Stapedial reflex threshold predicts individual loudness tolerance for people with autistic spectrum disorders.

People with autism spectrum disorder (ASD) frequently show the symptoms of oversensitivity to sound (hyperacusis). Although the previous studies have investigated methods for quantifying hyperacusis in ASD, appropriate physiological signs for quantifying hyperacusis in ASD remain poorly understood. Here, we investigated the relationship of loudness tolerance with the threshold of the stapedial reflex and with contralateral suppression of the distortion product otoacoustic emissions, which has been suggested to be related to hyperacusis in people without ASD. We tested an ASD group and a neurotypical group. The results revealed that only the stapedial reflex threshold was significantly correlated with loudness tolerance in both groups. In addition to reduced loudness tolerance, people with lower stapedial reflex thresholds also exhibited higher scores on the Social Responsiveness Scale-2.

Stimulation parameters differ between current anti-modiolar and peri-modiolar electrode arrays implanted within the same child.

OBJECTIVE: To compare stimulation parameters of peri-modiolar and anti-modiolar electrode arrays using two surgical approaches. METHODS: Impedance, stimulation thresholds, comfortably loud current levels, electrically evoked compound action potential thresholds and electrically evoked stapedial reflex thresholds were compared between 2 arrays implanted in the same child at 5 time points: surgery, activation/day 1, week 1, and months 1 and 3. The peri-modiolar array was implanted via cochleostomy in all children (n = 64), while the anti-modiolar array was inserted via a cochleostomy in 43 children and via the round window in 21 children. RESULTS: The anti-modiolar array had significantly lower impedance, but required higher current levels to elicit thresholds, comfort, electrically evoked compound action potential thresholds and electrically evoked stapedial reflex thresholds than the peri-modiolar array across all time points, particularly in basal electrodes (p < 0.05). The prevalence of open electrodes was similar in anti-modiolar (n = 5) and peri-modiolar (n = 3) arrays. CONCLUSION: Significant but clinically acceptable differences in stimulation parameters between peri-modiolar and anti-modiolar arrays persisted four months after surgery in children using bilateral cochlear implants. The surgical approach used to insert the anti-modiolar array had no overall effect on outcomes.

Assessment of auditory brainstem function in lead-exposed children using stapedius muscle reflexes.

The purpose of this study was to investigate the neurological integrity and physiological status of the auditory brainstem tracts and nuclei in children with chronic lead (Pb) exposure using non-invasive acoustic stapedius reflex (ASR) measurements of afferent and efferent-neuromuscular auditory function. Following audiological examinations, uncrossed (ipsilateral) and crossed (contralateral) brainstem ASR responses were evoked by pure tone (500, 1000, and 2000 Hz), and broadband noise (bandwidth: 125-4000 Hz) stimulus activators. The ASR threshold (ASRT), amplitude growth, and decay/fatigue were measured by conventional clinical middle ear immittance methods in a group of Andean children (age range: 2-18 years) with a history of chronic environmental Pb exposure from occupational Pb glazing. Blood lead (PbB) levels of the study group (n=117) ranged from 4.0 to 83.7 µg/dL with a mean PbB level of 33.5 µg/dL (SD: 23.6; median: 33.0: CDC III Classification). The PbB distribution data indicated that 77.8% (n=91) of the children had PbB levels greater than the CDC action line of 10 µg/dL. Repeatable, normal ASRTs were elicited for ipsilateral (mean: ≤90 dB HL) and contralateral (mean: ≤97 dB HL) stimulation for each acoustic activator. Spearman Rho correlation analysis indicated no significant association between PbB level and ipsilateral or contralateral ASRT for any of the stimulus activators. The ASR amplitude growth results showed typical growth functions with no Pb-associated aberrations. No statistical association was found between ASR decay/adaptation (ASRD) and PbB level for any of the stimulus activators. The results of stapedius muscle reflex testing using several stimulus activators showed no significant relationship between PbB level and the physiological integrity of the auditory brainstem mediated ASR responses in children with chronic Pb exposure and elevated PbB levels.

Reversed ipsilateral acoustic reflex pattern.

