Averaged F-wave conduction velocity of peroneal nerve

Averaged F-wave conduction velocities (a-FWCV) of peroneal nerve were measured on 38 healthy volunteers and 22 patients with clinical and electromyographic evidence of unilateral L5 or L5 + S1 radiculopathy. The peroneal nerve was stimulated supramaximally at the fibular head and the compound muscle action potential was recorded from the extensor digitorum brevis muscle. Averaged tracings from 32 consecutive stimuli were obtained. The averaged F-wave latency (Fp) and M-wave latency (Mp) were measured from the stimulating artifact to the peak of the waves. The distance (D) between the stimulating point and the T12 spinous process was measured. The value of a-FWCV was calculated as 2D/(Fp-Mp-1) m/second. In normal subjects, the average value of a-FWCV was 56 +/- 4, and there was no significant difference between males and females, nor between the right and left sides. The differences among the tests administered at different times on the same subject were also statistically insignificant. Of the 22 patients, 17 had subnormal value of a-FWCV if the lower normal limits were defined as mean minus 2.5 SD (i.e., 46 m/second) calculated from the normal control value. However, only one of them had subnormal value of FWCV calculated by the conventional method (without averaging technique). All the patients with two root (L5 + S1) involvement had subnormal a-FWCV. It is concluded that the a-FWCV is a more sensitive measure than the conventional FWCV in the assessment of L5 radiculopathy.