LAUSR

BACKGROUND The detailed pathophysiology of limb coldness in multiple system atrophy (MSA) is unknown. METHODS We evaluated cutaneous vasomotor neural function in 18 MSA patients with or without limb coldness, and in 20 healthy volunteers as controls. We measured resting skin sympathetic nerve activity (SSNA) and spontaneous changes of the sympathetic skin response (SSR) and skin blood flow (skin vasomotor reflex: SVR), as well as SVR and reflex changes of SSNA after electrical stimulation. The parameters investigated were the SSNA frequency at rest, amplitude of SSNA reflex bursts, absolute decrease and percent reduction of SVR, recovery time, and skin blood flow velocity. RESULTS Both the resting frequency of SSNA and the amplitude of SSNA reflex bursts were significantly lower in the MSA group than the control group (p<0.001 and p<0.05, respectively). There were no significant differences between the two groups with regard to the absolute decrease or percent reduction of SVR volume. The recovery time showed no significant difference between all MSA patients and control groups, but it was significantly prolonged in six MSA patients with limb coldness compared with that in the control group and that in MSA patients without limb coldness (p<0.01). The skin blood flow velocity was significantly slower in the MSA group than in the control group (p<0.001). CONCLUSION In MSA patients, limb coldness might occur due to impairments of the peripheral circulation based on prolongation of vasoconstriction and a decrease of skin blood flow velocity secondary to combined pre- and postganglionic skin vasomotor dysfunction.