Over time, persistently raised levels of blood sugar tend to injure your nerves throughout the body and impair their functions. The nerve injury caused by diabetes is called diabetic neuropathy or diabetic nerve damage. About 60 to 70 percent of people with diabetes are affected by some degree of nerve damage.
TYPES OF NERVE DAMAGE
The National Institute of Diabetes and Digestive and Kidney Diseases classifies nerve damage into four categories: peripheral, autonomic, proximal, and single nerve damages, depending on the site where the nerve damage occurs and how it affects the body.
PERIPHERAL NERVE DAMAGE
Nerves serving distant parts of the body (extremities) such as the toes, feet, legs, hands, and arms are affected by peripheral nerve damage. The symptoms may include pain or loss of sensation in these distant parts of the body. When sensory nerves of the foot are injured, for example, you may lose sensation and you will not experience pain from a foot injury. The injury may go unnoticed, develop into a wound, and spread infection to the bone that may lead to lower leg amputation in uncontrolled diabetes.
The usual symptoms of nerve damage in the extremities are:
- A sensation of crawling.
- Insensitivity to heat, cold, or pressure.
- Tingling and piercing pain, usually worse at night.
- Sharp cutting pain, even bed sheets and pants will hurt.
- Loss of balance, unsteady walking.
- Cramps or pain in calves; pain on walking.
AUTONOMIC NERVE DAMAGE
Autonomic nerves regulate those functions of your body that you cannot consciously control. Functions such as how the food digests in the stomach or at what speed the heart beats are automatic or involuntary functions. Autonomic nerve damage affects such kinds of involuntary functions. When diabetes injures the autonomic nerves, various organ systems can be affected:
There can be various kinds of digestive disorders, depending upon which particular part of the digestive tract has been affected:
- When the nerves in the esophagus (the tube that connects your throat with the stomach) are affected, you may feel difficulty in swallowing food or even drinking water.
- When the nerves controlling digestion are impaired, you may suffer from gastroparesis, a condition in which food remains stuck in the stomach for too long and empties into the intestines after a long delay. This condition causes bloating, nausea, and vomiting.
- Nerve damage in the small intestine may cause diarrhea, whereas nerve injury in the large intestine may cause constipation.
Dizziness from Low Blood Pressure
Contraction and expansion of the blood vessels regulate the flow of blood. When the autonomic nerves controlling contraction and expansion of the blood vessels are damaged, the blood does not flow as it should. In such a condition, if, for example, you suddenly rise from a lying position to a standing position, the vessels will not contract with sufficient force to supply the added amount of blood you need on rising, and your blood pressure will fall. This is a form of low blood pressure called orthostatic hypotension in which you may feel dizzy or even faint.
Increased Heart Rate
The vagus nerve, a part of the autonomic nervous system, regulates your heart rate in response to the normal body functions. When the vagus nerve is injured, control over the heart rate is impaired and the heart rate increases (such as more than 100 heartbeats per minute, at rest). This condition may cause nausea, headache, trembling, and even chest pain.
Autonomic nerves also control your pupils (the black center of the eye). The pupil works like the aperture or opening of a camera lens, regulating the amount of light entering the eye. The pupils expand to let in more light in the eyes when you are in a dark area, and contract to allow less light when you are in a bright field. Autonomic nerve damage may impair the control of the pupils to make these adjustments. As a result, you may have difficulty seeing such as when the light is turned on in a dark room, or from driving at night due to glare from the light of oncoming cars.
Damage to the nerves that control sweat glands causes a sweating disorder. This condition may cause abnormal sweating patterns, including sweating at night, sweating during eating, profuse sweating of the face or trunk, and sweating on one part of the body, while the rest of the body is dry.
Decreased Feeling for Pain
Diabetes tends to injure nerve impulses also. When the nerves that send messages of pain are injured, you will lose the perception of pain. In such conditions, people who have heart disease would not experience angina as a warning signal. Such people may even have painless heart attacks. These are serious conditions that can cause death.
Low Blood Sugar Unawareness
When your blood sugar becomes low, you will usually experience such symptoms as trembling of limbs, mental confusion, and nervousness. In autonomic nerve damage, however, you may fail to recognize these symptoms with the result that blood sugar may fall to dangerously low levels without your even recognizing this condition. This is a dangerous situation, which without treatment, can become life-threatening.
