Reliability and validity of late vertex-evoked response audiometry

Role of Cortical Auditory Evoked Potentials in Reducing the Age at Hearing Aid Fitting in Children With Hearing Loss Identified by Newborn Hearing Screening

Recording of free-field cortical auditory evoked potential (CAEP) responses to speech tokens was introduced into the audiology management for infants with a permanent childhood hearing impairment (PCHI) during 2011-2015 at a U.K. service. Children with bilateral PCHI were studied from two sequential cohorts. Thirty-four children had followed an audiology pathway prior to CAEP introduction, and 44 children followed a pathway after the introduction of CAEP and were tested with unaided and aided CAEP responses. Data analysis explored the age of diagnosis, hearing aid fitting, and referral for cochlear implant (CI) assessment for each of these groups. CAEP offered a novel educative process for the parents and audiologists supporting decision-making for hearing aid fitting and CI referral. Delays in hearing aid fitting and CI referral were categorized as being due to the audiologist's recommendation or parental choice. Results showed that the median age of hearing aid fitting prior to CAEP introduction was 9.2 months. After the inclusion of CAEP recording in the infant pathways, it was 3.9 months. This reduction was attributable to earlier fitting of hearing aids for children with mild and moderate hearing losses, for which the median age fell from 19 to 5 months. Children with profound hearing loss were referred for CI assessment at a significantly earlier age following the introduction of CAEP. Although there has also been a national trend for earlier hearing aid fitting in children, the current study demonstrates that the inclusion of CAEP recording in the pathway facilitated earlier hearing aid fitting for milder impairments.

Similarities in the neural signature for the processing of behaviorally categorized and uncategorized speech sounds

Recent human behavioral studies have shown semantic and/or lexical processing for stimuli presented below the auditory perception threshold. Here, we investigated electroencephalographic responses to words, pseudo-words and complex sounds, in conditions where phonological and lexical categorizations were behaviorally successful (categorized stimuli) or unsuccessful (uncategorized stimuli). Data showed a greater decrease in low-beta power at left-hemisphere temporal electrodes for categorized non-lexical sounds (complex sounds and pseudo-words) than for categorized lexical sounds (words), consistent with the signature of a failure in lexical access. Similar differences between lexical and non-lexical sounds were observed for uncategorized stimuli, although these stimuli did not yield evoked potentials or theta activity. The results of the present study suggest that behaviorally uncategorized stimuli were processed at the lexical level, and provide evidence of the neural bases of the results observed in previous behavioral studies investigating auditory perception in the absence of stimulus awareness.

Sensitivity of cortical auditory evoked potential detection for hearing-impaired infants in response to short speech sounds

Cortical auditory evoked potentials (CAEPs) are an emerging tool for hearing aid fitting evaluation in young children who cannot provide reliable behavioral feedback. It is therefore useful to determine the relationship between the sensation level of speech sounds and the detection sensitivity of CAEPs, which is the ratio between the number of detections and the sum of detections and non-detections. Twenty-five sensorineurally hearing impaired infants with an age range of 8 to 30 months were tested once, 18 aided and 7 unaided. First, behavioral thresholds of speech stimuli /m/, /g/, and /t/ were determined using visual reinforcement orientation audiometry. Afterwards, the same speech stimuli were presented at 55, 65, and 75 dB sound pressure level, and CAEPs were recorded. An automatic statistical detection paradigm was used for CAEP detection. For sensation levels above 0, 10, and 20 dB respectively, detection sensitivities were equal to 72±10, 75±10, and 78±12%. In 79% of the cases, automatic detection P-values became smaller when the sensation level was increased by 10 dB.

The results of this study suggest that the presence or absence of CAEPs can provide some indication of the audibility of a speech sound for infants with sensorineural hearing loss. The detection of a CAEP might provide confidence, to a degree commensurate with the detection probability, that the infant is detecting that sound at the level presented. When testing infants where the audibility of speech sounds has not been established behaviorally, the lack of a cortical response indicates the possibility, but by no means a certainty, that the sensation level is 10 dB or less.

High-pass filter settings affect the detectability of MLRs in humans

Auditory middle latency responses (MLRs) have been recorded in 217 patients ranging in age from 6 days to 20 years. The probability of obtaining MLR components Na and Pa was higher with a high-pass filter setting of 15 Hz, 12 dB/octave as compared to 3 Hz, 6 dB/octave. This effect was found at all ages tested. Age-related latency effects were apparent with 3 Hz but not 15 Hz filtering.

