Dysautonomia refers to a disorder of autonomic nervous system (ANS) function. While most physicians interpret dysautonomia as a failure of either the sympathetic or parasympathetic components of the ANS, it can also manifest as excessive ANS activity. Dysautonomia can present in various forms, such as localized conditions like reflex sympathetic dystrophy or generalized disorders like pure autonomic failure. It may be acute and reversible, as seen in Guillain-Barre syndrome, or chronic and progressive. Conditions like diabetes and alcoholism can include dysautonomia, either as a primary condition or in association with degenerative neurological diseases like Parkinson’s disease. Other diseases characterized by generalized, primary dysautonomia include multiple system atrophy and familial dysautonomia.
Key features of generalized dysautonomia resulting from sympathetic failure include impotence in men and a drop in blood pressure upon standing (orthostatic hypotension). Conversely, excessive sympathetic activity can manifest as hypertension or a rapid pulse rate.