Segmental Sensory Nerve Conduction Study in Vibration Exposed Subjects

The present study was performed to assess peripheral neural involvement by exposure to hand-arm vibration. Segmental sensory nerve conduction in the median and ulnar nerves were measured in shipyard workers exposed to vibration. The subjects were 47 male adults exposed to hand-arm vibration and 7 healthy male controls. The subjects underwent an extensive bilateral neurophysiological examination. Sensory compound nerve action potential (SNAP) of the median and ulnar nerves in palm-finger and wrist-palm segments were measured by antidromic method. And SNAP of the median and ulnar nerves in wrist-proximal finger and wrist-distal finger segments were measured by orthodromic method. Result of sensory nerve conduction study was abnormal in 31 patients $(66\%)$ and normal in 16 patients $(34\%)$ of subjects. The pathological pattern in the hand-arm vibration exposed group was 13 patients $(28\%)$ of carpal tunnel syndrome, 18 patients $(38\%)$ of distal sensory neuropathy, 7 patients $(15\%)$ of multifocal and 1 patient $(2\%)$ of Guyon syndrome. The present study indicates that vibration-induced nerve impairments exist both in the finger-palm and palm-wrist segment of median and ulnar sensory nerves. The results suggest that segmental sensory nerve conduction study would be useful as objective indication of peripheral nerve impairment induced by the hand-arm vibration.