(Nerve Pain · Peripheral Neuropathy)

In this condition factsheet:

• The facts on Neuropathy


• Causes of Neuropathy


• Symptoms and Complications of Neuropathy


• Diagnosing Neuropathy


• Treating and Preventing Neuropathy

The Facts on Neuropathy

Peripheral neuropathy refers to damage to the peripheral nerves – nerves that carry information between the central nervous system (the brain and spinal cord) and the rest of the body. Peripheral neuropathy occurs in about 2% to 8% of people and is more common as we age.

Peripheral neuropathy may be caused by a number of different medical conditions, such as diabetes, cancer, and nutritional deficiencies. Peripheral neuropathy can also be caused by medications and chemicals. It can interfere with the senses, with movement, or with the function of internal organs.

Damage to one nerve is called mononeuropathy, while damage to many nerves all at once is called polyneuropathy.

Causes of Neuropathy

Mononeuropathies are usually caused by pressure on a nerve that is just under the skin and near the knee, elbow, shoulder, or wrist. Mononeuropathies may also be caused by trapped or injured nerves. Sudden onset is most commonly caused by trauma such as forcible overextension or repeated tight gripping. Gradual onset may be caused by compression (e.g., from a tumor, crutches, or a cast).

Some nerves close to the surface of the body, such as the median nerve in the wrist, the ulnar nerve in the elbow, the radial nerve in the upper arm, and the peroneal nerve in the calf, are more easily injured than other nerves. The injuries result in the following mononeuropathies: carpal tunnel syndrome, ulnar nerve palsy, radial nerve palsy, and peroneal nerve palsy.

For example, repetitive wrist movements can put pressure on the median nerve in the wrist, causing carpal tunnel syndrome. There are several conditions (e.g., infections, sarcoidosis, connective tissue disorders) that can cause mononeuropathies in several places at a time–these are called multiple mononeuropathies.

Polyneuropathy has many causes, including alcoholism; diseases such as diabetes, cancer, and end-stage kidney failure; autoimmune diseases; infections; and exposure to poisonous toxic chemicals, heavy metals such as lead or mercury, and chemotherapeutic agents such as vincristine.

Hypothyroidism, a hormonal condition in which the thyroid gland doesn't work normally, can also cause neuropathy. Some neuropathies are due to inherited medical conditions that get worse with time, and others can be caused by certain medications (e.g., didanosine, dapsone, metronidazole, isoniazid, vincristine, amiodarone). Vitamin deficiencies (e.g., B12, folic acid) can also cause polyneuropathy.

Guillain-Barré syndrome is a very serious form of polyneuropathy. Sometimes people with the disease become paralyzed. It is probably caused by an autoimmune reaction. The body's immune system attacks the nerve's myelin sheath, a coating that helps carry a signal along the nerve. Guillain-Barré syndrome can develop suddenly between 5 days and 3 weeks after a person has had a respiratory infection or a gastroenteritis, a vaccine (the chance is less than 1 per 1,000,000 people vaccinated), or a surgery.

Symptoms and Complications of Neuropathy

The symptoms of neuropathy depend on the location and seriousness of the nerve damage.

Mononeuropathy appears as pain, weakness, or immobilization in the localized area of the affected nerve. If the affected nerve is purely a sensory nerve, there will be numbness but no weakness; if a motor nerve is involved, there will be weakness but no numbness.

Symptoms of polyneuropathy may develop suddenly or gradually. The first symptom of polyneuropathy is often mild tingling, which gets worse over time until the area becomes numb. People with diabetes often have neuropathy of the feet. This is a serious condition because they could get an infection or injure a foot and not be able to feel it.

Along with the tingling and numbness, people with chronic polyneuropathy may feel burning or shooting pain. Since they can't sense changes in temperature or feel pain caused by injuries, theyoften burn themselves or develop open sores from injuries they don't realize they have. They may also have trouble walking and standing because they can't tell what position their joints are in.

Neuropathy can also cause muscle weakness.

Sometimes the nerves controlling automatic functions of the body such as bowel and bladder contraction or blood pressure control are affected by neuropathy. When this happens, a person can have constipation, diarrhea, erectile dysfunction, bladder dysfunction, and high or low blood pressure.

The main symptom of Guillain-Barré syndrome is weakness that gets progressively worse over 2 to 3 weeks. The weakness starts in the legs and moves to the arms. The breathing and swallowing muscles can also become weak. Between 5% and 10% of people with the disease have to breathe using a respirator, and 1 in 10 can't swallow. Hearts of people with a serious case of the disease may beat with an abnormal rhythm, and their blood pressure may go up and down in an irregular and unpredictable way.