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PubMed1996

Cochlear implantation in a case of Wegener's granulomatosis.

Cochlear implantation is now a routine clinical procedure for deaf patients in many countries (Gibson, 1987). It replaces the function of damaged cochlear hair cells and therefore, detects sound and by electrical stimulation produces an appropriate signal in the remaining cochlear nerve fibres (House and Berliner, 1991). Wegener's granulomatosis is an uncommon auto-immune disease. It has a peak incidence at the fifth decade with slight male predominance. Nasal problems are the predominant presentation with otological manifestations presenting rarely. We report a case of Wegener's granulomatosis presenting with total hearing loss and after right cochlear implantation a free field threshold of 40 dB and 20 per cent Bamford-Kowal-Bench (BKB) speech test. We conclude that Wegener's granulomatosis is not an absolute contraindication for cochlear implantation.

Aged↗
PubMed1998

Immunohistochemical detection of vasoactive intestinal polypeptide (VIP) and the VIP receptor in the rat inner ear.

Vasoactive intestinal polypeptide (VIP) is a 28 amino acid peptide that was originally isolated from porcine duodenum. The presence of VIP has been demonstrated in the central nervous system and peripheral tissues. However, there have been few reports on VIP as a neurotransmitter, especially in the inner ear. To investigate the function of VIP in the rat inner ear, we examined the expression of VIP and the VIP receptor by immunohistochemistry. Using the anti-VIP and VIP receptor antibodies, scattered fibres in the cochlear nerve trunk demonstrating VIP-like immunoreactivity were found, and the spiral ganglion cells demonstrated ring-shaped VIP-like immunoreactivity. Immunoreactivity for the VIP receptor was predominantly found in the spiral ganglion cells. Our results suggest that VIP may play an important role as a possible neurotransmitter not only in the local control of cochlear blood flow, but also in the auditory system.

Animals↗
PubMed1999

NADPH-diaphorase histochemistry reveals an autonomic-like innervation in the postnatal hamster cochlea.

Previous studies used nicotinamide adenine diphosphate (NADPH)-diaphorase histochemistry as an indicator of nitric oxide synthase (NOS) expression in the adult mammalian cochlea. In this study, we investigated the early postnatal expression of diaphorase activity in the hamster cochlea. Two types of extrinsic fibers were intensely labeled as early as postnatal day 3 (P3) in the portion of the cochlear nerve that innervates the base of the modiolus. By P10, these fibers had reached the spiral ganglion and were projecting toward the organ of Corti. The perivascular type of fiber did not project into the organ of Corti; however, the nonperivascular type could be traced among the supporting cells below the outer hair cells. Spiral ganglion cell somata were also labeled as early as P3. The onset of diaphorase expression in the spiral ganglion cells corresponds to a critical period of synaptogenesis for these sensorineural cells. If NADPH-diaphorase activity is an indicator of NOS, then our results suggest that NO may play a role during postnatal cochlear development.

Animals↗
PubMed2000

Pathology of Madras type of motor neuron disease (MMND)--a histological and immunohistochemical study.

A neuropathological report of Madras type of motor neuron disease (MMND) is presented and the differences from other forms of MND are discussed. An 18-year-old girl presented with nerve deafness and slowly progressive bulbo-spinal muscular atrophy, characteristic of MMND. Post-mortem examination of the spinal cord showed a severe loss of anterior horn cells, prominent dilatation of vessels, diffuse, but sparse sprinkling of microglial cells and lymphocytes, and demyelination and sclerosis of the ventrolateral columns. Neuronal depletion and marked gliosis was noted in the cochlear nucleus on both sides, while other bulbar motor nuclei were also involved. The cochlear nerve showed demyelination and axonal loss. Trigeminal and vestibular ganglia revealed features of ganglionitis. The possibility of an inflammatory aetiology for MMND needs to be considered.

Adolescent↗
PubMed2001

Imaging evaluation of sensorineural hearing loss.

