Acceleration of the Median Nerve Distal Latency Time in Preterm Infants with Intrauterine Growth Retardation

Abstract

Extract: The distal latency time (DLT) of the median nerve was measured in infants at various stages of in utero and ex utero maturation.The DLT measured at 36° (DLT36) during the first 3 days of life was inversely related to gestational age in normal preterm infants. However, the DLT36 was significantly accelerated in infants with in utero growth retardation (IUGR).In normal infants the DLT36 was significantly related to the nerve conduction velocity of the proximal segment of the median nerve. This relation was lost in infants with IUGR, since the DLT36 was accelerated but not the nerve conduction velocity.In normal preterm infants the slope of change of DLT36 in utero with maturation was similar to the change ex utero. With IUGR the DLT36 shortened sharply during the first 2 weeks of postnatal life, and thereafter the DLT36 changed at the same rate as in normal infants.The DLT is sensitive to temperature change in the thenar muscle. The more immature the infant the greater the change of DLT with temperature.Apnea in preterm infants was not significantly related to the DLT36.Speculation: Intrauterine growth retardation accelerates the DLT of the median nerve but not the nerve conduction velocity of the proximal nerve. This study focused only on DLT changes with severe intrauterine growth retardation compared with normal preterm and term infants. Acceleration of the DLT may be a useful index of chronic stress in utero not associated with severe growth retardation.