Clinical Pearls & Morning Reports
Trigeminal neuralgia is a chronic neuropathic pain disorder characterized by spontaneous and elicited paroxysms of electric shock–like or stabbing pain in a region of the face. Read the NEJM Review Article here.
Q: What are the criteria for the diagnosis of trigeminal neuralgia?
A: The diagnosis of trigeminal neuralgia is clinical and is based on three main criteria: pain restricted to the territory of one or more divisions of the trigeminal nerve; paroxysms of pain that are sudden, intense, and very short (<1 second to 2 minutes, but usually a few seconds) and are described as a “shock” or an “electric sensation”; and pain triggered by innocuous stimuli on the face or intraoral trigeminal territory. Triggered paroxysmal pain is particular to trigeminal neuralgia and is reported by 91 to 99% of patients.
Q: Can continuous pain be a feature of trigeminal neuralgia?
A: Although paroxysmal facial pain is the hallmark of trigeminal neuralgia, 24 to 49% of patients report continuous or long-lasting pain between paroxysmal attacks. Background fluctuating pain, with a distribution that is consistent with that of the paroxysmal pain, is described as burning, throbbing, or aching. The mechanism underlying continuous pain is different from the mechanism underlying paroxysmal pain, as suggested by the lesser degree of alleviation of continuous pain, as compared with paroxysmal pain, after treatment with sodium-channel blockers or microvascular decompression.
A: Three types of trigeminal neuralgia have been delineated: classical, secondary, and idiopathic. The classical type, which is the most common, is caused by intracranial vascular compression of the trigeminal nerve root. The responsible vessel is usually the superior cerebellar artery, which induces morphologic changes in the adjacent trigeminal nerve root. Secondary trigeminal neuralgia, which accounts for approximately 15% of cases, is attributable to an identifiable neurologic disease such as multiple sclerosis or a tumor in the cerebellopontine angle, which alters the root entry zone of the trigeminal nerve or otherwise compresses the nerve in its extracranial course. Idiopathic trigeminal neuralgia, in which no apparent cause of nerve disturbance can be found, accounts for approximately 10% of cases.
A: Carbamazepine and oxcarbazepine are the first-choice treatments for control of paroxysmal pain in patients with trigeminal neuralgia, regardless of the cause. Although these treatments are not supported by data from randomized, controlled trials, clinicians consider the drugs to be highly effective, with meaningful pain control in almost 90% of patients. However, clinical improvement is often offset by side effects, including dizziness, diplopia, ataxia, and elevated aminotransferase levels, one or more of which may lead to treatment withdrawal in 23% of patients. Gabapentin, pregabalin, and antidepressant agents, which have been shown to be effective in the treatment of other neuropathic conditions characterized by continuous pain, may be tried as additional agents along with oxcarbazepine or carbamazepine. Microvascular decompression has become the surgical procedure that is now favored for most cases of classical trigeminal neuralgia that do not respond to medication. The neurosurgeon identifies the vessel that is compressing the trigeminal nerve root, moves it from under the nerve to over the nerve if necessary, and typically inserts a small sponge to keep the pulsating artery separated from the nerve root. At 1 to 2 years after undergoing the procedure, 68 to 88% of patients have pain relief, and 61 to 80% have pain relief at 4 to 5 years.