When you are healthy, you can control when to hold and release (void) your urine. When the nerves controlling the bladder are impaired, you lose control over the bladder, causing involuntary loss of urine (urine incontinence). Also, in the presence of impaired bladder control, you will not be able to release the urine in full. As a result, the remaining urine may go back to the kidneys and pollute them. Abladder problem is usually corrected through surgery. However, a simple measure such as urinating frequently and not letting the bladder be full at any time may help reduce uncontrolled urine leakages.
Male impotence (erectile dysfunction) is one of the long-term complications of diabetes. When the nerves that control blood vessels of the penis are injured from long-standing diabetes, blood flow to the penis is reduced, preventing its erection. In such conditions, although a man has a strong desire for sex, he is unable to perform the sexual function.
Female Sex Problems
Nerve damage in the vagina reduces vaginal lubrication , and women may experience problems in achieving orgasm (sexual climax). To reduce dryness of the vagina, medicated creams or lubricating vaginal suppositories may be used before sexual performance. Counseling by a health care professional may be helpful in resolving such sex problems. Single Nerve Damage Sometimes nerve damage occurs in one single nerve (focal neuropathy), affecting the part of the body it controls. In this condition, either the nerve is pinched or its blood supply is cut off due to a blocked blood vessel. The onset of this nerve disorder is sudden and painful, but improves in several weeks or months. Single nerve damage may present any of the symptoms such as:
- Pain in one leg
- Pain in the thigh
- Chest pain misinterpreted as angina
- Abdominal pain mistaken for appendicitis
- Excessive pain in the pelvis
- One-side facial paralysis (Bell’s palsy)
- Double vision
- Drooping eyelid
- Eye pain
NERVE DAMAGE CAUSED BY COMPRESSION
Sometimes compression of the nerves results in nerve damage. Nerve damage in the wrist (carpal tunnel syndrome) is very common in people with diabetes. In carpal tunnel syndrome, the median nerve (the nerve that travels through the wrist and controls the thumb side of the hand) is damaged. This nerve damage results in wrist pain and numbness to the thumb and the first two fingers of the affected hand. The pain may radiate in the arm and shoulders, becoming worse at night. Pain medications, including balms and creams, may relieve the pain at least temporarily. When the nerve pain is severe, it can be temporarily relieved by injecting corticosteroids (cortisone medication). If these methods do not help, the doctor may consider surgery to relieve pressure on the nerve to provide relief from your pain.
PROXIMAL NERVE DAMAGE
The nerves controlling the thighs, hips, or legs are usually affected in proximal nerve damage, leading to pain in these parts and a weakening of their muscles. Generally, pain starts on one side of the body, but with time, it usually spreads to both sides. Proximal nerve damage often occurs in people with type 2 diabetes and the elderly. When you are unable to stand from a sitting position to a standing position without help, chances are that you may be having proximal nerve damage.
CAUSE OF NERVE DAMAGE
The exact cause of nerve damage is not known, but it is believed that any of several factors can produce it or make it worse in diabetes. Some explanations are:
- Raised blood sugar. Over time, high blood sugar tends to damage the minute blood vessels that supply nutrients and oxygen to the nerves. As the blood vessels are damaged, the affected nerves are deprived of proper nutrition and their activity becomes defective.
- Raised blood levels of total cholesterol, LDL (bad) cholesterol, and triglycerides, tend to deform all blood vessels, including the minute vessels that serve the nerves. As a result, the affected nerves do not receive nourishment as they should and they become weak.
- Nerve inflammation caused by some defect in the body’s natural defense system called immune system.
- Inherited tendency to having nerve damage.
- Tobacco smoking and alcohol consumption.
- Impaired production of nitric oxide in the body.
- Albumin in the urine. Presence of albumin in the urine is now being recognized as a factor predicting severity of nerve damage.
- Some recent studies have suggested that regular use of the satin class of cholesterol lowering drugs may cause peripheral neuropathy. The reason is that these drugs, while reducing chemicals responsible for the production of cholesterol, also reduce a nerve supporting enzyme called coenzyme Q10, causing nerve damage.
PREVALENCE OF DIABETIC NERVE DAMAGE
When you have diabetes, you are at increased risk of developing nerve damage at any time, and this risk becomes higher with increased duration of diabetes. People with diabetes who are 40 years or older, who are smokers, and whose blood sugar is poorly controlled are at increased risk of diabetic nerve damage.
