Sores on the foot of a person sufering from diabetic neuropathy. Image credit: Royal Devon and Exeter NHS Trust.
Regions of the body affected by peripheral neuropathy.
Regions of the body affected by autonomic neuropathy.
In addition to skin conditions, people with diabetes can, over time, develop nerve damage throughout the body.. Some people with nerve damage have no symptoms. Others may have symptoms such as pain, tingling, or numbness in the hands, arms, feet, and legs. Nerve problems can occur in every organ system, including the digestive tract, heart, and sex organs.
About 60 to 70 percent of people with diabetes have some form of neuropathy. People with diabetes can develop nerve problems at any time, but the risk increases with age and duration of the disease. The highest rates of neuropathy occur among people who have had diabetes for at least 25 years and among people who have trouble controlling their blood sugar levels, as well as those with high levels of blood fat and blood pressure and those who are overweight.
Causes of diabetic neuropathies
The causes are probably different for different types of diabetic neuropathy. Researchers are studying how prolonged exposure to high blood glucose causes nerve damage. Nerve damage is likely due to a combination of factors:
Symptoms of diabetic neuropathies
Symptoms depend on the type of neuropathy and which nerves are affected. Some people with nerve damage have no symptoms at all. For others, the first symptom is often numbness, tingling, or pain in the feet. Symptoms are often minor at first, and because most nerve damage occurs over several years, mild cases may go unnoticed for a long time. Symptoms can involve the sensory, motor, and autonomic – or involuntary – nervous systems. In some people, mainly those with focal neuropathy, the onset of pain may be sudden and severe.
Symptoms of nerve damage may include
Symptoms that are not due to neuropathy, but often accompany it, include weight loss and depression.
Types of diabetic neuropathy
Diabetic neuropathy can be classified as peripheral, autonomic, proximal, or focal. Each affects different parts of the body in various ways.
Peripheral neuropathy, also called distal symmetric neuropathy or sensorimotor neuropathy, is nerve damage in the arms and legs. Your feet and legs are likely to be affected before your hands and arms. Many people with diabetes have signs of neuropathy that a doctor could note but feel no symptoms themselves.
Symptoms of peripheral neuropathy may include
These symptoms are often worse at night.
Peripheral neuropathy may also cause muscle weakness and loss of reflexes, especially at the ankle, leading to changes in the way a person walks. Foot deformities, such as hammertoes and the collapse of the midfoot, may occur. Blisters and sores may appear on numb areas of the foot because pressure or injury goes unnoticed. If foot injuries are not treated promptly, the infection may spread to the bone, and the foot may then have to be amputated. Some experts estimate that half of all such amputations are preventable if minor problems are caught and treated in time.
Autonomic neuropathy affects the nerves that control the heart, regulate blood pressure, and control blood glucose levels. Autonomic neuropathy also affects other internal organs, causing problems with digestion, respiratory function, urination, sexual response, and vision. In addition, the system that restores blood glucose levels to normal after a hypoglycemic episode may be affected, resulting in loss of the warning symptoms of hypoglycemia.
Normally, symptoms such as shakiness, sweating, and palpitations occur when blood glucose levels drop below 70 mg/dL. In people with autonomic neuropathy, symptoms may not occur, making hypoglycemia difficult to recognize. Problems other than neuropathy can also cause hypoglycemia unawareness.
Heart and blood vessels
The heart and blood vessels are part of the cardiovascular system, which controls blood circulation. Damage to nerves in the cardiovascular system interferes with the body's ability to adjust blood pressure and heart rate. As a result, blood pressure may drop sharply after sitting or standing, causing a person to feel light-headed or even to faint. Damage to the nerves that control heart rate can mean that your heart rate stays high, instead of rising and falling in response to normal body functions and physical activity.
Nerve damage to the digestive system most commonly causes constipation. Damage can also cause the stomach to empty too slowly, a condition called gastroparesis. Severe gastroparesis can lead to persistent nausea and vomiting, bloating, and loss of appetite. Gastroparesis can also make blood glucose levels fluctuate widely, due to abnormal food digestion.
