Vibration syndrome and autonomic nervous system.

It is well known that hand-arm vibration affects the hand and arm which are directly exposed to vibration. However, through the sympathetic nervous system, hand-arm vibration can affect the foot which is not directly exposed to vibration. Hand-arm vibration activates the sympathetic nervous system, and induces vasoconstriction in the four extremities. And patients with vibration syndrome have circulatory disturbances of the foot as well; some patients had Raynaud's phenomenon of both fingers and toes, those with VWF were likely to complain of coldness in the feet as well as the hands, and had low skin temperature of the fingers and toes. In addition, arterial pathological changes like medial muscular hypertrophy have been observed in both fingers and toes of the patients. Prolonged repeated vasoconstriction of the foot induced by hand-arm vibration through the sympathetic nervous system is supposed to result in arterial changes like medial muscular hypertrophy in the foot and eventually circulatory disturbances of the feet. Hyperactivity of the sympathetic nervous system to cold, which is shown in patients with VWF, also probably contributes to the foot disturbances. The effect of hand-arm vibration through the sympathetic nervous system should be considered in hand-arm vibration syndrome.