Cluster headaches explained

There are several types of headache disorders, not just migraine. That’s why it’s so important to see a true headache specialist. All headaches are not equal and treatments for each one can be very different. Sometimes patients get diagnosed with migraines when they really have another headache disorder. Some unlucky individuals meet criteria for more than one headache disorder.

We migraineurs are a little sensitive about the word “headache”. It can be used to trivialize the horrible symptoms we have to endure. So we’ve been conditioned to specifically use “migraine” or “migraine attack” to describe our symptoms. That’s a good thing. However, coping with our own stigma can set us up to inadvertently stigmatize other truly horrible headache disorders. That was the case for me until I experienced a nightmare that made migraines look like a walk in the park.

Fifteen years ago I experienced a headache unlike anything I have faced in 40 years of migraines. There really are no words to adequately describe a cluster headache, but I will try. The stabs hit fast and hard – no prodrome, no aura, no warning at all. They slammed like white-hot knives into my right eye, sending acidic tears pouring out. Ice and heat both felt like burning coals on my head. Medication had no effect. It was impossible to sleep or sit still. The fire in my head and face drove me to my feet. I screamed, cursed, and wailed in agony as I paced and rocked back and forth. I pulled my hair out in clumps and slammed my head against a cast iron tub. Convinced I was about to die, I begged my then 7 year-old daughter to call 911. Six long months later, I was finally diagnosed with Cluster Headaches and treated. 15 years later, I still get attacks every week in addition to migraines. There is no mistaking one for the other. The only thing these disorders have in common is that they cause head pain. The quality, nature, intensity, and character of the attacks are completely different.

I meet a lot of migraineurs who say they have “cluster migraines”. I try not to let it bother me because most of the time that person really doesn’t know how insulting that term is to someone diagnosed with cluster headaches. Generally when people say they have “cluster migraines” they mean that they have “clusters” of migraines for several days or weeks at a time that are difficult to treat, keep coming back, or recur seasonally or on a schedule. Many people were given this descriptive diagnosis from a well-meaning doctor who was not a headache specialist.

Cluster headaches affect about 0.1% of the population. Many are misdiagnosed with migraine and improperly treated. Still others suffer for years, undiagnosed, and untreated.

A pain like no other

Subjective pain scale ratings are part of the problem. We all have different levels of pain tolerance. The exact same leg fracture might be a “3” to one person and a “9” to another. There’s just no way to scientifically quantify the severity of a headache disorder by individual pain perception. However, the severity of pain is one of the hallmark symptoms of Cluster Headaches. This isn’t a case of “my pain is worse than yours” competitiveness. The pain of a cluster headache is some of the most severe pain known in medical science. Nothing really compares to it. Women with the disorder say that the pain of childbirth was “a breeze” compared to a cluster headache. Similar pain due to injury or illness usually renders a patient unconscious within minutes. Some cluster headache patients do pass out because of the pain. Most patients describe the pain as “a hot poker”, “an ice pick”, “burning”, or “boring”.

Speaking from experience, nothing has ever come close to the pain of a cluster attack, not even my worst "10" migraine. I'd rather have chronic daily migraines than face one more cluster attack. I'm not trying to start a "pain competition" between migraineurs and clusterheads. Both are terribly painful. However, I really don't know how to explain cluster headaches without comparing my own experience with both headache disorders.


As with migraine, the “gold standard” for diagnosing Cluster Headache is the International Classification of Headache Disorders, 3rd Edition. When patients and doctors use the term “cluster migraine” they really don’t understand how headache disorders are classified and diagnosed.

Cluster headaches are classified as a Trigeminal Autonomic Cephalalgia (TAC). Other headache disorders in this same classification are SUNCT (Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing), SUNA (Short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms), Hemicrania continua, and Paroxysmal hemicranias. All of these disorders activate the trigeminal parasympathetic reflex. Unilateral activation is a unique characteristic to all TAC disorders. Cortical spreading depression is not involved in TAC disorders nor are they classified as vascular headaches.

Diagnostic Criteria

  • The pain is severe to very severe and located in or around one eye. The pain may spread across the temple and over the ear. It lasts 15 minutes to 3 hours and can recur many times per day for months or years.
  • Other neurological symptoms affect only the painful side: excessive tears, nasal congestion or runny nose, swelling of the eyelid, excessive sweating, flushing of the face, sense of ear fullness, eyebrow and/or eyelid droop, and constricted pupils
  • Patients are restless and agitated. They pace and rock about, moaning, screaming, and even cursing uncontrollably.
  • Episodic cluster headaches occur in cycles lasting from 1 week to 1 year. Between attacks, there is a pain-free period of at least one month. These cycles are what give cluster headache its name.
  • About 10% of patients become chronic. Most do not get any breaks between cycles. A lucky few will get breaks of less than 30 days before starting up again.  Patients must have non-stop cycles or breaks of less than 30 days for at least 1 year before receiving this diagnosis.
  • Attacks can be triggered by alcohol, nitroglycerin, or histamine. Patients often report other triggers such as flashing/strobe/bright lights, loud noises, strong smells, etc. However, triggers appear to induce attacks only when the patient is “in cycle”. Between cycles, episodic patients can consume alcohol and risk exposure to other triggers without fear of an attack.
  • Typical age of onset is 20-40 years. Men outnumber women 3 to 1.


