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The orbicularis oculi reflexes in healthy premature and full-term newborns
1Laboratoire de Neurophysiologie, Faculté de Médecine, Amiens, France.
Insights
The blink reflex matures significantly during the last trimester of pregnancy, with full-term newborns exhibiting adult-like R1 latency. Premature infants show delayed maturation of the R2 contralateral response.
Area of Science:
- Neuroscience
- Developmental Pediatrics
- Ophthalmology
Background:
- The blink reflex, an involuntary response to stimuli, is crucial for ocular protection.
- Understanding its development in infants is key to assessing neurological maturation.
- Previous studies suggest variations in blink reflex components between preterm and full-term infants.
Purpose of the Study:
- To investigate the maturation of the blink reflex in healthy newborns and premature infants.
- To compare electrically and mechanically evoked blink responses.
- To determine the developmental timeline of specific blink reflex components, particularly R1, R2, and R3 responses.
Main Methods:
- Blink reflexes were elicited using mechanical tapping and electrical stimulation of the periorbital skin in 62 healthy infants (29 full-term, 33 preterm).
- Orbicularis oculi muscle electrical activity was recorded using bipolar surface electrodes.
- Analysis included latencies and presence of ipsilateral (R1, R2, R3) and contralateral (R2) responses, and R1 recovery curves.
Main Results:
- Both ipsilateral R1 and R2 responses were consistently obtained. A late R3 response was occasionally observed.
- The R2 contralateral response was absent in preterm infants but present in ~80% of full-term newborns.
- R1 latency decreased with post-conceptional age, from 18 ms (27 weeks) to 12.4 ms (37 weeks), with full-term newborns averaging 12.1 ms.
- Mechanical stimulation evoked bilateral R1, R2, and sometimes R3 responses across all ages.
Conclusions:
- Blink reflex maturation, particularly R1 latency, primarily occurs during the final months of gestation.
- Full-term newborns demonstrate blink reflex characteristics similar to adults.
- The presence of the R2 contralateral response in full-term infants suggests the development of central crossed connections late in gestation.
Abstract:
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.