The imaging evaluation of patients with sensorineural hearing loss (SNHL) focuses on the acoustic pathways from the cochlea to the auditory cortex. Magnetic resonance imaging (MRI) is the modality of choice for most patients with SNHL, though computed tomography (CT) also plays an important role in the evaluation of bony changes and in patients for whom MRI is contraindicated. Conventional enhanced MRI is the most commonly used technique in this clinical setting. High-resolution fast spin-echo T2 MRI is an adjunctive technique that provides exquisite evaluation of the cerebellopontine angle (CPA), internal auditory canal (IAC), cranial nerves, and membranous labyrinth, and plays a significant role in the diagnosis and surgical evaluation of SNHL. Categories of lesions that cause SNHL include brain lesions involving central auditory pathways; neoplasms of the CPA and IAC, the most common being schwannoma; other neoplastic, congenital, and cystic masses of the CPA and IAC; congenital anomalies of the inner ear; intrinsic cochlear nerve defects, inflammatory processes of the inner ear; and temporal bone trauma.

Cranial Nerve Neoplasms↗
PubMed1996

Vascular-decompression surgery for severe tinnitus.

Vascular compression of the eighth cranial nerve is increasingly recognised as a possible cause of incapacitating audiovestibular symptoms. There have been few reports of the efficacy of surgical microvascular decompression for tinnitus, and the practise is controversial. During the last 6 years, investigation by air computed tomography (CT) cisternography initially, and fast spin-echo magnetic resonance imaging (MRI) latterly has resulted in the diagnosis of cochlear nerve vascular compression in nine patients with a primary complaint of severe tinnitus who have subsequently undergone vascular-decompression surgery. The duration of symptoms ranged between 1 and 10 years, whilst their subjective tinnitus perception varied between 30 to 60 dB above threshold. Microvascular decompression was carried out by a retrolabyrinthine approach in four and by a retrosigmoid approach in the remaining five cases, with a postoperative follow-up of 1.3 to 5 years. Tinnitus was completely abolished in three (33%), very significantly improved to a sensation level of < or = 10 dB in four (33%), significantly improved to a level of 15 dB in one (11%), and unchanged in two (22%). Both failures had had tinnitus for 6 years and had transient abolition for 10 days after surgery. Subsequent revision decompression surgery was also unsuccessful. This small study suggests that cochleovestibular vascular compression may result in severe tinnitus, which can often be ameliorated surgically.

Adult↗
PubMed1987

Cochlear implant candidates: assessment with CT and MR imaging.

Eighty-seven patients with severe to profound hearing loss were evaluated for possible placement of a multichannel cochlear implant hearing device. After initial clinical screening, 42 patients underwent computed tomographic (CT) examination. Five of these patients were also examined with magnetic resonance (MR) imaging. Twenty-two patients received implants. CT of the middle and inner ear was normal in 24 patients (57.1%) and showed labyrinthine ossification in 12 (28.6%), cochlear or fenestral otosclerosis (or both) in four (9.5%), and congenital cochlear malformation in two (4.8%). The information provided by CT was used to (a) exclude patients in whom multichannel cochlear implantation would most likely be unsuccessful (owing to obliterative labyrinthine ossification, or congenital cochlear malformation, severe cochlear, or fenestral otosclerosis), (b) help select the best ear for implantation, and (c) provide a preoperative picture of normal variants and avoidable surgical pitfalls. MR experience is limited but assessment of the size of the cochlear nerve and the membranous labyrinth is possible with this modality and may provide additional information in the evaluation of these patients.

Adolescent↗
PubMed1997

Synaptophysin immunoreactivity in the cochlear nucleus after unilateral cochlear or ossicular removal.

This study determined if unilateral cochlear removal in adult guinea pigs led to synaptic loss followed by synaptogenesis in the cochlear nucleus (CN) and if unilateral middle ear ossicle removal led to synaptic loss in the CN. Synaptic endings were identified immunohistochemically, using a monoclonal antibody to synaptophysin. Immunolabeling was quantified densitometrically in the CN 4-161 days after cochlear removal and 161 days after ossicle removal. Fiber degeneration was visualized with the Nauta-Rasmussen silver method. Tissue shrinkage was measured from drawings of CN sections. Compared to the contralateral side, immunolabeling density ipsilaterally was reduced by 4 days in the anterior division of the anteroventral CN (a-AVCN) and by 7 days in the anterior part of the posteroventral CN (a-PVCN). At 7 days, preterminal fiber degeneration was abundant in both areas. These findings were consistent with the loss of cochlear nerve endings and fibers. At later times, immunolabeling density recovered. In the a-AVCN, tissue shrinkage explained approximately half the recovery of staining density; the rest was attributed to synaptogenesis. In the a-PVCN, the entire recovery was attributed to tissue shrinkage. In the polymorphic layer of the dorsal CN, immunostaining density increased transiently at 4 days, while at 7 days preterminal fiber degeneration was abundant. A net loss of synaptic endings was not detected immunohistochemically. The increased immunostaining density may reflect a transient growth of immature processes or presynaptic endings. Ossicle removal produced a deficit in immunolabeling density only in the ipsilateral a-PVCN, without fiber degeneration, suggesting a loss of presynaptic endings or of synaptophysin expression.