DIAGNOSING NERVE DAMAGE Nerve damage can be diagnosed in several ways, including:
- Observing the symptoms.
- Physical examination. The doctor checks for your muscle strength, reflexes, and pain response on touching. Knee jerks and ankle jerks are used to test how healthy your nerve reflexes are. A fall in blood pressure when you sit up from the lying position, for example, may indicate that the nerves, controlling contraction and expansion of your blood vessels, have been affected.
- Screening tests. The screening includes blood tests for a complete blood count, C-reactive protein, fasting blood sugar, kidney function, liver function, vitamin B12 deficiency; and urinary testing.
- Nerve conduction studies. In these studies, the doctor applies a mild electrical shock to your nerve and measures how fast and how strong the nerve transmits the signal. To test, small pads are placed on the skin of your legs, feet, arms, or hands, and an electrical impulse is passed into the nerve through the skin. Signals coming back from the nerve are detected on the screen. A signal from a healthy nerve is faster and stronger than a signal from an injured nerve.
- Electromyography (EMG). This is a technique that measures electrical activity in the nerves and muscles. In normal conditions, the nerves transmit constant electrical signals to the muscles. To perform this test, very thin needles are inserted into your muscles, and the electrical activity of the muscles is projected on a screen. If the nerve is injured, it will not send the signal properly and the received signal will be abnormal.
- Ultrasound uses sound waves to produce an image of internal organs. An ultrasound of the bladder, for example, can show how well the bladder is working, which in turn will indicate how healthy the nerves are that control the urinary function.
- Monofilament Test. A 3-inch long stiff nylon thread called Semmes Weinstein 5.07 (10 g) monofilament, or a tuning fork, is used to test how well your feet feel the touch sensation. People who cannot feel pressure of the filament have lost protective sensation and are at increased risk of foot ulcers and amputations.
PREVENTING NERVE DAMAGE
Keeping blood sugar within normal or near to normal range helps prevent diabetic nerve damage. The Diabetes Control and Complications Trial (DCCT) firmly established that tight control of blood sugar reduces the risk for nerve damage by 30 percent. Good control of blood sugar and keeping the hemoglobin A1C level at less than 7 percent is your best defense against nerve damage from diabetes. A new class of drug, called aldose reductase inhibitors, is reported to be useful in preventing and slowing nerve damage in people with diabetes. Aldose reductase is an enzyme that converts glucose into sugar alcohol (sorbitol); too much of this enzyme leads to damage of the nerve cells. Aldose reductase inhibitors are drugs that block the action of this enzyme and are helpful in reducing the nerve damage due to diabetes
TREATING NERVE DAMAGE
Here are some helpful measures:
- Controlling blood sugar, and keeping it as close to normal as possible is crucial in managing diabetes complications, including nerve damage. Although tight control of blood sugar will not reverse extensive nerve damage that has already occurred, it can reverse nerve damage in its early stages. Control blood sugar through diet, exercise, and when required, through medication.
- Topiramate, a drug that has long been in use for the treatment of epilepsy, has also been shown to treat symptoms of nerve damage, and improve nerve function in diabetes. In addition, this drug has been found beneficial in the treatment of cholesterol and other blood fat disorders, raised blood sugar, and high blood pressure.
- Some medicines and methods that will provide you at least temporary relief from nerve pain and discomfort are noted below:
- Simple pain killers such as aspirin and acetaminophen (Tylenol), or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin, Advil) reduce or relieve nerve pain. If these medications do not help, the doctor may prescribe stronger NSAIDs such as diclofenac sodium and diclofenac potassium for pain relief.
- Capsaicin cream, which contains an extract of chili peppers and is available over-the-counter, is also usually helpful in relieving nerve pain in most people. This cream, when rubbed on the skin where you feel pain, blocks pain signals.
- When the above medications fail to bring pain relief, the doctor may prescribe antidepressant drugs, which have been found effective in treatment of nerve pain also. Two classes of antidepressant drugs, namely, TCAs such as amitryptiline, and SSRIs such as fluoxetine (Prozac) are usually effective in relieving nerve pain. These drugs take several weeks to give the full benefit. (See chapter 11 for more information on antidepressants.) Another recently approved antidepressant drug, duloxetine, is also effective in relieving pain caused by diabetic nerve damage.
