Electrophysiological study of the peripheral nervous system in children. Changes in proximal and distal conduction velocities from birth to age 5 years.

Hoffman's reflex was evoked in the soleus muscle of 105 normal children from birth to age 5 years. This technique made it possible to determine conduction time and to estimate conduction velocity over the reflex arc. For 59 children, proprioceptive and motor distal nerve conduction velocities were calculated for the tibial nerve trunk. These measurements enabled the common changes for these three velocities to be described in terms of an exponential curve. Proximal conduction velocity has similar values to those of proprioceptive distal nerve fibres: it is always higher than motor nerve conduction velocity, but the difference gradually diminishes, remaining constant after the eighteenth month. Conduction time diminishes between birth and one year of age, whereas height increases. Then conduction time increases slowly, reaching at about age 5 years, when average height is 1050 mm, the value it had just after birth. For the child born at term, maturation of the nervous system is thus especially rapid during the first year of life.