Objective: F response is one of the late EMG responses occurring with peripheral motor nerve stimulation. It is generated by firing of anterior horn motor neurons as a result of antidromic propagation of the stimulus on the motor nerve. The aim of this study was to evaluate the feasibility of using average variability in consecutive F response latencies (F-jitter) as a new parameter.

Method: The fundamental characteristic of the F-jitter distinguishing it from other parameters is that it describes the chrono-dispersion among the neurons stimulated consecutively. The F-jitter was investigated in patients with polyneuropathy (PNP, n = 20), spasticity (SPS), ( n = 10) and in 30 healthy subjects.

Results: The sensitivity of F-jitter was observed to be at least as much as of other parameters.

Conclusions: It is therefore concluded that F-jitter might be a useful parameter to be included in new-generation digital EMG instruments beyond its significant contributions to physiological studies.

Significance: The F-jitter values in PNP and SPS groups were significantly different from the healthy group, and this difference was more prominent in the PNP group