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The prognostic value of electrocochleography in severely hearing-impaired infants
R Schoonhoven1, P J Lamoré, J A de Laat
1Leiden University Medical Centre, ENT Department, The Netherlands.
Insights
Electrocochleography effectively assesses residual hearing in infants with severe hearing loss. This electrophysiological method provides valuable frequency-specific threshold information, even when auditory brainstem responses are absent.
Area of Science:
- Pediatric Audiology
- Neurophysiology
- Otolaryngology
Background:
- Accurate hearing assessment in infants with severe hearing impairment is crucial for early intervention.
- Traditional audiometry can be challenging in this population.
- Electrophysiological methods offer objective measures of auditory function.
Purpose of the Study:
- To longitudinally evaluate electrocochleography for assessing severely hearing-impaired infants.
- To compare electrocochleography findings with later pure-tone audiometry results.
- To determine the reliability of electrocochleography in predicting audiometric thresholds.
Main Methods:
- Transtympanic electrocochleography was performed on 126 infants (0-6 years) using tone-burst stimuli (500-8000 Hz).
- Cochlear microphonics and compound action potentials (CAPs) were recorded.
- Results were compared with pure-tone audiometry at school age.
Main Results:
- Cochlear microphonics were detectable in nearly all ears, irrespective of hearing loss severity (≥90 dB).
- Compound action potential (CAP) thresholds correlated well with audiometric thresholds, with a prediction error of 15-20 dB.
- Electrocochleography yielded detectable responses in 68% of cases where auditory brainstem response (ABR) was absent, particularly in the 1000-4000 Hz range.
Conclusions:
- Electrocochleography is a valuable tool for assessing residual hearing in infants with suspected severe hearing impairment.
- It provides reliable frequency-specific threshold information, complementing or substituting for audiometry when needed.
- The method is particularly useful in cases where ABR is not elicited.
Abstract:
This paper presents a longitudinal evaluation of electrocochleographic assessment in severely hearing-impaired infants. Electrophysiological data were obtained by transtympanic electrocochleography to tone-burst stimuli at octave frequencies of 500 to 8000 Hz at the age of 0-6 years in a group of 126 subjects. The results are compared with auditory thresholds determined at school age in the same children by means of pure-tone audiometry. Cochlear microphonics could be recorded in virtually all ears, although the majority of subjects had hearing losses of 90 dB and more. Compound action potentials (CAPs) showed waveforms varying from normal to a wide range of abnormalities. Audiometric thresholds correlated generally well with the compound action potential (CAP) thresholds obtained in infancy. The error in the predicted audiometric thresholds is between 15 and 20 dB, as compared with 11 dB reported for more moderate hearing losses. It is shown that, in spite of the high stimulus levels used, substantial frequency-specific threshold information is retained. Occasional large discrepancies in thresholds were often associated with markedly abnormal response waveforms. Among the many cases in which no ABR could be elicited, 68 per cent produced detectable electrocochleographic responses in the 1000-4000 Hz range. It is concluded that electrocochleography is a valuable method for the assessment of residual hearing in infants suspected of having a severe hearing impairment.