding various types of head movements, whereas the peripheral bundle might contribute more to the detection of slow and long-lasting movements giving rise to tonus and posture changes. The canalicular nerve may code rotational acceleration of the head via function- and locus-specific nerve fiber bundles.

Animals↗

Retrosigmoid intracanalicular vestibular nerve section: an alternative surgical approach for Menière's disease.

Selective vestibular nerve section has been shown to be an extremely effective treatment for control of vertigo in Menière's disease. In recent years the retrolabyrinthine approach has popularized this form of treatment. An alternative to the retrolabyrinthine approach is presented. It consists of a retrosigmoid intracanalicular dissection, and approach used for acoustic neuroma surgery. A review of the surgical technique, the rationale for its selection over the retrolabyrinthine approach, and the initial results and operative complications during its first eighteen months of use are presented.

Humans↗

Headache prevention in retrosigmoid vestibular nerve section.

Most disorders of the inner ear resulting in vertigo can be managed medically with good results. Meniere's disease, one of the more common causes of recurring vertigo, does not respond adequately to medical management in 5% of the cases. These patients become candidates for surgical management. Selective vestibular nerve section has become the procedure of choice when one desires to preserve residual hearing. This paper reviews 22 cases of vestibular nerve section via a retrosigmoid approach. The disease entities treated, treatment results, operative morbidity, and complications are tabulated. The surgical technique is discussed in detail. The goals in reviewing these cases were to evaluate the impression that the incidence of severe and/or prolonged postoperative headache was infrequent and to compare surgical results with those reported by others in the literature.

Adult↗

Morphological aspects of the human vestibular nerve.

A quantitative study was made of the number of fibers, their diameters, and distribution in the nerves innervating individual vestibular receptor organs of three human temporal bones. The specimens were obtained from autopsies conducted within 4 hours postmortem. The temporal bones containing the nerves were fixed in 3% glutaraldehyde and decalcified with EDTA until they were soft enough to allow dissection of the nerve branches to the individual receptors. The nerve branches were processed for osmium staining, embedded in plastic, and cut serially in 1-micron-thick sections for light-microscopic histologic evaluation of their fiber composition. Quantitative evaluation of nerve-fiber characteristics was made with the aid of a laboratory computer and programs for graphic representation and statistical analysis. In the nerves to the individual cristae the number of fibers ranged between 1416 and 2335. Fibers with diameters between 2.5 microns and 3 microns were the most numerous. The number of fibers decreased exponentially with increased size. The thickest fibers had diameters up to 11.5 microns. The distribution of fibers in the nerve of each crista was different for the central and intermediate areas of the crista than it was for the ends. Thin fibers with diameters less than 2.5 microns, which represented 36% of the population, projected to the ends of the receptor area. Thick fibers with diameters greater than 4.5 microns, which represented 8% of the fibers, were distributed relatively uniformly except for the extreme ends of the crista, where they were nearly absent. Fibers with intermediate diameters were distributed throughout the crista, although they were more concentrated at the ends. In the nerves to three maculae, the number of fibers ranged from 3744 to 5538. The percentage of fibers of each size, however, was similar to that in the cristae. The greater portion of fibers had diameters between 3.0 microns and 3.5 microns. Because of the anatomical configuration of the maculae, it was not possible to compare fiber diameters from one area to another. The composition and differential projection of fibers to the crista in the human labyrinth were similar to those found earlier in squirrel monkeys and bullfrogs. On the basis of these similarities in the pattern of innervation, it is suggested that the physiological properties in humans must be similar to those in animals.

Aged↗

Galvanic stimulation evokes short-latency EMG responses in sternocleidomastoid which are abolished by selective vestibular nerve section.

OBJECTIVE: To describe vestibulocollic responses in sternocleidomastoid (SCM) evoked by transmastoid galvanic (DC) stimulation. METHODS: We studied the averaged responses in the unrectified EMG of SCM to transmastoid galvanic stimulation (5 mA/2 ms) and also to 100 dB clicks. Two patients with Meniere's disease were studied both before and after unilateral selective vestibular nerve section. RESULTS: Transmastoid galvanic stimulation produced a positive-negative biphasic EMG response at short latency in the SCM ipsilateral to the side of cathode placement, which resembled that which followed vestibular activation by loud clicks (p13/n23). Selective unilateral vestibular nerve section abolished this galvanic-evoked response. CONCLUSIONS: Galvanic-evoked vestibulocollic responses can be recorded in SCM. This is a new method of studying vestibular reflex function which may have application in the clinical assessment of vestibular disorders.

