Active vasodilation by sympathetic outflow to limb skin in a patient with progressive aphasia.

Despite considerable interest, a pure vasodilator response by skin sympathetic nerve activity (SSNA) bursts in human limbs has not been observed in previous studies. In a patient with progressive nonfluent aphasia, SSNA, sympathetic skin response, and skin blood flow were simultaneously recorded at rest and during electrical stimulation. There was a very low frequency of SSNA bursts at rest, and when electrical stimulation was delivered, reflex bursts of SSNA were always observed followed by a sympathetic skin response and an increase in skin blood flow. The reflex latency of SSNA was slightly prolonged and the mean amplitude of reflex SSNA bursts was lower after electrical stimulation, compared with the responses in healthy controls. We report for the first time that the active vasodilator component of cutaneous sympathetic activity in limbs was recorded without any vasoconstrictor component in a patient with progressive aphasia.