Changes In Middle Ear Impedance Research Articles

Middle ear impedance studies in elderly patients implications on age-related hearing loss

IntroductionControversies arise with respect to functioning of the middle ear over time. ObjectiveTo assess changes in middle ear impedance that may be related to aging, and/or if there was an association of these changes with those of the inner ear in the elderly patients. MethodsCross-sectional, comparative study of elderly patients managed in ear, nose and throat clinics. A structured questionnaire was administered to obtain clinical information. Pure tone audiometry, tympanometry, and acoustic reflexes were performed. Comparative analyses were performed to detect intergroup differences between clinico-audiometric findings and middle ear measures, viz. tympanograms and acoustic reflexes. ResultsOne hundred and three elderly patients participated in the study; 52.4% were male, averagely 70.0±6.3 years old, age-related hearing loss in 59.2%, abnormal tympanograms in 39.3%, absent acoustic reflex in 37.9%. There was no association between age and gender in patients with abnormal tympanograms and absent acoustic reflex. Significantly more patients with different forms and grades of age-related hearing loss had abnormal tympanometry and absent acoustic reflex. ConclusionSome abnormalities were observed in the impedance audiometric measures of elderly patients, which were significantly associated with parameters connected to age-related hearing loss.

Effects of tensor tympani muscle contraction on the middle ear and markers of a contracted muscle

Many otologic disorders have been attributed to dysfunction of the tensor tympani muscle, including tinnitus, otalgia, Meniere's disease and sensorineural hearing loss. The objective of this study was to determine adequate stimuli for tensor tympani contraction in humans and determine markers of the hypercontracted state that could be used to detect this process in otologic disease. Multiple types of studies. Studies included 1) measuring middle ear impedance changes in response to orbital puffs of air, facial stroking, and self-vocalization; 2) measuring changes in stapes and eardrum vibrations and middle ear acoustic impedance in response to force loading of the tensor tympani in fresh human cadaveric temporal bones; 3) measuring changes in acoustic impedance in two subjects who could voluntarily contract their tensor tympani, and performing an audiogram with the muscle contracted in one of these subjects; and 4) developing a lumped parameter computer model of the middle ear while simulating various levels of tensor tympani contraction. Orbital jets of air are the most effective stimuli for eliciting tensor tympani contraction. As markers for tensor tympani contraction, all investigations indicate that tensor tympani hypercontraction should result in a low-frequency hearing loss, predominantly conductive, with a decrease in middle ear compliance. These markers should be searched for in otologic pathology states where the tensor tympani is suspected of being hypercontracted.

Aural Symptoms in Patients With Temporomandibular Joint Disorders: Multiple Frequency Tympanometry Provides Objective Evidence of Changes in Middle Ear Impedance

Aural Symptoms in Patients With Temporomandibular Joint Disorders: Multiple Frequency Tympanometry Provides Objective Evidence of Changes in Middle Ear Impedance

Wideband Energy Reflectance Measurements of Ossicular Chain Discontinuity and Repair in Human Temporal Bone

Recent studies have suggested the potential of wideband energy reflectance (ER) for the assessment of middle ear disorders. The purpose of this study was to examine the use of wideband ER in the evaluation of an ossicular discontinuity and its repair in human cadaver temporal bones. ER measurements at ambient pressure were made on five human cadaver ears in three conditions: (1) baseline with intact ossicular chain, (2) with the ossicular chain cut using an argon laser, and (3) with the ossicular chain repaired. Laser Doppler vibrometry measurements of stapes footplate velocity were also made in the three conditions to monitor the effect of the experimental manipulations on sound transfer through the middle ear. Disarticulating the ossicular chain resulted in the appearance of a deep notch in ER in each specimen ranging in center frequency from 561 to 841 Hz. The average reduction in ER was 31% at a frequency of 630 Hz. Laser Doppler vibrometry measurements confirmed the effect of the disarticulation and then repair using ionomeric cement. The low-frequency notch in ER was eliminated following repair of the ossicular chain. There was a small decrease in average high-frequency ER for both the cut and repaired conditions. A simple series impedance model of the middle ear was used to model the change in ER based on changes in middle ear impedance. The primary finding of the modeling was that the low-frequency notch in ER in the disarticulated ear occurs at the resonance frequency at which the reactance goes through zero consistent with the data. A disarticulation of the ossicular chain in human cadaver ears produces a low-frequency notch in ER that recovers with repair of the disarticulation. These results suggest that ER has the potential for use in the diagnosis of ossicular discontinuity and to monitor the status of the repaired ossicular chain. More data are needed to compare ER results from patients undergoing surgery for ossicular discontinuity with those of patients with other ossicular disorders such as otosclerosis.

