Ipsilateral Acoustic Reflex Thresholds Research Articles

EVALUATION OF RECOVERY BY STAPES REFLEX IN PATIENTS WITH PERIPHERAL FACIAL PARALYSIS

Objective: The aim of this study was to investigate the acoustic reflex in different frequencies at the time of diagnosis, during the treatment and follow-up of patients with idiopathic peripheral facial nerve palsy and compare these results with House-Brackmann clinical scoring to determine the prognostic value of acoustic reflex in these patients. Material and Methods: Thirty-three adult patients with idiopathic peripheral facial palsy (aged 18-77 years, 16 male, 17 female) were included in the study. All the patients were clinically graded with House-Brackmann clinical scoring and acoustic reflex test was performed at the time of diagnosis, 1st, 2nd, 3rd, 4th weeks, 2nd and 3rd month. Ipsilateral acoustic reflex thresholds were measured from both ears with impedance audiometry using a 226 Hz probe tone. Results: Significant relation was observed between the presence of sequel and initial grade and absence of acoustic reflex at 0.5, 1, 2 kHz at time of diagnosis. In addition, after the 1st week, a significant relation was also detected at 4 kHz frequency during all the follow-up period. The risk of sequelae would increase more than 3 times as the initial grade value increased. Conclusion: The present study revealed the relation between the sequel and initial high grade, the absence of acoustic reflex at 0.5, 1, 2 kHz at time of diagnosis in addition with high age. Statistics does not support the same relation at 4 kHz frequency at time of diagnosis. However, statistic reveals that only the initial grade can best predict the risk of sequel, in addition, the risk of sequel increases more than 3 times as the initial grade value increase.

Neurodegenerative Diseases and the Auditory-Vestibular System

Neurodegenerative Diseases and the Auditory-Vestibular System

Effect of age-related hearing loss on the click-rate-induced facilitation of acoustic reflex thresholds

Objective: This investigation was designed to evaluate the effect of age-related hearing loss on the click-rate-induced improvement in the acoustic reflex thresholds. Design: Case–control study. Study sample: Data from five different adults ear-groups (15 ears each) were included in the study: 1. Younger with normal hearing. 2. Older with normal hearing. 3. Older with mild high-frequency loss. 4. Older with moderate high-frequency loss. 5. Older with low- and high-frequency loss. Ipsilateral acoustic reflex thresholds were obtained from the left and/or right ear/s by presenting clicks at the repetition rates of 50, 100, 150, 200 and 300 clicks/s. The rate-induced facilitation (RIF) was calculated by subtracting the lowest acoustic reflex threshold from the highest reflex threshold obtained across the various click-rates. Results: The click-RIF is significantly reduced in older individuals compared to younger adults. There is no significant difference in RIF across the four older adult groups suggesting that an age-related, mild to moderate hearing loss has no significant effect on the click RIF of the acoustic reflex thresholds. Conclusions: Click-RIF may allow us to document the effect of ageing on temporal processing within the auditory brainstem area, in a time-efficient and objective manner using commercially available equipment.

Time course and frequency specificity of sub-cortical plasticity in adults following acute unilateral deprivation

Auditory deprivation and stimulation can change the threshold of the acoustic reflex, but the mechanisms underlying these changes remain largely unknown. In order to elucidate the mechanism, we sought to characterize the time-course as well as the frequency specificity of changes in acoustic reflex thresholds (ARTs). In addition, we compared ipsilateral and contralateral measurements because the pattern of findings may shed light on the anatomical location of the change in neural gain. Twenty-four normal-hearing adults wore an earplug continuously in one ear for six days. We measured ipsilateral and contralateral ARTs in both ears on six occasions (baseline, after 2, 4 and 6 days of earplug use, and 4 and 24 h after earplug removal), using pure tones at 0.5, 1, 2 and 4 kHz and a broadband noise stimulus, and an experimenter-blinded design. We found that ipsi- as well as contralateral ARTs were obtained at a lower sound pressure level after earplug use, but only when the reflex was elicited by stimulating the treatment ear. Changes in contralateral ARTs were not the same as changes in ipsilateral ARTs when the stimulus was presented to the control ear. Changes in ARTs were present after 2 days of earplug use, and reached statistical significance after 4 days, when the ipsilateral and contralateral ARTs were measured in the treatment ear. The greatest changes in ARTs occurred at 2 and 4 kHz, the frequencies most attenuated by the earplug. After removal of the earplug, ARTs started to return to baseline relatively quickly, and were not significantly different from baseline by 4–24 h. There was a trend for the recovery to occur quicker than the onset. The changes in ARTs are consistent with a frequency-specific gain control mechanism operating around the level of the ventral cochlear nucleus in the treatment ear, on a time scale of hours to days. These findings, specifically the time course of change, could be applicable to other sensory systems, which have also shown evidence of a neural gain control mechanism.

