Altered response in cutaneous sympathetic outflow to mental and thermal stimuli in primary palmoplantar hyperhidrosis

Skin sympathetic nerve activities (SSNAs) were recorded simultaneously from the tibial and peroneal nerves by microneurography at an ambient temperature of 25°C in five subjects with primary palmoplantar hyperhidrosis. The resting activity of the tibial SSNA innervating the sole (glabrous skin) increased moderately (36.5±1.5 bursts/min), while mental arithmetic provoked marked responses (1,003.3±457.4% compared with the resting level) in the hyperhidrosis group compared with the control normohidrosis group ( n=5, 25.3±4.2 bursts/min and 142.2±58.4%, respectively). Differentiation of the tibial SSNA into sudomotor (innervating sweat glands) and vasoconstrictor (innervating presphincter of skin vessels) revealed that this SSNA enhancement was attributable to not only sudomotor but also vasoconstrictor components during mental arithmetic. In contrast, the responses in the peroneal SSNA (innervating the dorsum pedis, hairy skin) of the hyperhidrosis group were only slightly changed, exhibiting no significant difference from those in the normohidrosis group. Reflex bursts elicited by sound and electric stimulation were normal in amplitude and latency. When the ambient temperature was elevated to 30°C, the tibial SSNAs became more enhanced than did the peroneal SSNAs. The tibial SSNA was markedly enhanced in the hyperhidrosis group (290.0±78.5%) compared with the normohidrosis group (78.3±25.4%). We conclude that the excessive responses in SSNA to the palmar and plantar glabrous skin to both mental and thermal stimuli may be responsible for the profuse sweating in subjects with primary palmoplantar hyperhidrosis.