Ulnar nerve conduction velocity and H-reflex in infants and children

Measurements of conduction velocity of the motor fibers of the ulnar nerve in the segment between the upper part of the arm and the wrist were made in 6 premature infants, 42 full-term newborn infants and 98 children up through the age of 14 years. In premature infants, 21 – 40 days before full term, values ranged from 18 to 22 meters per second with a mean of 21. Full-term newborn infants had velocities that ranged from 21 to 33 m.p.s., with a mean of 28. The values in the newborn were about one-half those of normal young adults, which range from 47 to 73 m.p.s. (mean, 60). By the age of 3 years almost all values were in the lower part of the adult range and, at 5 years, the velocities were not significantly different from those of the adult. These observations are in harmony with information about the diameter of nerve fibers during growth in man. The H-reflex could be elicited by stimulation of the ulnar nerve in almost every newborn infant. By the age of 1 year and thereafter it could rarely be elicited. Between the elbow and wrist, afferent fibers subserving this reflex conducted with a mean velocity of 30 m.p.s. Data on the action potential of the hypothenar muscles, residual latency of conduction in the ulnar nerve, latency of the H-reflex and conduction in the peroneal nerve in infants and children are compared with those on adults. Submitted on July 15, 1959