Analysis of F-wave parameters in normal infants and children.
BACKGROUND
F-wave is a late response evoked by supramaximal stimulation to the nerve and occurring after direct muscle response.


METHODS
F-wave parameters were investigated in 167 normal Iraqi children, who were all below the age of 12 years. F-waves which were recorded from the abductor digiti minimi by stimulation of the ulnar nerve at the wrist were evaluated to assess developmental changes in the proximal segment of the nerve.


RESULTS
The mean F-wave minimal latency value remained constant in the various age groups during the first 6 months of life, then it was reduced in the next 6-<9 months age group. After that, it increased linearly in the successive age groups, while the mean F-wave maximal latency values remained without statistical changes in the age groups during the first year of life but increased with age afterwards. Two simultaneous processes: a rapid increase in conduction velocity due to maturation (increase in nerve fiber diameter and in myelination) and an increase in upper limb length due to growth were responsible for these latency changes.


CONCLUSIONS
F-wave minimal latency for the ulnar nerve have lower mean values in Iraqi children than in Western children due to height differences. Differences in the pattern of F-minimal and F-maximal latency changes with age reflect different rates of maturation in the different nerve fibers. F-chronodispersion (the difference between the F-maximal and F-minimal latencies) was used as a sensitive method to assess the variability between the changes affecting the fastest and the slowest proximal nerve fibers contributing to F-wave formation. The mean F-chronodispersion values were found to increase during the first year of life and reduce afterwards. This shows that the fastest conducting nerve fibers have more rapid and prominent changes than the slowest ones during the first year of life, after which the slowest conducting nerve fibers seem to have more gradual maturational changes than the fastest ones.
Nadeem
Ahmed S M
AS
Department of Physiology, College of Medicine, Baghdad University, Baghdad, Iraq.
El-Yassin
Dahfir I
DI
Al-Ani
Fakir
F