is a neurological disease that involves, as its most prominent feature, an immense degree of pain. "Cluster" refers to the tendency of these headaches
to occur periodically, with active periods interrupted by spontaneous remissions. The cause of the disease is currently unknown.
Signs and symptoms
Cluster headaches are excruciating unilateral headaches, of extreme intensity. The duration of the common attack is 15 minutes to three hours. Onset of an attack is rapid, and most often without the preliminary signs that are characteristic of a migraine
. However, some sufferers report preliminary sensations of pain in the general area of attack, often referred to as "shadows," that may warn them an attack is imminent. Though the headaches are almost exclusively unilateral, there are many documented cases of "side-shifting" between cluster periods, or, even rarer, simultaneously (within the same cluster period) bilateral headache. They are often initially mistaken for brain tumors and multiple sclerosis
until patients are treated with corticosteroids and then imaged. Trigeminal neuralgia
can also bring on headaches with similar qualities.
The degree of pain involved in cluster headaches is markedly greater than in other headache conditions, including migraine. It has been described by female patients as being more severe than childbirth.
The pain is lancinating or boring in quality, and is located behind the eye (periorbital) or in the temple, sometimes radiating to the neck or shoulder. Analogies frequently used to describe the pain are a red-hot poker inserted into the eye, or a spike penetrating from the top of the head, behind one eye, radiating down to the neck, or sometimes having a leg amputated without any anaesthetic. The condition was originally named Horton's Neuralgia after Dr. B.T Horton who postulated the first theory as to their pathogenesis. His original paper describes the severity of the headaches as being able to take normal men and force them to suicide. Indeed, cluster headaches are also known by the nickname "suicide headaches".
From Horton's 1939 original paper on cluster headache:
The cardinal symptoms of the cluster headache attack are ptosis (drooping eyelid), conjunctival injection (redness of the conjuctiva - the covering of the eyeball), lacrimation (tearing), rhinorrhea (runny nose), and, less commonly, facial blushing, swelling, or sweating. These features are known as the autonomic symptoms. The attack is also associated with restlessness, the sufferer often pacing the room or rocking back and forth. Less frequently, he or she will have an aversion to bright lights and loud noise during the attack. Nausea is not typical of cluster headache, though it has been reported. The neck is often stiff or tender in the aftermath of a headache, with jaw or tooth pain sometimes present.
Cyclical recurrence and regular timing
Cluster headaches are occasionally referred to as "alarm clock headaches", because of the regularity of its timing and its ability to wake a person from sleep. Thus it has been known to strike at the same time each night or morning, often at precisely the same time during the day a week later. This has prompted researchers to speculate an involvement of the brain's "biological clock" or circadian rhythm
In some cases, cluster headaches remain "steady" without cyclical ups and downs for days.
Episodic or chronic
In episodic cluster headache, these attacks occur once or more daily, often at the same times each day, for a period of several weeks, followed by a headache-free period lasting weeks, months, or years. Approximately 10–15% of cluster headache sufferers are chronic
; they can experience multiple headaches every day for years.
Cluster headaches occurring in two or more cluster periods lasting from 7 to 365 days with a pain-free remission of one month or longer between the clusters are considered episodic. If the attacks occur for more than a year without a pain-free remission of at least one month, the condition is considered chronic.
Chronic clusters run continuously without any "remission" periods
between cycles. The condition may change from chronic to episodic and from episodic to chronic. Remission periods lasting for decades before the resumption of clusters have been known to occur.
The first complete description of cluster headache was given by the London neurologist Wilfred Harris in 1926. He named the disease Migrainous neuralgia.
Cluster headaches have been called by several other names in the past including Erythroprosopalgia of Bing, Ciliary neuralgia, Erythromelagia of the head, Horton's headache (named after Bayard T. Horton, an American neurologist), Histaminic cephalalgia, Petrosal neuralgia, sphenopalatine neuralgia, Vidian neuralgia, Sluder's neuralgia, and Hemicrania angioparalyticia.
Sluder's neuralgia (syndrome) and cluster pain can often be temporarily stopped with nasal lidocaine drops.
are diagnosed more often in women, cluster headaches are diagnosed more often in men. The male-to-female ratio in cluster headache ranges from 4:1 to 7:1. It primarily occurs between the ages of 20 to 50 years. This
gap between the sexes has narrowed over the past few decades, and it is not clear whether cluster headaches are becoming more frequent in women, or whether they are merely being better diagnosed. Limited epidemiological studies have suggested prevalence rates of between 56 and 326 people per 100,000.
plays a role in the occurrence of cluster headaches, which are more common as one moves away from the equator
towards the poles.
