Autonomic neuropathy

Autonomic neuropathy is a type of peripheral neuropathy that affects involuntary body functions, including heart rate, blood pressure, perspiration, digestion and other processes. Instead of a specific disease, autonomic neuropathy refers to damage to the autonomic nerves that results in a variety of signs and symptoms. This damage disrupts signals between the brain and portions of the autonomic system such as the heart, blood vessels and sweat glands, resulting in decreased or abnormal performance of one or more involuntary body functions.

Autonomic neuropathy can be a complication of several diseases and conditions. Some medications cause autonomic neuropathy as a side effect, as well. Signs, symptoms and treatment vary widely depending on the cause, and on which nerves are affected.

Symptoms of autonomic neuropathy

Signs and symptoms of autonomic neuropathy vary widely, depending on which parts of your autonomic nervous system are affected. They may include:

  • Dizziness and fainting upon standing (orthostatic hypotension), caused by a drop in blood pressure
  • Urinary problems, including difficulty starting urination, overflow incontinence and inability to empty your bladder completely, which can lead to urinary tract infections
  • Sexual difficulties, including erectile dysfunction or ejaculation problems in men, and vaginal dryness and difficulties with arousal and orgasm in women
  • Difficulty digesting food (gastroparesis), which can cause a feeling of fullness after eating little, loss of appetite, diarrhea, constipation, abdominal bloating, nausea, vomiting and heartburn
  • Sweating abnormalities, especially decreased sweating, so the body can’t regulate its temperature; also excessive sweating, sometimes after eating
  • Sluggish pupil reaction, making it difficult to adjust from light to dark and causing difficulties with driving at night
  • Exercise intolerance, when your heart rate remains unchanged instead of increasing and decreasing in response to your activity level
  • Lack of usual warning signs of low blood sugar (hypoglycemia), which include shakiness, increased heart rate, sweating and palpitations

Causes

Autonomic neuropathy can be caused by a large number of diseases and conditions or as a side effect of treatment for diseases unrelated to the nervous system. Some common causes of autonomic neuropathy include:

  • Alcoholism, a chronic, progressive disease that can lead to nerve damage.
  • 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. This includes an abnormal attack by the immune system that occurs as a result of some cancers (paraneoplastic syndromes).
  • Diabetes, which can gradually cause nerve damage throughout the body.
  • Multiple system atrophy, a degenerative disorder that leads to loss and malfunction of some portions of the central nervous system.
  • Injury to nerves caused by surgery or trauma.
  • Treatment with certain medications, including some drugs used in cancer chemotherapy and anticholinergic drugs, sometimes used to treat irritable bowel syndrome and overactive bladder.
  • Other chronic illnesses, such as Parkinson’s disease and HIV/AIDS.

Having diabetes puts you at high risk of developing nerve damage, including autonomic neuropathy. Risk is greatest for people over 40 who’ve had the disease for more than 25 years and have difficulty controlling their blood sugar.

Untreated alcoholism, smoking, being overweight, and having high blood pressure or high levels of blood fat also increase your risk of nerve damage.

Diagnosis

Autonomic neuropathy is a possible complication of several diseases. You’ll most likely be getting medical care for diabetes, for example, before you develop signs and symptoms suggesting autonomic neuropathy, so the diagnosis will be fairly straightforward. Similarly, if you have cancer and it’s being treated with a drug known to cause nerve damage, your doctor will be on the lookout for signs of neuropathy.

If your symptoms point to autonomic neuropathy and you’re unaware of an underlying cause, the diagnosis is more difficult. Your doctor is likely to review your medical history, ask for a thorough description of your symptoms and do a physical exam. Tests that your doctor may use to aid in diagnosis will help to evaluate the reaction of several body functions controlled by the autonomic nervous system. These may include:

  • Breathing tests. These tests measure how your heart rate and blood pressure respond to breathing exercises such as the Valsalva maneuver, in which you exhale forcibly.
  • Tilt-table test. This test monitors how your blood pressure and heart rate respond to changes in posture and position, simulating what occurs when you stand up after lying down. You lie flat on a table, which is then tilted to raise the upper part of your body. Normally, your body compensates for the drop in blood pressure that occurs when you stand up by narrowing your blood vessels and increasing your heart rate. This response may be slowed or abnormal if you have autonomic neuropathy.
  • Gastrointestinal tests. Gastric emptying tests are the most common test to check for slowed movement of food through your system, delayed emptying of the stomach and other abnormalities. The testing can take various forms. One test may measure the rate at which food leaves your stomach, while another checks how well your stomach muscles relax after you eat.
  • Quantitative sudomotor axon reflex test (QSART). This test evaluates how the nerves that regulate your sweat glands respond to stimulation. A small electrical current passes through four capsules placed on your forearm, foot and leg, while a computer analyzes how your nerves and sweat glands react. You may feel warmth or a tingling sensation during the test.
  • Thermoregulatory sweat test. During this test, you’re coated with a powder that changes color when you sweat. You then enter a chamber with slowly increasing temperature. It causes your body temperature to increase 1 to 1.5 degrees Celsius, which makes most people sweat. Digital photos document the results. Your sweat pattern may help confirm a diagnosis of autonomic neuropathy or other causes for decreased or increased sweating.
  • Urinalysis. If you have bladder or urinary symptoms, a series of urine tests can evaluate bladder function.
  • Ultrasound. If you have bladder symptoms, your doctor may do an ultrasound, in which high-frequency sound waves create an image of the bladder and other parts of the urinary tract.

