Causes of Ongoing Cluster Headaches

A One-Sided Severe Headache That Follows a Circadian Pattern

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Cluster headaches cause significant pain on one side of the head, in the trigeminal nerve distribution (generally in or around the eye or temple).

While debilitating and extremely painful, cluster headaches are not dangerous. Their precise cause remains unknown, although experts strongly suspect the hypothalamus (a gland in the brain) plays a role.

This article will review what a cluster headache feels like and how it's managed. Potential causes and preventive therapies will also be explored.

An illustration with information about what is a cluster headache

Illustration by Paige McLaughlin for Verywell Health

Cluster Headaches: Describing Where Pain Is

Cluster headaches are one-sided (unilateral) headaches, localized in or around the eye, eyebrow, or near the temple area.

The pain of a cluster headache is sharp, stabbing, or burning in nature. It is reported as being more severe than childbirth, passing a kidney stone, or breaking a bone.

Cluster Headaches

Cluster headache attacks last 15 minutes to three hours and occur once every other day up to eight times daily. The pain is almost always accompanied by intense restlessness or agitation, such as pacing or rocking back and forth.

Also, one or more cranial autonomic symptoms are present on the same side as the cluster headache. Cranial autonomic symptoms occur when trigeminal pain-sensing nerve cells activate nerve fibers connected to facial structures like the eye and nose.

These symptoms include:

  • Eye redness and/or tearing
  • Runny and/or stuffy nose
  • Eyelid swelling
  • Forehead and facial sweating
  • Pinpoint pupils (miosis) and/or upper eyelid drooping (ptosis)

How Are Migraines Different From Cluster Headaches?

Migraine headaches are throbbing, last longer (four to 72 hours), and are associated with nausea and/or vomiting, not restlessness. Also, migraine headaches can occur on both sides of the head, whereas cluster headaches are always one-sided.

Causes: Why Do People Get Cluster Headaches?

While the exact cause of cluster headaches is unknown, experts suspect they start with activating the hypothalamus, a gland at the base of the brain that controls your sleep-wake cycles and circadian rhythm (internal clock).

Activation of the trigeminal-autonomic reflex (possibly via a connection with the hypothalamus) is suspected of generating cluster headaches.

The trigeminal-autonomic reflex describes an intricate nerve pathway connecting the trigeminal nerve to cranial nerve seven (facial nerve) and cranial nerve eight (vestibulocochlear nerve). These nerves carry parasympathetic signals to structures within the head, like the tear glands, eyes, and nose.

What Is the Parasympathetic Nervous System?

The parasympathetic nervous system is part of your autonomic nervous system, which controls body functions that occur automatically (e.g., blood pressure, digestion, and sweat production).

Lastly, genetics and hormone levels, namely melatonin (sleep hormone) and cortisol (stress hormone), may also play a role in causing cluster headaches. One study found lower melatonin and higher cortisol levels in participants with cluster headaches.

Timing of Cluster Headaches

Interestingly, cluster headaches follow a circadian pattern, occurring around the same time each day, often at night, one to two hours after a person falls asleep, or in the early morning.

They also follow a seasonal pattern, recurring at the same time each year, often in the spring and autumn. The circadian and circannual pattern of cluster headaches supports the role of the hypothalamus in its origin.

Another unique feature of cluster headaches is that the attacks occur in cluster cycles. Generally, individuals will have a cycle of cluster headache attacks for six to 12 weeks, followed by remission (no attacks), lasting months to years.

An exception to this is individuals with chronic cluster headaches. They experience remission periods of less than one month.

What Helps When You Have Cluster Headaches?

If you have been diagnosed with cluster headaches, you must be prepared for an attack. This means carrying medication with you or having it near your bed (if you tend to get cluster headaches at night) and taking it immediately at the start of your symptoms.

You might also carry a water bottle with cold water or an instant cold pack during a cluster cycle. Applying cold water or a cold pack to the area of pain has been found to be soothing for some people.

How Are Cluster Headaches Diagnosed?

Diagnosing a cluster headache involves giving a medical history, having a neurological exam, undergoing magnetic resonance imaging (MRI) of the brain, and sometimes getting blood tests.

The purpose of imaging or blood tests is to rule out mimicking conditions like giant cell arteritis, sinusitis, or brain tumor.

Medication for Cluster Headaches

The treatment of cluster headaches involves three components:

  • Abortive: Treatment given at the start of a cluster headache
  • Transitional: Treatment given at the start of a cluster cycle to reduce the number of attacks
  • Preventive: Treatment given at the same time as transitional and throughout the cluster cycle

Abortive

Oxygen and triptans are the primary abortive therapies for cluster headache attacks. Lidocaine given through the nose is less well studied but is usually considered an appropriate alternative abortive therapy.

Oxygen

Research has found that more than 70% of people with cluster headaches benefit from oxygen therapy.