Evaluation of Acoustic Reflex and Reflex Decay Tests in Geriatric Group.

To determine average acoustic reflex thresholds in geriatric groups by assessing ipsilateral and contralateral acoustic reflex and reflex decay tests. A total of 25 elders between ages 65-84 years (74.3±5.4) and 25 individuals between ages 18-45 years (30.4±4.2) were recruited for the study. After ear, nose, and throat examination, ipsilateral and contralateral acoustic reflex thresholds at 500, 1000, 2000, and 4000 Hertz (Hz) were determined and a reflex decay test at contralateral 500 Hz was conducted. Ipsilateral acoustic reflex thresholds were obtained with high-frequency band, low-frequency band, and wide band noise, and the results were compared with ipsilateral acoustic reflexes at 500, 1000, 2000, and 4000 Hz. There was no statistically significant difference between the two groups in ipsilateral and contralateral acoustic reflex measurements at 500, 1000, 2000, and 4000 Hz (p>0.05). Negative reflex decay was obtained in all participants and no statistically significant difference between the two groups was observed in terms of reflex decay thresholds (p>0.05). Acoustic reflex with high-frequency band noise was observed in five of nine elders whose acoustic reflexes were not obtained at 2000 and 4000 Hz, whereas acoustic reflex with low-frequency band noise was observed in one of six elders who did not show reflexes at 500 and 1000 Hz. It was concluded that although some changes were observed due to age, middle ear and stapes muscles work normally in geriatric group. In the reflex decay test, reliable results were obtained at contralateral 500 Hz. Acoustic reflex measurements with low- and high-frequency band noise may also be used to assess middle ear functions.

Acoustic reflex on newborns: the influence of the 226 and 1,000 Hz probes.

To analyze the occurrence of acoustic reflex and its threshold on newborns using the 226 and 1,000 Hz probes. Thirty-six newborns with "PASS" results in newborn hearing screening and tympanogram with one or two peaks for both probe tones were included. Group I comprised 20 full-term newborns without risk indicator for hearing loss, and Group II comprised 16 newborns with at least one risk indicator. The study about ipsilateral acoustic reflex thresholds was conducted in 500, 1,000, 2,000, and 4,000 Hz. The groups presented the acoustic reflex thresholds between 50 and 100 dB for both probe tones. In the comparison between the probes, there were differences in all frequencies evaluated in Group I, with the lowest threshold mean for the 1,000 Hz probe. In Group II, differences were detected at 2,000 Hz. The mean acoustic reflex thresholds were similar in both groups for the 226 Hz probe. There was a difference for the 1,000 Hz probe in all tested frequencies. The percentage of response was higher in both groups for the 1,000 Hz probe. The kappa test showed extremely poor agreement in the comparison of results between both probes. The occurrence of acoustic reflex was higher in newborns and its thresholds were lower with the 1,000 Hz probe both for healthy newborns and for newborns at risk.