Nerve damage to the esophagus may make swallowing difficult, while nerve damage to the bowels can cause constipation alternating with frequent, uncontrolled diarrhea, especially at night. Problems with the digestive system can lead to weight loss.
Urinary tract and sex organs
Autonomic neuropathy often affects the organs that control urination and sexual function. Nerve damage can prevent the bladder from emptying completely, allowing bacteria to grow in the bladder and kidneys and causing urinary tract infections. When the nerves of the bladder are damaged, urinary incontinence may result because a person may not be able to sense when the bladder is full or control the muscles that release urine.
Autonomic neuropathy can also gradually decrease sexual response in men and women, although the sex drive may be unchanged. A man may be unable to have erections or may reach sexual climax without ejaculating normally. A woman may have difficulty with arousal, lubrication, or orgasm.
Autonomic neuropathy can affect the nerves that control sweating. When nerve damage prevents the sweat glands from working properly, the body cannot regulate its temperature as it should. Nerve damage can also cause profuse sweating at night or while eating.
Finally, autonomic neuropathy can affect the pupils of the eyes, making them less responsive to changes in light. As a result, a person may not be able to see well when a light is turned on in a dark room or may have trouble driving at night.
Proximal neuropathy, sometimes called lumbosacral plexus neuropathy, femoral neuropathy, or diabetic amyotrophy, starts with pain in the thighs, hips, buttocks, or legs, usually on one side of the body. This type of neuropathy is more common in those with type 2 diabetes and in older adults with diabetes. Proximal neuropathy causes weakness in the legs and the inability to go from a sitting to a standing position without help. Treatment for weakness or pain is usually needed. The length of the recovery period varies, depending on the type of nerve damage.
Focal neuropathy appears suddenly and affects specific nerves, most often in the head, torso, or leg. Focal neuropathy may cause
Focal neuropathy is painful and unpredictable and occurs most often in older adults with diabetes. However, it tends to improve by itself over weeks or months and does not cause long-term damage.
People with diabetes also tend to develop nerve compressions, also called entrapment syndromes. One of the most common is carpal tunnel syndrome, which causes numbness and tingling of the hand and sometimes muscle weakness or pain. Other nerves susceptible to entrapment may cause pain on the outside of the shin or the inside of the foot.
Prevention of diabetic neuropathies
The best way to prevent neuropathy is to keep your blood glucose levels as close to the normal range as possible. Maintaining safe blood glucose levels protects nerves throughout your body.
Diagnosis of diabetic neuropathies
Doctors diagnose neuropathy on the basis of symptoms and a physical exam. During the exam, your doctor may check blood pressure, heart rate, muscle strength, reflexes, and sensitivity to position changes, vibration, temperature, or light touch.
Experts recommend that people with diabetes have a comprehensive foot exam each year to check for peripheral neuropathy. People diagnosed with peripheral neuropathy need more frequent foot exams. A comprehensive foot exam assesses the skin, muscles, bones, circulation, and sensation of the feet. Your doctor may assess protective sensation or feeling in your feet by touching your foot with a nylon monofilament – similar to a bristle on a hairbrush – attached to a wand or by pricking your foot with a pin. People who cannot sense pressure from a pinprick or monofilament have lost protective sensation and are at risk for developing foot sores that may not heal properly. The doctor may also check temperature perception or use a tuning fork, which is more sensitive than touch pressure, to assess vibration perception.
The doctor may perform other tests as part of your diagnosis.
Treatment of diabetic neuropathies
The first treatment step is to bring blood glucose levels within the normal range to help prevent further nerve damage. Blood glucose monitoring, meal planning, physical activity, and diabetes medicines or insulin will help control blood glucose levels. Symptoms may get worse when blood glucose is first brought under control, but over time, maintaining lower blood glucose levels helps lessen symptoms. Good blood glucose control may also help prevent or delay the onset of further problems. As scientists learn more about the underlying causes of neuropathy, new treatments may become available to help slow, prevent, or even reverse nerve damage.
