The assessment of sudomotor dysfunction in multiple system atrophy.

We studied sudomotor function in 21 patients with multiple system atrophy and in 11 age-matched controls. The extent and severity of the sudomotor deficit was assessed using the quantitative thermoregulatory sweat test. Central sudomotor function was studied by measuring sweating in response to raising body heat and administering thyrotropin-releasing hormone. Postganglionic sudomotor function was studied using the sudomotor axon reflex test evoked by nicotine. We conclude that in multiple system atrophy, thermoregulatory sudomotor dysfunction was more severe in the lower extremities. Heat stimulation increased the frequency of sweat expulsion and sweat rate on the forearm in moderate multiple system atrophy to a similar degree as controls but failed to do so on the thigh. Thyrotropin-releasing hormone enhanced sweating in moderate multiple system atrophy and controls. Results of the sudomotor axon reflex test indicate that in multiple system atrophy there is postganglionic sudomotor dysfunction which may be due to transsynaptic changes. These results suggest that the main lesion responsible for sudomotor dysfunction in multiple system atrophy is within the intermediolateral column cells of the spinal cord.