Chapter 21: Autonomic Disorders

DYSAUTONOMIA

General Considerations

Impairment throughout the nervous system by diverse processes—mass lesions, infections, strokes, multiple sclerosis plaques, seizures, and degenerative conditions—can produce autonomic symptoms. A much smaller number of disorders specifically targets autonomic structures, resulting in disordered autonomic control (dysautonomia).

The opposing sympathetic “fight-or-flight” and parasympathetic “rest-and-digest” systems comprise the autonomic nervous system. In most organs, dual control maintains unconscious, normal function. The systems are highly complex, however, with components in the cerebral cortex, limbic system, brainstem, spinal cord, autonomic ganglia, peripheral nerves, and specialized special sense and effector end organs. Sympathetic centers are located in the thoracic spinal cord and parasympathetic centers in the brainstem and the sacral spinal cord. The enteric nervous system of the gastrointestinal (GI) tract is considered by many to be an additional autonomous nervous system “mind of the gut.” Acetylcholine and norepinephrine are only two of a multitude of neurotransmitters that play important roles in autonomic control. Serotonin, for example, is a major enteric motor neuron neurotransmitter.

Clinical Findings

A. Symptoms and Signs

Many autonomic symptoms (Table 21–1) are nonspecific, and the diagnosis of dysautonomia can be missed when symptoms are atypical or each symptom is considered in isolation. For example, orthostatic hypotension—a significant decrease in blood pressure (BP) upon standing—can cause isolated postural pure vertigo, occipital headache, neck and shoulder “coat-hanger pattern” neck ache, cognitive changes, and fatigue in the absence of light-headedness. Inquiring about exacerbating conditions or medications can help distinguish orthostatic hypotension from other paroxysmal processes. Exacerbating conditions include:

1. Warm environment, hot bath, and fever

2. Large meals (carbohydrate load)

3. Valsalva maneuver

4. Volume depletion

5. Rapid postural change

6. Alcohol

Orthostatic hypotension is also aggravated in the postexercise period, in the early morning, and after rising ...