Wideband acoustic-reflex test in a test battery to predict middle-ear dysfunction

A wideband (WB) aural acoustical test battery of middle-ear status, including acoustic-reflex thresholds (ARTs) and acoustic-transfer functions (ATFs, i.e., absorbance and admittance) was hypothesized to be more accurate than 1-kHz tympanometry in classifying ears that pass or refer on a newborn hearing screening (NHS) protocol based on otoacoustic emissions. Assessment of middle-ear status may improve NHS programs by identifying conductive dysfunction and cases in which auditory neuropathy exists. Ipsilateral ARTs were assessed with a stimulus including four broadband-noise or tonal activator pulses alternating with five clicks presented before, between and after the pulses. The reflex shift was defined as the difference between final and initial click responses. ARTs were measured using maximum likelihood both at low frequencies (0.8–2.8kHz) and high (2.8–8kHz). The median low-frequency ART was elevated by 24dB in NHS refers compared to passes. An optimal combination of ATF and ART tests performed better than either test alone in predicting NHS outcomes, and WB tests performed better than 1-kHz tympanometry. Medial olivocochlear efferent shifts in cochlear function may influence ARs, but their presence would also be consistent with normal conductive function. Baseline clinical and WB ARTs were also compared in ipsilateral and contralateral measurements in adults.

Test–Retest Reliability of Acoustic Reflex Test in 6-Week-Old Healthy Infants

The aim of this study was to investigate the test-retest reliability of acoustic reflex (AR) test measured from a group of 6-week-old infants who passed a transient evoked otoacoustic emission test and an automated auditory brainstem response screening test. Ipsilateral acoustic reflex thresholds for a 2 kHz pure tone and broadband noise were recorded from 70 infants using a Madsen Otoflex Diagnostic Immittance meter with a probe tone of 1000 Hz. The mean AR thresholds obtained in the first test were 67.3 and 80.9 dB HL for the broadband noise and 2 kHz tone, respectively. The results for the retest condition did not differ significantly from those of the first test. The AR test also showed high test-retest reliability as demonstrated by intracorrelation coefficients across the test-retest conditions of 0.783 and 0.780 for the broadband noise and 2 kHz pure tone stimuli, respectively. Findings from this study suggest that the AR test could be used to establish reliable AR thresholds in 6-week-old infants.

Wideband Reflectance Measures of the Ipsilateral Acoustic Stapedius Reflex Threshold

The purpose of this study was to develop a method for acoustically measuring the ipsilateral acoustic stapedius reflex threshold by using wideband shifts in energy reflectance and admittance. A group of 27 young adult subjects with normal hearing participated in the study. Contralateral reflex thresholds were first measured for a 4000 Hz activator tone (maximum level, 92 dB SPL), using a clinical method with a 226 Hz probe tone. Ipsilateral and contralateral reflex thresholds were then measured by using an experimental wideband reflectance and admittance system that used a band-filtered click (200 to 2000 Hz) as the probe stimulus, presented simultaneously with the 4000 Hz activator tone. Reflex thresholds for the wideband system were determined by using statistical tests of the magnitude of the reflex responses as well as their correlation with other reflex responses. Clinical and experimental reflex thresholds were obtained for 9 of the 27 subjects for all conditions. Clinical reflex thresholds were absent for 8 subjects for whom experimental reflex thresholds were present and were present for 5 subjects who had absent experimental reflex thresholds for one or more conditions. An additional 5 subjects had absent reflex thresholds in all conditions, consistent with the low maximum level of the activator. Wideband measures of contralateral reflex thresholds were approximately 3 dB lower than those obtained with the clinical system. The magnitudes of the group means of the reflex responses were similar for ipsilateral and contralateral stimulations. Wideband measures of reflectance and admittance may be used to estimate the ipsilateral acoustic stapedius reflex threshold by separating in frequency the spectral energies of the wideband probe stimulus from the activator stimulus. This technique holds promise for measuring reflex thresholds for individuals with absent reflex thresholds through the use of standard clinical methods.

Unilateral hearing loss in children with shunt-treated hydrocephalus.