Adult↗

Superior vestibular nerve sectioning. Experimental studies in squirrel monkeys.

Spontaneous, positional, and paroxysmal positional nystagmus were studied before and after sectioning the superior division of the vestibular nerve and the anterior vestibular artery in squirrel monkeys. Histopathologic study of the temporal bones confirmed the degeneration of the macula utriculi with release of statoconia, but failed to identify the released utricular statoconia within the vestibular endolymphatic space in any animal. Postoperatively the animals consistently demonstrated direction-fixed spontaneous nystagmus until the end of the experiment (five months). Positional tests and Dix-Hallpike maneuver occasionally changed the intensity of the spontaneous nystagmus, but never elicited paroxysmal positional nystagmus. Possible reasons for not demonstrating paroxysmal positional nystagmus in the squirrel monkey are as follows: a resorption of statoconia; slight morphological alteration of the sensory epithelia of the posterior cristae; interference of the posterior crista function due to partial collapse of the membranous ampulla; the existence of interspecies difference; or possibly a faulty hypothesis regarding the etiologic mechanism of benign paroxysmal positional vertigo.

Animals↗

Latencies of response of eye movement-related neurons in the region of the interstitial nucleus of Cajal to electrical stimulation of the vestibular nerve in alert cats.

Recent studies have shown that the interstitial nucleus of Cajal (INC) in the midbrain reticular formation is involved in the conversion of vertical semicircular canal signals into eye position during vertical vestibulo-ocular reflexes. Secondary vestibulo-ocular relay neurons related to the vertical canals, which constitute the majority of output neurons sending signals from the vestibular nuclei directly to the oculomotor nuclei, have been shown to project axon collaterals to the region within and near the INC. To understand how the INC is involved in the signal conversion, latencies of response of neurons in the INC region to electrical stimulation of the vestibular nerve were examined in alert cats. The responses of 96 cells whose activity was clearly modulated by sinusoidal pitch rotation (at 0.31 Hz) were analyzed. These included 41 cells whose activity was closely correlated with vertical eye movement (38 burst-tonic and 3 tonic neurons), and 55 other cells (called pitch cells as previously). Twenty nine of the 96 cells (30%) were activated at disynaptic latencies following single shock stimulation of the contralateral vestibular nerve. Disynaptically activated cells were significantly more frequent for pitch cells than for eye movement-related cells (25/55 = 45% vs 4/41 = 10%; p less than 0.001, Chi-square test). Conversely, cells that did not receive short-latency activation (less than 6 ms) were more frequent among eye movement-related cells than pitch cells (26/41 = 63% vs 13/55 = 24%; p less than 0.001, Chi-square test).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Central projections of the vestibular nerve: a review and single fiber study in the Mongolian gerbil.

The primary purpose of this article is to review the anatomy of central projections of the vestibular nerve in amniotes. We also report primary data regarding the central projections of individual horseradish peroxidase (HRP)-filled afferents innervating the saccular macula, horizontal semicircular canal ampulla, and anterior semicircular canal ampulla of the gerbil. In total, 52 characterized primary vestibular afferent axons were intraaxonally injected with HRP and traced centrally to terminations. Lateral and anterior canal afferents projected most heavily to the medial and superior vestibular nuclei. Saccular afferents projected strongly to the spinal vestibular nucleus, weakly to other vestibular nuclei, to the interstitial nucleus of the eighth nerve, the cochlear nuclei, the external cuneate nucleus, and nucleus y. The current findings reinforce the preponderance of literature. The central distribution of vestibular afferents is not homogeneous. We review the distribution of primary afferent terminations described for a variety of mammalian and avian species. The tremendous overlap of the distributions of terminals from the specific vestibular nerve branches with one another and with other sensory inputs provides a rich environment for sensory integration.

Animals↗