Hemicrania Continua
Hemicrania continua: the one-sided headache that never fully stops
Hemicrania continua causes constant, one-sided head pain that goes on for months or years — with no pain-free intervals. If that description fits you, there is one important thing to know: this condition responds completely to a single medication, and finding the right diagnosis can change your life.
Key takeaways
- Hemicrania continua causes continuous, strictly one-sided head pain that lasts at least three months without switching sides.
- It is classified as a trigeminal autonomic cephalgia (TAC) — a group of headache disorders that cause pain on one side of the face and head along with eye or nose symptoms.
- The condition responds completely to therapeutic doses of indomethacin — and that response is itself part of the diagnostic criteria.
- It is often misdiagnosed as migraine, cluster headache, or sinus headache, sometimes for years.
- A headache specialist can confirm the diagnosis and guide safe, long-term management.
What is hemicrania continua?
Hemicrania continua (HC) is a primary headache disorder — meaning the headache itself is the condition, not a symptom of something else. It was first described in 1981 and formally classified as a trigeminal autonomic cephalgia (TAC) in the third edition of the International Classification of Headache Disorders (ICHD-3).¹
The name translates from Latin: "hemicrania" means one-sided head pain, and "continua" means continuous. Unlike migraine or cluster headache, which come and go, hemicrania continua involves a constant, baseline level of pain that never fully disappears on the affected side.
On top of that baseline, most people also have exacerbations — flare-ups of more intense pain — that can last anywhere from a few minutes to hours.
What does it feel like?
The ICHD-3 diagnostic criteria for hemicrania continua require all of the following:¹
- Continuous, strictly one-sided head pain lasting more than three months
- Moderate baseline pain that fluctuates, with exacerbations of severe pain
- At least one of the following during exacerbations, on the same side as the pain:
- Red or watery eye (conjunctival injection or lacrimation)
- Nasal congestion or runny nose
- Drooping eyelid or constricted pupil (ptosis/miosis)
- Eyelid swelling
- Sweating of the forehead or face
- Sense of restlessness or agitation
During a bad flare, the pain can feel sharp, stabbing, or throbbing. Some people also notice light sensitivity, sound sensitivity, or nausea — which is part of why hemicrania continua is so often mistaken for migraine.
One critical feature: the pain never switches sides. If you go to bed hurting on the right and wake up hurting on the left, hemicrania continua is not the diagnosis.
How is hemicrania continua different from migraine?
This is where many people spend years in diagnostic limbo. The conditions share some features — one-sided pain, sensitivity to light and sound, nausea — but there are clear differences.
The most important difference is indomethacin. Migraine does not respond completely to this medication. Hemicrania continua does — and that response is both diagnostic and therapeutic.
How is it diagnosed?
Diagnosing hemicrania continua is clinical, meaning it relies on your history and a careful exam rather than a blood test or scan.² Your clinician will ask detailed questions about where the pain is, whether it ever goes away completely, what other symptoms occur with flare-ups, and how long this has been going on.
Because secondary causes of continuous unilateral headache need to be ruled out, brain imaging — typically an MRI with contrast — is generally recommended before confirming the diagnosis.²
The diagnostic test that matters most is an indomethacin trial. An oral course is typically started at 150 mg daily and increased up to 225 mg daily if needed.¹ A complete response — the pain goes away entirely — confirms the diagnosis. An intramuscular injection of 50–100 mg, called the "Indotest," can produce a diagnostic response within two hours in a clinical setting.³
One population-based study found hemicrania continua present in about 2.2 people per 100,000 in the general population.³ Among people being evaluated for headache in specialty clinics, the rate is estimated at around 1.8%.³ These figures likely undercount the condition because it is so often misdiagnosed.
Why is hemicrania continua so often missed?
The delay between symptom onset and correct diagnosis can stretch to years, sometimes decades. Several factors drive this:
The condition is genuinely rare, so many clinicians — including some generalists — have limited experience with it. Its symptoms overlap with migraine and cluster headache, which are far more commonly known. And because it involves a continuous, background pain rather than discrete attacks, people with HC sometimes describe it in ways that don't immediately suggest the diagnosis — "I always have a headache," "my head just never feels right on this side."
Hemicrania continua has also been misdiagnosed as sinus headache (because of the nasal symptoms), cervicogenic headache (because of associated neck pain), and even dental pain. A headache specialist familiar with the full spectrum of primary headache disorders is best positioned to sort through these possibilities.
