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Diabetes and Neuropathy

Source: Diabetes Insight, May, 2002

Nervous System Impairment (Neuropathy)
Diabetic Neuropathy can affect virtually every part of the body. Diabetic nerve damage eventually affects some 65 percent of people with diabetes.

As with other diabetes complications, poor blood glucose control lies at the root of neuropathy. As average glucose level increases, so does risk of neuropathy. However, scientists still are not sure why high blood glucose levels should interfere with the nervous system. Oddly, neuropathy does not affect the brain or spinal nerves. But it can damage the rest of the nervous system. Symptoms may include: a loss of bowel or bladder control, problems with digestion, muscle weakness, sex problems, pain or a pins-and-needles feeling in the hands or feet, or a loss of pain sensation in the extremities, which may contribute to such problems as foot ulcers.

The symptoms of neuropathy also depend on which nerves and what part of the body is affected. Neuropathy may be diffuse, affecting many parts of the body, or focal, affecting a single, specific nerve and part of the body.

The two categories of diffuse neuropathy are peripheral neuropathy affecting the feet and hands and autonomic neuropathy affecting the internal organs.

Peripheral Neuropathy
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.

When the peripheral nerves become damaged, the result is problems in the arms and/or legs. Foot and ankle complications account for most of the hospitalizations due to neuropathy. An estimated 50 percent of diabetics eventually develop some degree of peripheral neuropathy. In addition to poor glycemic control, other risk factors include: being male, being tall, and having had diabetes for many years.

Common symptoms of this kind of neuropathy are:

  • Numbness or insensitivity to pain or temperature
  • Tingling, burning, or prickling
  • Sharp pains or cramps
  • Extreme sensitivity to touch, even light touch
  • Loss of balance and co-ordination

These symptoms are often worse at night and can affect:

  • Legs
  • Feet
  • Arms
  • Hands

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 spread into the bone and because this is almost impossible to treat, the foot, or lower leg, may 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.

Autonomic 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. The autonomic nervous system controls unconscious body functions, for example, digestion. Autonomic neuropathy eventually affects about 30 percent of diabetics, usually by slowing these functions down. It may affect:

  • Heart
  • Digestive System
  • Sexual organs
  • Urinary tract
  • Sweat gland

The best way to prevent neuropathy is to practice tight blood glucose control. In the Diabetes Control and Complications Trial (DCCT), a 10-year study sponsored by the National Institute of Health, some of the more than 1,000 participants practiced conventional blood glucose control, while others practiced tight control. Compared with the conventional group, those who practiced tight control reduced their risk of developing neuropathy by 69 percent.

Tight control also helps prevent worsening of neuropathy in those who already have it. In the DCCT, intensive glucose control decreased progression of neuropathy by 57 percent. Other researchers report that strict control also reduces pain and improves nerve conduction.

Urination & 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 (the outlet from the bladder).

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.

Cardiovascular System

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 to 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 the warning signs and therefore 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).

Focal Neuropathy (including Multiplex Neuropathy)

Occasionally, diabetic neuropathy appears suddenly and affects specific nerves, most often in the torso, leg, or head. Focal neuropathy may cause:

  • Pain in the front of a thigh
  • Severe pain in the lower back or pelvis
  • Pain in the chest, stomach, or flank
  • Chest or abdominal pain sometimes mistaken for angina, heart attack, or appendicitis
  • Aching behind an eye
  • Inability to focus the eye
  • Double vision
  • Paralysis on one side of the face (Bell’s palsy)
  • Problems with hearing

This kind of neuropathy is unpredictable and occurs most often in older people who have mild diabetes. Although focal neuropathy can be painful, it tends to improve by itself after a period of weeks or months without causing long-term damage.

Carpal Tunnel Syndrome
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.

This condition is caused by nerve damage in the wrist, and causes weakness, tingling, numbness in the hands. Muscle weakness may also occur. It eventually develops in about one-third of diabetics, particularly women and those who are obese.

Numbness and tingling of the hand are the most common symptoms. Muscle weakness may also develop.