Cutaneous Nerve Fibre Depletion in Vibration White Finger

Abstract

Vibration white finger or hand-arm vibration syndrome is the episodic blanching of the fingers in response to cold occurring in those who work with hand held vibrating tools. Clinically the condition differs from primary Raynaud's phenomenon as persistent paraesthesiae and pain are common in the hands and arms and these occur independently from the ‘white attacks’. Symptoms can become severe enough to warrant a change of occupation. Industrial compensation may be awarded for vibration white finger but, at present, no simple or reliable objective diagnostic test is available. Calcitonin gene-related peptide (CGRP) is a neuropeptide with powerful vasodilator properties. A deficiency of immunoreactive CGRP nerve fibres has been previously demonstrated in the digital cutaneous microvasculature of patients with primary and secondary Raynaud's phenomenon with the distribution and quantity of other types of nerve fibres not being significantly altered. To determine if the innervation of the cutaneous microvasculature in vibration white finger was also abnormal skin biopsy samples from the fingers of 15 patients with vibration white finger, six healthy age matched controls who worked with vibrating machinery and 26 healthy age matched controls who were heavy manual workers without exposure to vibrating machinery were examined by immunohistochemistry. To try to correlate any histological abnormalities with clinical neurological deficit sensory nerve conduction studies have so far been performed in six patients with vibration white finger. There was a significant reduction in both the number of CGRP and protein gene product 9.5 (PGP) immunoreactive nerve fibres in the digital cutaneous biopsies from the patients with vibration white finger when compared to the biopsies from the heavy manual workers and the healthy workers exposed to vibration. The pattern of the loss of CGRP immunoreactive nerve fibres was similar to that described previously in Raynaud's phenomenon and may account for the episodic vasospasm seen in both conditions. PGP is a constitutive protein of all nerves therefore the reduced PGP immunostaining indicates generalized structural neuronal damage which could account for the persistent pain and paraesthesiae characteristic of vibration white finger. The nerve conduction studies revealed sensory nerve action potentials within the low range of normal in five patients with vibration white finger and mild median nerve compression in the remaining patient implying that the neuronal damage in the patients with vibration white finger is confined mainly to the small unmyelinated nerve fibres. The immunohistochemical findings may provide the basis for a diagnostic test for vibration white finger.

Exposure to hand-held vibrating tools and biomarkers of nerve injury in plasma: a population-based, observational study

“… 5 Even data from skin biopsies of fingers in vibration-exposed workers indicate that there is a reduction in content of calcitonin gene-related peptide as well as intraepidermal nerve fibre density observed as staining for PGP-9.5 in the biopsies. 6 The structural changes in the peripheral nerve may also induce an increased susceptibility for peripheral nerve compression syndromes, like carpal tunnel syndrome (CTS), 7 in accordance with the relation between diabetic neuropathy and CTS. 8 9 The aim of the present observational study was to examine several nerve-related biomarkers, as a sign of neuropathy that can be measured in plasma in a cohort of subjects who were exposed to hand-held vibrating tools.…”

“…Such symptoms may be caused by structural changes, for example, extensive axonal degeneration, as observed in biopsies from the posterior interosseous nerve just proximal to the wrist in men exposed to vibrations 5. Even data from skin biopsies of fingers in vibration-exposed workers indicate that there is a reduction in content of calcitonin gene-related peptide as well as intraepidermal nerve fibre density observed as staining for PGP-9.5 in the biopsies 6. The structural changes in the peripheral nerve may also induce an increased susceptibility for peripheral nerve compression syndromes, like carpal tunnel syndrome (CTS),7 in accordance with the relation between diabetic neuropathy and CTS 8 9.…”