Clinical evaluation of the autonomic nervous system

Effective clinical evaluation of the autonomic nervous system depends crucially on obtaining an expert medical history and physical examination. Many autonomic function tests, which can be classified into physiologic, pharmacologic, neurochemical, neuroimaging, and genetic, are available. Different centers offer varying combinations of these tests. Sudomotor tests assess sympathetic cholinergic function. Physiologic tests assess sympathetic noradrenergic and parasympathetic cholinergic, reflexive, neurocirculatory regulation. Pharmacologic probes assess specific aspects of central neuronal outflows, neurotransmitter synthesis and metabolism, and vesicular and cell membrane transporters, and they target tissue receptors. Evaluation of adrenomedullary function requires access to sufficiently accurate and precise assay methods to detect low levels of epinephrine. Sympathetic neuroimaging can detect cardiac noradrenergic denervation, which characterizes Parkinson's disease, pure autonomic failure, and dementia with Lewy bodies.