Answer: Dysautonomia is a dysfunction of the autonomic nervous system.
The autonomic nervous system (ANS) is responsible for regulating several basic homeostatic aspects of the body. These features, such as breathing, digestion, heartbeat, and many others are carried out unconsciously.
The ANS is divided into two major branches.
The sympathetic branch originates in the thoracolumbar section of the spinal cord. These neurons, also called the preganglionic neurons, synthesize and release acetylcholine into different clumps of cell bodies and dendrites called ganglia. The largest of these ganglia are the sympathetic chain ganglia, which run adjacent to the spinal cord on each half of the body. Within these ganglia are the postganglionic neurons that synthesize and produce the neurotransmitter norepinephrine. Their fibers then innervate different internal organs, such as the heart, lungs, blood vessels, digestive tract, kidneys, and many others. For example, the norepinephrine released by these neurons activates noradrenergic receptors expressed on the heart, which function to increase the rate of contraction, thus sending more blood through the arteries. A second example: the lungs are also sensitive to the norepinephrine signal, which causes a dilation of the bronchioles, allowing for more oxygen intake. In sum, the sympathetic branch can be thought of as “driving up” activity and preparing the body for the “fight or flight” response.
On the other hand, the parasympathetic branch starts from two main areas in the cervicolumbar areas of the spinal cord. The cervical component originates at the vagus nerve, also called cranial nerve X. The vagus nerve sends acetylcholine projections to many of the same internal organs that receive sympathetic drive. The effect of acetylcholine is the opposite of that of norepinephrine: muscarinic acetylcholine receptors on the heart lead to decreased firing rate, for example. Another output of the parasympathetic branch originates from the sacral area of the spinal cord. These nerves contribute to regulation of the bladder and are important for sexual activity. In contrast to the effect of the sympathetic branch, activity of the parasympathetic branch leads to decreases in activity. Sometimes, this parasympathetic activity is called the “rest and digest” response.
Symptoms of dysautonomia
Dysautonomia is the symptom that occurs when these autonomic nervous system structures do not function as expected. These symptoms may either be a lack of function or an excess of function.
Male sexual impotence is one symptom of dysautonomia, as is excessive orthostatic hypotension, when blood pressure is unable to automatically adjust when moving from a sitting to standing position. Cardiovascular changes due to excess sympathetic drive can result in hypertension (high blood pressure) or elevated heart rate.
Some other side effects of dysautonomia may include local effects, such as a complex regional pain syndrome (CRPS). In CRPS, a person may experience neuropathic pain in one of more of their limbs. Usually, the pain is in the upper extremities. This is sometimes also called reflex sympathetic dystrophy (RSD). In RSD, there may be a burning sensation, tenderness, localized muscle weakness, joint pain or stiffness, and changes in sensory to hot and cold.
Causes of dysautonomia
Because dysautonomia is an umbrella term and not a disease itself, there are several related conditions that can produce the set of symptoms described as dysautonomia.
Excessive alcohol use or exposure to various toxic compounds such as heavy metals or even chemotherapy drugs can produce the symptoms. Inorganic lead, found in old paints or from other sources such as contaminated sources of drinking water, is known to produce autonomic system mediated abdominal pain and peripheral neuropathy (Peripheral neuropathy in chronic occupational inorganic lead exposure: a clinical and electrophysiological study). There is also strong evidence suggesting that chronic alcohol consumption, which may lead to thiamine deficiency, can produce dysautonomia (Alcohol-related peripheral neuropathy: nutritional, toxic, or both?)
Diabetes can produce dysautonomia. The appearance of autonomic neuropathy is correlated with the patient’s age. An estimated 20% of people with diabetes develop a cardiac autonomic neuropathy, which is known to increase risk of mortality.
Severe physical trauma can lead to dysautonomia symptoms. One study examined a group of patients who experienced traumatic brain injury (TBI). Of those enrolled in the study, none of them experienced any dysautonomia symptoms prior to their injury. However, afterwards, all of them experienced postural tachycardia, or dizziness upon standing, a symptom of the failure of the sympathetic nervous system to increase blood pressure when changing posture. (Autonomic dysfunction presenting as postural tachycardia syndrome following traumatic brain injury)
As a consequence of the neurodegeneration seen in Parkinson’s Disease, nearly 80% of people experience some sort of dysautonomia. Primarily, the symptoms include low blood pressure, issues with digestion, and sexual dysfunction. Sometimes, these symptoms are a side effect of the medications used to treat the Parkinson’s Disease. (Dysautonomia in Parkinson’s disease: neurocardiological abnormalities)
As another example, Guillain-Barre syndrome (GBS) is an inflammatory demyelinating disorder which has dysautonomia as a common symptom. A 2020 study (Dysautonomia in Guillain-Barré Syndrome: Prevalence, Clinical Spectrum, and Outcomes) suggested that nearly 40% of patients with GBS present with some form of dysautonomia among a sample of patients in the Saint Paul-Minneapolis area. However, a larger population suggests that the fraction is closer to two-thirds (https://onlinelibrary.wiley.com/doi/abs/10.1002/mus.880180202). Although there is not a great treatment for GBS, therapies like plasmapheresis or immunoglobulin therapy can help decrease the severity of the dysautonomia.
Celiac disease is a multisymptom autoimmune disorder that particularly targets the digestive tract. Celiac disease is estimated to affect about three million Americans, and neurological disorders including dysautonomia in up to 10% of these patients. Additionally, peripheral neuropathy and ataxia are some of the other symptoms found in patients with Celiac disease. (Autonomic neuropathy and coeliac disease)
Dysautonomia treatment
Unfortunately, there is not always a cure for dysautonomia. In some cases, dysautonomia can be reversible when the underlying condition resolves itself or is treated. There are, however, treatment strategies that can help people deal with their symptoms.
Among people with severe dysautonomia unrelated to another condition, long-term health outcomes may be worsened. Sometimes death may occur due to sudden respiratory failure or other cardiopulmonary side effects.
Resources for people with dysautonomia
Consider visiting the external websites and resources of the following organizations who may provide other up to date information about the state of dysautonomia research and other clinical interventions.
Dysautonomia International (https://dysautonomiainternational.org/)
Familial Dysautonomia Foundation (https://familialdysautonomia.org/)
FD Hope (http://www.fdhope.org/)