Frequently Asked Questions

The autonomic nervous system (ANS or visceral nervous system) is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal. Whereas most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind.

It is classically divided into two subsystems: the parasympathetic nervous system and sympathetic nervous system.

The parasympathetic nervous system is a division of the autonomic nervous system. The actions of the parasympathetic nervous system can be summarized as "rest and digest". They include body functions like digestion and urination.

The sympathetic nervous system is another part of the autonomic nervous system. The action of the SNS regulates the “housekeeping” processes, such as tightening blood vessels when you stand up and increasing heart rate and force of the heartbeat when you exercise. It is sometimes referred to as “flight or fight”.

Doctors may try a variety of non-drug treatments to see your response. For those patients that have a decreased ability to sweat, fluid intake may help alleviate some symptoms and decrease dehydration.

Your doctor may recommend a high salt diet. High salt intake tends to increase the volume of fluid in the body. Normally, when a patient takes in a high salt diet, the kidneys increase the amount of salt in the urine and this limits the increase in blood volume. Some drugs may be required to increase the blood volume if you are on a high salt diet.

Eating a big meal leads to shunting of blood toward the gut. In people with dizziness or lightheadedness when they stand up (orthostatic intolerance) or even with orthostatic hypotension, it is usually advisable to eat frequent small meals. Reducing the amounts of sugars or other carbohydrates in meals may help manage symptoms.

Deconditioning is adaptation of an organism to less demanding environment, or, alternatively, the decrease of physiological adaptation to normal conditions. Deconditioning may result from decreased physical activity, prescribed bed rest, orthopedic casting, paralysis, aging, etc. A particular interest in the study of deconditioning is in aerospace medicine, to diagnose, fight, and prevent adverse effects of the conditions of space flight.

Patients with autonomic dysfunction often have an inability to tolerate extremes of external temperature. When exposed to heat, patients with failure of the sympathetic nervous system may not sweat adequately to maintain the core temperature by evaporation of the sweat. Patients with chronic orthostatic hypotension as from pure autonomic failure, can have heat intolerance because of inability to perspire. When exposed to cold, these patients may not constrict blood vessels adequately in the skin, so that the body temperature falls (hypothermia).

Compression stockings are used to support the venous and lymphatic systems of the leg. They offer graduated compression where maximum compression is achieved at the ankle and decreases as you move up the leg. This compression, when combined with the muscle pump effect of the calf, aids in circulating blood and lymph fluid through the legs.

Autonomic testing is designed to determine how well your body is regulating your blood pressure and heart rate, and sometimes other functions. During these tests, your heart rate is measured using an electrocardiogram and your blood pressure using a cuff around your arm or finger. The tests include asking you to breathe deeply for two minutes, breathing as fast and as hard as you can for 30 seconds, maintaining a handgrip for three minutes, breathing against pressure for 15 seconds and placing your hand in ice water for one minute. All these tests are meant to stimulate your autonomic nervous system to produce changes in blood pressure and heart rate of short duration that reflect how well your involuntary nervous system is working.

The Valsalva maneuver is one of the most important clinical physiological tests for autonomic failure. It consists of blowing against a resistance for several seconds, then relaxing. The instant a person begins to blow, the sudden increase in chest and abdominal pressure forces blood out of the chest and down the arms. This increases blood pressure briefly (phase I). Soon afterwards, the amount of blood ejected by the heart with each beat (stroke volume) plummets, because the straining decreases entry of blood from the veins into the heart. Blood pressure progressively falls (phase II). The brain senses this fall and a rapid decrease in outflow in the parasympathetic nervous system to the heart. The increase in nerve traffic leads to more release of norepinephrine, which tightens blood vessels throughout the body. When the patient relaxes at the end of the maneuver (phase III), briefly, the blood pressure falls, but then blood rushes back into the chest and within a few heartbeats, the heart ejects this blood. The blood pressure increases (phase IV) and since the blood vessels are constricted, produces an overshoot of blood pressure, outflow to blood vessels falls and in response to this increase in blood pressure the heart rate falls. The pattern of these various perturbations gives physicians important information about both sympathetic and parasympathetic function.

In patients with autonomic dysfunction, the blood vessels fail to constrict reflexively (during phase II) and so blood pressure falls progressively and does not increase toward baseline at the end of phase II. During phase IV, because of the lack of tightening of blood vessels, there is no rapid increase in blood pressure and no phase IV overshoot of pressure. Instead, the blood pressure gradually increases slowly back to the baseline value.

