Abstract
Prolonged exposure to hand-held vibrating tools may cause a hand-arm vibration syndrome (HAVS), sometimes with individual susceptibility. The neurological symptoms seen in HAVS are similar to symptoms seen in patients with carpal tunnel syndrome (CTS) and there is a strong relationship between CTS and the use of vibrating tools. Vibration exposure to the hand is known to induce demyelination of nerve fibres and to reduce the density of myelinated nerve fibres in the nerve trunks. In view of current knowledge regarding the clinical effects of low nerve-fibre density in patients with neuropathies of varying aetiologies, such as diabetes, and that such a low density may lead to nerve entrapment symptoms, a reduction in myelinated nerve fibres may be a key factor behind the symptoms also seen in patients with HAVS and CTS. Furthermore, a reduced nerve-fibre density may result in a changed afferent signal pattern, resulting in turn in alterations in the brain, further prompting the symptoms seen in patients with HAVS and CTS. We conclude that a low nerve-fibre density lead to symptoms associated with nerve entrapment, such as CTS, in some patients with HAVS.
Highlights
Prolonged exposure to hand-held vibrating tools may cause a hand-arm vibration syndrome (HAVS), sometimes with individual susceptibility
The neurological symptoms of HAVS are similar to the symptoms found in carpal tunnel syndrome (CTS), which makes it difficult to distinguish between the two conditions
Findings in nerve biopsies from humans There is limited knowledge concerning the impact of nerve-fibre density as a risk factor in the development of peripheral neuropathy or nerve entrapment symptoms in humans [27]
Summary
We conclude that a) hand-arm vibration exposure is associated with an increased risk of CTS; b) hand-arm vibration exposure appears to be associated with diffuse demyelination of nerves in the hand/wrist area and later a reduction in the myelinated nerve fibers and c) these structural changes, seen as a low myelinated nerve-fibre density, may lead to symptoms associated with nerve entrapment, in particular CTS. A mechanism, based on a low myelinated nerve-fibre density similar to that observed in healthy and diabetic subjects with CTS, may be present in HAVS. The clinical symptoms seen in these patients are caused by changes both in the peripheral and central nervous systems. Patients with HAVS and clinical symptoms of CTS should be carefully considered for surgery since the outcome is not always favourable. Patients with HAVS and a suspicion of CTS should be evaluated, through a thorough patient history, careful clinical examination and appropriate blood samples to exclude other causes of neuropathy. Authors’ contributions All authors have contributed to the production of the manuscript. All authors read and approved the final manuscript
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