What Is It?
Diabetic neuropathies include several nerve disorders that affect people with diabetes.
Peripheral neuropathy. This is the most common type of diabetic neuropathy, affecting the longest nerves in your body. These nerves are part of your peripheral nervous system, the network of nerves that carry signals from your brain and spinal cord to the rest of your body and back. The most common symptoms of peripheral neuropathy are numbness or pain in the feet and lower legs.
Autonomic neuropathy. This neuropathy damages important collections of nerves that control your unconscious body functions. It especially may affect your digestion, your circulation and your sexual function.
Localized nerve failures (focal neuropathy). A nerve that controls a single muscle can lose its function. Examples of problems that this may cause are eye movement problems with double vision and drooping of the cheek on one side of the head (commonly known as Bell's palsy). One or more individual nerve failures sometimes is called mononeuritis multiplex.
Diabetic neuropathies occur in both type 1 and type 2 diabetes, and they are most common in people whose blood glucose (blood sugar) levels have not been well controlled. Although the various forms of diabetic neuropathy can occur in people who have had diabetes for a short time, they are most likely to affect those who have had the disease for more than a decade, and they are more common in people older than 40. Diabetics who smoke are especially at risk.
There are several changes in the nerves that combine to cause a diabetic neuropathy. When your nerve cells are surrounded by a high concentration of blood glucose, they must adjust their internal sugar content to be in balance with their surroundings, or else they would lose water through their cell membranes. To adjust to high blood glucose, nerve cells manufacture and store the sugar sorbitol. Sorbitol can gradually damage nerve cells. Damage to blood vessels also contributes to diabetic neuropathy, because the nerves may not get enough oxygen and nourishment.
More than half of all people with diabetes have developed some form of neuropathy by the time they have had diabetes for 25 years. Symptoms depend on the specific type of neuropathy.
Peripheral neuropathy. This form of neuropathy causes symptoms in the limbs, especially the lower legs and feet. Symptoms can include numbness, tingling, sharp or burning pain, cramps, hypersensitivity to touch, and problems in balance or coordination. If your feet are numb, you may not be aware when shoes don't fit properly, and this can lead to the formation of a callus. Calluses are serious problems for people with diabetes, because these thickened skin areas can break down over time and change into an open sore (ulcer) that may become infected.
Autonomic neuropathy. The symptoms of autonomic neuropathy are varied, depending on which of your automatic body functions have lost their normal nerve control. Any of the following problems can occur:
- Incomplete bladder emptying. This can cause you to urinate more often, including at night. Urinary infections can be a problem, and so can loss of bladder control.
- Sexual function problems. Problems with erection, ejaculation and libido (sexual drive) are common.
- Stomach and bowel problems. Slow emptying of the stomach, called gastroparesis, can cause nausea, vomiting or bloating. The normal rhythmic squeezing of the small and large intestines that is known as peristalsis can be slow or irregular, causing constipation or diarrhea. Swallowing may become difficult, and loss of control over bowel movements is possible.
- Dizziness when standing. Normally, your heart gears up to pump a little faster and harder when you are standing up, because it is pumping against gravity to move blood from your toes to your torso. Arteries help to keep your blood pressure steady by adjusting the squeeze of their muscular walls. Both your heart and arteries rely on nerve signals to know when to make these adjustments. These signals can fail in diabetes, leaving you with low blood pressure when you are standing. Low blood pressure that occurs when standing is also called orthostatic hypotension and is a common cause of lightheadedness or fainting in people with diabetes.
- Changes in the amount that you sweat. An inability to sweat can lead to dry and cracking feet, which can allow fungal infections to develop more often. Excessive sweating or bursts of sweating also can occur.
Focal neuropathy. Common symptoms are double vision, drooping of the cheek on one side of the head (commonly known as Bell's palsy), problems with speech and double vision. Focal neuropathy also can cause a sudden weakness in the ankle, called foot drop. Damage to a nerve that originates in the spinal cord is called radiculopathy, which can cause pain in the chest, stomach, back or pelvis or in the front of the thigh.
Your doctor usually can diagnose diabetic neuropathy based on your medical history, symptoms and the results of a physical examination. When necessary, more specialized testing may be done, such as:
Nerve conduction studies to check whether nerve impulses in the arms and legs are normal, and a test called electromyography to see how well arm and leg muscles move in response to nerve signals. These two tests usually are done together. They involve a series of momentary minor electric shocks through small needles or pads on the skin.