Cluster headaches are classified as vascular headaches. The intense pain is caused by the dilation of blood vessels which creates pressure on the trigeminal nerve. While this process is the immediate cause of the pain, the etiology (underlying cause or causes) is not fully understood.
Among the most widely accepted theories is that cluster headaches are due to an abnormality in the hypothalamus
; Dr Goadsby, an Australian specialist in the disease has developed this theory. This can explain why cluster headaches frequently strike around the same time each day, and during a particular season, since one of the functions the hypothalamus performs is regulation of the biological clock
abnormalities have also been reported in patients.
The hypothalamus is responsive to light—daylength and photoperiod; olfactory stimuli, including pheromones; steroids, including sex steroids and corticosteroids; neurally transmitted information arising in particular from the heart, the stomach, and the reproductive system; autonomic inputs; blood-borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, blood plasma concentrations of glucose and osmolarity, etc.; and stress. These particular sensitivities may underlay the causes, triggers, and methods of treatment of cluster headache.
| Functional Magnetic Resonance Imaging (fMRI) shows brain areas being activated during pain
| Voxel-based morphometry (VBM) shows brain area structural differences
The above Positron emission tomography pictures indicate the brain areas which are activated during pain only, compared to the pain free periods. These pictures show brain areas which are always active during pain in yellow/orange colour (called "pain matrix"). The area in the centre (in all three views) is specifically activated during cluster headache only. The bottom row Voxel-based morphometry (VBM) pictures show structural brain differences between cluster headache patients and people without headaches; only a portion of the hypothalamus is different.
There is a genetic
component to cluster headaches, although no single gene has been identified as the cause. First-degree relatives of sufferers are more likely to have the condition than the population at large.
However, genetics appears to play a much smaller role in cluster headache than in some other types of headaches.
(glyceryl trinitrate) can sometimes induce cluster headaches in sufferers in a manner similar to spontaneous attacks. Ingestion of alcohol
or chocolate is recognized as a common trigger of cluster headaches when a person is in cycle or susceptible. Exposure to hydrocarbons
(petroleum solvents, perfume) is also recognized as a trigger for cluster headaches. Some patients have a decreased tolerance to heat, and becoming overheated may act as a trigger. Napping causes a headache for some sufferers, while for others lack of sleep triggers them. The role of diet and specific foods in triggering cluster headaches is controversial and not well understood.
Nicotine may trigger cluster headaches, and the affliction is often found in people with a heavy addiction to cigarette smoking.
Cluster headaches often go undiagnosed for many years, being confused with migraine or other causes of headache.
Medically, cluster headaches are considered benign, but because of the extreme and often debilitating pain associated with them, a severe attack is nevertheless treated as a medical emergency by doctors who are familiar with the condition. Because of the relative rareness of the condition and ambiguity of the symptoms, some sufferers may not receive treatment in the emergency room and patients may even be mistaken as exhibiting drug-seeking behavior.
Over-the-counter pain medications (such as aspirin, paracetamol, and ibuprofen) typically have no effect on the pain from a cluster headache. Unlike other headaches such as migraines and tension headaches, cluster headaches do not respond to biofeedback.
Medications to treat cluster headaches are classified as either abortives or prophylactics (preventatives). In addition, short-term transitional medications (such as steroids) may be used while prophylactic treatment is instituted and adjusted. With abortive treatments often only decreasing the duration of the headache and preventing it from reaching its peak rather than eliminating it entirely, preventive treatment is always indicated for cluster headaches, to be started at the first sign of a new cluster cycle.
