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Article title: Diabetic Neuropathy The Nerve Damage of Diabetes: NIDDK
Main condition: Diabetic Neuropathy
DCCT: Can Diabetic Neuropathy Be Prevented?A 10-year clinical study that involved 1,441 volunteers with insulin-dependent diabetes (IDDM) was recently completed by the National Institute of Diabetes and Digestive and Kidney Diseases. The study proved that keeping blood sugar levels as close to the normal range as possible slows the onset and progression of nerve disease caused by diabetes. The Diabetes Control and Complications Trial (DCCT) studied two groups of volunteers: those who followed a standard diabetes management routine and those who intensively managed their diabetes. Persons in the intensive management group took multiple injections of insulin daily or used an insulin pump and monitored their blood glucose at least four times a day to try to lower their blood glucose levels to the normal range. After 5 years, tests of neurological function showed that the risk of nerve damage was reduced by 60 percent in the intensively managed group. People in the standard treatment group, whose average blood glucose levels were higher, had higher rates of neuropathy. Although the DCCT included only patients with IDDM, researchers believe that people with noninsulin-dependent diabetes would also benefit from maintaining lower levels of blood glucose.
How high blood glucose leads to nerve damage is a subject of intense research. The precise mechanism is not known. Researchers have discovered that high glucose levels affect many metabolic pathways in the nerves, leading to an accumulation of a sugar called sorbitol and depletion of a substance called myoinositol. However, studies in humans have not shown convincingly that these changes are the mechanism that causes nerve damage.
More recently, researchers have focused on the effects of excessive glucose metabolism on the amount of nitric oxide in nerves. Nitric oxide dilates blood vessels. In a person with diabetes, low levels of nitric oxide may lead to constriction of blood vessels supplying the nerve, contributing to nerve damage. Another promising area of research centers on the effect of high glucose attaching to proteins, altering the structure and function of the proteins and affecting vascular function.
Scientists are studying how these changes occur, how they are connected, how they cause nerve damage, and how to prevent and treat damage.
The most common type of peripheral neuropathy damages the nerves of the limbs, especially the feet. Nerves on both sides of the body are affected. Common symptoms of this kind of neuropathy are:
The damage to nerves often results in loss of reflexes and muscle weakness. The foot often becomes wider and shorter, the gait changes, and foot ulcers appear as pressure is put on parts of the foot that are less protected. Because of the loss of sensation, injuries may go unnoticed and often become infected. If ulcers or foot injuries are not treated in time, the infection may involve the bone and require amputation. However, problems caused by minor injuries can usually be controlled if they are caught in time. Avoiding foot injury by wearing well-fitted shoes and examining the feet daily can help prevent amputations.
(also called visceral neuropathy)
Autonomic neuropathy is another form of diffuse neuropathy. It affects the nerves that serve the heart and internal organs and produces changes in many processes and systems.
Urination and sexual response
Autonomic neuropathy most often affects the organs that control urination and sexual function. Nerve damage can prevent the bladder from emptying completely, so bacteria grow more easily in the urinary tract (bladder and kidneys). When the nerves of the bladder are damaged, a person may have difficulty knowing when the bladder is full or controlling it, resulting in urinary incontinence.
The nerve damage and circulatory problems of diabetes can also lead to a gradual loss of sexual response in both men and women, although sex drive is unchanged. A man may be unable to have erections or may reach sexual climax without ejaculating normally.
Autonomic neuropathy can affect digestion. Nerve damage can cause the stomach to empty too slowly, a disorder called gastric stasis. When the condition is severe (gastroparesis), a person can have persistent nausea and vomiting, bloating, and loss of appetite. Blood glucose levels tend to fluctuate greatly with this condition.
If nerves in the esophagus are involved, swallowing may be difficult. Nerve damage to the bowels can cause constipation or frequent diarrhea, especially at night. Problems with the digestive system often lead to weight loss.
Autonomic neuropathy can affect the cardiovascular system, which controls the circulation of blood throughout the body. Damage to this system interferes with the nerve impulses from various parts of the body that signal the need for blood and regulate blood pressure and heart rate. As a result, blood pressure may drop sharply after sitting or standing, causing a person to feel dizzy or light-headed, or even to faint (orthostatic hypotension).
Neuropathy that affects the cardiovascular system may also affect the perception of pain from heart disease. People may not experience angina as a warning sign of heart disease or may suffer painless heart attacks. It may also raise the risk of a heart attack during general anesthesia.
Autonomic neuropathy can hinder the body's normal response to low blood sugar or hypoglycemia, which makes it difficult to recognize and treat an insulin reaction.
Autonomic neuropathy can affect the nerves that control sweating. Sometimes, nerve damage interferes with the activity of the sweat glands, making it difficult for the body to regulate its temperature. Other times, the result can be profuse sweating at night or while eating (gustatory sweating).
Occasionally, diabetic neuropathy appears suddenly and affects specific nerves, most often in the torso, leg, or head. Focal neuropathy may cause:
People with diabetes are also prone to developing compression neuropathies. The most common form of compression neuropathy is carpal tunnel syndrome. Asymptomatic carpal tunnel syndrome occurs in 20 to 30 percent of people with diabetes, and symptomatic carpal tunnel syndrome occurs in 6 to 11 percent. Numbness and tingling of the hand are the most common symptoms. Muscle weakness may also develop.
