Assessment of peripheral neuropathies by mechanoreceptor-specific vibrotactile thresholds

Abstract

Mechanoreceptor-specific vibrotactile perception thresholds have been determined at the fingertips of 79 workers who regularly operate pulpwood chain saws (in Ontario), large-timber chain saws (in coastal British Columbia), or rock drills. The measurement procedure, which involves establishing the sensitivity of three receptor populations (types SAI, FAI, and FAII) from thresholds determined at up to six frequencies from 4 to 200 Hz, has been described elsewhere (A. J. Brammer and J. E. Piercy, Proceedings of the 5th International Conference on Hand-Arm Vibration, Kanazawa, 1989). Even after repeated screening to exclude peripheral neuropathies unrelated to work, and neuropathies confined to either the median or ulnar nerve, the results continue to reveal two patterns of abnormality. Within the group, 21% of hands exhibit similarly elevated thresholds at all frequencies, which is consistent with peripheral nerve degeneration. Thirty-seven hands (26%) exhibit elevated thresholds at frequencies mediated by only one or two receptor populations (almost always SAI and/or FAII types), which is suggestive of receptor-specific degeneration at or near the nerve endings. Seventy-one hands (50%) possess thresholds within the limits of normality.