The autonomic nervous system (ANS) controls several basic functions, including:
You don’t have to think consciously about these systems for them to work. The ANS provides the connection between your brain and certain body parts, including internal organs. For instance, it connects to your heart, liver, sweat glands, skin, and even the interior muscles of your eye.
The ANS includes the sympathetic autonomic nervous system (SANS) and the parasympathetic autonomic nervous system (PANS). Most organs have nerves from both the sympathetic and parasympathetic systems.
The SANS usually stimulates organs. For example, it increases heart rate and blood pressure when necessary. The PANS usually slows down bodily processes. For example, it reduces heart rate and blood pressure. However, the PANS stimulates digestion and the urinary system, and the SANS slows them down.
The main responsibility of the SANS is to trigger emergency responses when necessary. These fight-or-flight responses get you ready to respond to stressful situations. The PANS conserves your energy and restores tissues for ordinary functions.
Autonomic dysfunction develops when the nerves of the ANS are damaged. This condition is called autonomic neuropathy or dysautonomia. Autonomic dysfunction can range from mild to life-threatening. It can affect part of the ANS or the entire ANS. Sometimes the conditions that cause problems are temporary and reversible. Others are chronic, or long term, and may continue to worsen over time.
Diabetes and Parkinson’s disease are two examples of chronic conditions that can lead to autonomic dysfunction.
Dysautonomia is a general term used to describe a breakdown or abnormal function of the ANS. The autonomic nervous system controls much of your involuntary functions. Symptoms are wide-ranging and can include problems with the regulation of heart rate, blood pressure, body temperature, perspiration, and bowel and bladder functions. Other symptoms include fatigue, lightheadedness, feeling faint or passing out (syncope), weakness, and cognitive impairment.
Orthostatic intolerance refers to impairment in the body’s ability to handle gravity. When a person stands, blood pools in the abdomen and legs. Normally, the autonomic nervous system will compensate by constricting blood vessels and pushing the blood to the brain. When autonomic pathways are damaged, these reflexes, termed baroreflexes, do not function adequately. As a result, the person becomes dizzy, light-headed, and may faint.
In addition, digestion is controlled by the autonomic nervous system. When the ANS malfunctions, the “victim” commonly develops gastrointestinal problems. Symptoms include nausea, bloating, vomiting, severe constipation, and abdominal pain.
Autonomic dysfunction can occur as a secondary condition of another disease process, like diabetes, or as a primary disorder where the autonomic nervous system is the only system impacted. These conditions are often misdiagnosed.
Over one million Americans are impacted b
y a primary autonomic system disorder. The more common forms of these conditions include:
- Orthostatic hypotension (OH)
- Orthostatic intolerance (OI)
- Postural orthostatic tachycardia syndrome, also known as postural tachycardia syndrome (POTS)
- Neurogenic bowel (gastroparesis, intestinal dysmotility, constipation)
- Erectile dysfunction and neurogenic bladder
Types of autonomic dysfunction
Autonomic dysfunction can vary in symptoms and severity, and they often stem from different underlying causes. Certain types of autonomic dysfunction can be very sudden and severe, yet also reversible.
Different types of autonomic dysfunction include:
Postural orthostatic tachycardia syndrome (POTS)
POTS affects anywhere from 1 to 3 million people in the United States. Nearly five times as many women have this condition compared to men. It can affect children, teenagers and adults. It can be also associated with other clinical conditions such as Ehlers-Danlos syndrome, an inherited condition of abnormal connective tissue.
POTS symptoms can range from mild to severe. Up to one out of four people with POTS have significant limitations in activity and are unable to work due to their condition.
Neurocardiogenic syncope (NCS)
NCS is also known as vasovagal syncope. It’s a common cause of syncope, or fainting. The fainting is a result of a sudden slowing of blood flow to the brain and can be triggered by dehydration, sitting or standing for a long time, warm surroundings and stressful emotions. Individuals often have nausea, sweating, excessive tiredness, and ill feelings before and after an episode.
Multiple system atrophy (MSA)
MSA is a fatal form of autonomic dysfunction. Early on, it has symptoms similar to Parkinson’s disease. But people with this condition usually have a life expectancy of only about 5 to 10 years from their diagnosis. It’s a rare disorder that usually occurs in adults over the age of 40. The cause of MSA is unknown, and no cure or treatment slows the disease.
Hereditary sensory and autonomic neuropathies (HSAN)
HSAN is a group of related genetic disorders that cause widespread nerve dysfunction in children and adults. The condition can cause an inability to feel pain, temperature changes, and touch. It can also affect a wide variety of body functions. The disorder is classified into four different groups depending on age, inherited patterns, and symptoms.
