Definition
Neuralgia is pain that follows the path of a specific nerve.
Alternative Names
Nerve pain; Postherpetic neuralgia
Causes, incidence, and risk factors
The causes of neuralgia vary. Chemical irritation, inflammation, trauma (including surgery), compression of nerves by nearby structures (for instance, tumors), and infections may all lead to neuralgia. In many cases, however, the cause is unknown.
Neuralgia is most common in elderly persons, but it may occur at any age.
Trigeminal neuralgia is the most common form of neuralgia. For information on this condition, see the article on trigeminal neuralgia.
A related but rather uncommon neuralgia affects the glossopharyngeal nerve, which provides sensation to the throat. Symptoms of this neuralgia are short, shock-like episodes of pain located in the throat.
Neuralgia may occur after infections such as shingles. Shingles-related neuralgia produces a constant burning pain after the shingles rash has healed. The pain is worsened by movement of or contact with the affected area.
Postherpetic neuralgia may be debilitating long after signs of the original herpes infection have disappeared. Other infectious diseases that may cause neuralgia are syphilis and Lyme disease.
Diabetes is another common cause of neuralgia. Diabetes damages the tiny arteries that supply circulation to the nerves, resulting in nerve fiber malfunction and sometimes nerve loss. Diabetes can produce almost any neuralgia nearly anywhere in the body, including trigeminal neuralgia.
Other medical conditions that may be associated with neuralgias include chronic renal insufficiency and porphyria -- a hereditary disease in which the body cannot rid itself of certain substances produced after the normal breakdown of blood in the body. Certain drugs may also cause neuralgia.
Symptoms
- Pain located anywhere, usually on or near the surface of the body
- In the same location for each episode
- Sharp, stabbing pain or constant, burning pain
- Pain along the path of a specific nerve
- Impaired function of affected body part due to pain, or muscle weakness due to motor nerve damage.
- Increased sensitivity of the skin or numbness of the affected skin area (feeling similar to a local anesthetic, such as a Novocaine shot)
Any touch or pressure is interpreted as pain. Movement may also be painful.
Signs and tests
Neurologic examination shows tenderness occurring along a nerve tract. Trigeminal neuralgia usually causes pain along the second and third nerve divisions (lower face and jaw), and rarely involves the first nerve division (temple and forehead). Other signs of altered nerve function may be seen often, such as loss of deep tendon reflexes, local loss of muscle bulk, local lack of sweating (sweating is regulated by nerve function), and abnormal skin sensation.
There may be specific trigger points (areas where even a slight touch triggers pain). A dental examination is used to rule out dental disorders that may cause facial pain. The presence of other symptoms (such as redness or swelling) may indicate disorders causing the pain, such as infections, bone fractures, rheumatoid arthritis, or other disorders.
No tests are specific for neuralgia, but tests may be used to rule out other causes of the pain. Sometimes a nerve conduction study with electromyography (NCS/EMG), which examines the electrical activity of nerves, may confirm the diagnosis.
The first part of the test, the NCS, involves giving small electric shocks to skin areas overlaying specific nerve paths. The physician then determines whether the conduction of electricity is delayed or blocked through the particular nerve that was tested.
The second part of the test, the EMG, involves the careful insertion of a very fine needle into the skin. The needle is attached to an electric probe. This probe measures the electrical activity of a muscle of interest at rest and during motion. EMG indirectly provides useful clues regarding nerve function. Although the procedure sounds rather unpleasant, most patients are able to tolerate it with little discomfort.
There are a number of other laboratory tests doctors use to determine the cause of neuralgia. Blood tests to check blood sugar and kidney function are routinely used. When the diagnosis is not clear, other tests may be helpful -- particularly whenever there is suspicion of an underlying medical problem like arthritis, syphilis, vitamin deficiencies, or other less common disorders. If multiple sclerosis is suspected, the diagnosis usually can be confirmed with an imaging test of the brain such as an MRI.
A lumbar puncture (spinal tap) is often used to confirm the diagnosis of multiple sclerosis and other nerve disorders. It involves taking a sample of cerebrospinal fluid (CSF). Analysis of this fluid may show evidence of inflammation, helping to establish the correct diagnosis.
Print
