Hemicrania continua is a persistent, one-sided headache that never fully goes away. It belongs to a group of headache disorders called trigeminal autonomic cephalalgias, meaning the pain travels along the trigeminal nerve (the main sensory nerve in your face) and triggers involuntary responses like tearing, nasal congestion, or eyelid drooping on the same side as the pain. It’s rare, affecting roughly 2 out of every 100,000 people, and it’s nearly three times more common in women than men.
What the Pain Feels Like
The defining feature of hemicrania continua is that the headache is always there. It stays on one side of the head, 24 hours a day, seven days a week, for at least three months. Most people describe a low-to-moderate baseline pain that never fully lifts, punctuated by flare-ups of moderate or severe intensity. These two components, the constant background ache and the sharper exacerbations on top of it, are both important for recognizing the condition.
During flare-ups, you may notice symptoms on the same side as the headache:
- Eye changes: redness, tearing, or drooping of the eyelid
- Nasal symptoms: congestion or a runny nose on one side
- Facial sweating: particularly across the forehead
- Pupil changes: the pupil on the affected side may appear smaller
- Restlessness or agitation: an inability to sit still during severe episodes
Not everyone gets all of these symptoms, but at least one needs to be present alongside the headache for a formal diagnosis. The autonomic features can be subtle enough that people don’t connect them to the headache until specifically asked.
How It Differs From Similar Headaches
Hemicrania continua is often confused with chronic migraine or another condition called paroxysmal hemicrania. The critical distinction is continuity. People with paroxysmal hemicrania experience five or more discrete attacks of severe pain per day, each lasting up to 30 minutes, but they are typically pain-free between attacks. With hemicrania continua, the pain never fully disappears. There is always some level of discomfort, even during the calmest stretches.
Migraine can also be one-sided and chronic, but it doesn’t produce the same pattern of autonomic symptoms on the painful side, and it doesn’t respond to the specific treatment that defines hemicrania continua.
Remitting vs. Continuous Forms
The condition comes in two subtypes. In the continuous form, the headache is unbroken for months or years with no pain-free periods. In the remitting form, people experience stretches of daily headache interrupted by weeks or months of complete relief before the pattern returns. Pooled data from case series show the continuous form is roughly 1.8 times more common than the remitting form. The average age of onset is around 40, though cases have been reported in people as young as 5 and as old as 76.
How It’s Diagnosed
There is no blood test or brain scan that confirms hemicrania continua. Imaging is typically used to rule out other causes of persistent one-sided headache, like a structural lesion or blood vessel abnormality. The actual diagnosis rests on two things: the clinical pattern described above, and a complete response to indomethacin, a specific anti-inflammatory medication.
This response to indomethacin isn’t just helpful, it’s required. The International Headache Society’s diagnostic criteria state that hemicrania continua is “absolutely sensitive” to indomethacin, meaning the headache must resolve completely when treated with it. Some clinics use a formal test: an injection that should relieve the headache within 30 to 50 minutes. If it does, the diagnosis is essentially confirmed. If it doesn’t, the headache is something else.
This can be a double-edged sword. Because hemicrania continua is uncommon, many people cycle through years of migraine treatments before anyone tries indomethacin. The average diagnostic delay can stretch well beyond a decade in some case series.
Treatment With Indomethacin
Indomethacin is both the diagnostic test and the primary treatment. For most people, the headache disappears entirely within hours to days of starting the medication. The relief can feel dramatic after years of unrelenting pain.
The challenge is that indomethacin is a strong anti-inflammatory drug, and long-term use can irritate the stomach lining. In studies tracking patients over months and years, about 23% reported side effects, mostly gastrointestinal. Stomach-protective medications are commonly prescribed alongside it to reduce this risk. Kidney function and blood pressure also need periodic monitoring, since all drugs in this class can affect both over time.
An important reality: stopping indomethacin typically means the headache returns. For people with the continuous form, this often means taking the medication indefinitely. Finding the lowest effective dose becomes a practical priority, and many people can maintain relief on a modest daily amount once the initial flare is controlled.
When Indomethacin Isn’t an Option
Some people cannot tolerate indomethacin because of stomach problems, kidney concerns, or allergies. In those cases, alternatives exist, though none work as reliably. Options that have shown benefit in individual cases include COX-2 inhibitors (a related but gentler class of anti-inflammatory), topiramate, gabapentin, melatonin, and several others. The response to these alternatives varies widely from person to person, and finding the right one often involves trial and error.
For people whose headaches resist all medications, nerve stimulation has shown promise. A small long-term study of six patients with medically intractable hemicrania continua found that occipital nerve stimulation, where a small device delivers electrical pulses to the nerves at the back of the head, produced substantial improvement (80 to 95% reduction in pain) in four of the six patients at a median follow-up of about 13 months. Five of the six said they would recommend the device to others. This remains a specialized option, typically reserved for cases where nothing else works, but it offers a meaningful path forward for people who have run out of pharmaceutical choices.