The flexion withdrawal reflex increases in premature infants at 22–26 weeks of gestation due to changes in spinal cord excitability

AIM Our aim was to study the development of the cutaneous flexion withdrawal reflex among premature infants admitted to the neonatal intensive care unit of the Children's Hospital, University of Cologne, in 2013. METHODOLOGY This longitudinal cohort study explored the development of spinal cord excitability of 19 premature infants born at 22-26 weeks of gestation. We performed five investigations per subject and studied changes in the reflex threshold with increasing postnatal age at different behavioural states. The premature infants were stimulated with von Frey filaments on the plantar surface of the foot near the first metatarsophalangeal joint during the first 3 days of life and at postnatal ages of 10-14 days, 21-28 days, 49-59 days and a corrected gestational age of 37-40 weeks. RESULTS The mean gestational age of the premature infants included in the study was 24 weeks. Premature infants with a gestational age of less than 26 weeks presented a flexion withdrawal reflex with a low threshold (0.5-2.85 milli-Newton) in the first 72 hours of life. CONCLUSION The flexion withdrawal reflex among premature infants born at less than 26 weeks showed a continuous threshold increase with increasing postnatal age, reflecting changes in spinal cord excitability.