This study investigated the characteristics of hearing loss in children with ventriculoperitoneal (VP) shunted hydrocephalus. Twelve hydrocephalic children with patent VP shunts participated. The etiology of the hydrocephalus was either intraventricular hemorrhage or spina bifida. Audiometric examination included pure-tone air conduction thresholds, tympanometry, contralateral and ipsilateral acoustic reflex thresholds (ARTs), and distortion product otoacoustic emissions (DPOAEs). A unilateral, high-frequency, cochlear hearing loss was found in the ear ipsilateral to the shunt placement in 10 (83%) of the 12 shunt-treated hydrocephalic children. No hearing loss was observed in the ear contralateral to shunt placement. Based on the pure-tone audiometric findings, coupled with the decrease in DPOAE amplitude in the shunt ear, the hearing loss appears to be cochlear in nature. We suggest that cochlear hydrodynamics are disrupted as the result of reduced perilymph pressure, a consequence of cerebrospinal fluid (CSF) reduction due to the combined effects of a patent shunt and a patent cochlear aqueduct. In addition, a concomitant brain stem involvement is evidenced in the ART pattern, possibly produced by the patent shunt draining the CSF from the subdural space, resulting in cranial base hypoplasia.

Acoustic reflex thresholds at varying click rates in children

Objective: Previous studies conducted with young adults have shown that ipsilateral acoustic reflex thresholds improve with an increase in the click-rate. Older adults also show an improvement in acoustic reflex thresholds with an increase in the click-rate. However, the click-rate induced facilitation (RIF) of acoustic reflex thresholds is significantly reduced in older adults. These results suggest that slower temporal processing in older adults can be documented by measuring the click-RIF of acoustic reflex thresholds. Thus, the click-RIF of acoustic reflex thresholds may prove to be a valuable tool for the assessment of temporal processing disorders in young children. However, click-RIF of ipsilateral acoustic reflex thresholds has not been studied in young normal children. The purpose of this study was to evaluate and document the click-RIF in young normal children to provide normative data for this age-group. Methods: The study included a total of 30 participants (12 male and 18 female) with normal hearing between the ages of 6 and 10 years. Children with outer, middle ear, or neurological disorders were excluded from the study. Ipsilateral acoustic reflex thresholds were determined in the left and right ears with clicks presented at the rate of 50 and 100 per s. The frequency of the probe tone was 226 Hz and intensity was 85 dB SPL. A statistical analysis using a three factor mixed MANOVA was planned to explore differences between ears, click rates and gender. Results: The MANOVA revealed a significant effect ( P=0.0000) for the click-rate. There were no differences between ears or gender and no interactions. The mean click-RIF with an increase in the rate from 50 to 100 per s was 10.50 dB. Conclusion: Comparison of these results with previous results obtained from young adults suggests that young normal children show click-RIF that is similar to that apparent in young adults.

Can maximum comfortable loudness levels in hearing impaired listeners be predicted from ipsilateral acoustic reflex thresholds recorded with high frequency probes?

This study was designed to test the effectiveness of the ipsilateral acoustic reflex thresholds measured with low and high frequency probes in predicting the maximum comfortable loudness levels (MaxCLs) in hearing-impaired subjects using recently available sophisticated procedures for acoustic reflex and loudness measures. Loudness growth functions were measured in hearing-impaired subjects at .5, 1 and 2 kHz using a computerized procedure. The maximum level among those sound pressure levels judged as 'comfortable' was designated as the MaxCL. Acoustic reflex thresholds were measured for .5, 1 and 2 kHz activator signals using 226, 678 and 1000 Hz probes. Regression analyses suggested that acoustic reflex thresholds recorded with the 678 and 1000 Hz probes could provide an objective estimate of the MaxCLs for 1 and 2 kHz. Thus, acoustic reflex thresholds may be useful in fitting hearing aids for those subjects in whom reliable measures of MaxCLs cannot be obtained.

Effect of Probe Frequency and Gender on Click-evoked Ipsilateral Acoustic Reflex Thresholds

This study was designed to evaluate the effects of gender and probe frequency on the ipsilateral click-evoked acoustic reflex thresholds. Ipsilateral acoustic reflex thresholds were obtained from the left ear of each subject (12 male and 12 female normal young adults) by presenting clicks at the rate of 180/sec. The probe tone frequencies were 226, 678 and 1,000 Hz. The results revealed that acoustic reflex thresholds for the 678 Hz probe were significantly higher than those obtained with the 226 and 1,000 Hz probes. No gender differences were apparent. However, the static admittance was significantly correlated with the acoustic reflex thresholds for the 678 Hz probe in only the female subjects. For the 226 Hz probe, the elicitation of the reflex resulted in a decrease in static admittance in all the subjects. For the 678 Hz probe, the admittance decreased in 58% of the subjects and it increased in 42% of the subjects. For the 1,000 Hz probe, an increase in admittance was apparent in all of the subjects. The results suggest that either the 226 Hz or the 1,000 Hz probes can be used for the measurement of click-evoked acoustic reflex thresholds in adults.

