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Trigeminal neuralgia

Trigeminal neuralgia is commonly called “tic douloureux” or just “tic.” It is the most excruciating pain known to man. Characteristic intense, ‘electric shock’ like pain occurs over the face in one of the three divisions of the Vth cranial nerve (nerve carrying sensations from the face to brain). Attacks of pain may be triggered by chewing, gush of air, brushing, shaving or spontaneously. Pain occurs for brief periods, and may occur multiple times in a day. Sometimes a patient may have several tooth removals before a diagnosis of Trigeminal neuralgia is made.


What causes Trigeminal Neuralgia?
Although the exact cause of this extreme facial pain is not known, the most prevailing theory is compression of the Vth nerve by a blood vessel. This compression causes a loss of the protective layer of the nerve which leads to abnormal electric current transmission leading to pain.


 
Trigeminal neuralgia usually affects middle age group or older individuals. Women have a slightly higher incidence then men. Some patients affected by Multiple sclerosis may suffer from Trigeminal neuralgia.


How is diagnosis made?

Diagnosis is mainly clinical. Typical characteristic of the pain and location of the pain clinches the diagnosis. Trigeminal neuralgia most commonly involves the middle (second) and lower (third) branches but may involve the upper (first) branch alone, any two branches, or all three branches.
MRI of the brain is usually performed to rule out a mass lesion or multiple sclerosis. Certain MRI sequences may show the abnormal contacting blood vessel to the Vth nerve.

How can Trigeminal neuralgia be treated?
The initial mainstay of treatment is medical management. Anticonvulsants like Carbamezipine, Oxcarbamezipine, and Gabapentin are the mainstays of the medical therapy. Oxcarbamezipine is often used as a first choice drug in view of its better tolerability and lesser side effects.  Oxcarbamezipine causes more than 50% reduction in pain attacks, in more than 90% patients.
However, with time medicines may lose their effectiveness. The dose of these medications may be then elevated or a second drug may be added. Additional invasive procedures may be required.
Surgery- Microvascular decompression
Most patients with typical trigeminal neuralgia who become dissatisfied with medical treatment, or have developed tolerance are candidates for microvascular decompression surgery. The surgery is well tolerated by the elderly, although frail individuals or those with significant medical co-morbidities are directed to destructive procedures under local anesthetic as described in the following sections. Microvascular decompression surgery offers the advantages of attacking the presumed etiology, preserving the trigeminal nerve function, and providing the best chance for permanent pain relief.
The operation requires making an incision in the back of the head, creating a small hole in the skull, and lifting an edge of the brain to expose the trigeminal nerve, which is located approximately two inches deep. The incision is made behind the ear on the side of the head where the patient feels pain. The blood vessels that press on the nerve where the nerve leaves the brain are exposed and pushed away from the nerve. A small pad is inserted between the nerve and the vessels. This relieves the pain in most patients.
The surgery typically takes about 45-60 minutes. Most patients spend two nights in the hospital. Intensive care is usually not required. Pain relief is seen in more than 90% of the patients.  This surgery provides the longest duration of pain freedom, and has the most satisfying results.
Gamma knife.
Gamma knife is a form of radiation where focused radiation beams are targeted with great precision to the nerve causing pain. The beams are targeted using computer software to minimize the radiation fallout to the surrounding normal structures. The actual treatment takes about 40 minutes. However, the entire procedure from fixation of a frame to head to completion of the treatment may take 4-5 hours.

Radiosurgery usually takes 1-2 months to produce pain relief, so patients with more severe pain may be better off with a surgery or some percutaneous procedure to relieve pain. Approximately 50% of patients will eventually be pain free and off medications after radiosurgery. As with other procedures, some patients experience recurrent pain and require additional surgery. A relatively small number of patients experience facial numbness after radiosurgery, which is the only commonly reported side effect.


Percutaneous procedures
There are different percutaneous procedures available for relief of the trigeminal neuralgia pain. Some of them include Radio-frequency ablation of the nerve, Glycerol injection. These procedures give an immediate pain relief. However, the relief may be only short lasting. These procedures usually cause a little numbness in the area of the Vth nerve distribution.
The radiofrequency lesioning is performed in an operating room. The  patient lies supine on the back. A needle is passed into the cheek, starting just outside the angle of the mouth on the side of pain. under X-ray guidance the needle is passed through a small, natural opening in the base of the skull upto the trigeminal nerve ganglion.  With the needle in place,  a small test electric current is passed through the needle. If the needle is in right position, patient  usually feels the same kind of pain as her Tic. The patient is put to sleep again, and a  stronger radiofrequency current is passed through the needle. The stronger current destroys a part of the nerve. The patient is then awakened. The patient once awake will feel some numbness in the area of face, which is a normal occurence with this procedure.  After the procedure, corneal reflex is also checked as the fibers carrying sensations from the cornea may also get affected. The radiofrequency lesion procedure is repeated with the patient asleep until it has resulted in the desired numbness.


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