Biomedical subjects

C Muchnik

Publications and source records attributed to C Muchnik.

16 recordsLinked to original sources

PubMed1992

[Cochlear implantation].

Since the Israeli cochlear implant program was started in June 1989, 74 candidates have been evaluated for implantation. The main causes for hearing loss were meningitis (16 patients), aminoglycoside toxicity (9), congenital (6), viral (e.g. mumps) (6), and middle ear infection. Candidates were rejected mainly due to psychosocial factors (40%) and audiological parameters (30%). 16 postlingual deaf were implanted. In 7 of them (43.7%) the results were excellent, in 4 (25.0%) good, in 3 (18.7%) fair; 1 case is currently in a training program and 1 is a failure. There were 2 major complications: facial nerve palsy which necessitated surgical decompression, and insertion of the electrodes into the hypotympanic air cells, corrected by reoperation.

Cochlear Implants↗

PubMed1992

Temporary threshold shift due to noise exposure in guinea pigs under emotional stress.

One of the factors which can affect the amount of temporary threshold shift (TTS) due to acoustic overstimulation is known to be the general metabolic state of the exposed subject. The present study was conducted to elucidate how preexisting intense emotional stress in awake guinea pigs could influence the TTS induced by exposure of 4 kHz at 120 dB SPL for 20 min. Considering the hypersympathetic activity in both 'stress' and 'noise' it was assumed that the two factors would act synergetically on the cochlear function. However, an unexpected result was obtained. The mean threshold for the stressed animals following noise exposure was significantly lower (better) than that of the controlled, sedated, guinea pigs.

Acoustic Stimulation↗

PubMed1992

Cooperation of hearing-impaired elderly subjects for participation in a hearing screening program.

Presbyacusis, the auditory disorder which accompanies the aging process, is well known. However, the practical assistance available to alleviate the breakdown in the communication ability of the older person is unsatisfactory, and provision for public awareness of a rehabilitation strategy has not yet been established in many countries. Four hundred and ninety-eight elderly subjects, aged 65-94 years, were hearing tested in different setups, a geriatric nursing home and in the community. It was found that the need for rehabilitation was high and the willingness to participate in a hearing screening program was low even though the rehabilitation treatment was provided without charge.

Age Factors↗

PubMed1991

The effect of bilateral sympathectomy on noise induced temporary threshold shift.

The cochlea is innervated by sympathetic nerves originating or passing the superior cervical ganglion. The termination of one type (the vascular independent) is in the habenular region close to the auditory nerve fibers, and the other, the perivascular type, is associated with blood vessels, particularly in the spiral vessel of the tympanic lip. Suggested functions have so far received partial evidence in the literature. Borg (1982) suggested the protective value of sympathectomy of the ear in noise. Our experiments further elaborate this protective value, as it was seen that bilateral cervical sympathectomy diminished the temporary threshold shift in awake, sound exposed GP.

Acoustic Stimulation↗

PubMed1991

Sedation effect on temporary threshold shift induced by acoustic overstimulation.

The mechanism by which noise damages the inner ear has not as yet been fully elucidated. Experiments were done to study the influence of the sedation in temporary threshold shift (TS) induced by acoustic overstimulation, as barbiturates were found to improve the brain's tolerance to ischemia. Four groups of guinea pigs (GP) were used. The temporary TS was decreased with the reduction of the temperature in awake, as well as sedated, sound-exposed GP. However, the temporary TS in the sedated, but normothermic GP was as great as in the awake, normothermic group. The high temperature counteracts the protection effect of the sedation in nose-induced hearing loss.

Acoustic Stimulation↗

PubMed1991

Central auditory skills in blind and sighted subjects.

Three different central auditory skills were compared and evaluated in 56 blind and 40 sighted subjects. The study consisted of three experiments conducted in three subgroups. Experiment A was performed in order to evaluate the localization function; experiment B for the temporal auditory resolution ability of the blind adult, and experiment C to test the ability of the blind person to discriminate speech material in noise. In all three experiments the blind subjects obtained significantly better results than the sighted subjects. From these results it was concluded that there is supporting evidence of a certain superiority of the blind individual with regard to central auditory function.

Adolescent↗

PubMed1990

Blood viscosity and sensorineural hearing loss.

