Central and peripheral nervous system effects of hand-arm vibrating tool operation. A study of brainstem auditory-evoked potential and peripheral nerve conduction.

To examine the effects of hand-arm vibrating tool operation on the central and peripheral nervous system, the brainstem auditory-evoked potential (BAEP), median nerve conduction velocity and hearing level were measured in twelve chain saw operators (6 operators had a history of white finger attack) and in eight brush saw operators (none had a history of the attack). Control subjects, matched to each chain saw and brush saw operator by sex and age, were selected randomly from healthy adults without otitis, deafness and tinnitus. The I-V interpeak latency (conduction from cochlear nerve to brainstem) and V peak latency of BAEP were significantly prolonged in chain saw operators; the I-V interpeak latency was significantly correlated with working years in brush saw operators. The median nerve conduction velocity was significantly slowed in both chain saw and brush saw operators. Moderate hearing loss was observed in the two groups. It is suggested that vibrating tool operation, i.e. the combined stressors of local vibration, noise, climate and heavy work, affected not only the peripheral nervous system but also the brainstem portion of the auditory pathway; the brainstem effect, if any, is less advanced than the peripheral nervous system effect of local vibration.