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Trigeminal neuralgia is characterized by recurrent paroxysms of sharp pain radiating into the territory of one or more of the trigeminal sensory divisions and lasting seconds to minutes. The pain is often described as lancinating, stabbing, burning, or simulating an electric shock. Attacks may occur several times a day or a few times a month, with periods of spontaneous relapse and remission.
Proposed causes
The cause of trigeminal neuralgia is unknown, but several theories have been proposed implicating both the central and peripheral nervous systems. One view hypothesizes that redundant or tortuous blood vessels in the cerebellopontine angle impinge on the trigeminal sensory root to cause pain, and studies have reported this finding in a high percentage of patients with trigeminal neuralgia.
Features of the pain
In most patients, the diagnosis is made on the basis of facial pain that has trigeminal nerve distribution. Triggering stimuli are often reported and may include touching or washing the face, brushing the teeth, exposure to cold, chewing, and even talking. Most trigger points are in the central portion of the face, nose, and lips. During an attack, patients may cease all activity and barely move a muscle. They may even refrain from eating, resulting in trigeminal nuralgia.
The pain is typically unilateral, with the right side affected more often. Bilateral pain is found in 3% to 5% of patients.
Physical examination
The stabbing pain of trigeminal neuralgia most often affects the mandibular division, less often the maxillary division, and least often the ophthalmic division.2 Usually, no numbness or other objective findings in the distribution of the trigeminal nerve are noted.
Differential diagnosis
The face is a highly innervated area, and many conditions may partially or closely mimic trigeminal neuralgia. Careful history taking can exclude many causes of facial pain, including the following conditions:
• Common cluster headaches, although characterized by paroxysmal pain in the periorbital area, are usually accompanied by tearing.
• Postherpetic neuralgia, characterized by pain in the distribution of the trigeminal nerve, produces constant rather than paroxysmal
• Glossopharyngeal neuralgia is characterized by lancinating pain deep in the throat that often radiates to the ear.
• Dental infection may cause throbbing facial pain but is accompanied by swelling and alveolar pain.
• Temporomandibular joint pain is characterized by dull, preauricular pain that radiates to the jaw, temple, eye, and neck.
• Psychogenic facial pain usually does not follow the neurogenic pattern of distribution.
Treatment
The immediate aim of treatment of trigeminal neuralgia is elimination of pain. Medical and surgical treatment methods.
Medical therapy
The most effective pharmacologic agent is carbamazepine. It is usually started at 100 mg twice a day and can be increased to 200 mg.
four times a day for severe pain. Carbamazepine provides relief in 70% to 90% of patients. In fact, it is so effective that if patients with trigeminal neuralgia do not respond, other diagnoses should be considered.
Patients who cannot take or do not respond to carbamazepine can be given phenytoin (Dilantin), 300 to 400 mg twice a day. Phenytoin is not as effective as carbamazepine, providing sustained relief in only 20% of patients? It, too, has well-known side effects (eg, drowsiness, ataxia, diplopia), and about 10% of patients cannot tolerate the agent? Its main use is as a synergistic agent with baclofen (Lioresal) in patients who cannot tolerate carbamazepine.
Baclofen can be used in patients who do not respond to carbamazepine or phenytoin. It is started at 5 to 10 mg three times a day.
Method Initial Advantage Disadvantage(s)
MEDICAL
Carbamazepine 100 bid Most Side effects; effective
Phenytoin 300-400 bid Synergistic effect Less effective
(Dilantin) with baclofen
Baclofen 5-10 tid Fewer side Less effective
(Lioresal) effects
SURGICAL
Glycerol injection Effective High recurrence rate
Radiofrequency Effective Facial numbness, loss
thermocoagulation of corneal reflex
Microvascular Very effective Invasive procedure
decompression
Surgical therapy
When all medical treatment options have been exhausted, invasive treatment inevitably becomes necessary in patients with severe pain. The many hypotheses for the cause of trigeminal neuralgia have led to different surgical approaches.
Injection of glycerol, a neurotoxin, into the trigeminal ganglion can produce a ganglioplegic effect.
Radiofrequency thermocoagulation of the trigeminal ganglion and its posterior rootlets can destroy some of the hyperirritable axons responsible for the painful attacks, thus producing pain relief. Unfortunately, this method causes partial numbness of the face.
Microvascular decompression of the trigeminal nerve is the surgical procedure that produces the best results. Proponents believe that microvascular compression of the trigeminal nerve roots induces demyelinization and other secondary effects in the trigeminal nuclei, which may be responsible for intermittent bursts of neuronal hyperactivity that cause the typical attacks of trigeminal neuralgia. More than 80% of patients obtain pain relief with microvascular decompression, and when the procedure is fully successful, there are no However, because of the risks that accompany any major neurologic surgery.