Low Frequency Hearing Threshold Determination in Newborns, Infants and Mentally Retarded Children by Middle Latency Responses

Abstract

Middle latency (10–50 ms) responses (MLR) evoked by lone-pips (1000 Hz, 500 Hz) and early (0–10 ms) auditory evoked potentials (EAEP) evoked by clicks were recorded on 68 newborn babies (premature or at term), infants and children, some with central nervous system or psychiatric disorders, who had normal or impaired hearing. MLR were obtained either during sleep, chloral-hydrate sedation or ketamine anesthesia. Thresholds estimated from MLR and EAEP were compared to those from subsequent psychoacoustic pure tone testing. We confirm that MLR provide good threshold estimates for hearing in the low frequency range, whereas click evoked EAEP are good threshold indicators only for high frequencies.

Key Words:

• objective low frequency audiometry
• tone-pips
• MLR under Chloral-hydration sedation
• MLR under ketamine anesthesia