- Two drugs, carbmazepine and phenytoin, which are used to treat convulsions, have also been shown to decrease pain from nerve damage. Another anticonvulsant drug, gabapentin, has also been found to be effective, relatively safe, and better tolerated in treatment of pain from diabetic nerve damage. Doctors now usually prescribe gabapentin for treating nerve pain. Recently, the Food and Drug Administration (FDA) has approved another anticonvulsant drug, pregabalin, to treat nerve pain caused by diabetes. This drug is more powerful than gabapentin, and it is used to treat the burning and stabbing pain in the feet, legs, hands, or arms caused by nerve damage from diabetes.
- Another drug, mexiletine, which is usually used to treat irregular heart rhythm, has also been shown to relieve nerve pain.
- A study undertaken by American and Russian researchers has shown that alpha-lipoic acid, an antioxidant, can significantly reduce nerve pain, pin pricking sensation, numbness, and other symptoms of nerve damage.
- The pain management therapy called transcutaneous electronic nerve stimulation (TENS) is also used to relieve nerve pain in the extremities (legs, feet, arms, and hands). In this therapy, electrodes are placed on the skin and a small amount of electricity is passed through vibrations. The electric vibrations help provide pain relief by blocking the pain sensation.
- For pain reduction and improving blood circulation in muscles and joints, an infrared therapy called the Anodyne Therapy System has been shown to be helpful. The therapy applies strong infrared rays to the affected joints and muscles, increasing blood circulation in the area, thereby providing relief from pain. The therapy is used for about 20 to 45 minutes per treatment. The treatment program typically consists of three therapy sessions per week for 4 weeks. The actual frequency of the treatment will depend upon the severity of condition.
- Evidence shows that stretching exercises such as leg stretching and calf stretching can relieve muscle pain, spasms, and night cramps usually coexisting with nerve pain arising from nerve damage.
MEDICATIONS FOR AUTONOMIC NERVE DAMAGE
Some disorders from autonomic nerve damage and the medications to treat them are:
A prescription drug, metoclopramide (Reglan), is used to stimulate digestion and treat gastroparesis in diabetes. Another drug, clonidine, which is basically a drug to treat high blood pressure, has been found effective in controlling diabetic diarrhea and other bowel problems.
Increased Heart Rate
Beta-blockers, drugs that are used to treat high blood pressure, are also given to slow down increased heart rate caused by nerve damage.
Low Blood Pressure on Rising
If your blood pressure falls when you rise up from a sitting or lying position (orthostatic hypotension), do not sit up or stand up suddenly. Your movements should be slow and gradual to prevent loss of balance and to avoid a fall. Wearing elastic stockings may help you with this condition. Increased intake of salt may benefit some people in reducing the symptoms of this disorder; however, you must check up with your doctor before increasing your salt intake. A drug, midodrine, is often used to treat orthostatic hypotension. This drug, by tightening the blood vessels and increasing their resistance to the blood flow in the body, increases blood pressure.
Glycopyrrolate, a drug used to treat peptic ulcers, is also prescribed for reduction of sweating. Other drugs such as phenoxybenzamine and propantheline also help. Injections of a drug called botulinum toxin, popularly known as Botox, reduce sweating effectively.
Several drugs such as oxybutynin and tolterodine are available for controlling leakage of urine. These drugs help control overactive bladder, reducing urinary incontinence in most people. Oxybutynin also comes as a patch to be applied to the skin twice a week.
Various drugs and devices are available for men to overcome erectile dysfunction, and be able to perform sexual intercourse. These aids include drugs taken by mouth such as Viagra, Levitra, and Cialis, drugs injected and inserted into the penis, and various vacuum devices.
Your doctor may prescribe any or a combination of the above medications or devices to relieve pain and other disorders associated with diabetic nerve damage. The therapy is recommended to be initiated with low doses or low amounts, building up gradually and monitoring any possible adverse effects and interactions. Healthy eating and regular exercise help regenerate injured nerves in some mild to moderate cases of nerve damage. Some aerobic, muscle-strengthening, and stretching exercises help tone up the muscles of your body, reducing pain and discomfort in the long run. Research has conclusively established that by keeping your blood sugar as close to the normal range as possible, you can effectively reduce or postpone the risk of developing long-term complications of diabetes, including diabetic nerve damage.