Sympathetic outflow to the hand in patients with Raynaud's phenomenon.

Microelectrode recordings of skin nerve sympathetic activity were made in the median nerve supplying the right hand of nine patients with Raynaud's phenomenon and 10 control subjects. With subjects warmed up (finger temperature 33 to 34 degrees C) different manoeuvres were used to evoke strong, single sympathetic bursts, giving rise to vasoconstriction of the same magnitude in patients and control subjects. Immersion of the contralateral hand in ice water for 1 min elicited an increase in sympathetic outflow without any difference between patients and control subjects. It is concluded that neither hypersensitivity of the vessels to strong sympathetic bursts, nor abnormal increase of sympathetic outflow following shortlasting, local cold exposure, was present in the patients. A possible change of the functional relationship between nerve and vessel, the importance of which is uncertain, was observed in the patient group. The study provides direct evidence against a primary sympathetic hyperfunction and indirect support for a local fault mechanism in Raynaud's phenomenon.