Trigeminal Neuralgia – Causes, Symptoms And Treatment
Trigeminal neuralgia is the most common facial pain syndrome with paroxysmal character, representing one of the most unbearable pain. Also known as tic douloureux, trigeminal neuralgia has an incidence of 4.5 cases per 100,000 inhabitants and is characterized by recurrent episodes of pain, which starts in a small area of the face. Onset is most common in middle age, but have been reported cases with onset in childhood or in adolescence.
Trigeminal nerve is the largest of all the cranial nerves, is a mixed nerve and presents two components: a sensory component which is formed by somatic sensory fibers that carry pain, temperature and touch sensations from the face and a motor component formed by motor fibers that supply temporalis, pterygoid, tensor tympani, tensor palati, mylohyoid, and anterior belly of the digastric muscle.
Trigeminal Neuralgia Causes
The exact pathophysiology of trigeminal neuralgia is not well known, in most cases the cause is not evident, being an idiopathic trigeminal neuralgia. In a small percentage of cases, trigeminal neuralgia may occur due to structural lesions of the trigeminal nerve.
In most cases, trigeminal neuralgia is probably caused by the compression of an aberrant arterial or venous loop on the nerve root, produced where trigeminal root is entering into the pons. This mechanism first described by Jannetta in 1967 is still incriminated in 80% -90% of cases.
Pulsations of arterial or venous vascular loops that produce aberrant trigeminal root compression, are responsible for the appearance of demyelination areas in the trigeminal root, which causes a non-synaptic transmission between sensory, thick , myelinated fibers and small, thin fibers that transmit pain. Aberrant arterial loops most often originate from superior cerebellar artery and anterior inferior cerebellar artery.
In a lower proportion of cases, trigeminal neuralgia may be caused by a primary demyelination, as occurs in approximately 2% of cases of multiple sclerosis that is associated with trigeminal neuralgia.
Trigeminal Neuralgia Symptoms
The disease usually appears after age of 40 years, between 50 and 58 years, and most commonly affects females, the female/male ratio being 1,6:1 for women.
Trigeminal neuralgia is characterized by a paroxysmal, repetitive, very strong and lancianting pain that is lasting a few seconds, described by the patient as a sensation of electrical shocks that starts suddenly. Attacks occur daily for several weeks or months, followed by a period of remission that may last for years and then attacks may recur. The pain is always located unilaterally, is so strong and sudden that the patient is frightened, may grimace, wince, or make an aversive head movement, reason why trigeminal neuralgia is also called tic douloureux.
Paroxysmal pain attack lasts a few seconds, up to 20-30 seconds, rarely up to several minutes and during the day or night painful attacks can occur several times. The attack appear and disappear suddenly. Pain may occur spontaneously or is triggered by stimulation of specific areas located on the face, called trigger zones. Trigger zones are stimulated by low intensity stimuli, especially tactile or activities like teeth washing, yawning, talking, shaving and laughing. Pain may be precipitated by loud noises or bright stimuli. Most often the trigger zone is located on the nose or lips. After the active period of the disease, remissions can last for months or years, and recurrence of painful paroxysms is unpredictable.
Neuralgia occurs mostly on maxillary and mandibular branch, but were reported exceptional cases were neuralgia was located in the ophthalmic branch of the trigeminal nerve.
Neurological examination reveals no changes in trigeminal nerve territory, which is an argument for the diagnosis of idiopathic trigeminal neuralgia. In evolution, trigeminal neuralgia tends to deterioration, painful attacks have the tendency to increase in frequency and severity.
Trigeminal Neuralgia Treatment
Trigeminal neuralgia benefit from medical treatment and neurosurgical treatment. Because trigeminal neuralgia affects patients older than 50 years, medical treatment should represent the initial therapy. Medical therapy is often sufficient and effective, allowing surgical consideration only if pharmacologic treatment fails.
Carbamazepine is the drug of choice in the treatment of trigeminal neuralgia. Dose should be increased gradually to obtain a maximum effect of the drug. After several weeks of symptoms improvement, the dose of carbamazepine may be decreased gradually. The most common side effects of carbamazepine are represented by skin rash, liver problems, ataxia and dizziness. Oxycarbamazepine has fewer side effects compared with carabamazepina and represent an other choice in trigeminal neuralgia.
Phenytoin, clonazepam, baclofen, gabapentin and lamotrigine may be used either alone or in combination with carbamazepine.
Baclofen is the second choice in the treatment of trigeminal neuralgia, especially in relapse cases. Dose should be increased gradually to obtain a maximum effect and can be administered alone or in combination with phenytoin or carbamazepine.
Neurosurgical procedure are applied to cases that are unresponsive to drug therapy and consist of:
- Microvascular decompression;
- Percutaneous radiofrequency rhizotomy;
- Percutaneous radiofrequency trigeminal gangliolysis;
- Percutaneous microcompression with balloon inflation;
- Gamma knife surgery.