A normative study on human facial F waves

F waves from the nasalis muscle were obtained bilaterally after transcutaneous constant-current stimulation of the facial nerve in 37 of 42 (88%) healthy volunteers examined. F waves were of varying shape and latency. Standard parameters (latencies, amplitudes, ratios, chronodispersion) of F-wave analysis were assessed. Of these, minimum and mean F-wave latencies, the F ratio, and F-wave and peripheral conduction times (PCT) were approximately normally distributed, with a low standard deviation. Latencies and conduction times exhibited a significantly positive correlation with body height, as has been demonstrated for the F-wave latencies in limb muscles. Side and sex differences were present but without statistical significance. Chronodispersion and chronodispersion range, F-wave amplitudes, and F-wave frequencies were broadly scattered. It is concluded that F-wave latencies and conduction times are best suited to define a range of reference values. Moreover, facial F waves bear characteristics similar to those described for F waves recorded from limb muscles.