Hearing and whistling in the deep sea: depth influences whistle spectra but does not attenuate hearing by white whales (Delphinapterus leucas) (Odontoceti, Cetacea).

Hearing is attenuated in the aerial ear of humans and other land mammals tested in pressure chambers as a result of middle ear impedance changes that result from increased air density. We tested the hypothesis, based on recent middle ear models, that increasing the density of middle ear air at depth might attenuate whale hearing. Two white whales Delphinapterus leucas made dives to a platform at a depth of 5, 100, 200 or 300 m in the Pacific Ocean. During dives to station on the platform for up to 12 min, the whales whistled in response to 500 ms tones projected at random intervals to assess their hearing threshold at each depth. Analysis of response whistle spectra, whistle latency in response to tones and hearing thresholds showed that the increased hydrostatic pressure at depth changed each whale's whistle response at depth, but did not attenuate hearing overall. The finding that whale hearing is not attenuated at depth suggests that sound is conducted through the head tissues of the whale to the ear without requiring the usual ear drum/ossicular chain amplification of the aerial middle ear. These first ever hearing tests in the open ocean demonstrate that zones of audibility for human-made sounds are just as great throughout the depths to which these whales dive, or at least down to 300 m.

Middle ear influence on otoacoustic emissions. I: Noninvasive investigation of the human transmission apparatus and comparison with model results

Evoked otoacoustic emissions (EOAEs) are generated within the cochlea in response to external sounds, and they can be acoustically detected in the external auditory meatus after backward propagation through the middle ear. In addition to being used to probe the cochlear mechanisms, they are expected to be sensitive to minute changes in middle ear impedance. Systematic measurements of the changes in the vectorial components of EOAEs were carried out after various manipulations of the human middle ear in order to characterize the influence of stiffness and inertia of the stapes and tympanic-membrane systems. For this purpose, stapedius muscle contractions were elicited by high-level contralateral sound, controlled changes in middle ear pressure (range ±100 daPa) were produced and the tympanic membrane was loaded with water droplets. A computer model of the middle ear network was implemented using a standard lumped-element electric analog of the middle ear (Zwislocki’s model). Forward and backward transmission changes were simulated and model predictions were compared to experimental data. Apart from the case of positive middle ear pressures, a close qualitative correspondence was found between model and real-ear results. Each of the effects was characterized by a unique pattern of phase and magnitude changes as a function of frequency, in relation to the mechanical characteristics of the involved subsystem (i.e. stapes stiffness, tympanic-membrane stiffness or mass) and its resonance properties. Owing to their high sensitivity, EOAEs could be helpful for an accurate individual multifrequency analysis of middle ear impedance by comparisons under rest and test conditions.

First audiogram for marine mammals in the open ocean and at depth: Hearing and whistling by two white whales down to 30 atmospheres

In examining the potential impact of human-made sound on sea mammals, it was considered that whale hearing sensitivity might diminish with increasing ambient pressure. To test the effect of depth, two white whales made 885 dives to a platform at 5, 100, 200, or 300 m in the Pacific Ocean. At each stationing on the platform up to 12 min at a time, whales whistled when they heard a 500-ms tone from a hydrophone. With increasing depth, air density increase in the middle ear, sinuses, and nasal cavity changed each whale’s whistle response, but did not attenuate hearing as it does in the aerial ear (of humans and other land mammals tested in pressure chambers) due to middle ear impedance changes. The findings support theories that sound is conducted through whale head tissues to the ear without the usual ear drum/ossicular chain amplification of the aerial middle ear. These first ever hearing tests in the open ocean demonstrate that whales hear as well at depth as near the surface, therefore, zones of influence for human-made sounds are just as great throughout the depths to which whales dive, or at least to 300 m. [Work supported by Office of Naval Research N0001496WK30349.]

