Assessment of central, peripheral, and autonomic nervous system functions in vibrating tool operators: neuroelectrophysiological studies.

To evaluate the effects of vibrating tool operation (i.e., combined stressors of local vibration, noise, cold climate, and heavy work) on the central, peripheral, and autonomic nervous systems, the short-latency somatosensory and brain stem auditory evoked potentials (SSEP and BAEP), the distribution of sensory median nerve conduction velocities (DCV), conventional median nerve conduction velocities (NCV), and the electrocardiographic R-R interval variability (CVRR) were measured in three groups of male vibrating tool operators and age-matched male healthy adults. Two components of the CVRR reflecting parasympathetic activity (C-CVRSA) and sympathetic activity (C-CVMWSA) were also examined. In the first group of vibrating tool operators (15 chain saw operators), all parameters of DCV (V10-V90 velocities) and sensory and motor nerve conduction velocities of NCV were significantly slowed. All peak latencies of SSEP were significantly prolonged, while no significant differences were found in the interpeak latencies of SSEP. The N9 peak latency of SSEP was significantly related to total working days. In the second group of the operators (12 chain saw and 8 brush saw operators), the I-V interpeak and V peak latencies of BAEP were significantly prolonged in the 12 chain saw operators; the I-V interpeak latency of BAEP was significantly correlated with the working years in the 8 brush saw operators. In the third group of vibrating tool operators, i.e., 13 operators with a history of vibration-induced white finger (VWF group) and 11 operators without VWF (non-VWF group), both the CVRR and C-CVRSA were significantly reduced in the VWF group; only the CVRR was significantly reduced in the non-VWF group. Similarly, the faster velocities of DCV (V70, V80, and V90 velocities) were significantly slowed in both the VWF and non-VWF groups. In conclusion, it is suggested that vibrating tool operation affects the faster sensory and motor nerve fibers, the parasympathetic activity, and the auditory pathway from the acoustic nerve to the brain stem.