Diabetic neuropathy refers to several types of nerve damage associated with diabetes. The most common form is a slowly progressive degeneration of nerves in the arms and legs, in which the longest nerves (e.g., in the toes and feet) tend to be affected first and most severely. As nerve damage worsens, symptoms spread up the legs and begin in the hands. Neuropathy from diabetes can occur at any point, although typically it occurs in patients who have had diabetes for a longer period of time or in those who have had poorly controlled diabetes. This type of neuropathy from diabetes causes numbness, pain, weakness, and in severe circumstances can affect nerves that control basic bodily functions such as heart rate, digestion, sweating, blood pressure and others. Other types of diabetic neuropathy include isolated injury to one of the cranial nerves. Also, isolated nerves in the legs and arms may become acutely injured as a result of diabetes.
Scientists do not know how diabetic neuropathy occurs, although several factors interact together. High blood glucose causes chemical changes in nerves, impairing their ability to transmit nerve signals. High blood glucose also damages blood vessels that carry oxygen and nutrients to the nerves. Also, inherited factors probably unrelated to diabetes may make some people more susceptible to nerve disease than others.
Diabetic neuropathy appears to be more common in smokers, people over 40 years of age, and those who have had problems controlling the levels of glucose in their blood.
Types Of Diabetic Neuropathy
Doctors divide diabetic neuropathy into three main types:
Peripheral Neuropathy. The most common type of diabetic neuropathy, peripheral polyneuropathy affects nerves that transmit sensation, control muscle movement, and control bodily functions. Typically, symptoms start in the feet and spread up the legs. In more severe cases, hands and subsequently the face may become affected as well. Peripheral neuropathy usually involves nerves on both sides of the body. Some of the most common symptoms of this kind of neuropathy are:
- loss of coordination and balance
- extreme sensitivity to touch, even very light touch
- numbness or insensitivity to pain or temperature
- tingling, burning, or prickling
- sharp pains or cramps
- atrophy of muscles
- wounds that don't heal well and become easily infected
In more severe cases, the autonomic nerves (nerves that control bodily functions) are affected as well. Occasionally, these nerves may be the first nerves to be affected. Symptoms of autonomic nerve dysfunction include:>
- erectile or sexual dysfunction
- loss of bladder or bowel control
- abnormal sweating with inability to tolerate changes in temperature
- abnormal blood pressure control, causing lightheadedness when standing up
- trouble digesting food
Mononeuropathy (including "multiplex neuropathy") is isolated peripheral neuropathy, involving the distribution of only one or a few nerves. Occasionally, diabetic neuropathy appears suddenly and affects specific nerves, most often in the torso, leg or head. When mononeuropathy occurs, it may cause:
- double vision
- aching behind the eye
- inability to focus the eye
- pain in the front of the thigh
- paralysis on one side of the face (Bell's palsy)
- problems hearing
- severe pain in pelvis or lower back
- chest or abdominal pain sometimes mistaken for angina, heart attack, or appendicitis
This kind of neuropathy is unpredictable and occurs most often in older people who have mild diabetes. Although mononeuropathy can be very painful, it tends to improve by itself after a period of weeks or months without causing long-term damage.
Diagnoses depends on symptoms and signs of nerve dysfunction consistent with those seen in patients with diabetes. In many circumstances, symptoms may be the same as those seen in neuropathy from other medical causes. It is therefore often necessary to exclude other medical problems before establishing a diagnosis of diabetic neuropathy. Often, neuropathy may occur before a patient is known to be diabetic. Blood tests, including sugar measurements, can establish the diagnosis of diabetes. In some cases, very mild forms of diabetes can result in neuropathy. Routine glucose screening may be insufficient and other tests such as a glucose tolerance test are helpful in such cases.
Special tests of nerve function are also helpful to establish that the symptoms and findings on examination are due to neuropathy. The most commonly used tests are nerve conduction studies and electromyography. This test can confirm that there is neuropathy as well as quantify the severity. Occasionally, nerve conduction studies can identify other problems with nerves that may cause symptoms similar to diabetic neuropathy (such as pinched nerves in the back). In some cases, nerve damage to "small fiber nerves" may be the predominant feature. Such damage may not be appreciated on nerve conduction studies. A small skin biopsy may be helpful in detecting nerve damage in such cases, as the number of small nerve fibers can be measured by the use of a microscope. In other patients where autonomic nerve function is the predominant problem, special tests of autonomic nerves may also help in establishing the diagnosis. Such autonomic testing involves measurements of blood pressure, sweating, and changes in heart rate.
Left untreated, elevated blood sugar causes further nerve damage. There currently is no well-established treatment to reverse nerve damage. However, patients who have excellent sugar control may experience some improvement. Therefore, the primary goal is to control sugar as well as possible.
In patients who have developed neuropathy, treatment is directed at preventing complications and controlling symptoms of neuropathy. Patients should consult with a podiatrist. The loss of sensation in the feet exposes patients to injury and infection. Therefore, affected patients need to be trained in and regularly implement a program of foot hygiene.
Patients who have trouble walking either because of loss of balance or weakness may benefit from physical therapy and may require the use of an assistive device or bracing.
The most common and distressing symptom of diabetic neuropathy is pain. Most agents that are used to treat painful diabetic neuropathy are often used to treat other conditions such as epilepsy, depression, and other types of pain. Recently, there have been several new medications which have been proven effective in treating pain associated with diabetic neuropathy.
There are several other medications and therapies available to treat other symptoms such as abnormal blood pressure control, digestion disorders, and sexual dysfunction, among others.
What can be done to help prevent diabetic neuropathy?
How soon should a doctor be seen if neuropathy symptoms occur?
Are there any drugs that will help prevent neuropathy?
Are there any exercises that can be done to help reduce or prevent neuropathy?
Should a podiatrist be seen if there is evidence of peripheral neuropathy?
How should I care for my feet if I have diabetes? What should I do daily?
How do I treat corns and calluses?
How do I treat cold feet due to impaired circulation?
Maintaining optimal control of diabetes is the best way to prevent, or at least delay, the onset of diabetic neuropathy.
The National Institute of Diabetes and Digestive and Kidney Diseases recently completed a 10-year clinical study of 1,441 volunteers with insulin-dependent diabetes, which "proved that keeping blood sugar levels in as normal a range as possible slowed the onset and the progression of nerve disease caused by diabetes." Please see the link to the Diabetes Control and Complications Trial (DCCT) at the bottom of this report for more information.