Cluster headache is a rare primary headache disorder that consists of severe headaches on one side of the head associated with red or teary eyes, runny or stuffy nose, flushing or sweating of the face or a sense of restlessness and agitation. The term cluster headache comes from the recurrence of headache attacks usually in a series (cluster periods) lasting for weeks or months, separated by remission periods (periods of headache freedom) usually lasting months or years.
The term cluster headache should be used carefully as sometimes people will refer to their headaches as “cluster headaches” because they have headaches that occur in “clusters”, meaning headaches occurring back to back over subsequent days or headaches occurring frequently. The term “cluster headache” should not be used to describe just any frequently occurring headache but rather reserved for people meeting the diagnostic criteria for cluster headache as outlined by the International Headache Society. Please refer to the International Classification of Headache Disorders 3rd edition website for more information on the criteria used to diagnosis cluster headache.
Cluster headache is classified as a trigeminal autonomic cephalalgia or TAC:
- Trigeminal refers to cranial nerve 5, which is the nerve that controls sensation of the face. For this reason, the pain associated with cluster headache often localizes to the face particularly around and behind the eye.
- Autonomic refers to symptoms like red or teary eye, runny or stuffy nose, sweating or flushing of the face, drooping of the eyelid, or sense of fullness in the ear. In cluster headache, these symptoms occur on the same side as the pain.
- Cephalalgia refers to headache.
Cluster headache is known as the most common trigeminal autonomic cephalalgia.
Cluster headaches are often said to be the most painful of all headaches. They have been described as “boring,” “bearing,” “burning,” “like a hot poker in the eye,” and as “suicide headaches.” The age of onset of cluster headache is most often between 20 and 40, and they are more common in men than women at a ratio of 3:1.
Symptoms of Cluster Headache
Cluster headaches are attacks of severe pain lasting 15-180 minutes and occurring from once every other day up to eight times in one day—averaging 2 per day over typically 4-6 weeks then entirely disappearing for 6-12 months. Cluster headaches commonly occur overnight waking people from sleep. Cluster headaches are diagnosed as “episodic” when the attacks occur in periods lasting 7 days to 1 year separated by pain-free periods lasting 1 month or longer. In “chronic” cluster headaches, attacks occur for more than 1 year without remission or with remissions lasting less than 1 month. More than 80% have the episodic cluster headache form.
The pain is…
- Unilateral (on one side of the head)
- Orbital (near the orbit, the bone framing the eye), supraorbital (above the orbit), temporal (at the temple) or a combination of those sites and sometimes more towards the back of the head
These attacks also include one or more cranial autonomic symptoms on the same side as the pain (ipsilaterally):
- Red eye (conjunctival injection)
- Eyelid swelling (edema)
- Forehead and facial sweating
- Tearing (lacrimation)
- Abnormal small size of the pupil (miosis)
- Nasal congestion
- Runny nose (rhinorrhea)
- Drooping eyelid (ptosis)
Another typical feature is that most cluster headache patients are restless or agitated during attacks.
People suspected of having cluster headache should be carefully assessed by their doctor for an underlying cause, including imaging of the brain and vessels in the head. As well, they should be evaluated to make sure that they do not have a different primary headache disorder that can mimic cluster headache. Examples of other primary headache disorders that mimic cluster headache include migraine with prominent autonomic features, trigeminal neuralgia, paroxysmal hemicrania, short lasting unilateral neuralgiform headaches with red eye and tearing (conjunctival injection and tearing) (SUNCT/SUNA) and hemicrania continua.
There are no diagnostic tests to confirm cluster headache. Diagnosis is accomplished by reviewing personal and family medical history, considering associated symptoms, and an examination. Rare brain or vessel abnormalities detected only by brain imaging can cause cluster-like headache. Brain imaging, preferably with MRI, is necessary at initial diagnosis or during the course if atypical features develop or if the person does not respond to treatment. The brain imaging should include focused views of the pituitary gland and posterior fossa. Remember, response to treatment does not tell you whether the diagnosis is correct or not.