The effect of probe frequency on ipsilateral acoustic reflex thresholds

This study was designed to evaluate the effect of probe frequency on the ipsilateral acoustic reflex thresholds. Five young female subjects with normal hearing participated in the study. Ipsilateral acoustic reflex thresholds were established for each subject using 226-, 678-, and 1000-Hz probe tones. The criteria for reflex thresholds were based on the lowest hearing levels (HL) at which the following minimum changes in baseline admit- tance were apparent on at least two trials: for 226 Hz, 0.02 ml; for 678 Hz, 0.06 mmho; and for 1000 Hz, 0.09 mmho. The reflex activator frequencies were 0.5, 1, and 2 kHz. The repeated measures multivariate analyses of variance were performed on the data. The results revealed a significant effect of probe frequency and a significant activator and probe interaction. Further analyses with the least significant difference (LSD) test revealed that the reflex thresholds obtained with the 678-Hz probe were significantly higher than those obtained with the 226- and 1000-Hz probes. In addition, for the activator frequency of 1 kHz, the lowest reflex thresholds were obtained with the 226-Hz probe, and for the activator frequency of 2000 Hz the lowest acoustic reflex thresholds were obtained with the 1000-Hz probe tone. [Work supported by a Bloomsburg University Grant for Research and Disciplinary projects.]

The relationship between ipsilateral acoustic reflex thresholds and loudness judgments in young normal women

This study examined the relationship between ipsilateral acoustic reflex thresholds (ARTs) and loudness judgments. Eleven young women served as subjects. The ipsilateral ARTs were recorded for 0.5-, 1-, and 2-kHz activators using two probe frequencies: 678 and 1000 Hz. The subjects were also asked to judge the loudness of warble tones (0.5, 1, and 2 kHz) presented at various sound pressure levels in the following categories: not audible, very soft, soft, comfortable, loud, and very loud. From this data following levels were derived for each subject: very loud, average loud, maximum loud, average comfortable, and maximum comfortable. Correlation analyses were performed to examine the relationship of these levels with the ARTs. For 1 kHz, the maximum comfortable loudness levels were significantly correlated with the ARTs obtained with the 678-Hz probe tone and the average comfortable loudness levels were significantly correlated with the ARTs obtained with the 1000-Hz probe tone. For 2 kHz, the ARTs obtained with the 678-Hz probe tone were significantly correlated with the sound pressure levels that were judged as ‘‘very loud.’’ For 500 Hz, none of the loudness judgments were predictable from the ARTs. Detailed analyses and possible implications of the findings will be presented. [Work supported by a Bloomsburg University Grant for Research and Disciplinary projects.]

Improved intensity coding at faster click-rates within the acoustic reflex pathway.

This investigation was designed to study the effect of click repetition rates on the slopes of the ipsilateral acoustic reflex growth functions. Sixteen normal female subjects within the age range 20 to 26 years participated in the study. Following the determination of ipsilateral acoustic reflex thresholds at the click repetition rates of 50, 100, 150, 200, 250 and 300 clicks/sec, reflex amplitudes were measured at 5 and 10 dB above the threshold values. The amplitudes of the acoustic reflex grew more rapidly at higher click rates, resulting in steeper slopes of the acoustic reflex growth functions. These results suggest better coding of intensity at higher click repetition rates within the ipsilateral acoustic reflex pathway.

Effect of hearing impairment on the click‐rate induced facilitation of the acoustic reflex thresholds in older individuals.

