What Is Cluster Headache? Symptoms, Types, and Diagnosis
Reviewed by the Clusterbusters Medical Board
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Think you might have cluster headache? Start with our free diagnostic tool.
If you have never had a cluster headache, it is hard to describe what one feels like. An icepick driven behind the eye. A hot poker. A brain freeze that lasts an hour instead of a few seconds. None of these quite capture it, because cluster headache is widely considered one of the most painful conditions known to medicine.
The high frequency and intensity of the attacks dramatically decreases quality of life and may lead to suicidal ideations, as this condition is nicknamed “Suicide Headaches”.
This page covers what cluster headache actually is, what we know about why it happens, and how it differs from other headache conditions it is often mistaken for. If you suspect you or someone you love may have cluster headache, this is a starting point. You are not alone, and there are people in this community who have been where you are.
Key Takeaways
Cluster headache is widely considered one of the most painful conditions known to medicine, with attacks rated more severe than childbirth, kidney stones, and gunshot wounds.
Attacks come on fast, peak within minutes, last 15 minutes to 3 hours, and strike one side of the head around the eye or temple, often several times a day at the same time.
The condition comes in two forms: episodic (attacks in cycles with remission of at least a month) and chronic (near-daily attacks for more than a year). The difference is about cycle pattern, not pain intensity.
It is often mistaken for migraine, but the two differ in pain quality, duration, behavior during an attack (restlessness versus lying still), and the treatments that work.
It affects roughly 1 in 1,000 people, and the average patient waits about 6.6 years for an accurate diagnosis.
What is Cluster Headache? Symptoms & Signs
Cluster headache attacks come on fast, peak within minutes, and can last anywhere from 15 minutes to three hours. They strike one side of the head, usually centered around the eye or temple, and can hit several times a day, often at the same time each day.
The pain is so intense that it has earned an unwanted nickname in the medical community: the suicide headache. A cluster headache attack is rated to be significantly more painful than childbirth, kidney stones, gunshot wounds, and bone fractures. The chart below is a result of survey data collected from people that have suffered both pain events. For example, women that have given birth are the ones comparing their cluster attack pain to the pain they felt in childbirth.
These attacks cause patients to exhibit agitation and restlessness such as pacing and hitting themselves. Cluster headaches are typically localized around the eye and temple and may come with several one-sided autonomic symptoms like swollen or droopy eyelid, teary or red eye, forehead or facial sweating, runny or stuffy nose. While cluster headaches only affect one side of the head, they can switch sides.
How much does a cluster headache hurt?
In a survey of 1,604 patients, cluster headache was rated more intense than every other pain disorder examined, including childbirth and kidney stones.
72.1%
“Cluster headache is one of the most intensely painful human conditions.”
Source: Burish et al., Headache 2021;61(1):117–124.
View Study →
clusterbusters.org
In the video below, Dr. Mark Burish shares data, studies and examples of the painful event that is Cluster Headache.
Episodic vs. Chronic Cluster Headache
Cluster headache comes in two forms. About 85 to 90 percent of people with the condition have the episodic form. The remaining 10 to 15 percent have the chronic form.The distinction matters because some treatments work for one and not the other.
Episodic cluster headache means attacks come in cycles that usually last 6 weeks to 3 months and then completely remit for a month or longer. Many people with episodic cluster headache experience cycles in the spring or fall, almost like clockwork.
Chronic cluster headache means attacks happen on a daily or near-daily basis for more than a year, with no remission or with breaks that last less than a month. Chronic patients may go through high and low periods, but they do not experience the same true remission that episodic patients do.
The diagnostic criteria for chronic clusters vs. episodic have nothing to do with intensity or quantity of attacks. It’s about distinctive cycles versus a never ending cycle. Regardless of which form you have, the official diagnostic criteria from the International Headache Society require:
- Severe one-sided pain, located around the eye, temple, or forehead, lasting between 15 minutes and three hours
- Attack frequency between one every other day and eight or more per day
- At least one of the following autonomic symptoms on the same side as the pain:
- Red or watery eye
- Drooping or swollen eyelid
- Runny or stuffy nose
- Forehead or facial sweating
- Constricted pupil
- Restlessness or agitation during an attack (people with cluster headache often pace, rock, or hit themselves; this is different from migraine, where people typically want to lie still in a dark room)
There is also a category called "probable cluster headache" for people who meet all but one of these criteria. For example, restlessness is considered to be a differential symptom and can lead to a cluster headache diagnosis even if the person doesn’t experience a watery eye, drooping eyelid or runny nose.