OBJECTIVE: To determine the characteristics and possible origin of reversed ipsilateral acoustic reflex. STUDY DESIGN: Retrospective. SETTING: University hospital. PATIENTS: Sixty-three ears in 52 patients (mean age 37.6 years) with unilateral or bilateral sensorineural hearing loss and 45 age- and sex-matched persons as controls. METHODS: Audiometry and impedance audiometry examinations were studied retrospectively. Hearing test records were investigated, and patients with unilateral or bilateral sensorineural hearing loss were included. Forty-five age- and sex-matched persons served as controls. The ipsilateral and contralateral acoustic reflex patterns of these patients were investigated. Reflex-forming acoustic thresholds and latencies of ipsilateral reversed (positive) reflexes were compared with ipsilateral negative (upward) reflexes. RESULTS: The ipsilateral acoustic reflexes of 18 of 63 ears with sensorineural hearing loss were absent, and the remaining 45 were reversed (positive). A significant difference was found between ipsilateral reversed and ipsilateral negative acoustic reflex thresholds (p < .001) and latencies (p < .001). No statistically significant differences were found between ipsilateral and contralateral negative reflex latencies. CONCLUSIONS: The reversed acoustic reflex pattern is not an artifact but a physiologic event. This reflex does not appear to be related to stapedius or tensor tympani muscle contraction. We believe that the etiology of the reversed reflex is related to the system that contains the tympanic membrane, malleus, and incus and their ligaments but not the middle ear muscles.

Vestibular-evoked myogenic potentials in patients with otosclerosis using air- and bone-conducted tone-burst stimulation.

OBJECTIVE: Otosclerosis is a progressive disease with a remodeling process causing ossicular malformation and conductive hearing loss. The aim of this study was to investigate whether vestibular-evoked myogenic potential (VEMP) correlates with the progression of otosclerosis. DESIGN: Fifteen patients with otosclerosis (21 ears) without operation and 10 healthy subjects (20 ears) underwent VEMP test using air-conducted (AC) and bone-conducted (BC) tone-burst stimulation. SETTING: Tertiary referral university hospital. RESULTS: In 21 unoperated otosclerotic ears, 5 ears (24%) showed present AC-VEMPs, and 16 ears had absent AC-VEMPs. Conversely, 16 ears (76%) displayed present BC-VEMPs and 5 ears with absent BC-VEMPs. In those with both AC- and BC-VEMPs, none of them showed air-bone gap greater than 30 dB; in those with absent AC-VEMPs but present BC-VEMPs, 27% of the ears had air-bone gap greater than 30 dB; and in those with absence of both AC- and BC-VEMPs, 80% of the ears revealed air-bone gap greater than 30 dB. Thus, a significant relationship existed among the presence of AC-VEMPs, BC-VEMPs, and magnitude of conductive hearing loss. CONCLUSION: The presence of an AC-VEMP may indicate an earlier stage of otosclerosis, although absent BC-VEMP infers a later stage. Restated, AC-VEMPs may complement the results obtained with BC-VEMPs to classify the stage of otosclerosis.

Primary auditory neuropathy - an enigma.

OBJECTIVES: To report audiological and neuroradiological findings in patients with primary auditory neuropathy (PAN) from a tertiary institution in south India. MATERIAL AND METHODS: The auditory profiles in 24 patients were analyzed along with neurological and radiological findings. RESULTS: Puretone audiometry showed varied hearing acuity and configuration. The syllable recognition score (n=15) was above 80% except in three. The dichotic digit test (n=11) showed bilateral suppression except in two who showed unilateral suppression. The auditory brainstem responses and the acoustic stapedius reflex were absent with distortion product otoacoustic emission (DPOAE) present in all. The neurological and radiological studies were normal. CONCLUSION: The audiological profile is consistent with the presence of DPOAE and absence of acoustic stapedius reflex and auditory brainstem responses. In patients with adequately preserved syllable recognition in quiet conditions, there was a significantly poor performance on dichotic digit test. As these patients had no neurological deficits and absence of specific etiological factors, we propose to use the term PAN for this entity.

