Neuropathy is a general term that refers to diseases or malfunctions of the nerves. Any nerves at any location in the body can be damaged from injury or disease. Neuropathy is often classified according to the types or location of nerves that are affected. Neuropathy can also be classified according to the disease causing it. For example, neuropathy from the effects of diabetes is called diabetic neuropathy.
Peripheral neuropathy: Peripheral neuropathy is when the nerve problem affects the nerves outside of the brain and spinal cord. These nerves are part of the peripheral nervous system. Accordingly, peripheral neuropathy is neuropathy that affects the nerves of the extremities- the toes, feet, legs, fingers, hands, and arms. The termproximal neuropathy has been used to refer to nerve damage that specifically causes pain in the thighs, hips, or buttocks.
Cranial neuropathy: Cranial neuropathy occurs when any of the twelve cranial nerves (nerves that exit from the brain directly) are damaged. Two specific types of cranial neuropathy are optic neuropathy and auditory neuropathy. Optic neuropathy refers to damage or disease of the optic nerve that transmits visual signals from the retina of the eye to the brain. Auditory neuropathy involves the nerve that carries signals from the inner ear to the brain and is responsible for hearing.
Autonomic neuropathy: Autonomic neuropathy is damage to the nerves of the involuntary nervous system, the nerves that control the heart and circulation (including blood pressure), digestion, bowel and bladder function, the sexual response, and perspiration. Nerves in other organs may also be affected.
Focal neuropathy: Focal neuropathy is neuropathy that is restricted to one nerve or group of nerves, or one area of the body. Symptoms of focal neuropathy usually appear suddenly.
Regardless of the cause, neuropathy is associated with characteristic symptoms. Although some people with neuropathy may not have symptoms, certain symptoms are common. The degree to which an individual is affected by a particular neuropathy varies.
Damage to the sensory nerves is common in peripheral neuropathy. Symptoms often begin in the feet with a gradual onset of loss of feeling, numbness, tingling, or pain and progress toward the center of the body with time. The arms or legs may be involved. The inability to determine joint position may also occur, which can result in clumsiness or falls. Extreme sensitivity to touch can be another symptom of peripheral neuropathy. The sensation of numbness and tingling of the skin is medically known as paresthesia.
The loss of sensory input from the foot means that blisters and sores on the feet may develop rapidly and not be noticed. Because there is a reduced sensation of pain, these sores may become infected and the infection may spread to deeper tissues, including bone. In severe cases, amputation may be necessary.
When damage to the motor nerves (those that control movement) occurs, symptoms include weakness, loss of reflexes, loss of muscle mass, cramping, and/or loss of dexterity.
Autonomic neuropathy, or damage to the nerves that control the function of organs and glands, may manifest with a wide variety of symptoms, including:
- Nausea and vomiting, or abdominal bloating after meals.
- Urinary symptoms, such as incontinence, difficulty beginning to urinate, or feeling that the bladder was not completely emptied.
- Impotence (erectile dysfunction) in men.
- Dizziness or fainting.
- Constipation or diarrhea.
- Blurred vision.
- Heat intolerance or decreased ability to sweat.
- Hypoglycemia unawareness: Low blood sugar levels (hypoglycemia) are associated with trembling, sweating, and palpitations. In people with autonomic neuropathy, these characteristic symptoms may not occur, making dangerously low blood sugar levels difficult to recognize.
Nerve damage may be caused by a number of different diseases, injuries, infections, and even vitamin deficiency states.
- Diabetes: Diabetes is the condition most commonly associated with neuropathy. The characteristic symptoms of peripheral neuropathy often seen in people with diabetes are sometimes referred to as diabetic neuropathy. The risk of having diabetic neuropathy rises with age and duration of diabetes. Neuropathy is most common in people who have had diabetes for decades and is generally more severe in those who have had difficulty controlling their diabetes, or those who are overweightor have elevated blood lipids and high blood pressure.
- Vitamin deficiencies: Deficiencies of thevitamins B12 and folate as well as other B vitamins can cause damage to the nerves.
- Autoimmune neuropathy: Autoimmune diseases such as rheumatoid arthritis, systemic lupus, and Guillain-Barre syndrome can cause neuropathies.
- Infection: Some infections, including HIV/AIDS, Lyme disease, leprosy, and syphilis, can damage nerves.
- Post-herpetic neuralgia: Post-herpetic neuralgia, a complication of shingles (varicella-zoster virus infection) is a form of neuropathy.