Oxygen therapy involves inhaling 100% oxygen with a flow rate of 6 to 15 liters per minute (L/minute). The oxygen inhalation is delivered via a face mask for 15 to 30 minutes, even if the pain eases up before then, to help prevent headache recurrence.

While a disadvantage of oxygen therapy is its lack of portability, there is no limit to how often it can safely be used. This makes it a good choice for those who endure multiple cluster attacks daily.

Triptans

Triptans are prescription drugs that target specific serotonin (a brain chemical) receptors (docking sites).

Research suggests that a triptan injected subcutaneously (in the fatty tissue, above the skin) or inhaled through the nose effectively treats acute cluster headaches. Oral triptans are inadequate at providing relief since the pain of a cluster headache peaks very rapidly.

The triptans primarily used for cluster headaches are Imitrex (sumatriptan), available as an injection or nasal spray, and Zomig (zolmitriptan), a nasal spray.

A drawback of triptans is that they cannot be used in people with certain underlying health conditions, namely heart disease, stroke, peripheral artery disease, or significant hypertension (high blood pressure).

Lidocaine

Lidocaine (a numbing agent) administered through the nose (e.g., spray or drops) may be an option for people with cluster headaches who do not respond to oxygen or a triptan.

Transitional

Transitional medication is started at the same time as preventive medication and usually involves a corticosteroid ("steroid") taken by mouth, namely prednisone. The steroid can be slowly stopped after the cluster cycle has ended.

Preventive

Preventive medications are intended to decrease the number of attacks and the duration and severity of the cluster cycle.

Verapamil is the most commonly used preventive medication for cluster headaches. Available under the brand names Calan and Verelan, verapamil is a calcium channel blocker, a class of drugs used to treat various heart conditions like angina (a type of chest pain) and arrhythmias ( irregular heartbeat)

Emgality (galcanezumab) is another preventive medication for cluster headaches. It's a calcitonin gene-related peptide (CGRP) antibody injected monthly in the thigh, back of the upper arm, or buttocks. Emgality is usually stopped one month after the cluster cycle ends.

What Is CGRP?

CGRP is a protein in the trigeminal nerve that dilates (widens) cranial blood vessels. It plays a role in the development of both cluster and migraine headaches.

Finally, surgical procedures targeting specific nerves are under investigation to treat cluster headaches that do not respond to oxygen or medication.

One such treatment, occipital nerve stimulation, involves the surgical placement of electrodes at the base of the skull with leads connected to a pulse generator (a power source) implanted in the chest or abdomen. The pulse generator sends electrical charges to the occipital nerve, intending to interfere with pain signals.

Self-Care for Cluster Headaches

Cluster headache attacks are excruciating and debilitating and can negatively affect relationships, daily functioning, and quality of life.

Besides seeking care from a headache specialist, you may consider seeing a therapist with experience in cluster headaches or other pain disorders. This is because people with cluster headaches are more likely to experience symptoms of depression and suicidal ideation than the general population.

Seek Emergency Care

If you have thoughts of suicide, dial 988 to contact the 988 Suicide & Crisis Lifeline and speak with a trained counselor. If you or a loved one are in immediate danger, call 911.

Other self-care strategies to help optimize your cluster headache care include:

  • Keeping a headache diary to identify triggers
  • Reaching out to loved ones to avoid isolation, especially during a cluster cycle
  • Utilizing educational resources and connecting with others living with cluster headaches (consider checking out the nonprofit organization ClusterBusters)

While acupressure (pressing on specific trigger points on the hand, head, neck, or foot) has been studied for some other primary headache disorders (such as migraine), research is lacking for cluster headache.

Avoiding Cluster Headaches Triggers

Scientists have identified various cluster headache triggers. These factors may signal the brain (especially the hypothalamus) to undergo changes that create the headache and its associated symptoms.

Commonly cited triggers for cluster headaches include:

  • Alcohol
  • Nitroglycerin (a drug used to ease chest pain in people with heart disease)
  • Food containing nitrates, like cured meats
  • Strong odors, like petroleum/gasoline, paint fumes, or nail varnish

If you have cluster headaches, trying to avoid these triggers during a cluster cycle is essential. Once the cycle is over, confirm with your healthcare provider, but you can probably drink alcohol and/or be reexposed to the above triggers.  

Lastly, smoking increases a person's risk of developing cluster headache disorder. That said, smoking does not trigger individual cluster headaches. Whether stopping smoking can help is unclear, but it is recommended for many other health reasons.

Summary

Cluster headaches cause a sharp, piercing one-sided pain in or around the eye, eyebrow, or temple area. The cause is unknown but likely starts with activation of the hypothalamus (a gland in your brain).

Living with cluster headaches is not an easy feat, physically or mentally. Treatment often entails avoiding triggers during a cycle of cluster headache attacks, taking medication, and ensuring emotional support, as depressive symptoms are common.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Colleen Doherty, MD
 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.