Effect of white noise on vestibular evoked myogenic potentials.

OBJECTIVES: To clarify if p13-n23 of vestibular evoked myogenic potentials (VEMPs) is independent of cochlear afferents. METHODS: Twenty normal volunteers and 10 patients with hemifacial palsy enrolled into this study. VEMP and auditory brainstem responses (ABRs) were recorded with or without white noise (WN, 75 dBnHL or 95 dBnHL) ipsilaterally or contralaterally to the stimulated ear. Short tone bursts (STBs) of 0.5 kHz (95 dBnHL, rise/fall time=1 ms, plateau time=2 ms) were presented though headphones. For recording VEMPs surface electromyographic activity was recorded in the supine subjects form symmetrical sites over the upper half of each SCM with a reference electrode over the upper sternum. RESULTS: The amplitude of p13-n23 significantly decreased during exposure of the contralateral ear as well as the ipsilateral ear to 95 dBnHL WN in normal volunteers (41% reduction by the ipsilateral exposure and 38% reduction by the contralateral exposure). Exposure to 75 dBnHL WN caused only minimal reduction of the amplitudes of p13-n23 (5% reduction) although it caused remarkable reduction of the amplitudes of V-SN(10) (ABRs) (23% reduction). However, 95 dBnHL WN exposure showed no effect on the amplitudes of p13-n23 in the ipsilateral side to hemifacial palsy. CONCLUSION: Overall the data are in favor of the hypothesis that cochlear afferents could affect the amplitude of p13-n23 only through the stapedial reflex, although our data might not be strict proof of an absence of influence of cochlear afferents' activity.

Effect of stimulus duration on stapedius reflex threshold in electrical stimulation via cochlear implant.

The effect of stimulus duration on the threshold of the contralateral stapedius reflex was investigated in patients supplied with a Vienna cochlear implant (analog stimulation via CI) and compared to results of a normal-hearing reference group in case of acoustic stimulation. Changes in reflex threshold were determined at four frequencies (125, 500, 1,000 and 2,000 Hz in case of electrostimulation and at 500, 1,000, 2,000 and 4,000 Hz for acoustic stimulation) and for five durations (30, 50, 100, 300 and 500 ms). The comparison of the two stimulation modes was accomplished by using the same instrumentation and procedure. Reflex threshold was evaluated according to an objective criterion based on the individual noise distribution of recordings without reflex and by subjective judgement. For both stimulation modes a strong effect of stimulus duration on reflex threshold was observed (p < 0.001). The amount of temporal integration reflected by the threshold difference between 500 and 50 ms was approximately 2-4 dB for electrical stimulation via CI and 6 dB for acoustic stimulation in normal-hearing individuals. In case of electrostimulation, the reflex threshold for stimuli of 30 ms was most often above the limit of uncomfortable loudness sensation; the increase in reflex threshold for acoustic stimulation between 500 and 30 ms was approximately 14 dB. There was no evidence of frequency effect on reflex threshold nor an interaction between frequency and stimulus duration for either stimulation mode.

Dynamic range of the contralateral stapedius reflex in cochlear implant patients.

The dynamic range of the contralateral Stapedius reflex elicited by analog electrostimulation via cochlear implant was investigated in 8 subjects supplied with a Vienna prosthesis. The study comprised patients fitted with intracochlear devices as well as patients with extracochlear devices. Sinusoidal bursts of 125, 500, 1,000 and 2,000 Hz were used as stimulation signals. Only in one patient was saturation of reflex amplitude observed. The dynamic range of the Stapedius reflex was defined either by the difference in stimulus level for reflex saturation or individual uncomfortable loudness level and reflex threshold. Two different methods were used, yielding values between 0.1 and 12 dB, with a median of 4 dB. The individual results were compared with individual psychoacoustic quantities, i.e. subjective dynamic range (difference between sensation threshold and uncomfortable loudness level) and residual dynamic range (difference between most comfortable loudness level and uncomfortable loudness level). The reflex dynamic range is located within the residual dynamic range of electrostimulation. Thus the Stapedius reflex dynamic range can be applied as a rough estimate of minimum residual dynamic range.