What is the treatment?
Indomethacin is the cornerstone of treatment and, when the diagnosis is correct, it works.² Most people achieve complete or near-complete relief. Maintenance doses — often lower than the doses used to confirm the diagnosis — are used long-term for most patients.
The main challenge with indomethacin is gastrointestinal side effects: nausea, stomach pain, and ulcer risk. Taking it with food and a stomach-protecting medication (a proton pump inhibitor) significantly reduces these risks. Regular monitoring of kidney function is also recommended with long-term use.
For people who cannot tolerate indomethacin, alternatives have been used with varying success:²
- COX-2 inhibitors such as celecoxib
- Topiramate (an anti-seizure medication also used in migraine prevention)
- Gabapentin
- Melatonin
- Nerve blocks (occipital or sphenopalatine ganglion)
None of these alternatives have the same level of evidence as indomethacin. If you cannot take indomethacin, the conversation with your clinician about alternatives is important and worth having with a headache specialist who knows the literature.
Are there subtypes?
Yes. The ICHD-3 recognizes two subtypes:¹
- Unremitting: pain is present every day with no pain-free periods lasting 24 hours or longer, for at least one year.
- Remitting: continuous pain is interrupted by pain-free periods of at least 24 hours — meaning some people do experience spontaneous remissions.
Knowing your subtype can influence how your clinician approaches dose management, particularly whether to taper indomethacin during pain-free periods.
Frequently asked questions
Is hemicrania continua a type of migraine?
No — they are separate diagnoses with distinct features. Hemicrania continua is classified as a trigeminal autonomic cephalgia in ICHD-3, not as a migraine subtype. The two can coexist in the same person, which adds to diagnostic complexity, but the treatment approaches differ significantly.
Will I need indomethacin forever?
Many people do use it long-term, though some find they can taper during remission periods. The right approach depends on your subtype and how your body responds over time. This is a question to revisit regularly with your clinician.
Can hemicrania continua be cured?
There is no cure, but for most people the condition can be very well controlled with indomethacin. Many people on the right dose describe their pain as gone or near-gone. The key is getting the correct diagnosis so the right treatment can begin.
What if indomethacin doesn't work at all?
A complete lack of response calls the diagnosis into question. Your clinician may need to reconsider whether another headache disorder — such as new daily persistent headache or a secondary cause — better explains your symptoms. A partial response may still be consistent with HC; the diagnostic criteria require a complete response, but clinical reality is sometimes more nuanced.
Is hemicrania continua dangerous?
The headache itself is not dangerous — it is a primary headache disorder with a benign course. The main risks relate to long-term NSAID use (gastrointestinal and renal effects), which is why ongoing monitoring matters.
Getting the right diagnosis matters
Hemicrania continua is one of the more treatable headache disorders once it is correctly identified. If you have had constant one-sided head pain for months — pain that never fully goes away on that side, even on good days — it is worth bringing that description specifically to a headache specialist.
At Haven, we evaluate the full spectrum of headache and migraine disorders, including the rarer ones that often go undiagnosed for years. You don't have to keep living with a headache that has a name and a treatment. Learn more about care at Haven.
Medically reviewed by: Karissa Secora, DMSc, PA-C, AQH, Haven Headache & Migraine Center and peer reviewed by Nada Hindiyeh, MD, Haven Headache & Migraine Center
References
- Headache Classification Committee of the International Headache Society. The International Classification of Headache Disorders, 3rd edition — Hemicrania continua. https://ichd-3.org/3-trigeminal-autonomic-cephalalgias/3-4-hemicrania-continua/
- Mays E, Cyprian N. Hemicrania Continua. StatPearls [Internet]. 2024. https://www.ncbi.nlm.nih.gov/books/NBK557568/
- Vu L, Liao K. Hemicrania Continua: Diagnosis and Treatment. Neurology Advisor. 2026. https://www.neurologyadvisor.com/ddi/hemicrania-continua/
- Prakash S, Adroja B. Hemicrania continua: clinical review, diagnosis and management. J Headache Pain. 2017;18(1):66. https://pmc.ncbi.nlm.nih.gov/articles/PMC5499960/
This article is for general education and is not medical advice. It is not a substitute for care from a qualified health professional. Always talk with your clinician before starting, stopping, or changing any treatment. If you have a sudden, severe headache, the worst headache of your life, or a headache with new symptoms like weakness, trouble speaking, or vision loss, seek emergency care right away.