Neuralgias

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Neuralgias Diagnosis & Tests

Neurologic examination shows tenderness occurring along a nerve tract. Trigeminal neuralgia has pain usually 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 can be often encountered, such as loss of deep tendon reflexes, local loss of muscle bulk, local lack of sweating (sweating is mediated 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, 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 can figure out whether or not 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, which is attached to an electric probe. The physician can measure the electrical activity of the sampled muscle at rest and during motion, which provides, indirectly, 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 often used by physicians 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 can be helpful, particularly whenever there is suspicion of an underlying medical problem like arthritis, syphilis, vitamin deficiencies or other less common disorders. If there is concern about multiple sclerosis, usually the diagnosis can be confirmed with an imaging test of the brain such as MRI.

A lumbar puncture is often used to back up the diagnosis of multiple sclerosis and other nerve disorders. It involves inserting a needle into the lower back in order to reach a spot called the subarachnoid space, which is filled with cerebrospinal fluid (CSF). Analysis of this fluid may show evidence of inflammation, helping to establish the correct diagnosis.