Acceleration of the median nerve distal latency time in preterm infants with intrauterine growth retardation.

Abstract

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 degrees (DLT-36) during the first 3 days of life was inversely related to gestational age in normal preterm infants. However, the DLT-36 was significantly accelerated in infants with in utero growth retardation (IUGR). In normal infants the DLT-36 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 DLT-36 was accelerated by not the nerve conduction velocity. In normal preterm infants the slope of change of DLT-36 in utero with maturation was similar to the change ex utero. Wigh IUGR the DLT-36 shortened sharply during the first 2 weeks of postnatal life, and thereafter the DLT-36 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 DLT-36.