Ipsilateral click thresholds can improve by approximately 21 dB, with in increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24 199–205 (1995)] in young normal individuals. This improvement is significantly reduced in older individuals [Rawool, J Gerontol. Biol. Sci. (in press)]. The current investigation was designed to evaluate the effect of age‐related hearing impairment on the rate‐induced improvement in the acoustic reflex thresholds. Ipsilateral acoustic reflex thresholds were obtained from 60 older ears in the age range of 50 to 74 years. The subjects were divided into four groups: (I) Normal. Hearing within normal limits (20 dB). (II) Mid high‐frequency impairment. Hearing within normal limits up to 2 kHz, and an average impairment of 17.5 to 25 dB at 3, 4, 6, and 8 kHz. (III) Moderate high‐frequency impairment. Hearing within normal limits up to 2 kHz and an average impairment of 35 to 61 dB at 3, 4, 6, and 8 kHz. (IV) Flat hearing impairment. Hearing impairment across the test frequencies. Ipsilateral acoustic reflex thresholds were obtained from the left and/or right ear by presenting clicks at the repetition rates of 50, 100, 150, 200, and 300 clicks/s. No significant differences were apparent in the rate‐induced improvement (11 to 14 dB) in the acoustic reflex thresholds across the four groups.

Is higher acoustic energy at faster rates necessary for the click‐rate‐induced improvement in acoustic reflex thresholds?

Ipsilateral click thresholds can improve by approximately 21 dB, with an increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24, 199–205 (1995)]. When click‐trains are presented over the same duration (e.g., 1.5 s), the number of clicks presented at the lower rates is less than the number of clicks presented at the higher repetition rates. Thus there is more total energy for the higher repetition rates. Therefore, it has been proposed that an important factor contributing to the threshold advantage for higher repetition rates could be the number of clicks. This investigation was designed to evaluate acoustic reflex thresholds at various repetition rates using a constant number of clicks (constant acoustic energy). Ipsilateral acoustic reflex thresholds were obtained from 19 normal female left ears by presenting 300 clicks at the repetition rates of 50, 100, 150, 200, and 300/s. The frequency of the probe tone was 226 Hz (85 dB SPL). The results showed a significant improvement (mean = 17 dB) in acoustic reflex thresholds with the increase in repetition rates. Thus the improvement in acoustic reflex thresholds with the increase in the repetition rate can occur as a function of the rate itself, even if a constant number of clicks are presented at each rate.

Effect of probe frequency on the click‐rate‐induced facilitation of the acoustic reflex thresholds.

Ipsilateral click thresholds obtained with a 226‐Hz probe tone can improve by approximately 21 dB, with an increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24, 199–205 (1995)]. This investigation was designed to evaluate the effect of higher probe frequencies on the click‐evoked acoustic reflex thresholds and on the rate‐induced improvement in the acoustic reflex thresholds. Twelve female and six male subjects with normal hearing participated in the study. Ipsilateral acoustic reflex thresholds were obtained from the left ear of each subject by presenting clicks at the repetition rates of 60, 120, 180, 240, and 300 clicks/s. The results were obtained for three probe tone frequencies: 226, 678, and 1000 Hz. All the subjects showed a decrease in admittance for the 226‐Hz probe and an increase in the admittance for the 1000‐Hz probe. For the 678‐Hz probe, some subjects showed an increase in admittance and others showed a decrease in admittance. The acoustic reflex thresholds were significantly elevated for the 678‐Hz probe tone. The rate‐induced improvement in acoustic reflex thresholds for each subject was calculated as the difference between the minimum and maximum acoustic reflex thresholds. This improvement (13 to 17 dB) was not significantly different for the three probe tones.

Click-rate induced facilitation of the acoustic reflex using constant number of pulses.

This investigation was designed to evaluate acoustic reflex thresholds at various repetition rates using a constant number of clicks (constant acoustic energy). Ipsilateral acoustic reflex thresholds were obtained from 19 left ears by presenting 300 clicks at the repetition rates of 50, 100, 150, 200 and 300/s. The results showed an improvement in the acoustic reflex thresholds with an increase in the repetition rates (rate integration). Thus for the test conditions used in the study, rate-induced facilitation of the acoustic reflex thresholds can be demonstrated even if the acoustic energy in the stimuli at various rates is held constant. Greater acoustic energy at higher repetition rates is unnecessary for such facilitation.