Medication Summary
The goal of pharmacologic therapy is to reduce pain. Carbamazepine is regarded by most as the medical treatment of choice. Some advocate a trial of baclofen since it has fewer adverse effects. Oxcarbazepine may be better tolerated. The synergistic combination of carbamazepine and baclofen may provide relief from episodic pain though convincing clinical evidence is weak at best.
Other anticonvulsants including phenytoin, oxcarbazepine, clonazepam, lamotrigine, valproic acid, and gabapentin are reportedly beneficial in some patients; however, controlled trials have not been performed. The American Academy of Neurology published a practice parameter that concluded that carbamazepine is effective in controlling pain of patients with classic trigeminal neuralgia, and that oxcarbazepine is probably effective and may be better tolerated. [3] In another AAN guideline, baclofen, lamotrigine, and pimozide were rated as possibly effective. The practice parameter stated that there was insufficient evidence to support or refute efficacy of clonazepam, gabapentin, phenytoin, tizanidine, topical capsaicin, or valproate for pain control in patients with classic trigeminal neuralgia. [8] The writing group was unable to find sufficient evidence to support or refute the use of intravenous medications in acute exacerbations of trigeminal neuralgia.
A small randomized placebo-controlled trial using intraoral 8% lidocaine applied by the patient to the painful oral area suggested some benefit in patients with trigeminal neuralgia and severe intraoral pain. [14] More study is needed.
Anticonvulsants
Class Summary
These agents may help control paroxysmal pain by limiting the aberrant transmission of nerve impulses.
Carbamazepine (Tegretol)
Anticonvulsant effective in the treatment of psychomotor and grand mal seizure. DOC for TN. May reduce polysynaptic responses and block post-tetanic potentiation.
Once patient responds to therapy, attempt to reduce dose to minimum effective level, or attempt to discontinue at 3-mo intervals.
Skeletal muscle relaxants
Class Summary
These agents are useful in the treatment of TN, although not FDA-approved for this indication. They have CNS depressant properties as indicated by the production of sedation with somnolence, ataxia, and respiratory and cardiovascular depression. A recent review of nonepileptic drugs for trigeminal neuralgia concluded that there was insufficient evidence from randomized controlled trials to show significant benefit from nonantiepileptic drugs. [15]
Baclofen (Lioresal)
Most often used after therapy with carbamazepine has been initiated. Effects may be synergistic with those of carbamazepine. May induce hyperpolarization of afferent terminals and may inhibit both monosynaptic and polysynaptic reflexes at spinal level. As a structural analog of the inhibitory neurotransmitter GABA, may stimulate GABA-B receptor subtype.
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Microscopic demonstration of demyelination in primary trigeminal neuralgia. A tortuous axon is surrounded by abnormally discontinuous myelin. Electron microscope, 3, 300 X.
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MRI with high resolution on the pons demonstrating the trigeminal nerve root. In this case, the patient with trigeminal neuralgia has undergone gamma-knife therapy, and the left-sided treated nerve (arrow) is enhanced by gadolinium.
