Trigeminal neuralgia: ICHD-3 criteria and treatment

Brief, electric, triggered unilateral facial pain is trigeminal neuralgia; image every patient with MRI, start carbamazepine or oxcarbazepine, and offer microvascular decompression for classical disease when drugs fail or are not tolerated.

1. ICHD-3 defines the attack. Recurrent unilateral paroxysms in one or more trigeminal divisions, lasting a fraction of a second to 2 minutes, severe, shock-like or stabbing, and provoked by innocuous stimuli in the affected territory. Pain may spread to another division but stays within trigeminal dermatomes ¹.
2. Classical means compression with root change. Classical trigeminal neuralgia requires MRI or surgical demonstration of neurovascular compression, not simple contact, with morphological change such as atrophy or displacement of the root ².
3. MRI is mandatory. EAN advises high-resolution MRI in every patient because no clinical feature excludes secondary trigeminal neuralgia ³.
4. Carbamazepine or oxcarbazepine first. These are first-choice drugs; lamotrigine, gabapentin, pregabalin, baclofen, botulinum toxin A and phenytoin may be used alone or as add-ons ³.
5. Surgery when drugs fall short. Offer surgery if pain is insufficiently controlled or drugs are poorly tolerated; microvascular decompression is first-line surgery in classical disease, and neuroablation is preferred when MRI shows no neurovascular contact ³.
6. Screen before carbamazepine. Its boxed warnings cover SJS/TEN, strongly linked to HLA-B*1502 in at-risk Asian ancestry, and aplastic anemia and agranulocytosis ⁴.

Oxcarbazepine is not a safe workaround for HLA-B*1502 carriers, and it causes clinically significant hyponatremia; check sodium, especially with diuretics or other sodium-lowering drugs ⁵.

• Neurovascular contact on MRI should not be used to confirm the diagnosis; it helps decide on referral for decompression ³.
• Acute exacerbations can be treated with intravenous fosphenytoin or lidocaine ³.
• Carbamazepine for trigeminal neuralgia starts at 200 mg/day, rising by up to 200 mg/day as needed, not exceeding 1200 mg ⁴.
• Most patients are maintained on 400–800 mg/day; try to reduce or stop the dose at least every 3 months ⁴.
• Carbamazepine is not a simple analgesic and should not be used for trivial aches ⁴.
• Oxcarbazepine hyponatremia below 125 mmol/L occurred in about 2.5% in controlled epilepsy studies ⁵.
• ICHD-3 secondary causes include multiple sclerosis and space-occupying lesions; classical and idiopathic forms may be purely paroxysmal or have concomitant continuous pain ¹.
• Secondary trigeminal neuralgia is generally treated on the same principles as primary disease ³.

• Skipping MRI because the history is typical; no clinical feature excludes a secondary cause ³.
• Assuming decompression is clearly superior in idiopathic disease; EAN makes no recommendation between it and neuroablation ³.
• Diagnosing classical disease from vascular contact alone ².
• Switching an HLA-B*1502 carrier to oxcarbazepine as if it were risk-free ⁵.