As previously noted, the term cluster headache must be used with caution. Many migraineurs with frequent repeat or return (recurrence) of their migraine are given an incorrect diagnosis of cluster headache because their migraines “cluster” together. This is in large part due to the lack of information about the correct diagnosis of cluster headache. Cluster headaches last without treatment much less than four hours on average. Migraine generally lasts much more than four hours.
Cranial autonomic symptoms can occur in migraine. Lai et al. identified one or more cranial autonomic symptoms in 56% of migraineurs and 95% of cluster headache patients. But in general, migraineurs had less number of cranial autonomic symptoms; they were less prominent or less consistently related to attacks, and more likely to be on both sides of the face compared with patients with cluster headache. Another important clinical difference between migraine and cluster headache is location of headache. Specifically, that cluster headaches are one sided (unilateral) typically without changing sides of the head from one attack to another. Migraine typically changes sides, although a side preference is common. Cranial autonomic symptoms and light and noise sensitivity are on the same side of headache in cluster headache, but not necessarily in migraine.
Another typical feature is that most cluster headache patients are restless or agitated during attacks. Unlike migraineurs they find it hard to be still and rarely lay down. Cluster sufferers characteristically pace the floor during attacks.
A cluster headache can be successfully treated in most cases with sufficient quality of life by individualizing acute and preventive drug treatment. The American Headache Society has recently published evidence-based guidelines for treatment of cluster headache.
The most commonly used therapies to shorten or abort a cluster attack are:
- High-flow 100% oxygen (O2) by mask
- Sumatriptan nasal spray or in the skin (subcutaneous) injection
- DHE-45 nasal spray or injection
- Zolmitriptan nasal spray
A cluster attack typically increases rapidly to severe intensity over just minutes. For treatment to shorten attacks, effective acute treatment must be used just as rapidly. Insurance often limits access to any/all of these options. Providers must often educate both patient and insurance about cluster headache.
The most commonly used preventive medications are:
- Suboccipital steroid injections (injections of steroids into the back of the head)
- Steroids (commonly prednisone)
Doses of Verapamil are typically double or more than that used for other disorders. The greatest preventive error is typically not using Verapamil to its limitation. Experts recommend an EKG to monitor QTc intervals. Obtain an EKG for every dose increase, and for continuing dose every six months for safety.
Disability and Prognosis
Cluster headache is severely disabling while active. Because of the severity of pain and frequency of disturbing sleep, cluster headache is often more debilitating than other primary headache disorders. Cluster headache sufferers may injure themselves when trying to stop the pain. Concern about stroke risk exists mainly due to the high frequency of smoking and other cardiovascular risk factors present in many older cluster headache patients with the use of artery narrowing (vasoconstricting) drugs. Attention to reduction of stroke risk factors is appropriate. As a person with cluster headache, if others are not educated about cluster headache, it is particularly important that efforts be made to inform them.
Cluster headache is one type of trigeminal autonomic cephalalgia (TAC). It is one of the most severe and devastating pain syndromes. People suspected of having cluster headache should be carefully assessed by their doctor for an underlying cause, including imaging of the brain and vessels in the head. As with other forms of headache, it is necessary to have an accurate diagnosis and effective treatment plan. This requires the use of the acute treatment as early as possible. Once diagnosed with cluster headache, it is important to minimize the frequency of attacks through optimal prevention.
- The International Headache Society. https://www.ichd-3.org/3-trigeminal-autonomic-cephalalgias/3-1-cluster-headache/
- Lai T-H, Fuh J-L, Wang S-J. Cranial autonomic symptoms in migraine: characteristics and comparison with cluster headache. J Neurol Neurosurg Psychiat 2009;80:1116–1119.
- Robbins MS, Starling AJ, Pringsheim TM, Becker WJ, Schwedt TJ. Treatment of cluster headache: The American headache society evidence-based guidelines. Headache 2016;56:1093-1106.
- Dodick DW, Rozen TD, Goadsby PJ, Silberstein SD. Cluster headache. Cephalalgia 2000; 20:787.