Robert D. Fealey, M.D.
Consultant in Neurology, Mayo Clinic and Mayo Foundation
Assistant Professor of Neurology, Mayo Medical School

　Autonomic failure can result from degenerative, immune mediated, toxic, inherited or metabolic disorders of the nervous system. The thermoregulatory sweat test (TST) is ideally suited to study autonomic function in such disorders as it will be effected by lesions that involve either central (preganglionic) or peripheral (postganglionic) autonomic pathways. When combined with a test of postganglionic sudomotor function, such as the Quantitative Sudomotor Axon Reflex Test (QSART), anatomical localization of lesions is possible.
　Recently (Vernino et al., 1998) we described TST abnormalities in patients with neuronal nicotinic Ach receptor antibody and subacute autonomic neuropathy. TST deficits were highly suggestive of sympathetic ganglionectomy (some preganglionic or synaptic) rather than a length dependent peripheral nerve process. Remarkably, longitudinal studies in 6 patients with autoimmune autonomic neuropathy show dramatic reversal of severe TST deficits in 3 patients correlating well with ganglionic receptor antibody titers. (Vernino et al accepted for publication in the NEJM). Evidence for a block in ganglionic transmission will be presented.
　Multiple System Atrophy (MSA) is often difficult to distinguish from less severe disorders such as Parkinson’s Disease, early on in the course of the disorder. Neuropathological and limited experimental evidence (Kihara et al., 1991) suggests the early development of preganglionic autonomic failure (often affecting the intermediolateral cell columns of the spinal cord) is most characteristic of MSA. Demonstration of preganglionic involvement via the combined use of TST and QSART may offer a way to diagnose MSA early in the course of the disorder when therapeutic interventions might be more effective. Evidence of this hypothesis will be presented.

References:
1) Kihara M, Sugenoya J, Takahashi A (1991) The assessment of sudomotor dysfunction in multiple system atrophy. Clin Auton Res, 1, 297-302.
2) Vernino S, Adamski J, Kryzer TJ, Fealey RD, Lennon VA (1998) Neuronal nicotinic ACh receptor antibody in subacute autonomic neuropathy and cancer-related syndromes. Neurology, 50, 1806-13.