As described in the following sections, additional treatment depends on the type of nerve problem and symptom. If you have problems with your feet, your doctor may refer you to a foot care specialist.
Doctors usually treat painful diabetic neuropathy with oral medications, although other types of treatments may help some people. People with severe nerve pain may benefit from a combination of medications or treatments. Talk with your health care provider about options for treating your neuropathy. Medications used to help relieve diabetic nerve pain include
Duloxetine and pregabalin are approved by the U.S. Food and Drug Administration specifically for treating painful diabetic peripheral neuropathy.
You do not have to be depressed for an antidepressant to help relieve your nerve pain. All medications have side effects, and some are not recommended for use in older adults or those with heart disease. Because over-the-counter pain medicines such as acetaminophen and ibuprofen may not work well for treating most nerve pain and can have serious side effects, some experts recommend avoiding these medications.
Treatments that are applied to the skin – typically to the feet – include capsaicin cream and lidocaine patches (Lidoderm, Lidopain). Studies suggest that nitrate sprays or patches for the feet may relieve pain. Studies of alpha-lipoic acid, an antioxidant, and evening primrose oil have shown that they can help relieve symptoms and may improve nerve function.
A device called a bed cradle can keep sheets and blankets from touching sensitive feet and legs. Acupuncture, biofeedback, or physical therapy may help relieve pain in some people. Treatments that involve electrical nerve stimulation, magnetic therapy, and laser or light therapy may be helpful but need further study. Researchers are also studying several new therapies in clinical trials.
To relieve mild symptoms of gastroparesis – indigestion, belching, nausea, or vomiting – doctors suggest eating small, frequent meals; avoiding fats; and eating less fiber. When symptoms are severe, doctors may prescribe erythromycin to speed digestion, metoclopramide to speed digestion and help relieve nausea, or other medications to help regulate digestion or reduce stomach acid secretion.
To relieve diarrhea or other bowel problems, doctors may prescribe an antibiotic such as tetracycline, or other medications as appropriate.
Dizziness and weakness
Sitting or standing slowly may help prevent the light-headedness, dizziness, or fainting associated with blood pressure and circulation problems. Raising the head of the bed or wearing elastic stockings may also help. Some people benefit from increased salt in the diet and treatment with salt-retaining hormones. Others benefit from high blood pressure medications. Physical therapy can help when muscle weakness or loss of coordination is a problem.
Urinary and sexual problems
To clear up a urinary tract infection, the doctor will probably prescribe an antibiotic. Drinking plenty of fluids will help prevent another infection. People who have incontinence should try to urinate at regular intervals – every 3 hours, for example – since they may not be able to tell when the bladder is full.
To treat erectile dysfunction in men, the doctor will first do tests to rule out a hormonal cause. Several methods are available to treat erectile dysfunction caused by neuropathy. Medicines are available to help men have and maintain erections by increasing blood flow to the penis. Some are oral medications and others are injected into the penis or inserted into the urethra at the tip of the penis. Mechanical vacuum devices can also increase blood flow to the penis. Another option is to surgically implant an inflatable or semirigid device in the penis.
Vaginal lubricants may be useful for women when neuropathy causes vaginal dryness. To treat problems with arousal and orgasm, the doctor may refer women to a gynecologist.
People with neuropathy need to take special care of their feet. The nerves to the feet are the longest in the body and are the ones most often affected by neuropathy. Loss of sensation in the feet means that sores or injuries may not be noticed and may become ulcerated or infected. Circulation problems also increase the risk of foot ulcers.
More than half of all lower-limb amputations in the United States occur in people with diabetes – 86,000 amputations per year. Doctors estimate that nearly half of the amputations caused by neuropathy and poor circulation could have been prevented by careful foot care.
Follow these steps to take care of your feet:
If you need help taking care of your feet, make an appointment to see a foot doctor, also called a podiatrist.