Holmes-Adie syndrome (HAS)
HAS mostly affects the nerves controlling the muscles of the eye, causing vision problems. One pupil will likely be larger than the other, and it will constrict slowly in bright light. Often it involves both eyes. Deep tendon reflexes, like those in the Achilles tendon, may also be absent.
HAS may occur due to a viral infection that causes inflammation and damages neurons. The loss of deep tendon reflexes is permanent, but HAN isn’t considered life-threatening. Eye drops and glasses can help correct vision difficulties.
Autonomic dysfunction can affect a small part of the ANS or the entire ANS. Some symptoms that may indicate the presence of an autonomic nerve disorder include:
- dizziness and fainting upon standing up, or orthostatic hypotension
- an inability to alter heart rate with exercise, or exercise intolerance
- sweating abnormalities, which could alternate between sweating too much and not sweating enough
- digestive difficulties, such as a loss of appetite, bloating, diarrhea, constipation, or difficulty swallowing
- urinary problems, such as difficulty starting urination, incontinence, and incomplete emptying of the bladder
- sexual problems in men, such as difficulty with ejaculation or maintaining an erection
- sexual problems in women, such as vaginal dryness or difficulty having an orgasm
- vision problems, such as blurry vision or an inability of the pupils to react to light quickly
- You can experience any or all of these symptoms depending on the cause, and the effects may be mild to severe. Symptoms such as tremor and muscle weakness may occur due to certain types of autonomic dysfunction.
Orthostatic intolerance is a condition whereby your body is affected by changes in position. An upright position triggers symptoms of dizziness, lightheadedness, nausea, sweating, and fainting. Lying down improves the symptoms. Often this is related to an improper regulation of the ANS.
Orthostatic hypotension is a type of orthostatic intolerance. Orthostatic hypotension occurs when your blood pressure drops significantly as you stand up. This can cause lightheadedness, fainting, and heart palpitations. Injury to nerves from conditions like diabetes and Parkinson’s disease can cause episodes of orthostatic hypotension due to autonomic dysfunction.
Other types of orthostatic intolerance due to autonomic dysfunction include:
- postural orthostatic tachycardia syndrome
- neurocardiogenic syncope or vasovagal syncope
Many health conditions can cause autonomic neuropathy. It can also be a side effect of treatments for other diseases, such as cancer. Some common causes of autonomic neuropathy include:
Abnormal protein buildup in organs (amyloidosis), which affects the organs and the nervous system.
Autoimmune diseases, in which your immune system attacks and damages parts of your body, including your nerves. Examples include Sjogren’s syndrome, systemic lupus erythematosus, rheumatoid arthritis and celiac disease. Guillain-Barre syndrome is an autoimmune disease that happens rapidly and can affect autonomic nerves.
An abnormal attack by the immune system that occurs as a result of some cancers (paraneoplastic syndrome) can also cause autonomic neuropathy.
Diabetes, especially with poor glucose control, is the most common cause of autonomic neuropathy. It can gradually cause nerve damage throughout the body.
Certain medications, including some drugs used in cancer chemotherapy.
Certain infectious diseases. Some viruses and bacteria, such as botulism, Lyme disease and HIV, can cause autonomic neuropathy.
Your doctor will treat autonomic dysfunction by addressing the symptoms. If an underlying disease is causing the problem, it’s important to get it under control as soon as possible.
Often, orthostatic hypotension can be helped by lifestyle changes and prescription medication. The symptoms of orthostatic hypotension may respond to:
- elevating the head of your bed
- drinking enough fluids
- adding salt to your diet
- wearing compression stockings to prevent blood pooling in your legs
- changing positions slowly
- taking medications like midodrine
- Nerve damage is difficult to cure. Physical therapy, walking aids, feeding tubes, and other methods may be necessary to help treat more severe nerve involvement.
While certain inherited diseases that put you at risk of developing autonomic neuropathy can’t be prevented, you can slow the onset or progression of symptoms by taking care of your health in general and managing your medical conditions.
Follow your doctor’s advice on healthy living to control diseases and conditions, which might include these recommendations:
Control your blood sugar if you have diabetes.
Avoid alcohol and smoking.
Get appropriate treatment if you have an autoimmune disease.
Take steps to prevent or control high blood pressure.
Achieve and maintain a healthy weight.
Inherited disorders. Certain hereditary disorders can cause autonomic neuropathy.