Understanding Hemicrania Continua: What Causes It and How to Spot the Symptoms

If you’ve ever had a headache that just won’t quit—lasting for days, even weeks on one side of your head—you might be dealing with a condition called hemicrania continua. It’s not a typical headache, and it’s definitely not “just stress.” In fact, it’s a rare but real chronic headache disorder that can significantly affect your quality of life.

Let’s break down what hemicrania continua is, what causes it, and how to recognize its symptoms so you can get the help you need. 

What Is Hemicrania Continua?

Hemicrania continua is a long-lasting headache that only affects one side of the head—hence the name “hemicrania,” meaning “half skull.” What makes this condition stand out is that the pain is continuous. It’s there every day, without going away completely, although it may fluctuate in intensity, for as long as months.

Some people experience flare-ups—periods when the pain becomes much more intense and is accompanied by other symptoms like eye tearing, nasal congestion, or drooping eyelids on the affected side. (More on this below.)

What Causes Hemicrania Continua?

The exact cause of hemicrania continua isn’t fully understood. Like many headache disorders, it appears to involve changes in brain function, particularly in areas that control pain perception. There’s some evidence suggesting that the trigeminal nerve—a nerve responsible for facial sensation and pain—may play a role.

Hemicrania continua may also have something to do with parts of the brain that regulate autonomic functions (things your body does automatically, like breathing or tear production). The autonomic nervous system is made up of two main divisions: the parasympathetic nervous system (known as the “rest and digest” system”) and the sympathetic nervous system (responsible for your body’s “fight or flight” response). Hemicrania continua has been associated with overactivity of the parasympathetic system and decreased sympathetic system activity.^[1]

While rare, in some cases, people have developed hemicrania continua after a head injury, neck trauma, or surgery.^[2] Researchers also believe that hormonal shifts and neurological imbalances could be contributing factors. The fact of the matter is that many people don’t have a clear trigger at all.^[3]

What makes this condition even more frustrating is that standard brain imaging (like MRIs or CT scans) usually looks normal, which can lead to delayed diagnosis.

Common Symptoms of Hemicrania Continua

Hemicrania continua can be tricky to identify because it mimics other types of chronic headaches, including migraine and cluster headache. But it does have some telltale signs. Some of the most common symptoms include:

• Constant, one-sided head pain – usually described as a dull ache or pressure.
• Pain that never completely goes away, although it may get worse at times.
• Episodes of increased intensity (called exacerbations) that can last from a few minutes to a few hours.
• Eye-related symptoms on the same side as the pain, including:
  • Redness
  • Tearing
  • Drooping eyelid (ptosis)
  • Pupil constriction (miosis)
• Nasal symptoms like congestion or runny nose on the same side.
• Sensitivity to light and sound during intense flare-ups

Why Early Diagnosis Matters

Because hemicrania continua is rare and shares symptoms with other headache disorders, it’s often misdiagnosed or overlooked. Many people go years thinking they have chronic migraine or sinus headaches. Getting the right diagnosis is crucial because it opens the door to more effective treatment options—and relief.

Finding Relief: A Non-Drug Option

One unique feature of hemicrania continua is that it typically responds very well to a medication called indomethacin, a type of nonsteroidal anti-inflammatory drug (NSAID). This “indomethacin response” is actually one of the key criteria doctors use to diagnose the condition.

While indomethacin is often effective, it’s not a long-term solution for everyone. It can cause side effects, especially when taken daily, such as stomach issues or kidney problems.

That’s where non-drug treatments, like gammaCore™ non-invasive vagus nerve stimulator (nVNS) can make a significant difference. gammaCore nVNS is FDA-cleared to treat and prevent certain types of headache disorders, including hemicrania continua. It works by gently stimulating the vagus nerve through the skin on the side of the neck, helping regulate pain signals without the need for medication. For people looking for a drug-free, clinically supported option, gammaCore can be an important part of their headache management toolkit.

Hemicrania continua is a chronic condition, but with the right diagnosis and treatment, relief is possible. If you’ve been dealing with one-sided headaches that never seem to go away, don’t dismiss it as just another bad headache. Talk to your doctor and explore your options—including non-drug therapies like gammaCore—to take control of your symptoms and get back to feeling like yourself.

To see if gammaCore is right for you, visit our clinic finder to locate a health care provider near you, or contact our dedicated Customer Experience team at 888-903-2673 or customerservice@electrocore.com.