Two groups of 33 subjects each, one experimental and one control, matched one-to-one for age and occupation, were chosen from a large number of subjects who were covered by special insurance for annual medical control at our hospital. The periodical checkups included cardiovascular, nervous, and renal systems, as well as vision and hearing. In addition routine blood tests, including whole blood viscosity, were also performed. The experimental group consisted of subjects in whom a bilateral, slight, and unexplained sensorineural loss of hearing was detected in the routine audiological testing, without any known reason. In the control group, the routine hearing tests demonstrated normal hearing. The differences between the two groups were statistically significant in pure-tone threshold level and in speech discrimination score, when the test was performed at a -5dB signal-to-noise ratio. The results of the vestibular tests were normal in both groups. Hematocrit and whole blood viscosity were slightly but significantly higher in the experimental group if compared with the control group. The number of subjects with abnormal whole blood viscosity results was higher in the experimental group. The whole blood viscosity as the etiological factor responsible for the hearing deterioration is described.

Adult↗

PubMed1990

Iontophoresis with an adrenergic alpha-blocker in acoustic overstimulation.

To study the influence of sympathetic innervation on the amount of threshold shift (TS) induced by sound overstimulation, iontophoresis with phentolamine, a known adrenergic alpha-blocker, was performed on awake guinea pigs. The sound exposure following this induced a significantly lesser degree of TS when compared with the control group. These findings indicate that iontophoresis may be of great help in transporting specific ionized chemical compounds through the intact cochlear walls in a completely non-invasive manner for studying cochlear physiology.

Acoustic Stimulation↗

PubMed1990

The influence of the efferent system on acoustic overstimulation.

Since the first anatomical description by Rasmussen, the efferent innervation of the ear has been extensively investigated in order to establish its role in the hearing process. It is accepted that the olivocochlear bundle (OCB) influences the activity of the afferent fibers and through it, the peripheral ear is controlled by higher centers as well as connected to the other ear. Cody and Johnstone (1982) and Rajan and Johnstone (1983) concluded that the amount of ipsilateral temporary threshold shift (TTS) was reduced by simultaneous contralateral acoustic stimulation or by destroying the contralateral cochlea. They attributed the results to the efferent system. It was our aim to investigate whether, and under which conditions, the amount of TTS would be influenced by the efferent system. The efferent innervation was eliminated by cutting the superior vestibular nerve. Two factors influenced the magnitude of TTS; the integrity of the OCB and the functional condition of the contralateral ear.

Acoustic Stimulation↗

PubMed1990

Perilymphatic fistula in the guinea pig.

Clinical reports on perilymphatic fistulae (PLF) of the round window membrane (RWM) have shown different degrees of hearing loss. However, the hearing can also be entirely unaffected. Experimentally induced PLF of the RWM in animals showed results similar to those of the clinical reports, although some researchers have concluded that perforation of the RWM per se does not necessarily induce significant hearing loss. The purpose of the present study was to clarify if, and how, PLF of RWM in the guinea pig actually affects the auditory action potentials. During 1 h of observation following perforation of the RWM, the immediate and continuous effect of the PLF was evaluated. In more than 50% of the animals, different amounts of threshold shift were obtained. In another group of guinea pigs an attempt was made to clarify the findings by reducing the cerebrospinal fluid pressure before perforating the RWM.

Animals↗

PubMed1989

Validity of tympanometry in cases of confirmed otosclerosis.

The otoadmittence or impedance measurements are common procedures in the diagnosis of middle ear pathologies. The present study was undertaken for the purpose of studying the clinical validity of static admittance values in 42 confirmed otosclerotic ears. For both 220 Hz and 660 Hz probe tones only one third of the otosclrotic ears had low admittance values, as expected. The remainder showed admittance values in the normal or high ranges. No significant correlation was found between air bone gap (ABG) and the admittance values.

Acoustic Impedance Tests↗

PubMed1989

Auditory and vestibular findings in Waardenburg's type II syndrome.

A group of 33 patients with the autosomal dominant form of Waardenburg Type II syndrome underwent hearing and vestibular examination. A bilateral, symmetrical, sensorineural hearing loss was found in 51 per cent of the tested subjects. The severity of hearing loss varied from mild to severe. Strong evidence indicated the possible progressive nature of the hearing loss. Concerning the frequency of vestibular findings, the study highlights the frequent divergence between cochlear and vestibular involvement.

Abnormalities, Multiple↗

PubMed1989

Low frequency air-bone gap in Menière's disease without middle ear pathology. A preliminary report.