Diabetic Neuropathy Can Affect Virtually Every Part of the Body
Diffuse (Peripheral) Neuropathy
Diffuse (Autonomic) Neuropathy
A simple screening test to check point sensation in the feet can be done in the doctor's office. The test uses a nylon filament mounted on a small wand. The filament delivers a standardized 10-gram force when touched to areas of the foot. Patients who cannot sense pressure from the filament have lost protective sensation and are at risk for developing neuropathic foot ulcers. Physicians may order the filament (with instructions for use) free from the Lower Extremity Amputation Prevention Program, (LEAP) Bureau of Primary Health Care, Division of Programs for Special Populations, 4350 East West Highway, 9th floor, Bethesda, MD 20814; telephone (301) 594-4424.
Nerve conduction studies check the flow of electrical current through a nerve. With this test, an image of the nerve impulse is projected on a screen as it transmits an electrical signal. Impulses that seem slower or weaker than usual indicate possible damage to the nerve. This test allows the doctor to assess the condition of all the nerves in the arms and legs.
Electromyography (EMG) is used to see how well muscles respond to electrical impulses transmitted by nearby nerves. The electrical activity of the muscle is displayed on a screen. A response that is slower or weaker than usual suggests damage to the nerve or muscle. This test is often done at the same time as nerve conduction studies.
Ultrasound employs sound waves. The sound waves are too high to hear, but they produce an image showing how well the bladder and other parts of the urinary tract are functioning.
Nerve biopsy involves removing a sample of nerve tissue for examination. This test is most often used in research settings.
If your doctor suspects autonomic neuropathy, you may also be referred to a physician who specializes in digestive disorders (gastroenterologist) for additional tests.
Another important part of treatment involves special care of the feet, which are prone to problems.
A number of medications and other approaches are used to relieve the symptoms of diabetic neuropathy.
The doctor may also prescribe a therapy known as transcutaneous electronic nerve stimulations (TENS). In this treatment, small amounts of electricity block pain signals as they pass through a patient's skin. Other treatments include hypnosis, relaxation training, biofeedback, and acupuncture. Some people find that walking regularly or using elastic stockings helps relieve leg pain. Warm (not hot) baths, massage, or an analgesic ointment such as Ben Gay may also help.
To relieve diarrhea or other bowel problems, antibiotics or clonidine HCl, a drug used to treat high blood pressure, are sometimes prescribed. The antibiotic tetracycline may be prescribed. A wheat-free diet may also bring relief since the gluten in flour sometimes causes diarrhea.
Neurological problems affecting the urinary tract can result in infections or incontinence. The doctor may prescribe an antibiotic to clear up an infection and suggest drinking more fluids to prevent further infections. If incontinence is a problem, patients may be advised to urinate at regular times (every 3 hours, for example) since they may not be able to tell when the bladder is full.
Muscle weakness or loss of coordination caused by diabetic neuropathy can often be helped by physical therapy.
In women who feel their sexual life is not satisfactory, the role of diabetic neuropathy is less clear. Illness, vaginal or urinary tract infections, and anxiety about pregnancy complicated by diabetes can interfere with a woman's ability to enjoy intimacy. Infections can be reduced by good blood glucose control. Counseling may also help a woman identify and cope with sexual concerns.
At least 15 percent of all people with diabetes eventually have a foot ulcer, and 6 out of every 1,000 people with diabetes have an amputation. However, doctors estimate that nearly three quarters of all amputations caused by neuropathy and poor circulation could be prevented with careful foot care.
To prevent foot problems from developing, people with diabetes should follow these rules for foot care:
Researchers are exploring treatment with a compound called myoinositol. Early findings have shown that nerves in diabetic animals and humans have less than normal amounts of this substance. Myoinositol supplements increase the levels of this substance in tissues of diabetic animals, but research is still needed to show any concrete lasting benefits from this treatment.
Another area of research concerns the drug aminoguanidine. In animals, this drug blocks cross-linking of proteins that occurs more quickly than normal in tissues exposed to high levels of glucose. Early clinical tests are under way to determine the effects of aminoguanidine in humans.
One approach that appeared promising involved the use of aldose reductase inhibitors (ARIs). ARIs are a class of drugs that block the formation of the sugar alcohol sorbitol, which is thought to damage nerves. Scientists hoped these drugs would prevent and might even repair nerve damage. But so far, clinical trials have shown that these drugs have major side effects and, consequently, they are not available for clinical use.
|Some General Hints
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American Diabetes Association National Service Center
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American Dietetic Association
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American Heart Association
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Juvenile Diabetes Foundation International
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A private, voluntary organization that funds research on diabetes and promotes public awareness. Local chapters located across the country sponsor programs and fund-raising activities. Information about local groups is available in telephone directories or from the national office.
National Diabetes Information Clearinghouse
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A program of the National Institute of Diabetes and Digestive and Kidney Diseases, the Federal Government's lead agency for diabetes research. The clearinghouse distributes a variety of publications to the public and to health professionals.
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E-mail: National Diabetes Information Clearinghouse
The National Diabetes Information Clearinghouse (NDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health under the U.S. Public Health Service. Established in 1978, the clearinghouse provides information about diabetes to people with diabetes and their families, health care professionals, and the public. NDIC answers inquiries; develops, reviews, and distributes publications; and works closely with professional and patient organizations and government agencies to coordinate resources about diabetes.
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NIH Publication No. 95-3185
e-text last updated: October 1999
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