Peripheral Neuropathy Health Article

Description

Similar to electrical wiring in a house, the body has a highly complex network of nerves made up of bundles of neurons, axons, and dendrites. This network originates in the brain and extends down through the spinal cord. These nerves branch off at junctures along this pathway to connect each portion of the body to the brain and spinal cord, the central nervous system. Nerves relay necessary information to and from every area, notifying the brain of sensations and external conditions. The brain, in turn, sends messages back to those areas. With peripheral neuropathy, damage has occurred to the nerves that connect peripheral portions of the body, and the patient feels pain or numbness.

Peripheral neuropathy is not usually considered a disease. It is more often thought of as a symptom of other diseases or conditions, or results from damage caused by the introduction of toxic substances. There are an estimated two million Americans who suffer from peripheral neuropathy. It becomes more common as people age, and the majority of its victims are 65 years old or older.

Causes & symptoms

The symptoms of peripheral neuropathy depend upon which type of nerve fiber is affected. Sensory nerve fiber damage is more likely to generate various sensations, while motor nerve fiber is more apt to result in weakening and wasting of muscle tissue in the affected area. It is a condition that develops quite gradually, usually over a period of months or even years. A tingling, prickly sensation in the toes and/or feet is commonly the first sign that is noticed, or there may be numbness in this area. Typically this feeling progresses to the lower legs, fingers, hands, arms, and then the trunk of the body in severe cases. As the situation worsens, the tingling sensation feels more like burning or severe discomfort followed by sharp, almost electric shock-like jabs of pain. These sensations may begin in the toes and feet, and then progress to other affected areas. Later symptoms often include increasing muscle weakness, poor coordination, numbness, and lack of feeling. Urinary incontinence, diarrhea, constipation, impotence, and postural hypotension (dramatic drops in blood pressure when a person stands) causing dizziness or dangerous falls are other potential negative effects, especially in the elderly.

Peripheral nerves are extended and delicate, easily damaged by a variety of things. Diabetes, alcoholism, diseases of the autoimmune system such as rheumatoid arthritis and lupus, and exposure to health damaging substances can cause peripheral neuropathy. Chronic liver and kidney disease, thyroid gland imbalances, bacterial or viral infections, and cancer can also cause the damage. Many of the strong anticancer drugs used and certain vitamin deficiencies can also lead to this condition. Repetitive mechanical actions that put pressure on a particular nerve, like the wrist in carpal-tunnel syndrome, or even inherited abnormalities in the body can cause peripheral neuropathy. However, in many cases no one single reason for this condition can be found.

Guillain-Barre syndrome, also called acute polyneuritis or ascending paralysis, is the only form of peripheral neuropathy that develops differently. It is a rare and very serious form that is believed to be caused by an autoimmune reaction to infection. Its primary difference from other types of peripheral neuropathy is the terrific rapidity of its onset.

A few rare forms of peripheral neuropathy are inherited. The best known inherited peripheral neuropathy is called Charcot-Marie-Tooth syndrome, or CMT. More than 20 different genes and loci on human chromosomes are now known to be associated with CMT.

Diagnosis

Because peripheral neuropathy can be caused by a variety of factors, outcomes vary depending upon the reason for the nerve damage. Some causes, such as vitamin or metabolic deficiencies, can be reversed if caught early; other causes may not be reversible. Because of these factors, early diagnosis is very important. A neurologist (a doctor who specializes in the nervous system) can diagnose the disorder, try to determine the cause, and assess the extent of the damage. Sensations of pain, temperature, and touch in various parts of the body are tested by observing the person's ability to respond to a stimulus. If areas of either hypersensitivity or loss of sensation are found, the boundaries of that feeling are mapped by further testing.

An electromyogram (EMG) tests the electrical activity occurring in muscles and can be used in the diagnostic process. X rays, blood tests, and muscle biopsies are common tests used in determining the cause of peripheral neuropathy. For example, blood tests that show elevated blood sugar would indicate diabetes, or elevated liver function tests or thyroid levels could indicate liver or thyroid disease.