Biomedical subjects

M Hildesheimer

Publications and source records attributed to M Hildesheimer.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1990

Genetic mapping of X-linked albinism-deafness syndrome (ADFN) to Xq26.3-q27.I.

X-linked albinism-deafness syndrome (ADFN) was described in one Israeli Jewish family and is characterized by congenital nerve deafness and piebaldness. The ADFN mutation probably affects the migration of neural crest-derived precursors of the melanocytes. As a first step toward identifying the ADFN gene, a linkage study was performed to localize the disease locus on the X chromosome. The family was found to be informative for 11 of 107 RFLPs along the X, and two-point analysis showed four of them--factor 9 (F9), DXS91, DXS37, and DNF1--to have definite or suggestive linkage with ADFN. Multipoint linkage analysis indicated two possible orders within this cluster of loci, neither of which was preferable. In both orders F9 was the most distal, and the best estimate for the location of ADFN was between F9 and the next proximal marker (8.6 cM from F9 [Z = 8.1] or 8.3 cM from F9 [Z = 7.9]). These results suggest that the ADFN is at Xq26.3-q27.1. Disagreement between our data and previous localization of DXS91 at Xq11-q13 was resolved by hybridization of the probe pXG-17, which detects the DXS91 locus, to a panel of somatic cell hybrids containing different portions of the X chromosome. This experiment showed that this locus is definitely at Xq24-q26. Together with the linkage data, our results place DXS91 at Xq26 and underscore the importance of using more than one mapping method for the localization of molecular probes.

Albinism↗

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

Cochlear hypoxia and the compound action potentials.

A relatively restricted area, including the ear, was perfused in guinea pigs with hypoxic blood having a pO2 of 10, 20, and 30 mm Hg, respectively. The changes induced to the cochlear action potentials were analyzed and the results compared with those obtained in a previous study in which the guinea pigs were rendered hypoxemic by ventilating them with air entrapped in a closed circuit from which the CO2 was continuously absorbed. The changes induced to the cochlear action potentials by both methods were very similar. However, while using the territorial model for inducing hypoxia, 75% of the animals showed a threshold shift at a blood pO2 of 20 mm Hg and with the general model all the animals showed a threshold shift at 25 mm Hg blood pO2. In other words, if the hypoxic condition affected the whole body, other factors such as a slight, but continuous tendency to acidosis with significant increase in blood lactic acid concentration could join the oxygen deficit in affecting cochlear function.

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↗

PubMed1987

Cochlear action potentials threshold and systemic arterial pO2.

A progressive decrease in arterial pO2 was induced in Hartley guinea pigs (GP) by having them rebreathe the air entrapped in a closed circuit from which the CO2 was continuously absorbed. Following this slow-developing hypoxemia, a sequence of events concerning the ear could be observed. Firstly, a fluctuation in cochlear action potentials (CAP) was noted. This appeared only at stimulus intensities near the threshold and was not evident at higher intensities. At a mean arterial pO2 level of 30 mm Hg, this phenomenon was observed in 60% of the GP. At a mean pO2 of 24.66 mm Hg, a shift in threshold occurred in all GP. Finally, when the blood pO2 reached an average of 14.92 mm Hg, no CAP response could be elicited, even at click intensity of 120 dB SPL. The 30 mm Hg oxygen concentration in the arterial blood was considered as a "critical level" at which the cochlear function starts to deteriorate in guinea pigs.

Animals↗

PubMed1985

Basic metabolic rate in emotional stress: its potential influence on cochlear function.

Using a model previously described, prolonged emotional stress was induced in guinea pigs. Under this condition, arterial blood gases, blood glucose level, PO2 and PCO2 in the expired air, and the heat irradiated by the animals were measured and compared to those of the anesthetized guinea pigs. From the present study, two important findings should be mentioned. First, the metabolic rate of the animals under stress was 30% higher than in the anesthetized group. Second, the arterial PO2 level of the animals under stress was significantly lower than that in the anesthetized ones. Evaluating the noxious effect of severe and/or prolonged emotional stress, one should not neglect the increased oxygen demand resulting from the high metabolic rate of the subject. This factor, together with the decreased arterial blood PO2 level, reinforce the hypoxic effects on the cochlear function, caused by the vasoconstriction of the labyrinthine vessels.

Action Potentials↗

PubMed1985

Problems in interpretation of brainstem-evoked response audiometry results.

This report describes 6 cases - 3 adults and 3 children - in which no response could be obtained during the brainstem-evoked response audiometry (ABR) examination. This, in spite of the fact that maximal click intensity was used during the test, and despite the patients' nearly normal hearing sensitivity. All of the cases presented a slight degree of neurological deficiency, which could explain the faulty synchronization of the biological response to clicks. Attention is drawn to the fact that lack of response in ABR in cases with central nervous system involvement is not necessarily proof of severe hearing loss, and could supply important diagnostic cues.

Adult↗

PubMed1985

Minimal time interval in auditory temporal resolution.

Human auditory temporal resolution was measured. Normal-hearing adults in 3 age groups (I: mn age: 24 yrs, N:55; II: mn age: 44.5 yrs, N: 25; III: mn age: 66.4 yrs, N:18) were required to indicate in which of 2 successive noise bursts of relatively low frequency (concentrated from .1-.5 kc/s) a brief temporal gap was inserted. The noise was created by passing a 100-c/s square wave through an electronic switch with virtually instantaneous rise-fall time and through a clinical audiometer to the associated earphone. The level was set at about the loudness of each S's HTL at .25 kc/s. The minimum detectable time interval (delta t) varied lawfully and significantly (p less than .001) with burst duration and with age. For all ages delta t was approximately equal to 3 msec when the burst duration was longest (85 msec), but at the shortest duration (10 msec) it rose to 17.6, 22.2, and 29.9 msec for Grps I-III, respectively. The interaction between age and duration was also significant (p less than .001). It was suggested that establishment of delta t by this or a similar procedure could offer an important parameter for evaluation of auditory function.

Adult↗