Neuropathy is a term that refers to general diseases or malfunctions of the nerves. 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.)
Types of 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 term proximal neuropathy has been used to refer to nerve damage that specifically causes pain in the shoulders, 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. These 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.
What Causes Neuropathy?
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 overweight or have elevated blood lipids andhigh blood pressure.
- Vitamin deficiencies: Deficiencies of the vitamins 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 to kidney 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.