The tilt table is done to see if standing up provokes a sudden fall in blood pressure (neurally mediated hypotension), an excessive increase in pulse rate (Postural tachycardia syndrome) or fainting (neurally mediated syncope). The patient lies on a stretcher-like support. Straps like seatbelts are attached around the abdomen and legs and the patient is tilted upright at an angle. The exact angle varies and may be from 60 to 90 degrees. The tilting goes on for up to 45 minutes. The patient is gradually tilted to an upright position until systolic blood pressure drops to 70 mm Hg or the appearance of orthostatic symptoms such as dizziness, lightheadedness or faintness. The purpose is to hopefully reproduce the patient’s problem in a controlled laboratory setting. It may not be performed on all patients, such as patients with a persistent fall in blood pressure each time they stand up (orthostatic hypotension) because the blood pressure will fall progressively beginning as soon as the tilting starts.

Sweat tests evaluate a particular part of the autonomic nervous system. The brain increases sweating by directing an increase in sympathetic nervous system traffic to sweat glands in the skin. The chemical messenger, acetylcholine, is released, which acts on the sweat glands to stimulate the production of sweat. The QSART is a special form of sweat test. It tests the ability of sympathetic nerve terminals in the skin to release acetylcholine and increase sweat production. A drug is applied to a nearby patch of skin. This evokes sweating at the site, but it also allows the body to release its own acetylcholine, resulting in sweat production. If a person had a loss of sympathetic nerve terminals that release acetylcholine, applying the patches would not lead to increased sweating. By this sort of neuropharmacologic test, doctors can distinguish sympathetic cholinergic failure due to loss of cholinergic terminals from failure due to abnormal regulation of sympathetic nerve traffic to intact cholinergic terminals.

In this test, the patient dunks a hand into ice-cold water for 1-2 minutes. This rapidly increases the blood pressure by increasing activity of the sympathetic nervous system.

A g-suit is an anti-gravity garment worn by fighter pilots. When they are pulling positive G's, the suit inflates and prevents blood from pooling in their feet and legs which would cause them to lose consciousness. NASA astronauts also wear g-suits when they experience Orthostatic Intolerance (OI). For more information about the g-suit, go to: OI Resource

Catecholamines are sympathomimetic "fight-or-flight" hormones that are released by the adrenal glands in response to stress. They are part of the sympathetic nervous system. They are called catecholamines because they contain a catechol group, and are derived from the amino acid tyrosine. The most abundant catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine, all of which are produced from phenylalanine and tyrosine.

Orthostatic hypotension is a debilitating symptom of diverse etiology. In a few cases, identification of the etiology and treatment is easily performed. However, we study patients in whom orthostatic hypotension is of a more complex etiology. Patients can have orthostatic hypotension due to failure of the autonomic nervous system (hypoadrenergic orthostatic hypotension) as seen in primary autonomic failure (idiopathic orthostatic hypotension), multiple system atrophy (Shy-Drager syndrome), secondary autonomic failure (autonomic neuropathy secondary to diabetes mellitus, porphyria, chronic renal failure, amyloidosis, etc.).

Also see: NINDS Orthostatic Hypotension Information Page

Dysautonomia (autonomic dysfunction) is a broad term that describes any disease or malfunction of the autonomic nervous system. This includes postural tachycardia syndrome (POTS), vasovagal syncope, mitral valve prolapse dysautonomia, pure autonomic failure, Neurocardiogenic syncope (NCS), Neurally Mediated Hypotension (NMH) autonomic instability and a number of lesser-known disorders such as cerebral salt-wasting syndrome. Dysautonomia is also associated with Multiple System Atrophy (Shy-Drager syndrome).

Also see: NINDS Dysautonomia Information Page

When orthostatic symptoms occur in patients, but blood pressure does not fall as much as 20/10 mmHg on assumption of upright posture, the patient has orthostatic intolerance (OI). Additional criteria used for the diagnosis of OI at Vanderbilt’s Autonomic Dysfunction Center include an increase in heart rate of at least 30 beats per minute with standing, and a standing plasma norepinephrine level of at least 600 pg/ml. Because upright heart rate is usually greatly increased, the term Postural Tachycardia Syndrome (POTS) is commonly used.

