The causes of neuralgias are varied. Chemicals can cause nerve irritation. Inflammation, trauma (including surgery), compression by adjacent structures (tumors or inflamed tissues), and infections can all lead to neuralgias. In many cases, however, the cause is unknown or unidentifiable.
Neuralgias are most common in elderly persons, but they can occur at any age.
Trigeminal neuralgia is the most common form of neuralgia. It affects the main sensory nerve of the face, the trigeminal nerve ("trigeminal" literally means "three origins", referring to the division of the nerve into three branches). This condition involves sudden and short attacks of severe pain on one side of the face, along one of the areas supplied by the trigeminal nerve. The pain attacks may be severe enough to cause a facial grimace, which is classically referred to as a painful tic (tic douloureux).
The cause of trigeminal neuralgia is occasionally a blood vessel or small tumor pressing on the nerve. Disorders such as multiple sclerosis (an inflammatory disease affecting the brain and spinal cord), certain forms of arthritis, and diabetes (high blood sugar) can also cause trigeminal neuralgia, but most commonly a cause is not identified.
In this condition, certain movements such as chewing, talking, swallowing, or touching an area of the face may trigger a spasm of excruciating pain.
A related but rather uncommon neuralgia affects the glosso-pharyngeal nerve, one of the nerves that provide sensation to the throat. Symptoms of this neuralgia are short, shock-like episodes of pain located in the throat.
Some other neuralgias occur after certain infections such as shingles, which is caused by the varicella-zoster virus, a type of herpesvirus (postherpetic neuralgia). This can produce a constant burning pain after shingles rash has healed. The pain is worsened by movement or contact with the affected area.
Postherpetic neuralgia can be debilitating long after signs of the original herpes infection have disappeared. Two other infectious diseases that can cause neuralgias are syphilis and Lyme disease.
Diabetes is another common cause of neuralgias. This very common medical problem affects almost one out of every 20 Americans during adulthood. 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, including trigeminal neuralgia, carpal tunnel syndrome (a condition characterized by pain and numbness of the hand and wrist), and meralgia paresthetica (problem manifested by numbness and pain in the thigh, due to damage to the lateral femoral cutaneous nerve). Strict control of blood sugar may prevent diabetic nerve damage and may accelerate recovery in patients who do develop neuralgia.
Other medical conditions that can be associated with neuralgias are chronic renal insufficiency and porphyria (a hereditary disease in which the body can not get rid of certain substances produced after the normal breakdown of blood in the body). Certain drugs can also cause this problem.
