Autonomic function testing

Autonomic function testing fulfills the goals of demonstrating the presence and severity of autonomic failure. It is also helpful in detecting milder forms of autonomic dysfunction and differentiating the etiology of orthostatic symptoms. A standardized battery of autonomic function testing has been developed, which comprises tests to assess postganglionic sympathetic sudomotor, cardiovagal, and cardiovascular adrenergic function. Discussed in detail here are indications and preparation for autonomic testing, the practical details of performing selected autonomic tests, pitfalls, and the physiology and pathophysiology underlying normal and abnormal autonomic function tests, including deep breathing, Valsalva maneuver, and head-up tilt.