Influence of static middle ear pressure on transiently evoked otoacoustic emissions and distortion products.

Otoacoustic emissions (OAE) are influenced in their amplitude and frequency spectra by the middle ear. The effects of changes in the middle ear transmission mechanisms on transiently evoked OAE (TEOAE) and distortion product emissions (DPOAE) were investigated as a function of static ear canal pressure in 25 normal-hearing test persons aged 18-35 years. The ear canal pressure was varied stepwise between positive and negative values of 200 daPa. TEOAE and DPOAE amplitudes were attenuated significantly with changes of the static ear canal pressure, with greatest changes at low frequencies (< 2 kHz). The alterations of OAE amplitude were slightly dependent on the polarity of the pressure, with positive pressure producing a greater attenuation (0.6 dB). The results demonstrate that changes in middle ear impedance can cause a misinterpretation of OAE. To avoid this problem, tympanometry should always precede OAE measurements. Alternatively, both methods can be combined using one acoustic probe, so that the emissions can be evoked at the peak of middle ear compliance.

Evoked Otoacoustic Emissions in Children in Relation to Middle Ear Impedance

The influence of changes in middle ear impedance with and without serotympanon on the measurement of evoked otoacoustic emissions (EOAE) was investigated in 108 children between 3 and 12 years of age. Children with proven serotympanon never showed good EOAE. In those who only had changes in middle ear impedance without a serotympanon, the decrease in EOAE amplitude was more related to the magnitude of conductive hearing loss than to the change in impedance itself. These results are compared with those of a neonatal screening project in which some of the 532 healthy fullterm newborns showed poor emissions in the first days of life. It seems reasonable to assume that this is due to incomplete pneumatization of the middle ears of these children, especially as a control audiogram later in their lives showed normal hearing thresholds.

Response losses in cats with tympanic-membrane perforations: External canal effects

Response losses due to small tympanic-membrane (TM) perforations were assessed in cats with surgically shortened ear canals (EAM) and four extensions of different lengths, volumes, and leakiness. Changes in input, required for a criterion microphonic response, were recorded, both in terms of voltages across the transducer (loudspeaker and earphone) and SPLs (at the entrance of the EAM and at the TM). At the TM, SPL changes increasingly sloped toward lower frequencies (12 dB/octave). Flat response losses, as seen audiometrically in clinical patients, were found only (1) in the presence of a leaky EAM—low frequencies, (2) when SPLs were measured at the entrance of the EAM—midfrequencies, and (3) when voltages across the transducer (precalibrated SPLs)—mid and high frequencies. Audiometric results, which depend upon precalibrated SPLs, may not adequately measure hearing losses due to changes in middle ear impedance. [Supported by NIH and HEW grants.]

Relative impedance measurements in young children.

RELATIVE impedance measurements in adults have shown that contractions of the stapedius muscles result in changes in middle ear impedance and that the contractions occur as bilateral reflexes to relatively intense acoustic stimulation (70 to 90 db sensation level).^1,2Jepsen,¹testing both ears of 91 normal subjects, detected stapedius reflex contractions in all but one of the ears tested. Clinical application has shown that this technique can be used in differentially diagnosing conductive hearing losses,³sensorineural losses with recruitment,^1,2,4,5and, in certain instances, pseudohypacusis.^1,2,6At present, a lack of information regarding relative impedance measurements in children limits the effective clinical use of this technique with this population. We have been able to locate reports of only two studies in which children participated, the ages reported being seven⁷and 10 years.¹ This study was undertaken to obtain information regarding the use of relative impedance