Temperature and vibration perception thresholds in workers exposed to hand-arm vibration.

Exposure to hand-arm vibration causes damage in the peripheral nerves of the upper extremities, and a method for early detection of neuropathy induced by vibration is needed. The thin nerve fibres seem to be the most sensitive to vibration and may be damaged first. In the present study, vibration and thermal thresholds in workers exposed to hand-arm vibration were compared in a case-control study. Previously, both vibration perception and temperature sense have been impaired in workers exposed to hand-arm vibration. The study population consisted of 15 workers exposed to hand-arm vibration (mean age 37.1 yrs) and 15 controls matched for age (mean age 36.1 yrs). The vibration perception thresholds (VPT) were measured with modified Bruel & Kjaer's equipment with the limits technique method. Thermal sense was measured by the Marstock method with a thermostimulator, in which the Peltier element controls the temperature of a thin metal plate (surface 35 x 40 mm) in contact with the skin. The lumberjacks had lower cold thresholds and wider neutral zones of temperature sensation in the hands and slightly higher VPTs at the high frequencies (125-500 Hz) than the controls. The results for the matched pairs showed 80-87% of the lumberjacks to have wider neutral zones, but only 53-66% of them had higher VPTs than the controls. In an intraindividual comparison of the lumberjacks (the newly scaled results with the mean and standard deviation of the controls), the temperature sense was often (66-73%) deteriorated more than the VPTs at 125-500 Hz. In addition, the newly scaled results showed the width of the neutral zone to be significantly more deteriorated than the VPTs at 125 and 250 Hz in the fingers. This indicates that measurement of the temperature sense is useful in the prevention of nerve damage caused by vibration and might be more sensitive to vibration than vibration perception.