Treatment

The first goal of treating autonomic neuropathy is to manage the disease or condition damaging your nerves. For example, if the underlying cause is diabetes, you’ll need to control your blood sugar to keep it as close to normal as possible. In some cases, treating the underlying disease stops autonomic neuropathy from progressing, and the damaged nerves can even repair themselves or regenerate.

Beyond managing the underlying disease, there are other treatments available to relieve the symptoms of autonomic neuropathy. Treatment is based on which organ system is most affected by nerve damage.

Gastrointestinal symptoms. Your doctor may first recommend increasing your fiber and fluid intake to relieve gastrointestinal symptoms. Your doctor may also prescribe metoclopramide (Reglan, Metoclopramide HCL), which helps your stomach empty more rapidly by increasing the contractions of the digestive tract, or tricyclic antidepressants, such as imipramine (Tofranil) or nortriptyline (Pamelor) to treat diarrhea and abdominal pain.

Urinary symptoms. If your bladder problems are mild, your doctor may recommend following a schedule of when to drink fluids, and then urinating at regular intervals to “train” your bladder. Medications such as tolterodine (Detrol) or oxybutynin (Ditropan) treat an overactive bladder, or bethanechol (Urecholine) improves complete emptying of the bladder. Antibiotics may be prescribed to clear up a urinary tract infection. A few people with autonomic neuropathy need to have intermittent urinary catheterization, a procedure in which a tube is threaded through your urethra to empty your bladder.

Sexual dysfunction. For men with erectile dysfunction, your doctor may prescribe sildenafil (Viagra), vardenafil (Levitra) or tadalafil (Cialis). If you’re a woman with sexual symptoms, your doctor may prescribe vaginal estrogen cream (Premarin, Estrace) or vaginal estrogen rings (Estring) to improve vaginal lubrication.

Heart rhythm and blood pressure symptoms. If you get dizzy or feel faint when you stand up, your doctor may prescribe fludrocortisone acetate (Florinef), which helps your body retain salt, or a blood pressure regulator such as midodrine (ProAmatine). If your heart rate doesn’t respond normally to changes in activity level, your doctor may prescribe beta blockers to regulate the heart rate. A high-salt, high-fluid diet may help if you experience a racing heartbeat when you stand up.

Sweating. If you experience excessive sweating, your doctor may prescribe a medication that decreases sweating, such as glycopyrrolate (Ribinul, Robinul Forte) or clonidine (Catapres).

Prevention

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 good care of your health in general and managing your medical conditions. Follow your doctor’s advice to control diseases and conditions, which may include these recommendations:

  • Control your blood sugar if you have diabetes
  • Seek treatment for alcoholism
  • Get appropriate treatment for any autoimmune disease
  • Take steps to prevent or control high blood pressure
  • Achieve and maintain a healthy weight
  • Stop smoking
  • Exercise regularly

Self-care

  • Posture changes. To decrease dizziness when standing, try standing slowly, in stages. It may also help to flex your feet and grip your hands for a few seconds before standing up, to increase blood flow. After you stand up, try tensing your leg muscles while crossing one leg over the other a few times to increase blood pressure.
  • Digestion. If you have gastrointestinal symptoms, try eating small, frequent meals. Increase your fluid intake, and choose foods that are low in fat and high in fiber, which typically aid in digestion.
  • Diabetes management. Maintain low blood sugar if you have diabetes. Not only will it lessen symptoms, it may also prevent or delay new problems from developing.

Coping skills

Living with a chronic illness or disability presents daily challenges. Some of these suggestions may make it easier for you to cope:

  • Set priorities. Decide which tasks you need to do on a given day, such as paying bills or shopping for groceries, and which can wait until another time. Stay active, but don’t overdo.
  • Seek and accept support. Having a support system and a positive attitude can help you cope with the challenges you face. Ask for or accept help when you need it. Don’t shut yourself off from family and friends.
  • Prepare for challenging situations. If something especially stressful is coming up in your life, such as a move or a new job, knowing what you have to do ahead of time can help you cope.
  • Talk to a counselor or therapist. Depression and impotence are possible complications of autonomic neuropathy. If you experience either, you may find it helpful to talk to a counselor or therapist in addition to your primary care doctor. There are treatments that can help.