Auditory postauricular responses in patients with peripheral facial nerve palsy.

Auditory postauricular response (PAR) was determined in 52 subjects with normal hearing and 83 patients with unilateral peripheral facial nerve palsy. PAR was induced bilaterally by bilateral aural stimulation in 50 (96%) of the 52 subjects. Determination of PAR in the 83 patients disclosed that the prognosis was significantly (p less than 0.01) better for those in whom PAR occurred within 4 weeks of onset, in comparison with those without PAR. PAR determination was thus considered to be a useful procedure for determining the prognosis of peripheral facial nerve palsy.

Stapedius reflex threshold in cochlear implant patients.

The contralateral stapedius reflex elicited by sinusoidal electrostimulation via cochlear implant was investigated in 12 patients. Contraction of the middle ear muscle was monitored by time-resolved synchronized digital sampling of the impedance change in the contralateral ear. The reflex was detected in all patients in whom the uncomfortable loudness level (UCLL) could be reached and who had intact middle ear function. Generally, the reflex threshold is located in the upper part of the dynamic range between the most comfortable loudness (MCL) and the UCLL. The demonstrated method may provide suitable assistance in speech processor adjustment in difficult-to-test patients.

A technique for detecting the ipsilateral acoustic reflex.

A technique was explored for detecting the ipsilateral acoustic reflex using one acoustic signal (226-HZ tone) both to elicit the reflex and to measure the impedance of the ear. By eliminating the presentation of two acoustic signals to the same ear, artifactual responses that result from interactions between two signals are avoided. The method provided reflex threshold estimates for five normal subjects that averaged 99.8 dB SPL, in close agreement with previously reported data. A sixth subject, with otosclerosis, showed no evidence of a reflex. With some refinement, the method could become a quick, reliable measurement procedure that avoids some of the problems of conventional methods.

A comparison of stapedial reflex fatigue with repetitive stimulation and single-fiber EMG in myasthenia gravis.

The pattern of stapedial reflex fatigue in response to pulsed acoustic stimulation was measured and compared to results of repetitive nerve stimulation and single-fiber electromyography (EMG) in 89 patients with myasthenia gravis. Studies were also made on 22 patients with other neuromuscular disorders and 40 control subjects with no evidence of neuromuscular impairment. Stapedial reflex fatigue exceeded normal control values in 84% of the patients with myasthenia gravis. Repetitive stimulation and single-fiber EMG measurements were abnormal in 56% and 91% of this same population, respectively. Stapedial reflex abnormalities were most prevalent in patients with mild forms of myasthenia (predominantly ocular or oropharyngeal weakness). Of 22 nonmyasthenic patients with neuromuscular disease tested, 6 had abnormal stapedial reflex fatigue according to our normal values, indicating that this form of testing also detects other diseases of the motor unit. The measurement of stapedial reflex fatigue is painless, is easy to perform, and requires minimal patient cooperation. Due to the relatively high occurrence of abnormal stapedial reflex fatigue in patients with myasthenia gravis, this procedure appears to have considerable potential value in screening and monitoring patients for the presence of defects in neuromuscular transmission.

Effect of sensorineural hearing loss on the stapedius reflex growth function in the elderly.

The effect of sensorineural hearing loss upon stapedius reflex growth functions was studied in the elderly. The reflex activators were pure tones (500, 1000, and 2000 Hz) and broadband noise; reflex magnitude was expressed in decibels relative to static acoustic impedance. When expressed in decibels relative to reflex threshold, the mean growth functions of the elderly were reduced compared to previous data for young subjects [Silman, Popelka, and Gelfand, J. Acoust. Soc. Am. 64, 1406--1411 (1978)] and the noise functions differed in terms of both shape and magnitude. When expressed in SPL, the mean growth functions of the normal hearing elderly demonstrated saturation at high activator levels, whereas saturation was not observed in the mean growth functions of the hearing loss subjects. In the normal elderly, saturation was found to be frequency dependent. The saturation effect is discussed in terms of energy integration of the reflex response in the aging ear.