NCIt definition : An acute or chronic disorder, affecting the sympathetic or parasympathetic nervous
system. It can be primary, the result of central nervous system degeneration, or secondary
due to diabetes or alcoholism. Patients with the chronic form of this disorder usually
have a progressive clinical course and a poor prognosis.;
Alternative definition : ACC/AHA: A condition in which there is a severe imbalance in the autonomic nervous
system.;