- Alcoholic neuropathy: Alcoholism is often associated with peripheral neuropathy. Although the exact reasons for the nerve damage are unclear, it probably arises from a combination of damage to the nerves by alcohol itself along with the poor nutrition and associated vitamin deficiencies that are common in alcoholics.
- Genetic or inherited disorders: Genetic or inherited disorders can affect the nerves and are responsible for some cases of neuropathy. Examples include Friedreich's ataxia and Charcot-Marie-Tooth disease.
- Amyloidosis: Amyloidosis is a condition in which abnormal protein fibers are deposited in tissues and organs. These protein deposits can lead to varying degrees of organ damage and may be a cause of neuropathy.
- Uremia: Uremia (a high concentration of waste products in the blood due tokidney failure) can lead to neuropathy.
- Toxins and poisons can damage nerves: Examples include, gold compounds, lead, arsenic, mercury, some industrial solvents, nitrous oxide, and organophosphate pesticides.
- Drugs or medication: Certain drugs and medications can cause nerve damage. Examples include cancer therapy drugs such as vincristine (Oncovin, Vincasar), and antibiotics such as metronidazole (Flagyl), and isoniazid (Nydrazid, Laniazid).
- Trauma/Injury: Trauma or injury to nerves, including prolonged pressure on a nerve or group of nerves, is a common cause of neuropathy. Decreased blood flow (ischemia) to the nerves can also lead to long-term damage.
- Tumors: Benign or malignant tumors of the nerves or nearby structures may damage the nerves directly, by invading the nerves, or cause neuropathy due to pressure on the nerves.
- Idiopathic: Idiopathic neuropathy is neuropathy for which no cause has been established. The term idiopathic is used in medicine to denote the fact that no cause is known.
The treatment of neuropathy involves measures to control the symptoms as well as treatment measures that address the underlying cause of neuropathy, if appropriate. Medical treatments for diabetes, autoimmune diseases, infections, kidney disease, and vitamin deficiencies are varied and are directed at the specific underlying condition.
In many cases, treatment of the underlying disease can reduce or eliminate the symptoms of neuropathy. Some cases, especially those involving compression or entrapment of nerves by tumors or other conditions, can be relieved by surgery.
Control of blood glucose (sugar) levels is important in the treatment of diabetic neuropathy to help prevent further damage to nerves.
Clinical trials are underway to help find new and more effective treatments for neuropathy. For example, treatments that involve electrical nerve stimulation or magnetic nerve stimulation are being studied.
Special and careful care of the feet is important in people with neuropathy to reduce the chance of developing sores and infections. The nerves to the feet are the nerves most commonly affected by neuropathy.
Proper foot care includes:
- wash the feet with warm water each day and thoroughly dry feet after washing (especially between the toes);
- never go barefoot or wear improperly-fitting, damaged, or too-tight footwear;
- inspect the feet daily, looking for cuts, blisters, or other problems;
- cut and file toenails when needed;
- thick, seamless socks can help prevent irritation of the feet;
- call your health care practitioner if you have any problems with your feet;
- massaging the feet can improve circulation;
- smoking cessation can further improve blood circulation, since smoking damages circulation to the extremities and may worsen foot problems.
The treatment for peripheral neuropathy depends on its cause. The first step in treatment is, therefore, to look for the cause.
- Vitamin deficiencies can be corrected.
- Diabetes can be controlled, although control may not reverse the neuropathy. The goal with diabetes is early detection to prevent the occurrence of neuropathy.
- Neuropathies that are associated with immune diseases can improve with treatment of the autoimmune disease.
- Neuropathy caused by nerve entrapment can be treated by physical therapy, injections or surgery.
- Prompt treatment with sympathetic injections can minimize the chance of shingles progressing to post herpetic neuralgia.
If a specific treatment isn't available, the pain of the neuropathy can usually be controlled with medications. The simplest treatment is acetaminophen,ibuprofen, or aspirin. Tricyclic antidepressants such as amitriptyline (Elavil) and anti-seizure medications, such as carbamazepine (Tegretol) have been used to relieve the pain of neuropathy. Capsaicin, the chemical responsible for chili peppers being hot, is used as a cream to help relieve the pain of a peripheral neuropathy.
Pregabalin (Lyrica) has recently been approved by the FDA for the treatment of post herpetic neuralgia and diabetic peripheral neuropathy, while duloxetine (Cymbalta) has been approved for diabetic peripheral neuropathy. The addition of these drugs to our set of tools to treat peripheral neuropathy is very exciting and indicates the interest in this area.
If you believe you have a peripheral neuropathy, you should contact your healthcare practitioner since many causes of peripheral neuropathy can be successfully treated.