The audiograms of some patients suffering from Meniere's disease show an unexplained conductive component, or air-bone gap (ABG), predominantly in the low frequencies. Neither the history nor physical findings support poor eustachian tube function, ossicular chain abnormalities, chronic ear disease, physical trauma, or otosclerosis as a cause of this audiometric finding. In the present study, 40 patients diagnosed as suffering from classical Meniere's disease were evaluated audiometrically. Thirteen (32.5%) of these patients demonstrated a low frequency ABG. An otologic evaluation was performed on each patient who exhibited the abnormal finding, but no middle ear pathology was discovered. An otherwise unexplained low frequency ABG in patients with Meniere's disease suggests the possibility of an "inner ear" conductive hearing loss. This conductive component may result from endolymphatic hydrops or perilymphatic hypertension (i.e., an inner ear hyperpressure exerted against the medial surface of the stapedial footplate) rather than from middle ear pathology. "Inner ear" conductive hearing loss is thought to be caused by an increase in inner ear fluid volume (endolymphatic hydrops) and pressure (endolymphatic or perilymphatic hypertension), which dampens footplate mobility medially and which is directly related to a relative inner ear or labyrinthine hyperpressure. Since the footplate mobility is only dampened and not fixed, a stapedial reflex may still be elicited.

Adolescent↗

PubMed1988

Chronic labyrinthine ischemia.

The purpose of the present study was to describe the audiological and vestibular deficit in patients presumed to suffer from chronic impairment of the blood supply to the labyrinth. Thirty-nine subjects affected by various pathologies often impairing systemic blood circulation, which also presented labyrinthine damage of unclear origin, were evaluated for a possible relationship between these two conditions. At the time of this study 80 per cent of the subjects showed also a certain degree of increased blood viscosity. The most common finding in the group was slow and progressive bilateral sensorineural loss of hearing. In most of the subjects the labyrinthine damage began with high-tone loss which, in time, became a flat curve. Less common, but still found in many patients, was a fluctuation in threshold. Short periods of spontaneous subjective improvement in hearing were accompanied by a better result in the Pure Tone Audiogram and Speech Reception Threshold. The discrimination scores remained generally lower than expected. Vestibular examination revealed pathological results for all the subjects in at least some of the tests. The mild subjective complaints concerning equilibrium could be explained by a central nervous system compensation.

Aged↗

PubMed1988

ECoG results in perilymphatic fistula: clinical and experimental studies.

Patients with perilymphatic fistula have been described as having symptoms similar to Meniere's disease and endolymphatic hydrops. Direct clinical or experimental evidence linking the two inner ear disorders has been lacking. An enhancement of the summating potential observed with electrocochleography suggests a diagnosis of ELH in both of these inner ear disorders. In this study, ECoG results of 27 patients with surgically confirmed PLF are reported. Fourteen patients with surgically confirmed spontaneous PLF had abnormal ECoG. Six of these 14 patients had normal hearing. The ECoG changes in patients with Meniere's disease and those with surgically confirmed PLF are identical, indicating the underlying pathologic change in both is hydrops. But there is no specific diagnostic abnormality on ECoG that differentiates these two inner ear disorders. Also, an experimental model of PLF was developed and studied in guinea pigs. "Inactive" PLF is defined as "an opening was made into the cochlea, but if no perilymph moved out through the fistula, it was defined as inactive" An "active" PLF occurs when perilymph actually moves from the inner ear out to the middle ear. ECoGs were recorded before and after creation of an "active" PLF. ECoG abnormalities were seen in "active" PLF and correlated with histologic data demonstrating ELH. An abnormally enhanced summating potential was demonstrated after active removal of perilymph through the experimentally created fistula. Cochlear duct histology showed hydropic distention of Reissner's membrane in the experimental ears and no changes in the membranous labyrinths of the unoperated, control ears.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1987

Surgical approach to the superior vestibular nerve in guinea pigs.

The superior vestibular nerve carries homo- and contra-lateral efferent fibers to the cochlea. The subarcuate fossa, a tube-like structure in the temporal bone of the guinea pig, can be used to reach the superior vestibular nerve at the level of the internal acoustic meatus. Normally, this structure accommodates the dorsal and ventral floccular extension of the cerebellum. This technique has several advantages. Firstly, a reduced cranial opening is necessary; secondly, less cerebellar tissue is sacrificed. Then there is the relative insulation of the operative field, and finally, it presents a straight guide to the internal auditory meatus and vestibular nerve.

Animals↗