What is trigeminal neuralgia?
Trigeminal neuralgia is also known as Tic douloureux. This is a common disorder of middle age and later life and consists of intermittent lancinating (shock like) pain which lasts for a few seconds in the distribution of the fifth cranial nerve. The pain never lasts more than few seconds. The fifth cranial nerve is the largest cranial nerve in the head and it is responsible for carrying sensation like pain, touch, hot and cold sensation from the face, oral cavity and throat to the brain. Annual incidence is 4 cases per 100,000 persons. In between the attacks of pain, the patient will be pain free for weeks to months.
What is the cause for trigeminal neuralgia?
Trigeminal neuralgia is due to the erratic transmission of signals in the damaged trigeminal nerve. The damage can be caused by compression of a blood vessel on the trigeminal nerve, or a brain tumor causing pressure on the nerve or conditions like multiple sclerosis. In about 2000 cases of trigeminal neuralgia in one study 16 patients had brain tumor.
What are the triggering factors for trigeminal neuralgia?
The characteristic feature of trigeminal neuralgia is the initiation of pain by stimulation of certain areas of the face, lips , gums as in shaving or brushing the teeth or by movements of these parts in chewing ,talking, or yawning-the so called trigger zones. The pain is can also be induced by environmental factors like cold air.
How can you diagnose trigeminal neuralgia?
Trigeminal neuralgia can be diagnosed based on the symptoms of the patients only and it needs good history taking by the physician. Imaging studies like Magnetic resonance imaging, CT scan of the brain will usually be normal in a typical case of trigeminal neuralgia.
What other conditions may confuse trigeminal neuralgia?
Conditions like Herpes zoster may also cause pain over the face but it will be continuous. There will be eruptions over the face (small vesicles filled with fluid). In trigeminal neuralgia the pain nerve lasts longer than a few seconds. Dental disease and any problem in the eye can also cause pain over the face. Intracranial brain tumor and temporal arteritis should be ruled out.
What are the treatment options available?
Trigeminal neuralgia can be treated both by medical and surgical means. Initially patient can be managed with drugs and when the patient is not responding to drugs or the side effect of the drugs is severe, surgical treatment is indicated.
Anticonvulsant medications are usually used to control and prevent the pain in trigeminal neuralgia. Carbamazepine is the commonly used drug. It can be given up to a maximum dosage of 1200 mg per day. Baclofen and gabapentin are the other drugs which are useful.
In refractory cases of trigeminal neuralgia, various surgical treatment options are available. All procedures aim in reducing the abnormal signal conduction in the damaged trigeminal nerve. These are:
- Injection of local anaesthetic agents to block the branches of the nerve in the face (old technique).
- Percutaneous glycerol rhizotomy (injecting glycerol into the trigeminal ganglion in the head).
- Percutaneous balloon compression of the ganglion.
- Percutaneous trigeminal radiofrequency rhizotomy.
- Microvascular decompression of the nerve.
- Stereotactic radiosurgery (newer technique in which X-rays are used to destroy the damaged nerve).
Success rate of the surgical procedure varies from 30-85% depending of the procedure used and the accuracy of surgery. Recurrence after surgery is also a possibility. After surgery, the medicines can be stopped gradually. Complications of surgery include meningitis, weakness of the face and damage to the cornea of the eye due to loss of sensation over the face.