Afferent and efferent nerve injury in vibration white fingers.

To study afferent pain and efferent sympathetic nerve function in vibration-induced Raynaud's phenomenon, 10 patients and 11 healthy controls were examined. Thresholds for mechanically and thermally induced pain were determined on the left side of the tip of the second finger, on the skin fold between thumb and second finger and on the ear lobe. Superficial skin blood flow was simultaneously measured by laser Doppler technique on the right third finger. The patients had higher pain thresholds than controls on the vibration-exposed index finger but not on other stimulation areas. Thus receptors or pain-mediating nerve fibres in the fingers are affected by work with vibrating tools. The controls demonstrated vasoconstriction on pain stimulation, whereas the patients showed no or weak vasoconstriction in response to the stimulation. This was true also when areas not included in the disease process were stimulated, indicating that also sympathetic vasoconstrictor nerves or receptors are affected in vibration syndrome.