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PubMed1987

Pathological findings in the human auditory system following long-standing gentamicin ototoxicity.

The clinical, audiovestibular and histopathological findings in a patient who suffered from a long-standing gentamicin-induced deafness are reported. In both temporal bones, the organ of Corti was completely absent, with only a few nerve fibres remaining in the apical part of the cochlea. Regenerative ingrowth of nerve fibers into the area of the degenerative organ of Corti was present apically in both ears. The stria vascularis exhibited considerable degeneration in all turns and loss of microvasculature was found in the basilar membrane. The spiral ganglion cells, the cochlear nerve and the central auditory pathways and nuclei appeared to be unaffected.

Adult↗
PubMed1992

[Cochlear implants in children].

The development of surgically implantable hearing aids that are placed directly in the cochlea where they send electrical impulses to the cochlear nerve is a major break-through for patients whose hearing loss is so severe as to make conventional electroacoustic hearing aids ineffectual. Initially used only in adults, this method has gradually been extended to pediatric patients. To benefit from a cochlear implant, the patient must fulfill a number of criteria which are specified in this article. Following preoperative investigations, the decision is taken during a meeting of all the care providers involved, i.e., the surgeon, ENT phoniatrist or audiophonologist, hearing aid specialist, special education provider, speech therapist, psychologist, and other members of the health care staff. Team work is thus essential both before and after the procedure. The implant selected can be intracochlear or extracochlear and single-channel (one electrode) or multi-channel (several electrodes). Each team selects the implantation technique and type of implant they use according to their preferences and specific criteria. The authors use a multi-channel intracochlear system except in the rare instances where complete ossification of the cochlea requires use of an intracochlear mono-channel system. They have inserted implants in 29 patients to date. The cochlear implant has unquestionably had a significant impact of the life of these patients.

Child↗
PubMed1993

Endoscopy of the internal auditory canal during hearing conservation acoustic tumor surgery.

Hearing conservation acoustic neuroma surgery is technically demanding. This is attributable primarily to the formidable anatomic obstacles. The axis of the internal auditory canal (IAC) is oriented at an obtuse angle relative to the posterior petrous ridge. In addition, the labyrinth blocks the view of the lateral 2 to 3 mm of the IAC. These two factors prohibit an unobstructed view of the fundus of the IAC with a standard operating binocular microscope. However, angled rigid endoscopes (30 and 70 degrees) offer excellent views of the lateral portion of IAC. The facial nerve, cochleovestibular nerve, transverse crest, and vertical crest (Bill's bar) can be seen endoscopically. Neuroendoscopic examination is helpful to ensure complete tumor removal in the lateral IAC during acoustic tumor surgery. It is also helpful in visually verifying the continuity of the facial and cochlear nerves at the end of the operation.

Adult↗
PubMed1989

The human brain at stage 16, including the initial evagination of the neurohypophysis.

Thirty-nine sectioned embryos of stage 16 were studied. Up to this stage the amygdaloid body is derived entirely from the medial eminence, which was purely diencephalic in stage 14, but now extends also to the telencephalon. The area of the future olfactory bulb is indicated by the presence of olfactory fibres entering the brain wall; the future olfactory tubercle is characterized by cellular islands. The presence of the hippocampal thickening and various histological features make it possible to outline the main, future cortical areas already at this early stage: archi-, paleo-, and neopallium. Hippocampus and area dentata correspond to the areas identified by Hines (1922) and Bartelmez and Dekaban (1962) but not to those identified by Humphrey (1966). The interventricular foramen is wide. The cerebral hemispheres grow rostrally and dorsally, thereby forming the beginning of the longitudinal fissure. Apart from the commissure of the superior colliculi, which began to appear in advanced embryos of stage 14, fibres of the posterior commissure are now present in some specimens. The neurohypophysis is apparent in fewer than half of the embryos. The marginal ridge (zona limitans intrathalamica) separates the dorsal from the ventral thalamus. Cranial nerve 3 emerges from M2. M1 has become shorter. Important pathways are beginning: the olfactory route by the olfactory fibres and the medial forebrain bundle; the vestibular by vestibulocerebellar and vestibulospinal fibres; gustatory by chorda tympani, nervus intermedius, and tractus solitarius. Fibres of the cochlear nerve are noted. The first parasympathetic ganglia, submandibular and ciliary, are identifiable. Asymmetry of the cerebral hemispheres was noted in one specimen.

Brain↗
PubMed2002

Acoustic tensor tympani response and vestibular-evoked myogenic potential.

