Hemicrania continua is a rare headache disorder that causes a continuous, one-sided headache lasting three months or longer, with episodes of worsening pain. It belongs to a group of conditions called trigeminal autonomic cephalalgias, and its defining feature is that it responds completely to a medication called indomethacin.
That response to indomethacin is not just a treatment detail. It is part of how the condition is diagnosed. The pain does not switch sides. It stays on one side of the head, day and night, for months or years if it is not treated. Between the steady background pain, there are bouts of severe throbbing that can last minutes to days.
What Is Hemicrania Continua Causes Symptoms Treatment?
Hemicrania continua is a primary headache disorder, meaning it is not caused by another medical condition. It is classified as a trigeminal autonomic cephalalgia, a family that also includes cluster headache and paroxysmal hemicrania.
The name breaks down simply. “Hemicrania” means one-sided head pain. “Continua” means continuous. The hallmark is a moderate, persistent headache on one side that never fully goes away, interrupted by flares of more intense pain.
What causes it is not fully understood. Researchers believe the hypothalamus, a region deep in the brain that helps regulate the body’s internal clock, plays a role. The trigeminal nerve, which carries sensation from the face and head, and the autonomic nervous system, which controls functions like tearing and nasal congestion, are also involved. But the exact trigger remains unknown.
There is no evidence that hemicrania continua is caused by stress, diet, or lifestyle. It is not a sign of a brain tumor or another structural problem. It is a distinct neurological condition with its own diagnostic criteria.
How Common Is Hemicrania Continua?
Hemicrania continua is rare. It is far less common than migraine or tension-type headache. Because it is uncommon and often mistaken for other headache types, the true number of people affected is not known with certainty.
It can begin at any age, but it most often starts in adulthood. Some research suggests it affects women more often than men, though the evidence on this point is not entirely consistent across studies.
Many people with hemicrania continua go years without a correct diagnosis. They are frequently told they have chronic migraine or cluster headache. This delay matters because the treatment for hemicrania continua is different from the treatment for those conditions.
What Are the Symptoms of Hemicrania Continua?
The central symptom is a continuous, one-sided headache. The pain is usually moderate but can be severe during flares. It does not change sides. If the pain moves from one side of the head to the other, hemicrania continua is unlikely.
Along with the pain, many people have symptoms linked to the autonomic nervous system on the same side as the headache. These can include:
- Redness or tearing of the eye
- Drooping or swelling of the eyelid
- Nasal congestion or a runny nose
- A sense of restlessness or agitation during flares
- Sensitivity to light or sound
These autonomic symptoms are a key reason hemicrania continua is grouped with cluster headache and similar conditions. They reflect activation of the trigeminal-autonomic reflex, a nerve pathway that connects the trigeminal nerve to the autonomic system.
The severity of symptoms varies. Some people have mostly background pain with occasional flares. Others have frequent, intense flares that disrupt sleep, work, and daily life.
How Is Hemicrania Continua Diagnosed?
Diagnosis rests on three things: the pattern of symptoms, the exclusion of other conditions, and the response to indomethacin.
The International Classification of Headache Disorders sets out the criteria. These include a one-sided headache lasting more than three months, moderate or severe pain with flares, and at least one autonomic symptom on the same side, among other features.
The indomethacin test is central. A doctor gives a course of indomethacin, and if the headache disappears completely, that strongly supports the diagnosis. A complete response is the expected result. A partial response or no response points toward a different diagnosis.
Imaging such as an MRI may be ordered to rule out other causes of one-sided headache, including problems in the brain or blood vessels. This is done to be thorough, not because hemicrania continua shows up on scans. It does not.
How Is Hemicrania Continua Treated?
Indomethacin is the established treatment, and it is remarkably effective for this condition. Most people who have hemicrania continua get complete relief from their headache when they take an adequate dose.
Indomethacin is a nonsteroidal anti-inflammatory drug, or NSAID. It is usually taken by mouth. Because it must be taken regularly to keep the headache away, and because NSAIDs carry risks with long-term use, doctors monitor patients carefully.
Long-term NSAID use can cause stomach irritation, ulcers, and kidney problems. To reduce stomach risk, indomethacin is sometimes combined with a medication that protects the stomach lining. Some clinicians recommend periodic blood tests to check kidney function and other markers during ongoing treatment.
When indomethacin cannot be tolerated or does not work, doctors may try other options. These include other NSAIDs, certain medications also used for migraine, and in some cases nerve blocks or other interventions. The evidence for these alternatives is much weaker than for indomethacin. They are used when the standard treatment is not an option, not because they are well proven.
It is worth being clear about the limits here. There is no cure for hemicrania continua. Treatment controls the headache. When treatment stops, the headache typically returns.
How Does Hemicrania Continua Compare to Other Headaches?
Hemicrania continua is often confused with other one-sided headache conditions. The differences matter because the treatments differ.
| Condition | Pain Pattern | Response to Indomethacin |
|---|---|---|
| Hemicrania continua | Continuous one-sided pain with flares | Complete relief |
| Cluster headache | Attacks lasting 15 to 180 minutes, often in clusters | Usually no response |
| Paroxysmal hemicrania | Frequent short attacks, one-sided | Complete relief |
| Chronic migraine | Headache on 15 or more days per month, often both sides | Usually no response |
The overlap between hemicrania continua and paroxysmal hemicrania is notable. Both respond completely to indomethacin. The main difference is the pattern. Paroxysmal hemicrania comes in short, frequent attacks with pain-free periods between them. Hemicrania continua is continuous, with no fully pain-free periods.
Cluster headache does not respond to indomethacin in the same way, which is one of the clearest ways to tell the conditions apart.
What Is the Outlook for People With Hemicrania Continua?
For most people, the outlook is good once the condition is correctly identified. Indomethacin usually controls the headache completely, allowing a return to normal daily life.
The challenge is getting the diagnosis in the first place. Because the condition is rare and often mistaken for migraine or cluster headache, many people spend years on treatments that do not help.
Hemicrania continua is generally a long-term condition. Some people have periods where it eases, and others have it continuously. The evidence on how it changes over many years is limited, so it is hard to predict the long-term course for any one person.
Anyone with a continuous one-sided headache lasting more than three months should see a doctor, ideally a neurologist or headache specialist. A headache that never goes away, especially with eye or nasal symptoms on the same side, is a pattern worth evaluating properly.
Frequently Asked Questions
Is hemicrania continua the same as a migraine?
No. Hemicrania continua is a separate diagnosis with continuous one-sided pain that never fully goes away, while migraine typically comes in episodes. The two conditions also respond to different treatments, with hemicrania continua responding completely to indomethacin.
Does hemicrania continua ever go away on its own?
It is generally a long-term condition, and there is no reliable evidence that it resolves without treatment. Some people experience periods where symptoms ease, but the pattern varies and is hard to predict.
Why does indomethacin work for hemicrania continua?
The exact reason is not known, but the complete response to indomethacin is a defining feature used to confirm the diagnosis. It is not fully understood why this specific drug works so well when others do not.
Can hemicrania continua affect both sides of the head?
No. By definition, the pain stays on one side of the head. If the pain switches sides, another diagnosis should be considered.
