Neuropathic pain is caused by damage to or dysfunction of the nerves, spinal cord, or brain.
Neuropathic pain may result from
Compression of a nerve—for example, by a tumor, by a ruptured intervertebral disk, or as occurs in carpal tunnel syndrome
Nerve damage—as occurs in disorders that affect the whole body (such as diabetes mellitus) or only one or a few parts (such as shingles)
Abnormal or disrupted processing of pain signals by the brain and spinal cord
Neuropathic pain can contribute to anxiety and/or depression. Anxiety and depression can also worsen pain.
Neuropathic pain may also develop after surgery, such as removal of a breast (mastectomy) or lung surgery (thoracotomy).
Neuropathic pain may be felt as burning or tingling or as hypersensitivity to touch or cold. Sometimes the pain is deep and aching. People may become very sensitive to touch. A light touch may cause pain.
If movement is painful, people may be reluctant to move the painful part of their body. In such cases, muscles that control the painful part may waste away, and movement may become limited.
People continue to feel pain long after the cause resolves because structures in the nervous system have been changed, making the structures more sensitive to pain.
Doctors base the diagnosis of neuropathic pain mainly on the following:
Depending on the symptoms, doctors may do tests to check for disorders that could be causing the pain. Tests may include magnetic resonance imaging (MRI) and blood tests.
Understanding what the nature of neuropathic pain is and what to expect often helps people feel more in control and better able to manage their pain.
Treatment of neuropathic pain can vary depending on the specific disorder causing it. For example, if the cause is diabetes, better control of blood sugar levels may help slow the progression of the nerve damage that causes pain. Often, treatment begins with drugs.
Pain relievers (analgesics) may be given to reduce the pain. Pain relievers include the following:
Adjuvant analgesics are drugs that change the way the nerves process pain and that thus affect pain intensity. Many of these drugs are usually used to treat other problems (such as seizures), but they were found to sometimes relieve pain, including neuropathic pain. These drugs include antidepressants and anticonvulsants.
Opioid analgesics partially relieve neuropathic pain in some people.
Drugs applied to the skin (topical drugs), such as a capsaicin cream or a patch that contains lidocaine (a local anesthetic), may be effective.
Psychologic factors that may contribute to the pain, such as anxiety and depression, if present, are treated.
However, drugs often provide only partial relief and typically only in fewer than half of people with neuropathic pain.
Physical and/or occupational therapy help people do the following:
Surgery may be needed if the pain results from an injury that puts pressure on a nerve.
Electrical stimulation (from electrodes placed over the spine or other areas) is helpful for certain types of chronic neuropathic pain.
Nerve blocks are used to disrupt a nerve pathway that transmits or enhances pain signals. Nerve blocks may be used in people with severe, persistent pain when drugs cannot relieve the pain. Various techniques may be used:
Injecting the area around the nerves with a local anesthetic to prevent the nerves from sending pain signals (doctors commonly use ultrasonography to help them locate the nerves to be treated)
Injecting the area around collections of nerve cells called ganglia to help regulate the transmission of pain signals
Injecting a caustic substance (such as phenol) into a nerve to destroy it
Freezing a nerve (called cryotherapy)
Burning a nerve with a radiofrequency probe
Phantom limb pain is pain that seems to be felt in an amputated part of the body, usually a limb. It differs from phantom limb sensation—the feeling that the amputated part is still there—which is much more common.
Phantom limb pain cannot be caused by a problem in the limb. Rather, it must be caused by a change in the nervous system above the site where the limb was amputated. But the brain misinterprets the nerve signals as coming from the amputated limb. Usually, the pain seems to be in the toes, ankle, and foot of an amputated leg or in the fingers and hand of an amputated arm. The pain may resemble squeezing, burning, or crushing sensations, but it often differs from any sensation previously experienced. For some people, phantom limb pain occurs less frequently as time passes, but for others, it persists.
Massage can sometimes help, but drug therapy is sometimes necessary.
Mirror therapy is a relatively new treatment. A health care practitioner teaches people how to use this therapy. People sit with a large mirror facing their unaffected leg. The mirror reflects the image of the unaffected limb, giving people the impression that they have two normal limbs. People are then instructed to move the unaffected limb while watching its reflected image. Thus, people feel as if they are moving two normal limbs. If people do this exercise for 30 minutes a day for 4 weeks, pain may be substantially reduced. This therapy changes the pathways in the brain that interpret pain signals in the body.
Shingles is caused by reactivation of the varicella-zoster virus, the virus that causes chickenpox.
What causes postherpetic neuralgia is unknown. But it is more likely to develop if the shingles rash is severe or if people are older when shingles develops.
The pain is felt as a constant deep aching or burning, as a sharp and intermittent pain, or as hypersensitivity to touch or cold. The pain may be debilitating.
Vaccination with the shingles (herpes zoster) vaccine can help reduce the risk of getting shingles and postherpetic neuralgia. If people get shingles and postherpetic neuralgia, vaccination can help reduce the severity of symptoms.
Pain relievers and other drugs may be required, but no treatment is routinely effective.