Sensory group la proximal conduction velocity

Abstract

The fastest median and ulnar velocities derived by recording motor and mixed nerve action potentials, F waves, H‐reflexes, and somatosensory evoked potentials (SEPs) were compared. H‐reflex recording was facilitated by employing selective group la excitation during voluntary muscular contraction. Mixed nerve, SEP, and H velocities, considered to predominantly reflect group la conduction, measured 63.2 ± 3.2 m/sec, 63.4 ± 4.5 m/sec, and 67.2 ± 4.3 m/sec, respectively, between the wrist and elbow. Conventional motor conduction velocity was significantly slower (58.3 ± 5.1 msec), but F velocity, which although nonuniform is also a measure of motor conduction, was 68.4 m/sec. Mean F latency was considered more reliable and representative than minimum F latency. F and H velocities accelerated proximally by 4.5 m/sec. They complement each other when evaluating motor and sensory group la conduction. The H‐reflex and SEP use identical stimulus characteristics and when simultaneously recorded allow direct comparison of the fastest conducting peripheral and central sensory pathways.