Also see: NINDS Postural Tachycardia Syndrome Information Page

Pure autonomic failure is dysfunction of many of the processes controlled by the autonomic nervous system, such as blood pressure. It is not fatal. The cause is usually unknown but sometimes is an autoimmune disorder. The most common symptom is an excessive decrease in blood pressure when a person stands (orthostatic hypotension). People may sweat less and become intolerant of heat. The pupils may not widen (dilate) and narrow (constrict) normally. Vision may be blurred. People may have difficulty emptying the bladder (urine retention). They may be constipated or lose control of bowel movements. Men may have difficulty initiating and maintaining an erection (erectile dysfunction).

Patients with PAF have a generally good outlook; many live for decades after the onset of their disease. The most common cause of death in these patients is pulmonary embolus or recurrent infection. The incidence of both myocardial infarction and stroke does not appear to be significantly increased in this disorder.

In Multiple System Atrophy, there is widespread autonomic failure associated with impairment in other neurological systems. The other neurological systems may be cerebellar, extrapyramidal, neuromuscular, or pyramidal. The pathological hallmark of MSA is neuronal loss and gliosis within multiple sites in the brain.

The prognosis is more guarded in the Multiple System Atrophy patient than in Pure Autonomic Failure. It is rare for a patient to survive 10 years. The autonomic abnormalities are seldom the direct cause of death. A significant number of patients develop laryngeal stridor and difficulty swallowing, which can lead to pneumonia. In addition, many patients with MSA experience Cheyne-Stokes or periodic respiration and in some cases this may lead to a critical loss of respiratory drive. Pulmonary hypertension may occur during apnea. The most common causes of death in patients with MSA are pulmonary embolus, apnea, and intercurrent infection.

Also see: NINDS Multiple System Atrophy Information Page

Also see: NINDS Multiple System Atrophy with Orthostatic Hypotension Information Page

Dementia with Lewy Bodies (DLB) is a progressive degenerative disease or syndrome of the brain. It shares symptoms - and sometimes overlaps - with several diseases, especially with two common diseases of older adults, Alzheimer’s and Parkinson’s.

Persons who develop DLB have behavioral and memory symptoms of dementia like those of Alzheimer’s disease and, to varying extents, the physical, motor system symptoms seen in Parkinson’s. However, the mental symptoms of a person with DLB might fluctuate frequently, motor symptoms are milder than for Parkinson’s disease, and DLB patients usually have vivid visual hallucinations.

DLB is named after smooth round protein lumps, called Lewy bodies, that are found in the nerve cells of affected brains. Lewy bodies are often present in the nuclei (nerve cells) of brains afflicted with a variety of disorders. In DLB, the Lewy bodies are found throughout the outer layer of the brain (the cerebral cortex) and deep inside the midbrain or brainstem. These “abnormal protein structures” were first described in 1912 by Fredrich Heinrich Lewy, M. D., a contemporary of Alois Alzheimer who first identified the more common form of dementia that bears his name.

Because Lewy bodies are also often found in the brains of those diagnosed with Alzheimer’s, Parkinson’s, Down Syndrome and other disorders, researchers agreed in 1995 to use the term “Dementia with Lewy Bodies” to describe both a single disease (sometimes called “pure DLB”) and a spectrum of disorders with similar or related pathology.

It is believed that DLB, as a defined disease process, accounts for as many as 20% of the seven million cases of dementia in the United States and for as much as one-third of dementing illness in elderly Americans. This makes DLB the second most common form of dementia after Alzheimer’s.

Also see: NINDS Dementia With Lewy Bodies Information Page

POTS is characterized by the body's inability to make the necessary adjustments to counteract gravity when standing up. The defining symptom of POTS is an excessive heart rate increment upon standing. However, as you will discover, there are a multitude of other symptoms that often accompany this syndrome. As such, POTS can be a difficult disorder to detect and understand.

PAF is a degenerative disease of the peripheral nervous system characterized by a marked fall in blood pressure upon standing (orthostatic hypotension). The orthostatic hypotension leads to symptoms associated with cerebral hypoperfusion, such as dizziness, fainting, visual disturbances and neck pain. Other symptoms such as chest pain, fatigue and sexual dysfunction may also occur. Symptoms are worse when standing and are sometimes relieved by sitting or lying flat.

Supine hypertension is high blood pressure while lying down. Supine hypertension is a common problem that affects at least 50% of patients with primary autonomic failure. Supine hypertension can be severe, with systolic pressure in many cases >200 mm Hg, and complicates the treatment of orthostatic hypotension. Drugs used for the treatment of orthostatic hypotension (eg, fludrocortisone and pressor agents), worsen supine hypertension. High blood pressure may also cause target organ damage in this group of patients. The pathophysiologic mechanisms causing supine hypertension in patients with autonomic failure have not been defined.

