Multifocal neural conduction impairment in forestry workers exposed and not exposed to vibration.
OBJECTIVE
The aim of the study was to assess peripheral neural involvement induced by exposure to hand-arm vibration.


METHODS
Twenty lumberjacks, working regularly with chain-saws and exposed to hand-arm vibration (group E) and 20 forestry workers performing heavy manual work and not exposed to vibration (group NE) were matched with a control group of 20 healthy non-manual workers (group C). The subjects of groups E and NE, all symptomatic, and of group C underwent extensive bilateral neurophysiological examination consisting of: sensory conduction (velocity and amplitude) of radial, median and ulnar nerves in digit-wrist segments; sensory conduction (velocity) of median nerve in wrist-elbow segment; mixed conduction (velocity and amplitude) of median and ulnar nerves in palm-wrist segments; motor conduction velocity, including distal motor latencies, and amplitude of median (elbow-wrist) and ulnar (elbow-wrist and across the elbow) nerves.


RESULTS
Electrophysiological abnormalities were found in 85% of group E's limbs, versus 62.5% of group NE's limbs. The most frequent pathological pattern in group E was a 'multifocal' impairment (multiple sites of several nerve segments), with a prevalent involvement of sensory rather than motor fibres in the hand, seldom extending to the forearm. Multivariate analysis showed that the neurographic parameters which better characterized workers exposed to hand-arm vibration had a pattern different from that usually found in idiopathic carpal tunnel syndrome (CTS).


CONCLUSIONS
These results suggest that vibration-induced neural involvement can be considered neither pure digital neuropathy, nor definite CTS, as previously described.
Giannini
F
F
Istituto di Clinica delle Malattie Nervose e Mentali, Università di Siena, Policlinico le Scotte, Italy. gianninif@unisi.it
Rossi
S
S
Passero
S
S
Bovenzi
M
M
Cannavà
G
G
Mancini
R
R
Cioni
R
R
Battistini
N
N
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D016468:Forestry; D006801:Humans; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology*; D016273:Occupational Exposure; D010523:Peripheral Nervous System Diseases / Q000209:etiology*; D014732:Vibration / Q000009:adverse effects*