Pediatric Audiology: A Review of Assessment Methods for Infants

Behavioral, electrophysiological and electroacoustic methods of assessing hearing in infants and young children are reviewed. Pediatric hearing evaluations include determination of pure tone thresholds and speech perception abilities. Behavioral methods for determining pure tone thresholds are based upon operant conditioning techniques and are applicable for infants aged 6 to 24 months of age. Below that age, behavioral observation of the infant's response to sound will yield unrepeatable results unless the rigors of an observer-based psychophysical procedure are adopted. Electrophysiological methods for estimating hearing threshold include electrocochleography, auditory brainstem response and auditory steady-state responses. Electroacoustic methods include measurement of evoked otoacoustic emissions that indicate the integrity of cochlear outer hair cells. There is a heavy reliance upon electrophysiological and electroacoustic methods for infants too young (i.e. <6 months) or those with visual or motor impairments that preclude testing with behavioral techniques. Methods for assessing infant speech perception abilities are not well developed. Standardized tests of speech sound discrimination require a receptive language age of nearly 3 years. Speech sound discrimination may be tested using a visual-reinforcement procedure similar to that used for threshold tests; however, the stimuli and response recording methods do not have widespread clinical use at this time. Event-related (evoked) potentials to speech sounds offer promise as a method for assessing speech perception abilities, but the variability of results limits the technique to evaluating group (not individual) performance.