Vibration-induced neuropathy in the hand

University dissertation from Department of Hand Surgery, Malmö University Hospital, S-205 02 Malmö, Sweden

Abstract: The aim of this study was to investigate clinical, pathophysiological and structural aspects of vibration-induced peripheral neuropathy since work with hand-held vibrating tools may lead to progressive neurological and vascular hand symptoms. Symptomatic vibration-exposed men were examined clinically and by neurography, tactilometry, and vibrometry and by measurement of temperature perception thresholds. Studies on regeneration and morphology of nerves were done in vibration-exposed rats and humans. Three groups of hand symptoms could be distinguished: sensorineural symptoms, vasospastic symptoms, and a combination of both. Cold intolerance emerged as a separate symptom in half of the patients with sensorineural symptoms only. Tactilometry in referents showed that the vibrotactile perception thresholds depended on the frequency of stimulus and on age. Equations make correction for age possible. Neural conduction, vibrotactile sense, and temperature sense were impaired in all groups of patients. Cold intolerance, severe sensorineural – but not vascular – symptoms, bilateral symptoms, and muscular weakness were associated with further impairment of the vibrotactile sense. Neurography showed involvement of the median nerve in the carpal tunnel and distally, but no changes in the ulnar nerve. Neither did it show any difference between patients with and without clinical carpal tunnel syndrome. Vibrotactile thresholds – but not neurography – differed between the sensorineural stages. The regenerative capacity of vibration-exposed rat sciatic nerves was impaired probably due to an effect on the neurone and on non-neuronal cells. Morphologically, the dorsal interosseous nerve in vibration-exposed patients showed demyelination in various stages of development, endoneurial and perineurial fibrosis, and loss of axons. The results of this study underline the importance of the neurological component of vibration-induced injury. Subjectively experienced and objectively shown, it may severely interfere with hand function.

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