OBJECTIVE: To investigate the acoustic response properties and the vestibular-evoked myogenic potential (VEMP) in various lesions. STUDY DESIGN: Retrospective study of the clinical records of patients. METHODS: Neurotological tests including acoustic response and VEMP were performed and analyzed in 62 patients with facial palsy, otosclerosis, ossicular chain interruption, sensorineural hearing loss, or acoustic tumor. RESULTS: Inverted acoustic responses were observed in 25 of 38 (65.8%) patients with facial palsy, in 5 of 6 (83.3%) patients with acoustic tumor, and in all patients with otosclerosis, ossicular chain interruption, or sensorineural hearing loss. These inverted responses were obtained only when ipsilateral stimulation was used. The thresholds of the inverted responses were statistically significantly higher than those of the normal response. CONCLUSIONS: The vibration of the eardrum is thought to stimulate the ipsilateral trigeminal nerve, leading to contraction of the tensor tympani muscle. The stapedius response had an inhibitory effect on the inverted response. Vibration of the stapes footplate (which requires a normal middle ear conduction system) is necessary to induce the VEMP, whereas the functioning of the facial and cochlear nerves is independent of the VEMP response.

Adult↗
PubMed2002

Intraosseous dural arteriovenous fistula of the skull base associated with hearing loss. Case report.

The most common clinical presentations of dural arteriovenous fistulas (DAVFs) are bruit, headache, increased intracranial pressure, and intracranial hemorrhage. In particular locations, such as the cavernous sinus or middle cranial fossa, cranial nerve involvement due to dural arterial steal or venous occlusion may develop. A case in which a DAVF is associated with hearing loss, however, has not previously been reported. The authors report a case in which an intraosseous DAVF and associated hearing loss probably resulted from cochlear nerve or vascular compression caused by the draining vein or nidus of the DAVF.

Adolescent↗
PubMed2001

Value of high-resolution MR in patients scheduled for cochlear implantation.

OBJECTIVE: To determine sensitivity and specificity of high-resolution MR imaging and of high-resolution axial CT (HRCT) and to compare the two modalities in predicting the surgical and functional success of cochlear implantation. MATERIAL AND METHODS: The presurgical MR images (2D T2W TSE, 3D T2*W CISS, plain and contrast-enhanced 3D T1W MP-RAGE) and axial HRCT findings of 26 patients were evaluated with regard to the predictive value concerning the success of cochlear implantation. RESULTS: We found a high correlation between MR and HRCT and the success of cochlear implantation. In all 26 patients, the MR-based predictions concerning the success of cochlear implantation were correct. In 10 patients, MR gave additional information to HRCT. In all patients, MR gave sufficient information about the status of the inner ear, inner auditory canal and cochlear nerve to aid the surgeon during the operation. CONCLUSION: A high-resolution MR protocol consisting of coronal 2D T2W TSE, 3D T2*W axial CISS, plain and contrast-enhanced sagittal T1W 3D MP-RAGE is recommended for the evaluation of candidates scheduled for cochlear implantation. It provides information which cannot be obtained by HRCT.

Adolescent↗
PubMed1994

Inhibitory inputs modulate discharge rate within frequency receptive fields of anteroventral cochlear nucleus neurons.

1. The amino acid neurotransmitters gamma-aminobutyric acid (GABA) and glycine function as inhibitory neurotransmitters associated with nonprimary inputs onto spherical bushy and stellate cells, two principal cell types located in the anteroventral cochlear nucleus (AVCN). These neurons are characterized by primary-like (including phase-locked) and chopper temporal response patterns, respectively. 2. Inhibition directly adjacent to the excitatory response area has been hypothesized to sharpen or limit the breadth of the tonal frequency receptive field. This study was undertaken to test whether GABA and glycine circuits function primarily to sharpen the lateral edges of the tonal excitatory response area or to modulate discharge rate within central portions of the excitatory response area of AVCN neurons. 3. To test this, iontophoretic application of the glycineI antagonist, strychnine, or the GABAA antagonist, bicuculline, was used to block inhibitory inputs after obtaining control families of isointensity contours (response areas) from extracellularly recorded AVCN neurons. 4. Blockade of GABA and/or glycine inputs was found to increase discharge rate primarily within the excitatory response area of neurons displaying chopper and primary-like temporal responses with little or no change in bandwidth or in off-characteristic frequency (CF) discharge rate. 5. The principal sources of inhibitory inputs onto AVCN neurons are cells located in the dorsal cochlear nucleus and superior olivary complex, which appear to be tonotopically matched to their targets. In agreement with these morphological studies, the data presented in this paper suggest that most GABA and/or glycine inhibition is tonotopically aligned with excitatory inputs. 6. These findings support models that suggest that GABA and/or glycine inputs onto AVCN neurons are involved in circuits that adjust gain to enable the detection of signals in noise by enhancing signal relative to background.

