Evaluation of Autonomic Disorders

The main aims of autonomic evaluation are to determine the presence and distribution of autonomic dysfunction; to recognize patterns of autonomic failure; and to detect potentially treatable disorders. The evaluation of patients with autonomic disorders requires a careful history and physical examination, selected laboratory tests, and laboratory assessment of autonomic function. This includes tests of sudomotor function, such as the thermoregulatory sweat test and quantitative sudomotor axon reflex tests; tests of cardiovagal function such as the heart rate responses to deep breathing or the of the Valsalva maneuver (VM); and tests of adrenergic function such as the beat-to beat blood pressure responses to the VM and head-up tilt. Neuroimaging, electromyogram, and special studies, such as polysomnography, urodynamic studies, and gastrointestinal motility studies, may be helpful in specific conditions. Some studies, such as measurement of plasma catecholamines or punch skin biopsy, can be helpful in special circumstances.