A man in his fifties came to see me after two years on carbamazepine for “trigeminal neuralgia.” The drug helped, some — his neurologist back home had gotten the dose up to 800 mg a day — but he was still getting twenty, thirty stabs of pain around his right eye on a bad day, and every time, that eye would go red and start watering before the pain even faded. If your facial pain medicine is only half-working and one eye reacts during the attacks, the diagnosis may be wrong. What he had wasn’t classic trigeminal neuralgia. It was SUNCT — a different, rarer condition that responds to a different drug.
SUNCT (Short-lasting Unilateral Neuralgiform headache attacks with Conjunctival injection and Tearing) and its close cousin SUNA (the same thing without both of those eye signs) are two of the more overlooked diagnoses in headache medicine. They get lumped in with trigeminal neuralgia because both cause brief, severe, one-sided facial stabs. But they’re a different disease, they show up on brain imaging differently, and — this is the part that matters in clinic — they barely respond to the drug most people are handed first.
The clue most people — and some doctors — miss
Classic trigeminal neuralgia is electric, split-second, and quiet: a fraction of a second of pain, then nothing, often with a brief window afterward where touching the trigger spot again won’t set it off. SUNCT and SUNA attacks are built differently. Under the ICHD-3 diagnostic criteria, they last anywhere from one second up to ten minutes, can come as a single stab, a series of stabs, or a “sawtooth” run of pain that climbs and falls, and — critically — at least one of the eye or nose runs with it: tearing, a red eye, a stuffy or runny nostril, or eyelid swelling on the same side as the pain. Patients often mention this detail only when asked directly, because nobody told them it mattered. It’s the single most useful thing you can tell your doctor if your “trigeminal neuralgia” isn’t behaving the way trigeminal neuralgia should.
The other tell is frequency. True trigeminal neuralgia usually comes in clusters of attacks with real pain-free stretches between them. SUNCT can fire dozens to over a hundred times in a single day. If you’re counting attacks in the double or triple digits, that number alone should reopen the diagnostic question.
Why carbamazepine doesn’t fully work
This is the piece that changes management. Carbamazepine and oxcarbazepine are excellent for genuine trigeminal neuralgia — most patients get substantial relief. In SUNCT and SUNA, the response rate to carbamazepine is far lower, in the range of a quarter of patients. Lamotrigine, not carbamazepine, is the drug with the best track record here, with meaningfully better response rates in the published case series and the one placebo-controlled trial we have. Oxcarbazepine, topiramate, duloxetine, gabapentin, and pregabalin are the other options tried when lamotrigine alone isn’t enough. So if you’ve been pushed to a high dose of carbamazepine and you’re still breaking through with attacks — and especially if your eye is doing something during them — that’s not a sign to just push the dose higher. It’s a sign the underlying diagnosis needs a second look.
The scan that has to happen before we settle on this diagnosis
I don’t order an MRI for every headache — for straightforward migraine with a normal exam, it usually isn’t necessary. SUNCT and SUNA are the exception. A meaningful minority of cases turn out to be secondary to a structural problem: a pituitary lesion, a posterior fossa abnormality, a cerebellopontine angle tumor, or a blood vessel pressing on the trigeminal nerve root. Because of that, dedicated brain MRI with attention to the pituitary and posterior fossa is standard before a primary SUNCT/SUNA diagnosis is finalized, not an optional extra. If you’ve been treated for months on facial pain medication and nobody has ordered imaging, that’s worth raising directly at your next visit.
What actually helps once the label changes
Lamotrigine is first-line, but it has to be started low and titrated up slowly over several weeks — that’s not a formality, it’s how the risk of a serious rash is kept low, so patience with the titration schedule matters more than it does with most headache preventives. For a bad flare that needs to be broken quickly, a short inpatient course of intravenous lidocaine can shut down a cluster of attacks while an oral preventive is being titrated up. Occipital nerve blocks are sometimes used as a bridge as well. For the small number of patients who don’t respond to medication at all, occipital nerve stimulation and, in carefully selected cases with a compressive vessel identified on imaging, microvascular decompression are options worth discussing with a headache specialist or neurosurgeon.
None of this is a reason to panic — SUNCT and SUNA are rare, and most facial stabbing pain really is ordinary trigeminal neuralgia responding to carbamazepine as expected. But if your current treatment has plateaued at “partly better,” the eye on the painful side is doing something during attacks, or nobody has scanned your brain yet, it’s a reasonable, specific thing to bring up. For a broader look at why headache and facial pain treatment sometimes stalls even when you’re doing everything you were told, I’ve written more on why your headache isn’t getting better. If facial pain has been the working diagnosis, it’s also worth reading my guide to trigeminal neuralgia treatment to see how your case compares, and my piece on a related pattern of misdiagnosis in cluster headache that’s actually paroxysmal hemicrania. If imaging hasn’t been done yet, this piece on what a normal MRI actually rules out is a useful next read.
Free resource: not sure whether your symptoms need urgent attention? Use my free headache red-flag checklist to check. If you’d like a second opinion on a facial pain or headache diagnosis that isn’t responding the way it should, you can book a consultation here.
This article is for educational purposes and does not replace an in-person medical evaluation. It is not a substitute for individualized care from your own physician. If you’re experiencing a sudden, severe, “worst headache of your life,” new neurological symptoms, or any emergency warning sign, seek emergency care immediately.
From the textbook. Chapter 29, “SUNCT and SUNA: Short-lasting Unilateral Neuralgiform Headache Attacks,” of my clinical textbook Headache Medicine covers this topic in full for doctors, with the evidence and decision pathways behind it. About the book →