Dopamine beta-hydroxylase (DBH) deficiency is a very rare form of primary autonomic failure characterized by a complete absence of norepinephrine and epinephrine in plasma together with increased dopamine plasma levels. The prevalence of DBH deficiency is unknown. Only a limited number of cases with this disease have been reported. DBH deficiency is mainly characterized by cardiovascular disorders and severe orthostatic hypotension. First symptoms often start during a complicated perinatal period with hypotension, muscle hypotonia, hypothermia and hypoglycemia. Children with DBH deficiency exhibit reduced ability to exercise because of blood pressure inadaptation with exertion and syncope. Symptoms usually worsen progressively during late adolescence and early adulthood with severe orthostatic hypotension, eyelid ptosis, nasal stuffiness and sexual dysfunction. Limitation in standing tolerance, limited ability to exercise and traumatic morbidity related to falls and syncope may represent later evolution. The syndrome is caused by heterogeneous molecular alterations of the DBH gene and is inherited in an autosomal recessive manner. Restoration of plasma norepinephrine to the normal range can be achieved by therapy with the synthetic precursor of norepinephrine, L-threo-dihydroxyphenylserine (DOPS). Oral administration of 100 to 500 mg DOPS, twice or three times daily, increases blood pressure and reverses the orthostatic intolerance. It was first described by David Robertson and colleagues in 1986.

Syncope is a sudden and transient loss of consciousness and postural tone, usually described as “fainting” or “passing out”. It is a common problem, accounting for 3% of emergency room visits. A history of an isolated episode of syncope will be found in as many as 25% of healthy young adults, especially in settings that precipitate fear, disgust or anxiety, and if not repeated does not warrant further work-up. Repeated episodes, however, may be caused by a wide variety of medical problems, and require diagnosis and treatment. It is important to distinguish syncope from “dizziness”, which generally refers to an alteration in balance, vision, or perception of the environment, without the loss of consciousness. Causes of syncope can be differentiated into two major classifications, cardiac and noncardiac. Examples of cardiac syncope are heart rhythm disturbances or abnormalities in the structure of the heart.

Baroreflex Failure is often confused with efferent autonomic failure. Baroreflex failure may present as uncontrolled severe hypertension, due to damage to the glossopharyngeal or vagal nerves.

Patients with baroreflex failure may present with severe hypertension, either sustained or episodic. Blood pressures can reach 170-280/110-135. Accompanying tachycardia may suggest the diagnosis of pheochromocytoma, which is supported by sensations of warmth and or flushing, palpitations, headache, and diaphoresis.

Etiologies may include:

  • Surgery and irradiation for cancer of the throat.
  • Injury to the contralateral glossopharyngeal and vagus nerves, or tumors in the vagal or glossopharyngeal distributions, also known as the familial paraganglioma syndrome.
  • Cell loss bilaterally in the nuclei of the solitary tract in the setting of a degenerative neurologic disease of medullary and higher structures.

For many of those who suffer from Baroreflex failure, an etiology is unattainable.

Between 25,000 and 100,000 Americans are believed to have Multiple System Atrophy. The incidence (new cases per 100,000 person years) for ages 50-99 years is 3-5.

Disease progression in MSA is quicker than in Parkinsonism. About 80% of patients are disabled within 5 years of onset of the motor symptoms, and only 20% survive past 12 years. The mean survival after diagnosis is roughly 6 years. The rate of progression differs in every case and speed of decline may vary widely in individual patients.

The probable outcome is poor. There is a progressive loss of physical functions until general debilitation develops. Early death is likely. Most people who are diagnosed with Shy-Drager syndrome die within seven to 10 years after symptoms begin.

Pneumonia is the most common cause of death, although irregularities in heartbeat or brearhing may be responsible for death in some patients. Breathing problems such as aspiration, stridor (high-pitched breathing sounds due to airway obstruction), or cardiopulmonary arrest can occur.

If there is a contact person listed with the trial information you can talk to them yourself, or have your doctor call on your behalf.

The ADC Contact Registry is a method by which patients with autonomic disorders can register themselves with the ADC in order to be contacted in the future about clinical research opportunities and updates on the progress of the ADC research projects. The contact registry is anonymous and free of charge. Patients with autonomic disorders are strongly encouraged to join the ADC Contact Registry.

A list of support groups and agencies dedicated to autonomic dysfunction patients can be found here: Find patient groups and national organizations

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