Auditory middle latency responses in children: effects of age and diagnostic category

The nature of auditory middle latency responses (MLRs) in children has been the subject of considerable debate. In order to study MLRs as a function of age, MLRs were obtained in 217 subjects ranging in age from 6 days to 20 years, all with normal auditory brain-stem responses (ABRs). Subjects were classified into several diagnostic categories: normal; communicative disorders (language delay, learning disability); mentally retarded, multiply handicapped; and post-meningitic. Age effects, the effects of diagnostic category, and possible differences in MLRs of males vs. females and right vs. left ears were examined. The detectability of both Na and Pa was found to increase significantly as a function of age. Detection of these MLR components became similar to adult values (approaching 100% detectability) at approximately 10 years of age. No significant differences were found among diagnostic categories. There were also no significant differences in the detectability of MLRs in males as compared to females, and there were no right vs. left ear differences. The strong age effect which appears to exist in the MLR influences their clinical use. When responses are present, they may be useful indicators of hearing sensitivity, but the absence of MLRs in children cannot be taken as an indication of hearing loss. Similarly, absent or abnormal MLRs cannot be interpreted as a manifestation of auditory pathway dysfunction, since there appears to be little difference in MLRs in normal subjects and MLRs in patients with a wide range of neurologic, cognitive, and speech and language disorders.

Hearing disorders in childhood, some procedures for detection, identification and diagnostic evaluation

Hearing disability in childhood is a sign/symptom which should be detected, in order to avoid developmental disorders in language, speech, psychological and mental behavior. For proper treatment the hearing thresholds should be identified and the site of lesion evaluated in order to obtain a classification of the hearing loss. The causative factor(s) of the hearing disorder should be evaluated by means of an interdisciplinary cooperation. This review summarizes the results obtained in a series of investigations dealing with some procedures for detection, identification and nosological classification of hearing impairment in childhood. Based on these investigations a model for an examination program is proposed. This model requires interdisciplinary cooperation, preferably established at assessment centers. Prospective studies performed at these centers may offer precise data on the epidemiology of hearing disorders. Consequently preventive measures may be applied in order to reduce the number of children suffering from the symptom of hearing loss.

Slow cortical responses and the diagnosis of central hearing loss in infants and young children

To evaluate the usefulness of slow cortical responses (ERA) for threshold estimation in infants and young children, 83 children were investigated with combinations of pure-tone audiometry, electrocochleography (ECochG) and ERA. The deviations between ECochG/ and ERA thresholds were correlated to brain function in order to diagnose central hearing losses. By comparing corresponding values of 2 kHz pure-tone and ERA thresholds, 32% (10/31) errors were found, mainly below 35 dB HL. In a group of patients with no sign of brain disorder, an overall error rate of 37% (20/53) was found. Below 35 dB HL, 72% (11/15) errors were found. In a group of patients with brain dysfunction, the overall rate was 70% (21/30), below 35 dB HL it was 84% (21/25). In the range below 35 dB HL, no significant difference (p greater than 0.05) in errors was found between the groups with and without brain disorders. It is concluded that ERA is unreliable for the estimation of moderate hearing losses and cannot per se detect a central hearing dysfunction. Elevated ERA thresholds may indicate a central hearing loss, but to establish this topical diagnosis, ECochG and neuropsychological examinations are necessary.

Reliability of slow vertex response audiometry in young children with sensorineural hearing loss

In order to supplement our previous report on the reliability and validity of slow vertex response (SVR) audiometry, the detectability of the response, the agreement among scorers and test-retest reliability were studied in 6 children aged 2-4 years who have sensorineural hearing loss of 60-75 dB for the test frequency (1 000 Hz). Mean percentage of positive response increased from 20.6 to 62.2% as stimulus intensity was increased from 60 to 80 dB. Such a sharp increase in the detectability of the response at a level of stimulus intensity close to the auditory threshold of the subjects was not observed in normal children. The results indicate that SVR audiometry is more reliable and valid in children with sensorineural hearing loss than in normal children.

Comparison of hearing threshold determined by auditory pathway electric responses and by behavioural responses

In order to evaluate their reliability for determing the hearing threshold, the cochlear microphonic potentials, the auditory nerve and brain stem neural evoked responses as well as the cortical evoked responses were compared with the behavioural hearing thresholds of the same subjects in the same session. The threshold for recording the cochlear microphonic potnetial was found to be appreciably higher than the behavioral threshold. The threshold for recording the auditory nerve and brain stem responses was within a few decibels of the behavioural threshold. The thresold of the cortical evoked response was several decibels higher. It is concluded that (1) the auditory nerve and brain stem neural evoked responses are the best indicators of hearing threshold; (2) the cortical evoked responses are usually comparable, and (3) all types of evoked responses are indispensable aids in the evaluation of hearing and the determination of site of lesion in the auditory system.

Use of heart rate response for the assessment of hearing in infants

The clinical utility of the heart rate (HR) response as an index of hearing in infant children under 12 months of age was investigated. The most prominent component of the averaged HR response elicited with a short tone burst of 100 msec duration was a brief HR deceleration which mostly occurred between the first and second beats after stimulation. The mean response detectability for tones of 250 Hz and 1 kHz were 50, 82 and 100%, with stimulations of 40, 60 and 80 dB above subjective threshold of normal adults, respectively. The detectability decreased a little at 4 kHz stimulation. Though there was an individual variability in the appearance of the response, the method was considered to be useful as a supplementary tool for evaluating hearing in infant children.