During the onset of a cluster headache, some patients respond to rapid inhalation of pure oxygen
(12-15 litres per minute in a non-rebreathing apparatus). Because those experiencing a cluster headache tend to hyperventilate from pain and hyperactivity, a non rebreathing mask system such as O2PTIMASK™ with different mask sizes, a sturdy protected valve and large bag is required that can provide a tight facial seal and continuously functioning valve, consistently deliver at or close to 100% oxygen, handle the high flow rates and have a bag size sufficient to support hyperventilation. Standard disposable 1 adult size fits all non breathing masks with 1 liter bags and exposed flimsy valves on the mask itself, are designed for use in respiratory therapy where lower flow rates are used, hyperventilation and rough handling are not common. When used at the onset this can abort the attack in as little as 5 minutes. Once an attack is at its peak, oxygen therapy appears to have little effect. Alternative first-line treatment is subcutaneous administration of triptan
drugs, like sumatriptan
. Because of the rapid onset of an attack, the triptan drugs are usually taken by subcutaneous injection
rather than by mouth. While available as a nasal spray, these are seldom effective to sufferers of cluster headaches due to the swelling of the nasal passages during an attack.
In many cases, some doctors have tried the use of beta blockers as a treatment.
Some non-narcotic treatments that have shown mixed levels of success are botox injections along the occipital nerve, as well as sarapin (pitcher plant extract) injections. Some people have claimed relief from kudzu, but the evidence is purely anecdotal at this point.
Recently, researchers have linked low testosterone as a possible cause of cluster headaches, which can be especially troublesome since the most effective pain medications for clusters, like morphine, reduce testosterone levels.
Lidocaine and other topical anesthetics sprayed into the nasal cavity may relieve or stop the pain, normally in a few minutes, but long term use is not suggested due to the side effects and possible damage to the nasal cavities.
Previously, vaso-constrictors such as ergot compounds were also used, and sufferers report a similar relief by taking strong cups of coffee immediately at the onset of an attack.
Other abortive remedies that work for some include ice, hot showers, breathing cold air, caffeine, and drinking large amounts of water in the early stages of an attack. Vigorous exercise has been shown in some cases to be very effective in relieving and aborting an acute attack by increasing the levels of oxygen within the body. This could also be due to an increase in adrenaline and changes in blood pressure. Some people report that sexual intercourse and specifically orgasm may terminate an attack possibly by acutely modulating hypothalamic function.
Some sufferers report that constricting the blood flow to the head by pressing hard on one or both carotid arteries can temporarily abort an attack.
Hyperbaric oxygen therapy has been used successfully in treating cluster headaches though it was not shown to be more successful than surface oxygen.
A wide variety of prophylactic
medicines are in use, and patient response to these is highly variable. Current European guidelines suggest the use of the calcium channel blocker verapamil
at a dose of at least 240 mg daily. Steroids
, such as prednisolone
, are also effective, with a high dose given for the first five days before tapering down. Methysergide
and the anticonvulsant topiramate
are recommended as alternative treatments.
Muscle relaxants and atypical anti-psychotics have also been used.
Magnesium supplements have been shown to be of some benefit in about 40% of patients. Melatonin has also been reported to help some.
Other neuropathic pain alleviating agents can also be used such as the Tricyclic antidepressants including Amitriptyline and Nortriptyline
Non-established and research approaches
There is substantial anecdotal evidence that serotonergic psychedelics
such as psilocybin
(mushrooms) and LSD
and LSA d-Lysergic acid amide
seeds) abort cluster periods and extend remission periods. Melatonin
, and the triptan abortive drugs are closely-related tryptamines
Dr. Andrew Sewell and Dr. John Halpern at McLean Hospital in Boston have investigated the ability of low doses of psilocybin ("magic mushrooms") to treat cluster headaches. Dr. Sewell examined medical records of 53 patients who had taken hallucinogenic mushrooms and reported in Neurology that the majority of them found partial or complete relief from cluster attacks. A clinical study of these treatments under the auspices of MAPS is being developed by researchers at Harvard Medical School, McLean Hospital.
Within the United States, the Controlled Substances Act (CSA) of 1970 makes it illegal to possess hallucinogens (including psilocybin and LSD), classifying them as Schedule I drugs with no legitimate medical use. Patients who use psilocybin to treat their symptoms face legal prosecution, although there are no known convictions.
Other types of headache
- Chronic Paroxysmal Hemicrania (CPH) is a condition similar to cluster headache, but CPH responds well to treatment with the anti-inflammatory drug indomethacin and the attacks are very much shorter, often lasting only seconds.
- Some people with extreme headaches of this nature (especially if they are not unilateral) may actually have an ictal headache. Anti-convulsant medications can significantly improve this condition so sufferers should consult a physician about this possibility.
- It is also possible to have two or more different types of headaches, complicating diagnosis and treatment.