Afferent Pathways↗
PubMed2004

Males lose hearing earlier in mouse models of late-onset age-related hearing loss; females lose hearing earlier in mouse models of early-onset hearing loss.

Gender-related differences in human hearing have been attributed to genetic, environmental, and/or genetic x environmental interactive factors. These differences tend to increase with age, with males showing greater high frequency threshold elevations. An appropriate animal model could aid in prediction, treatment, and prevention of some of these losses. This paper examines inbred strains of mice that are widely used as models of late- (CBA/J and CBA/CaJ) and early- (C57BL/6J) onset age-related hearing loss. In the former two genotypes, the thresholds to high frequency stimuli of the auditory brainstem response (ABR) are higher in the male than in the female. This gender difference was less pronounced in thresholds to the cochlear nerve envelope response of the CBA/CaJ, although this response was more sensitive to the influence of age than was the ABR. In contrast, the male C57BL/6J had more sensitive thresholds than the female, with both measures showing massive loss of sensitivity with increasing age. The data are discussed in terms of the applicability of these animals as tools for examining factors that degrade cochlear function.

Aging↗
PubMed1985

Autoradiographic demonstration of deoxyglucose uptake in guinea pig cochlea.

The 2-deoxyglucose autoradiographic method was applied to whole-body cryosectioning to include the cochlea. The highest levels of 2-deoxyglucose uptake were observed in the vascular stria, spiral ligament and spiral prominence. The cochlear nerve showed the next highest level of uptake, while the organ of Corti and the spiral ganglion showed low levels. The functional significance of the results was briefly discussed.

Animals↗
PubMed1993

[Results of 100 consecutively operated patients with acoustic neuroma].

The results from 100 patients with 103 acoustic neurinomas who were operated on between February 1979 and April 1992 are presented. All patients were placed in the half-sitting position and operated on by the same surgeon using the suboccipital-trans-meatal approach. Postoperative facial nerve function was good in 56%, moderate in 20% and poor in 24% of our patients. Preservation of useful hearing was achieved in 21%: the smaller the tumor, the better the functional result. However, the early symptoms of acoustic neuromas (tinnitus, dizziness, feeling of unsteadiness) were only slightly improved by the operation. The result concerning tinnitus seemed to be better after sacrificing the cochlear nerve. The number of patients with ataxia increased postoperatively, although objective ataxia decreased. Dizziness improved regardless of the tumor size.

Auditory Threshold↗
PubMed1982

Neurophysiological studies in adrenomyeloneuropathy. A report on five cases.

Neurophysiological studies were performed in 5 patients in two families suffering from adrenomyeloneuropathy (AMN). The diagnosis was supported by electron microscopy of nerve twigs in all cases and by the demonstration in 2 cases of increased levels of saturated very long chain fatty acids in cultured fibroblasts (Moser, personal communication). Measurements of the sensory-motor conduction velocities demonstrated the variability of the peripheral nerve damage in AMN, further confirmed by quantitative studies of sensory nerve biopsies. Somatosensory evoked potentials (SEP) were abnormally delayed and their configuration was abnormal, mainly following stimuli applied to the lower limbs. Our data suggest a more severe involvement of the fasciculus gracilis and an extension of the lesions to the medial lemnisci in agreement with the few postmortem reports showing multifocal demyelination. Brain stem auditory evoked potentials (BAEP) were delayed, pointing towards lesions between cochlear nerve and superior olivary nucleus and also at lateral lemniscal level. Morphological confirmation is lacking but the close topographical relationship between the secondary auditory pathways and the medial lemnisci indicates that even small lesions could damage simultaneously both pathways. Neurophysiological studies contribute to the diagnosis of AMN, they confirm the inter- and intrafamilial variability of the clinical features and help to explain the signs and symptoms of this condition.

Adrenal Insufficiency↗
PubMed1992

[Functional results of preservation of cranial nerves in removal of acoustic neurinoma].

