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The Nerve Damage of Diabetes

What Causes Diabetic Neuropathy? continued...

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.

What Are the Symptoms of Diabetic Neuropathy?

The symptoms of diabetic neuropathy vary. Numbness and tingling in feet are often the first sign. Some people notice no symptoms, while others are severely disabled. Neuropathy may cause both pain and insensitivity to pain in the same person. Often, symptoms are slight at first, and since most nerve damage occurs over a period of years, mild cases may go unnoticed for a long time. In some people, mainly those afflicted by focal neuropathy, the onset of pain may be sudden and severe.

What Are the Major Types of Neuropathy?

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.

Diffuse Neuropathy

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. 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 coordination
  • These symptoms are often worse at night

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.

WebMD Public Information from the U.S. National Institutes of Health

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