Study of nerve conduction and late responses in normal Chinese infants, children, and adults.

Healthy Chinese individuals (n = 168), aged from 24 hours to 30 years, were studied to establish the following normal values: (1) motor conduction velocity, distal latency, amplitude, and F-wave velocity in the median, ulnar, tibial, and peroneal nerves; (2) H-reflex velocity and latency in the tibial nerve for all subjects as well as in the median and ulnar nerves in infants; (3) sensory conduction velocity, latency, and amplitude in the median, ulnar, and sural nerves; and (4) the difference in minimal latencies of both H-reflex and F-waves between corresponding nerves in opposite limbs and between two nerves in the same limb. The motor conduction velocities, sensory conduction velocities, F-wave velocities, and H-reflex velocities in newborns were approximately 50%, 40%, 40 to 45%, and 40 to 45% of adult values, respectively. At age 3 years, the normal values were in the adult range for all motor conduction velocities and for the sensory conduction velocities in the upper limbs. The sensory conduction velocities, H-reflex velocities, and F-wave velocities in the lower limbs did not reach adult values until age 6 years whereas the upper limb F-wave velocities reached adult levels between 6 and 14 years in different nerves. These results indicate that adult values for nerve conduction velocities, including the late responses, are reached earlier in the lower extremities; however, conduction velocities at any age are always faster in the upper limbs and in the proximal compared to the distal segments. The maturation process occurs most rapidly during the first 3 to 6 years of life, especially in the first year. This parallels the histologic development of peripheral nerves during childhood.