Biomedical subjects

Haim Sohmer

Publications and source records attributed to Haim Sohmer.

22 records · Page 2Linked to original sources

PubMed2002

Functional impairment of the vestibular end organ resulting from impulse noise exposure.

OBJECTIVES/HYPOTHESIS: To assess the effect of exposure t o impulse noise, known to cause damage tothe cochlea, on the vestibular part of the inner ear using short latency vestibular evoked potentials (VsEPs), which is a direct and objective test for evaluating the function of the vestibular end organs. STUDY DESIGN: Prospective animal study. METHODS: Sand rats (Psammomys obesus) underwent baseline measurements of VsEPs in response to linear and angular acceleration stimuli and measurement of the auditory nerve and brainstem evoked response (ABR). The animals were then exposed to 10 gunshots generating impulse noise at an intensity of approximately 160 dB sound pressure level (SPL). Repeat measurements of the evoked potentials were conducted 2 to 4 hours, 1 week, and 6 weeks after the exposure. The amplitude and latency of the first wave of VsEPs in response to linear and angular acceleration stimuli, reflecting the function of the otolith organs and semicircular canals respectively, were compared between baseline and post-exposure measurements, as were ABR thresholds. RESULTS: The amplitude of the first wave of the VsEPs in response to linear acceleration was significantly (P <.001) reduced and the latency significantly (P <.005) prolonged 2 to 4 hours after the exposure in comparison to baselinemeasurements. The latency prolongation persisted in follow-up measurements, whereas the amplitude showed partial recovery. The first wave of VsEPs in response to angular acceleration was unchanged long-term. ABR thresholds were elevated in the long-term by 60 dB. CONCLUSION: It seems that impulse noise not only damages the cochlea, but also causes clear functional impairment to the vestibular end organs, mainly the otolith organs.

Animals↗

PubMed2002

An animal model for assessment of amniotic fluid clearance from the middle ear.

HYPOTHESIS: To determine the time needed for clearance of amniotic fluid from the middle ear after birth, an animal model study was performed. BACKGROUND: Before birth, the middle ear is full of amniotic fluid, and there is controversy about the time it takes for it to clear postnatally. This is of importance because it is suspected that amniotic fluid in the middle ear of the newborn may affect results of screening of hearing when using otoacoustic emissions. METHODS: Adult and neonatal guinea pigs underwent a right-side cochleotomy followed by baseline otoscopy, tympanometry, and auditory nerve- and brainstem-evoked response (ABR) measurements of the left ear. Subsequently, the animals' left middle ears were filled with saline through a hole drilled in the bulla. Over the next few days, assessment of saline clearance was conducted by repeated left-side otoscopy, tympanometry, and measurement of ABR. RESULTS: After filling the middle ear with saline, the tympanic membrane was opaque, a type B tympanogram was obtained, and the ABR threshold was elevated. After an average of 6.3 +/- 3.0 days, air bubbles were seen in otoscopy, a type C tympanogram was obtained, and the ABR threshold improved. Finally, after an average of 9.5 +/- 2.7 days, all 3 parameters returned to their baseline values. CONCLUSION: Taking into consideration that this is an animal study, the results suggest that clearance of amniotic fluid from the newborn middle ear takes longer than has been generally thought. In addition, an animal model for assessing the clearance of fluid from the middle ear has been developed.

Acoustic Impedance Tests↗

PubMed2002

Bone conduction hearing on the teeth of the lower jaw.

Bone conduction stimulation of the teeth of the lower jaw initiates auditory sensations. However the lower jaw is only loosely coupled to the skull by the temporo-mandibular joint. Therefore the 'classical' bone conduction pathway involving skull vibration transmission entirely along bone to the temporal-petrous bone requires further consideration. Bone conduction hearing thresholds to stimulation at the forehead and at the teeth of the upper and lower jaw were determined in human subjects. Thresholds on the teeth were better than those on the forehead and there was no difference between the thresholds measured following stimulation of the upper and lower teeth. Experiments in guinea-pigs provided evidence that vibration of the teeth leads to transmission of the audio-frequency vibrations by means of soft tissue, through skull foramina, into the skull cavity (brain and CSF) and from there by fluid channels directly into inner ear fluids, exciting the cochlea.

Acoustic Stimulation↗

PubMedDate not supplied

Susceptibility of young adult and old rats to noise-induced hearing loss.

This study was designed to test whether old rats show signs of presbyacusis and whether they would be either similarly or more or less susceptible to noise-induced hearing loss than young adult rats. Old (24 months) and young adult (3-4 months) Wistar rats were exposed to a broad-band noise of 113 dB SPL for a duration of 1 h (producing temporary threshold shifts) or 3 days (12 h noise/12 h quiet; permanent shifts). Auditory brainstem response (ABR), distortion product otoacoustic emissions (DPOAEs) and transient evoked otoacoustic emissions (TEOAEs) were measured before and after exposure. At the initial recording (before exposure), old rats demonstrated a small mean ABR threshold elevation, a reduction in amplitude of wave I (WI), a shortening of WI latency and a prolongation of the interpeak interval between WI and WIV, as compared to the young rats. The old rats also demonstrated a small DPOAE amplitude reduction and a reduction of peak-to-peak amplitude in the TEOAE response 2 ms after stimulus, but no reduction in TEOAE energy content between 2 and 4 kHz. These are signs of presbyacusis in the old rats. The noise exposures caused elevations in ABR threshold and reductions in DPOAE amplitude and TEOAE energy content that were similar in both the old and young rats. Their recovery from the noise-induced loss was also similar. Thus, the results of this study show that old and young adult rats, at least when considering clinically relevant intensities and durations of noise exposure, are equally susceptible to the effects of the exposure.

Age Factors↗