Neuropathy is a condition in which the peripheral nerves ( the nerves in your body, aside from your spinal cord and brain) are damaged or not working correctly. Disorders of peripheral nerves are among the most frequent neurological complications of HIV infection. With increasing survival of patients with HIV, the number of patients who have neuropathy is increasing worldwide. It is estimated that nearly one-third of people with HIV/AIDS experience some peripheral nerve damage. There are hundreds of different types of neuropathies and many different ways to categorize them, including by the type of nerve damaged, the causes of the nerve damage, or the pattern of nerve damage.

The condition is generally referred to as peripheral neuropathy, and it is most commonly due to damage to nerve axons. Neuropathy usually causes pain and numbness in the hands and feet. It can result from traumatic injuries, infections, metabolic disorders, and exposure to toxins. Neuropathy can affect nerves that control muscle movement (motor nerves) and those that detect sensations such as coldness or pain (sensory nerves). In some cases - autonomic neuropathy - it can affect internal organs, such as the heart, blood vessels, bladder, or intestines.

There are many causes of painful polyneuropathy. The most common cause is diabetes, both Type 1 and Type 2. Other causes include old age, certain drugs (such as some chemotherapy drugs), alcohol abuse, AIDS, environmental toxins, and inherited neurological neuropathies. However, in up to one-third of patients with painful polyneuropathy, no underlying cause can be found. Importantly, the chance of obtaining pain relief with proper treatment is the same for patients with or without a known etiology.

The actual injury to the nerves may result from several different problems. Possible injuries include:

- not enough blood supply to the nerves, resulting in loss of oxygen and other needed nutrients to the nerve and thus damage to the nerve, and
- abnormal function of the nerve itself, such that the nutrients within the nerve are not properly metabolized. In any individual patient, it is not possible to find out which type of problem exists. However, it does not matter which problem is present with regard to pain treatment.

The symptoms of painful polyneuropathy start in the toes and feet (right and left). In some patients the symptoms gradually rise up the calves and into the knees. This is called a stocking pattern. Then, in some the symptoms may also begin in the fingers and hands -- causing a stocking and glove pattern. It cannot be predicted how any one patient's symptoms will spread. In some patients, the pain does not spread beyond the toes or feet; in others, the progression to calves and hands occurs in months; and yet in others the spread is very gradual, over many years.

Patients who develop pain with polyneuropathy describe the pain using a variety of words, including "burning," "raw skin," "skin sensitivity," "sharp," "electric-like," "deep ache," "freezing cold," "like walking on ground glass," "itchy," and others. Some patients say they don't have pain but have unpleasant and irritating sensations, which may include "buzzing," "like bugs crawling," and "aching." Some patients have constant pains, day and night, whereas others only have noticeable pain at bedtime. Often, patients may complain that the pain interferes with their sleep.

Some patients with polyneuropathy may have difficulty feeling things with their feet or hands. Therefore, it is very important that these patients examine their affected skin areas regularly to make sure they haven't injured themselves (cuts, burns, infections, etc.). Also, some patients with neuropathy have trouble with their balance when walking; these patients should keep a nightlight on in their bedrooms and bathrooms, so they do not fall when they get up at night.

As with all chronic pain, patients with painful polyneuropathy may develop depression and sleep problems.