Animals↗
PubMed1988

Transtemporal planned partial resection of bilateral acoustic neurinomas.

In an attempt to overcome the complete auditory deprivation of young patients with bilateral acoustic nerve schwannomas (Morbus v. Recklinghausen) a planned partial resection of the tumour was carried out in 11 hearing ears. The cerebello-pontine angle was exposed by the enlarged middle fossa approach (Wigand et al., HNO 1985). A strip of tumour was left in contiguity to the facial and cochlear nerves. Hearing was initially preserved in all cases. Four of them, however, developed total deafness after 3-39 months. Recurrent tumour growth was checked by CT scans. During the observation time one resting tumour became invisible, five remained unchanged. Two grew larger. Three cases dropped out of the follow-up. With regard to the high value of preserved auditory function during the first decades of life the planned partial resection may be considered preferable for cases of bilateral acoustic neuromas.

Adolescent↗
PubMed1978

Speech audiometry in acoustic neuroma.

The importance of speech audiometry in cases of sensori-neural deafness has been stressed. Four cases have been described clearly elucidating this point. Speech audiometry is within the means of most practising otologists. The appropriate apparatus is not expensive, nor is the method excessively time-consuming. In acoustic neuroma the damage to the cochlear nerve fibres may produce very little reduction in the hearing threshold level for pure tones, but a disproportionately large reduction in the discrimination score, often when the tumour is large enough to be causing brain stem compression. The disproportion is an important indicator to the presence of retro-cochlear pathology, of which acoustic neuroma is the most likely cause, a diagnosis which must be considered in every case of unilateral sensori-neural deafness.

Adult↗
PubMed1987

[Complete excision of acoustic neurinoma. Preservation of the facial nerve and hearing].

Using microtechniques, total removal of acoustic neuromas with facial nerve preservation is possible today in most cases. The next barrier of operative treatment is hearing preservation which is routinely attempted, with the help of intraoperative brainstem auditory evoked responses monitoring. The present series deals with 176 operations performed sub-occipitally in 159 patients from 1970 up to 1985. Twelve patients were operated upon 29 times. According to the W.T. Koos classification, there were 16 type II, 39 type III and 121 type IV neuromas. Ten patients died postoperatively. In seven of these, death was related to surgery, in two it was caused by respiratory failure. In the last patient unexplained sudden death occurred. 169 patients had no facial weakness preoperatively, in 158 of these the facial nerve was anatomically preserved (93.5%). Facial nerve function was judged by evaluation of function of face at least 12 months after operation. Up to 36 months after surgery, a good facial result may be expected in cases where the facial nerve was macroscopically spared at completion of removal. Functional results have been reviewed in 151 patients according to the J.W. House's International Evaluation System, with an excellent or good result in 66 (44%), fair in 65 (43%), bad or poor in 20 (13%). The anatomical preservation of the cochlear nerve could be achieved in 80 patients of the group of 169 in whom the auditory function had not been damaged by a previous operation. In fact, the auditory function preservation could be reasonably attempted in 79 patients: showing a hearing loss below 70 dB on tone audiometry, whatever may be the result of speech discrimination score. 59 patients (75%) of this later group had their auditory nerve preserved, 14 (18%) showed preserved hearing function postoperatively, 10 of these with a speech discrimination score over 50%. Two of these showed an improvement of preoperative hearing, two others showed a total recovery of hearing function after removal.

Adolescent↗
PubMed1984

Exaggerated acoustic reflex response in a patient with transient facial palsy and hyperacusis.

An unusual acoustic reflex response was documented by immittance recording in a patient with acute facial palsy. The amplitude of the stapedial response to sustained stimulation was reduced when recorded from the affected side, suggesting the facial nerve was affected proximal to the stapedius muscle. In addition, the impedance change at onset of intense acoustic stimulation of the affected side was unusually large, regardless of which stapedius response was recorded. The large change was coincident with the reported hyperacusis in the stimulated ear. This suggested the cochlear nerve as site of involvement of hyperacusis in this case of facial palsy.

Adult↗
PubMed2000

Neurotrophin 3 potentiates glutamatergic responses of IHC afferents in the cochlea in vivo.

