MLRs in children are consistently present during wakefulness, stage 1, and REM sleep.

Auditory middle latency responses (MLRs) were recorded continuously from normal children, ages 4 to 9 years, during natural sleep. Concurrently obtained EEG recordings were used to determine stages of sleep. Wave Pa was consistently present during wakefulness, alpha, stage 1, and REM sleep. Wave Pa detectability was poor during stage 4 sleep. The probability of obtaining wave Pa during stage 4 increased systematically with age. During stages 2 and 3, Pa detectability was variable. The inconsistency of MLRs in children currently limits their clinical use. These data indicate that the occurrence of MLRs in children is not haphazard, and that the MLR in children can be reliably obtained during certain states of arousal. A straightforward clinical application of these findings is that efforts to obtain MLRs be concentrated during periods favorable for recording the response. We suggest practical strategies for detecting optimal sleep stages.