The orbicularis oculi reflexes in healthy premature and full-term newborns.

Blink reflexes were evoked both by mechanical tapping and electrical current delivered to the skin of the periorbital region in 62 healthy babies distributed in 2 groups: 29 full-term newborns and 33 prematures. The electrical activity of the orbicularis oculi muscle was recorded by means of bipolar surface electrodes in all cases. Both ipsilateral R1 and R2 electrically evoked responses were obtained. Occasionally we also observed a late R3 ipsilateral response. The R2 contralateral electrically evoked response was never observed in premature babies; it was present in about 80% of the full-term newborns. The R1 recovery curves obtained by delivering two successive shocks are similar in our two groups of babies to those observed in adults. The R1 latency decreases from 18 msec (27 weeks of post-conceptional age) to 12.4 msec (37 weeks). The average value for the full-term newborns was 12.1 +/- 1.1 msec. Whatever the age mechanical stimulation evokes bilateral R1, R2 and occasionally R3 responses. The existence of central crossed connections is possible. The maturation of the blink reflex occurs essentially during the last months of pregnancy. Indeed the R1 latency measured in full-term newborns is similar to that given for adults.