As with migraine, treatment involves both prevention and acute treatment. Unfortunately, there are no OTC medications that will touch the pain of a cluster headache.


Oxygen – 100% pure oxygen at a high flow rate (10-15 lpm) for 15-20 minutes using a non-rebreather mask will abort most attacks.

Lidocaine – 1 ml of a 4% solution of lidocane used as nasal drops can abort some attacks. It can be repeated after 15 minutes if still needed.

DHE – Intramuscular injections work best. Nasal sprays are effective for some patients.

Sumatriptan injections – This little gem can usually abort an attack within 15 minutes. As with migraine, it does nothing to prevent attacks. As often as patients experience attacks while in cycle, prevention is absolutely essential.

Zomig nasal spray – This new delivery method was recently approved for the treatment of acute cluster attacks. However, this option is very expensive. A case of 9 single-use sprays can cost as much as $300.00.

Transitional therapies

Oral corticosteroids can be tapered over one week at home. An IV infusion over a few days is used in a hospital or clinic setting under medical supervision. Both are usually effective at stopping a cluster headache cycle, giving long-term preventives time to work. Corticosteroids should not be used more than once a year to prevent serious side effects.


Verapamil  is usually the first-line preventive. Unlike its use for migraine preventives, only immediate-release Verapamil given in three daily doses is effective at preventing cluster headaches. Doses tend to go much higher than for migraine. Some patients need up to 800 mg per day to achieve remission. Higher doses require routine EKGs to monitor for a rare but serious AV heart block. The most common side effects are constipation, fatigue, and dizziness.

Lithium has a high rate of side effects, so one of the other options is usually considered first. However, Lithium has good track record of cluster headache remission. Typical doses are 600 – 900 mg per day. Regular blood tests are required to monitor patients for therapeutic levels and toxicity.

Depakote can be administered in slow-release single doses of 1,000 – 2,000 mg per day. Clinical trials have demonstrated a 50% reduction in number of attacks.

Topamax doses are similar to its use as a migraine preventive. Doses of 200 – 400 mg per day have shown similar efficacy to Depakote.

Melatonin has been shown to work as well as Verapamil in episodic patients. Typical dose is 9-10 mg at bedtime. Most cluster headache patients have low melatonin levels, particularly during active cycles. This is the only OTC preventive currently recommended by headache specialists.

Psilocybin use is illegal in the U.S. and highly controversial. However, there are a number of cluster headache patients who have achieved remission using psilocybin.

Surgical & experimental treatments

Deep brain stimulation and occipital nerve stimulation are the two medically recognized surgical treatments for cluster headache that does not respond to pharmaceutical intervention.

A variety of other surgical interventions on the trigeminal nerve and sphenopalatine ganglion have been attempted with varying degrees of success. As with migraine, more research is desperately needed. Unlike migraine, cluster headache is so rare, it doesn’t get a dime of research funding from NIH.

Two clinical trials are currently underway:

gammaCore vagus nerve stimulation – Clinical trials are complete and results are pending.
Sphenopalatine Ganglion Stimulation – Clinical trials are now taking applications for participants

Theories on Causation

Attacks have shown to activate the posterior hypothalamic grey matter. No cortical spreading depression is present. Vascular inflammation is secondary to onset of attack.

They have been nicknamed “alarm clock” headaches because they tend to occur with precision-like regularity at the same time each day. It is thought that human “biological clock” is disrupted as many patients are wakened by attacks in the early morning hours. Cluster attacks have a preference for REM sleep so many patients wake to an attack just a few hours after falling asleep. Sleep disorders are common.

For some patients, sleep apnea is an aggravating factor. Once treated with a CPAP, these patients will see a dramatic reduction in nighttime and early morning attacks.

Burden of Cluster Headache

Cluster headaches are also called “suicide headaches” because many patients deliberately take their own lives to escape the pain. Some patients who were not suicidal have seriously injured or killed themselves with their desperate attempts to stop the pain. It is not uncommon to observe a patient beat his head against the wall, hit his head with hard objects, or tighten belts around the head during the worst of an attack. If not treated, the risk of fatal injury is quite high.

“There is no more severe pain than that sustained by a cluster headache sufferer and if not for the rather short duration of attacks most cluster sufferers would choose death rather than continue suffering.”   -- Dr. Todd Rozen

Take home points

  • Cluster headache is a unique headache disorder, separate and distinct from migraine in both cause and symptom profile. It is often misdiagnosed and under-treated.
  • If you are having symptoms that make you think cluster headache is a more accurate diagnosis, please see a headache specialist right away. This isn’t a headache disorder you can manage with a couple of Excedrin and a nap.
  • If you think you might have both migraine and cluster headache, it is imperative that you see a headache specialist who can safely and effectively treat both headache disorders.
  • If you have been diagnosed with “cluster migraine”, please see a headache specialist for an accurate diagnosis and appropriate treatment. And please, out of respect for your clusterhead brothers and sisters, refrain from using the word “cluster” to refer to anything but a true cluster headache.

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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