Blink reflex elicited by auditory stimulation: clinical study in newborn infants

Blink reflex can be elicited by sudden strong auditory stimulation. Using a special transducer wer recorded this reflex which appears as a microvibration of the eyelid, and named it auditory-evoked eyelid microvibration (AMV). As the reflex pathway of AMV exists in the brainstem, AMV is an easy and useful way of knowing the function of the brainstem, especially in newborn periods. AMV was studied in infants from 25 to 43 weeks in conceptional age, to establish the normal value and to analyse the change of AMV in cases of neonatal asphyxia and intracranial hemorrhage. The mean latency of AMV in full-term infants was 31.0 +/- 67. msec. After 33 weeks in conceptional age, AMV was observed constantly with almost the same latency and amplitude as adult values. AMV appeared during both waking and sleep stages, except in active sleep. Marked change in AMV was noted such as delayed latency or disappearance of the response in neonatal asphyxia or intracranial hemorrhage. Infants who continued to have these abnormalities for a certain period, died or exhibited neurological sequelae.