Neuropathic Pain

aa

People usually think of pain as having some physical cause. Get rid of the cause, and the pain goes away. However, nerves themselves can also generate pain, and this pain often doesn't go away easily. It is called neuropathic pain (from the Greek neuro, meaning nerves, and pathy, meaning abnormality). It can be puzzling and frustrating for people who have it and for doctors who treat it.

Neuropathic pain often seems to have no cause. It responds poorly to standard pain treatment and may get worse instead of better over time. For some people, it can lead to serious disability.

The most dramatic and mysterious example of neuropathic pain is called "phantom limb syndrome." This occurs when an arm or a leg has been removed because of illness or injury, but the brain still gets pain messages from the nerves that originally carried impulses from the missing limb. These nerves now seem to misfire and cause troubling pain.

What causes pain?

Most pain is felt when special nerve endings, called nociceptors (no-si-SEP-turs), sense something is wrong. We have millions of nociceptors throughout our bodies--probably about 1,300 per square inch of skin. The nociceptors all have different jobs: Some detect burns, others cuts, infection, chemical changes, pressure, and many other sensations. Nociceptors use nerve impulses to send messages to other nerves, which move the messages on to the spinal cord and brain at lightning speed.

The brain interprets the messages as pain, sometimes through an "emotional screen" that remembers previous painful or frightening experiences. That might be why so many people have stronger pain at the dentist's office than while playing rough-and-tumble sports. Also, cultural patterns affect how you "feel" pain. For example, people who were taught to "grin and bear it" may dismiss painful sensations more readily than others would.

Why do some pains last longer than others?

Pain is usually described as acute or chronic. Acute pain is related to the physical sensations caused by an injury. It can last from a few seconds to many weeks, but it usually goes away when normal healing occurs. Chronic pain lasts beyond the typical healing time. With neuropathic pain, the nerve fibers themselves may be damaged or injured. They then send incorrect signals to other pain centers. The pain you feel is real, but the cause is not easy to discover.

Chronic pain can result from diseases, such as diabetes and shingles (an infection related to chickenpox), or from trauma, surgery, or amputation. It can also occur without any known injury or disease. The nerves are sending pain messages, even though there is no identifiable cause for such messages.

How is neuropathic pain diagnosed?

When you have a pain with no known cause, your doctor will probably ask some specific questions:

• Do you have any accompanying conditions, such as diabetes, shingles, multiple sclerosis, or HIV infection?
• How would you describe your pain? (Neuropathic pain is often described as shooting, stabbing, burning, or searing.)
• Is your pain worse at any time of the day or night? (Neuropathic pain is usually worse at night.)
• Does the pain seem to follow a certain physical path or specific sequence?
• Does the pain come from an area that has missing or injured nerves?
• Is the pain triggered by minor irritation, such as rubbing against the sheets at night?

These questions often help define the type of pain involved. Once your doctor knows what is happening, treatment can begin. Interesting research in the field of pain is offering a wide range of new ideas for treatment, and many people can now be helped. Anticonvulsant and antidepressant drugs and various pain relievers seem to work in some cases. If another condition, such as diabetes, is involved, better management of that disorder may alleviate the neuropathic pain.

Everyone has pain. We would be in serious trouble if we couldn't feel what is happening in our bodies. But pain that doesn't quit is worrisome. Be sure you see your doctor if you have pain that seems to be coming from nowhere and doesn't go away. Help is available.

Common causes of neuropathic pain

Alcoholism

Amputation

Back, leg, and hip problems (sciatica)

Cancer chemotherapy

Diabetes

Facial nerve problems (trigeminal neuralgia)

HIV infection or AIDS

Multiple sclerosis

Shingles (herpes zoster virus infection)

Spine surgery

Advanced Pain Medicine