F-response studies in neonates, infants and children

F-response has been found to be useful in the evaluation of peripheral nerve conduction in adults and may be especially useful in paediatric nerve conduction studies. In newborns, the nerve conduction velocity is very slow compared to adults because of immaturity of myelination. To assess the effect of age on F-response in 20 neonates, (1 to 28 days), infants (1 mo- 1 y) and children (2-12 y), motor nerve conduction velocity of median, peroneal; sensory conduction velocity of median and F-response from abductor pollicis brevis (APB) by stimulation of median nerve at the wrist were evaluated. The nerve conduction velocity in the neonates was nearly half of that in children and was significantly related to age. F-minimal latency (F-min) showed biphasic distribution; in neonates it was 17 ms, in infants 15 ms and in children 16 ms. The amplitude of F-response was higher compared to infants and children (P less than 0.001). H-reflex in ABP was elicited in all neonates and 55% of infants, its mean latency was 17.9 ms and 15.7 ms respectively. Long latency and high amplitude of F-response and presence of H-reflex in ABP in neonates and infants are due to the immaturity of the nervous system and should be kept in mind while interpreting F-responses in newborns.