Seventeen patients with acoustic neurinoma were reviewed on the basis of postoperative preservation of facial and acoustic nerve functions. The sizes of tumors were intracanalicular in 5 cases, smaller than 20mm in diameter in 2 cases, smaller than 30mm in 5 cases, and larger than 30mm in 5 cases. In all cases, the facial nerve was anatomically preserved at operation. Functional recoveries of the facial nerve in follow-up were excellent in 7 cases out of 17 (41%), good in 5 (29%) and poor in 5 (29%). Although the functional preservation for the facial nerve was related to the size of the tumor, it was favorable in cases of cystic tumor even with a size larger than 20mm. By pure tone audiogram, hearing was found to be preserved in 12 cases before operation. At operation, the acoustic nerve was anatomically preserved in 4 cases. Postoperative hearing was maintained in two cases, one of which showed a successful preservation of serviceable hearing. In this case, tumor resection was performed with intraoperative monitoring of auditory brain stem reactions (ABRs). Discussion was made concerning a possible surgical candidates for the hearing preservation, and it was proposed that every effort should be made to preserve the cochlear nerve if following conditions were verified in the case: 1) normal or nearly normal hearing (less than 40-50dB hearing loss), 2) the size of tumor is intracanalicular or smaller than 2cm in diameter, 3) there is no deterioration of intraoperative ABR.

Adult↗
PubMed1994

Neural responses to electrical stimulation of the cochlea in guinea pigs.

A special bridge circuit was constructed to compensate stimulus artifact to determine the effects of an alternating current (AC) in the range of 3 to 20 kHz and direct current (DC) stimulation on the activity of cochlear nerve fibers. When AC and DC stimulation of the same fiber were compared, a greater current intensity was required to change the spike rate with AC stimulation than DC stimulation. While positive DC stimulation reduced activity, negative DC stimulation increased the spike rate. AC stimuli excited fibers in a manner similar to that observed with negative DC stimulation. Thresholds increased with stimulus frequency, suggesting that the effects of AC stimulation on the discharge rate are independent of the CF (characteristic frequency) of a fiber. The effects of short-time AC and DC stimulation on cochlear fiber activity lasted only during the stimulation, and the spontaneous activity did not significantly differ before and after electrical stimulation.

Animals↗
PubMed1998

Intra-operative monitoring in acoustic neuroma surgery.

Intra-operative neurophysiologic monitoring (IOM) is rapidly evolving as an important adjunct during acoustic neuroma surgery to reduce the incidence of neurologic deficits. Monitoring alerts the surgeon to ongoing changes in neural function. The benefit of facial nerve monitoring in reducing the incidence of facial palsy during acoustic tumor resection appears clear and is now recommended by the National Institutes of Health (Consensus Development Conference on Acoustic Neuroma, 1991). Auditory monitoring is not as effective as facial monitoring but hearing preservation can be enhanced particularly if used with facial monitoring because the latter alerts the surgeon to traumatic manipulations that may affect both facial and cochlear nerves. Monitoring is not a replacement for surgical experience. 'Poor monitoring is worse than no monitoring'.

Action Potentials↗
PubMed1990

Central and peripheral nervous system effects of hand-arm vibrating tool operation. A study of brainstem auditory-evoked potential and peripheral nerve conduction.

To examine the effects of hand-arm vibrating tool operation on the central and peripheral nervous system, the brainstem auditory-evoked potential (BAEP), median nerve conduction velocity and hearing level were measured in twelve chain saw operators (6 operators had a history of white finger attack) and in eight brush saw operators (none had a history of the attack). Control subjects, matched to each chain saw and brush saw operator by sex and age, were selected randomly from healthy adults without otitis, deafness and tinnitus. The I-V interpeak latency (conduction from cochlear nerve to brainstem) and V peak latency of BAEP were significantly prolonged in chain saw operators; the I-V interpeak latency was significantly correlated with working years in brush saw operators. The median nerve conduction velocity was significantly slowed in both chain saw and brush saw operators. Moderate hearing loss was observed in the two groups. It is suggested that vibrating tool operation, i.e. the combined stressors of local vibration, noise, climate and heavy work, affected not only the peripheral nervous system but also the brainstem portion of the auditory pathway; the brainstem effect, if any, is less advanced than the peripheral nervous system effect of local vibration.

Adult↗