What is Diabetic Neuropathy?

Diabetic neuropathy is the damage to nerves that occurs after ten or more years of exposure to high blood glucose (sugar).    It affects 60 percent of people with diabetes who have the disease that long.  The actual signs and symptoms can vary from loss of sensation in the feet and legs to inability to move muscles that are controlled by specific motor nerves.   Still another type of neuropathy is called autonomic neuropathy and refers to loss of nerves that control the automatic functions of the body like the movement of heart muscle, the movement of the diaphragm to bring air into the lungs and the movement of food through the intestines.

Just why the nerves are damaged is not clear.  The explanation varies from loss of blood supply to the involved nerve or nerves to damage from toxins (poisons) that result from years of high blood glucose levels.  Diabetic neuropathy can lead to foot ulcerations, foot infections and amputations.  This is completely preventable.

There are several conditions that make neuropathy worse in addition to high blood glucose.  These include:

  • Age: since neuropathy takes years, it is going to be worse in older people who have had the disease longer
  • Height:   taller individuals have longer nerve fibers to damage
  • Alcohol consumption: even small amounts of alcohol worsen diabetic neuropathy

Doctors check the various kinds of nerve fibers by testing with a tuning fork, hot and cold items and a filament that detects loss of light touch.  Here are the ways that this is done:

  • Vibration testing, using a tuning fork, for example, can bring out abnormalities of long nerve fibers when the vibration is not felt.
  • Temperature testing, using hot or cold items, tests for damage to small fibers, which are very important in diabetes.  When small fibers are damaged, the patient can lose his ability to realize that he is entering a burning hot bath.
  • Light touch testing, perhaps the most important test that is done, detects the inability of large fibers to detect light touch.  The test is done with a thin filament.  The thickness of the filament determines how much force is necessary to bend it so that it is felt.  For example, a filament that bends with 1 gram of force can be felt by normal feet.  If a patient can feel a filament that bends with 10 grams of force, it is not likely that he will fail to feel an irritant that could damage the feet.  However, if a patient can’t feel a filament that requires 75 grams of force to bend, that patient is considered to have lost all sensation in that area.

The next articles will deal with specific syndromes in patients with diabetes due to loss of various nerves.

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