Ultrasound scan of the urinary bladder or drainage of the bladder through a catheter to evaluate how efficiently your bladder empties.
Gastric (stomach) emptying study to test how quickly food moves through your stomach. In this test, you eat a portion of specially prepared food that has been marked with radioactivity. A series of pictures is taken by a machine that detects the radioactive signal.
Nerve biopsy, which involves taking a small sample of a nerve to be examined under a microscope.
Peripheral and autonomic neuropathies are usually long-term problems, but most cases of focal neuropathy last only a few weeks or months.
Because diabetic neuropathy is caused by abnormally high levels of blood glucose, diabetics can help to prevent this problem by regulating their blood sugar levels intensely. In a 10-year study conducted by the National Institute of Diabetes and Digestive and Kidney Disease (NIDDK), diabetics who kept their blood glucose levels close to normal reduced their risk of peripheral neuropathy by 60%. Avoiding smoking can help to prevent or delay neuropathies, one of several important reasons that people with diabetes should not smoke.
Treatment of diabetic neuropathy focuses on:
Tighter control of blood glucose
A regular exercise program to burn glucose and build muscle strength
Medications to treat autonomic problems and prevent bladder infections
Meticulous care of the feet
To relieve the pain of peripheral neuropathy, your doctor may prescribe a medicine. A growing number of medicines are available to reduce nerve pain, including low doses of tricyclic medications, such as amitriptyline (Elavil), nortriptyline (Aventyl, Pamelor) and desipramine (Norpramin and other brand names). Other medicines that may help include gabapentin (Neurontin), pregabalin (Lyrica), duloxetine (Cymbalta) and carbamazepine (Tegretol). For persisting pain, your doctor may suggest that you take aspirin, acetaminophen (Tylenol) or ibuprofen (Advil, Motrin and other brand names) by mouth or that you rub on a pain-relieving cream containing capsaicin. In more severe cases, doctors may prescribe narcotic medicines.
To treat mild digestive problems caused by slow stomach emptying, your doctor may suggest that you eat small, frequent meals that are low in fat and fiber. For more severe symptoms, your doctor may prescribe the medication metoclopramide (Reglan and other brand names) to help digestion. A device called a "gastric pacemaker" has helped a few people to have improved symptoms, but the utility and safety of this strategy has not been tested in patients for very long and it is not yet in wide use.
There are many available treatments for constipation and diarrhea. Constipation can be treated effectively by drinking more nonalcoholic beverages and exercising regularly. You also can take fiber and stool bulking and softening agents such as psyllium (Metamucil, Konsyl and other brand names) or methylcellulose (Citrucel), stool lubricants such as docusate sodium (Colace), enemas, or laxative agents. For diarrhea, your doctor may prescribe fiber, bulking agents (which help to change liquid stool into a soft solid stool), diphenoxylate with atropine (Lomotil) or loperamide (Imodium).
Antibiotics also are used to treat infections associated with poor emptying of the urinary bladder, and your medication list can be adjusted to minimize medicines that could contribute to the problem of incomplete bladder emptying. Catheters can be used to empty the bladder when neuropathy is severe.
For impotence, your doctor may prescribe the medication sildenafil (Viagra), vardenafil (Levitra) or tadalafil (Cialis). Other treatments that commonly are used to treat impotence include a vacuum cylinder with a hand pump, injections into the penis of a drug that promotes erections, or surgery to implant a small inflatable balloon inside the penis, which can be filled or deflated as needed.
Dizziness when standing can be treated by drinking more fluids and by using medicines that increase your body salt and water.
If peripheral neuropathy affects your feet, you should wash your feet every day and check them for any cuts, sores or swellings. You should wear soft, clean socks and well-fitting shoes and never go barefoot. Cut your toenails straight across to avoid ingrown toenails. Never try to remove calluses or warts yourself. Always show them to your doctor. All diabetics should visit a podiatrist once each year.
When To Call a Professional
If you have diabetes, call your doctor whenever you have a cut or sore that becomes infected or doesn't heal, especially on your feet. It is extremely important to react promptly to injuries and infections, however minor. Also, see your doctor for help if you develop new or worsening symptoms of neuropathy.
In most cases of focal neuropathy, muscle weakness or pain subsides within a few weeks or months with no long-term damage. Peripheral and autonomic neuropathies are persistent problems. Some people who have peripheral neuropathy find that symptoms are easier to tolerate after the pain turns to numbness, as occurs for many people after months or years.
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