In the video below, Dr. Mark Burish discusses the cluster headache diagnosis criteria and nuances.
Cluster Headache vs. Migraines
Cluster headache and migraine are often confused, but they are two distinct conditions with different patterns, different triggers, and different treatments.
Getting the diagnosis right matters because the most effective treatments for cluster headache, including high-flow oxygen, are different from migraine treatments.
Diagnosis
Since there are over 150 headache disease diagnoses it is sometimes difficult to get a proper diagnosis. Despite the severe nature of cluster headaches and the depression, isolation, and suicidal thoughts that accompany the attacks, it takes an average 6.6 years for a patient to be accurately diagnosed.
A significant percentage of people end up suffering from more than one confirmed disease. Getting an accurate diagnosis is the most important first step in finding a treatment plan that will work for you.
Clusterbusters helped refine a diagnostic tool, if you suspect you may have cluster headache and have not yet been diagnosed this is a good starting point.
Free Diagnostic Tool
The Computerized Headache Assessment Tool (CHAT) is an algorithm-based online tool developed to help in the recognition of primary headache diseases, such as migraine, tension-type headache, and cluster headache. It was initially developed by Morris Maizels MD along with Patient Tools Inc. With the assistance of Robert Wold and Clusterbusters, it was evaluated in over 250 people as part of a formal research study, and found to be very accurate for the recognition of cluster headache. You may print out your survey and review the results with your health care provider if the assessment is different from your current headache diagnosis.
CHAT-III is intended as a screening instrument, and not intended to replace medical assessment. ClusterBusters and PatientTools Inc accept no responsibility for the use of CHAT-III.
Finding the Right Care
Finding the right doctor, headache specialist, or neurologist for you may take trial and error. It’s an overwhelming, aggravating process that can take years for some patients. Once you’ve gotten the appropriate care and have a treatment plan in place, you may still have to advocate for yourself at your local pharmacy, oxygen supplier, as well as face problems at work and with friends, family members, and coworkers.
From there, finding a neurologist with experience in cluster headache, not just general headache or migraine, is critical. For an in-depth look on finding the right care, visit our “Finding Care” Page. We maintain a list of doctors who know how to diagnose and treat CH patients.
What Causes Cluster Headaches?
The honest answer is that nobody knows for certain. There is a theory that points to a dysfunction in the hypothalamus, a small region deep in the brain that controls sleep cycles, hormone production, body temperature, and your sense of time. The hypothalamus is essentially the body's internal clock, which helps explain one of the most distinctive features of cluster headache: attacks that arrive at the same time of day, in cycles that often follow the change of seasons.
Other parts of the nervous system are also involved. The trigeminal nerve, which carries sensation from the face, can swell to seven times its normal size during an attack. REM sleep, when most of us dream, is the most common trigger for an attack, which is one more clue pointing back to the hypothalamus.
Cluster headache affects approximately 1 in 1,000 people (.1% of the population), which makes it roughly as common as multiple sclerosis. It is rare enough that many doctors will go their entire careers without seeing a case, but common enough that there are hundreds of thousands of people living with it right now. The rarity, combined with the severity, is part of why patients so often go undiagnosed or misdiagnosed for years.
Frequently Asked Questions
What does a cluster headache feel like?
People describe it as an icepick driven behind the eye, a hot poker, or a brain freeze that lasts an hour instead of seconds. The pain is one-sided, centered around the eye or temple, and is widely considered one of the most painful experiences known to medicine.
How are cluster headaches different from migraines?
Cluster attacks are shorter (15 minutes to 3 hours), strike up to 8 times a day often at the same time, and cause restlessness and pacing. Migraines last longer, occur less often, and usually make people want to lie still in a dark, quiet room. The most effective cluster treatments, like high-flow oxygen, are also different.
Is cluster headache treatable?
Yes. While there is no cure, many people achieve significant relief through a combination of preventive treatments, which reduce or eliminate cycles, and abortive treatments, which stop individual attacks. High-flow oxygen is the most effective and consistently reliable abortive for most people. Our Treatment Options page covers what is available.
How long does it take to get diagnosed with cluster headache?
On average about 6.6 years. The condition is rare enough that many doctors never see a case, which is why a screening tool like CHAT and a specialist familiar with cluster headache can make a real difference. Visit our finding care page for more support.
Not every doctor knows cluster headache
Our guide helps you find one who does, and shows you how to prepare so your appointment counts.