Somatosensory evoked potentials in very preterm infants

Objective: Cross-sectional and longitudinal reference values of cortical N1 peak latency of the median nerve SEP in very preterm infants. Methods: In infants in a placebo control group within an -thyroxine supplementation trial, born at less than 30 weeks’ gestation, cortical N1 peak latency was measured at 2 weeks, at term and at 6 months corrected age. Cross-sectional N1 latency values obtained in 50 infants and complete series of longitudinal values obtained in 15 infants were analyzed in relation to postmenstrual age (PMA). Results: Mean N1 latency decreased from 66 ms at 2 weeks to 38 ms at term and 20 ms at 6 months corrected age. Possible confounding factors did not have any significant effect on N1 latency at 2 weeks or at term age except cranial ultrasound abnormalities at 2 weeks of age. Conclusions: Longitudinal N1 latency values were consistent with cross-sectional N1 latency values. The observed N1 latency at term and at 6 months corrected age suggest that extrauterine maturation of the somatosensory pathway in infants born at less than 30 weeks’ gestation is delayed by extrauterine life.