Trigeminal nerve in trigeminal neuralgia, trigeminal neuropathy and TMJ disorders.

Advances in MRI imaging have allowed visualizing the trigeminal nerve and a group of Australian researchers reported on their findings in three conditions which cause facial pain. Trigeminal nerve supplies sensation to the face and facial pain of any kind is also transmitted to the brain through this nerve. Their report, which appeared in The Journal of Pain, suggests that imaging trigeminal nerve may help in making a more accurate diagnosis, which is turn may lead to more appropriate treatment.

Trigeminal neuralgia is an extremely painful condition which is characterized by very brief electric-like pains in the face. The pain is triggered by chewing, talking, brushing teeth, touching a specific spot on the face, and at times occurring without any provocation. This condition usually results from compression of the trigeminal nerve by a blood vessel as it exits the brain stem. Treatment usually involves epilepsy drugs, such as carbamazepine (Tegretol) or oxcarbazepine (Trileptal), Botox injections, nerve destruction (radiofrequency thermocoagulation) or if nothing else works, surgery (microvascular decompression of the trigeminal nerve).

Trigeminal neuropathy also causes pain in the face, but it is less intense, usually continuous and is often burning in character. It can result from an injury to the trigeminal nerve in the periphery rather than near the brain stem. Dental procedures and facial injuries can trigger this pain. This pain tends to respond better to antidepressants, such as amitriptyline (Elavil), nortriptyline (Pamelor), protriptyline (Vivactil), and an epilepsy drug, gabapentin (Neurontin).

Temporomandibular joint disorders can result from arthritic changes in this joint, displacement of the cartilaginous disc inside the joint, or from muscle spasm and inflammation around the joint.

Using special MRI techniques the researchers discovered that patients with trigeminal neuralgia had thinning of the nerve, while those with trigeminal neuropathy had thicker trigeminal nerves than normal controls. Patients with temporomandibular disorders had normal thickness of their trigeminal nerves. This is a very useful finding, particularly when the diagnosis is not clear since some patients may have symptoms of both neuralgia and neuropathy. We often have to try several drugs before finding one that is effective and does not cause side effects, so it would be helpful to know from the start which drugs are more likely to work.

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