Neurotrophins have traditionally been regarded as slow-acting signals essential for neuronal survival and differentiation. Recent studies with neuronal slices, cultures and nerve ending preparations have shown that neurotrophins generate acute changes in nerve activity. Among the secondary sensory cells are the inner hair cells (IHC) and taste buds, cells which express the neurotrophic factors necessary for the survival of their innervating neurons. If in these cells neurotrophins acutely affect the nerve activity of their afferent neurons, as in the central nervous system (CNS), this may have important functional implications for the corresponding sensory transduction processes. The neurotrophin NT-3 has been reported to be expressed in IHCs. We chose an in vivo application system for the microiontophoretic supply of NT-3 in the subsynaptic region of the IHC. The effect of NT-3 on spontaneous and evoked afferent cochlear nerve activities in adult guinea pig inner ear was studied. We observed that NT-3 rapidly increases the spontaneous and glutamate-evoked firing rate of IHC afferents. Moreover, firing induced by both N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) were specifically enhanced during the presence of NT-3, a process which was selectively blocked by the tyrosine kinase receptor inhibitor K252a. Because we localized NT-3 mRNA not only in IHCs but also in the spiral ganglion, we propose that similar to other sensory systems, afferent and autocrine neurotrophin activities may be responsible for survival of cochlear neurons. In addition, NT-3 in IHCs may operate as a signal-dependent, intrinsic neuromodulator and/or neuroprotector.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1986

Differential effects of benzodiazepines on cochlear and auditory nerve responses.

The influence exerted by chlordiazepoxide or midazolam upon auditory nerve compound action potential (cAP) and cochlear microphonic (CM) has been analyzed in chronic as well as in acutely prepared guinea pigs. Pre-receptorial variables were carefully controlled. The benzodiazepines dissociated the cochlear recorded potentials, increasing the cAP amplitude, in response to clicks, and decreasing the CM area, produced by a coherent pure tone pip. Both responses were dose related. A direct effect upon the cochlea was eliminated by local infusion of the drugs. It was also demonstrated to be a specific benzodiazepinic action because the use of an antagonist, Ro 15-1788, abolished the effect. Benzodiazepines could have increased the GABAergic activity at the pontine origins of the olivo-cochlear bundle or in the reticulo-cochlear fibers. These are the only central pathways that could be responsible for the effects obtained at the cochlea or auditory nerve levels. We suggest that this is the cause of the withdrawal of inhibitory tonus from the primary afferent fibers mediated by the efferent system (lateral superior olive), as may occur during dishabituation. It may also be the cause of the CM decrement, but the effect in this case would be exerted mainly through another set of efferent fibers (trapezoid body nucleus).

Action Potentials↗
PubMed1992

Patient performance with two types of multiple electrode intracochlear implant.

The functional results of 9 persons implanted with the Symbion Ineraid and 8 persons implanted with the Nucleus cochlear implant with the F0, F1, F2 coding strategy are reported. All patients were postlingually totally deaf, the patients implanted with the Symbion Ineraid were all above 40 years of age, while the Nucleus patients were with one exception under 40 years of age. The CID Everyday Sentences Test, the Helen Test and the Speech Tracking Test showed that all patients improved their communication skills when sound through the implant was added to lip-reading. The patients' ability to understand without lip-reading was tested with the CID everyday sentences test, with the Helen test, with spondees, with three-choice vowels and with a consonant confusion test. These showed that all 9 Symbion Ineraid patients achieved some degree of open speech understanding. Four of the 8 Nucleus patients achieved some degree of open speech understanding. Difference limen tests for intensity and frequency indicated that 2 of the Nucleus patients who did not achieve open speech understanding probably had extensive cochlear nerve damage, while the remaining 2 Nucleus patients without open speech understanding had good frequency and intensity discrimination.

Acoustic Stimulation↗
PubMed2006

Oscillating neurons in the cochlear nucleus: II. Simulation results.

A computer model of sustained chopper neurons in the ventral cochlear nucleus is presented and investigated. In the companion paper, the underlying neurophysiological and neuroanatomical data are demonstrated. To explain the preference of chopper neurons for oscillations with periods which are multiples of a 0.4 ms synaptic delay, we suggest a model of circularly connected chopper neurons. In order to simulate chopper neurons within a physiological dynamic range for periodicity encoding, it is necessary to assume that they receive an input from onset neurons. Our computer analysis of the resulting simple neuronal network shows that it can produce stable oscillations. The chopping can be triggered by an amplitude-modulated signal (AM). The dynamic range and the synchronous response of the simulated chopper neurons to AM are enhanced significantly by an additional input from onset neurons. Physiological properties of chopper neurons in the cat, such as mean, standard deviation, and coefficient of variation of the interspike interval are matched precisely by our simulations.

Acoustic Stimulation↗