Signs and symptoms

Cluster headache sufferers typically experience very severe headaches of a piercing quality near one eye or temple that last for fifteen minutes to three hours. The headaches are usually unilateral and occasionally change sides.

Pain

Persons who have experienced both cluster headaches and other painful conditions (childbirth, migraines) report that the pain of cluster headaches is far worse, significantly more severe than a migraine.^[1] The pain has been described as akin to being stabbed repeatedly in the eye with an ice pick^[2] or hot poker. ^[3] It has been described in medical journals as one of the most severe pain syndromes suffered by human beings.^[4]

Other symptoms

A hallmark feature is that the person is restless and cannot sit still and may pace or even become severely agitated during an attack.

Cluster headaches are frequently associated with Horner's syndrome:^[5] ptosis (drooping eyelids), conjunctival injection (which results in red, watery eyes), lacrimation (tearing), miosis (constricted pupil), eyelid edema, nasal congestion, rhinorrhea (runny nose), and sweating on the affected side of the face. The neck is often stiff or tender in association with cluster headaches afterwards, and jaw and teeth pain are sometimes reported.

Sensitivity to light is more typical of a migraine, as is vomiting, but both can be present in some sufferers of cluster headache, although rare.

Cyclical recurrance 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 at a certain period after falling asleep, or 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. They may also be described as "suicide headaches", a reference to the excruciating pain and resulting desperation that has culminated in actual suicide.^[6]

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.^[7] 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.

Other names

Cluster headaches have been called by several other names in the past including Erythroprosopalgia of Bing, Ciliary neuralgia, Migrainous neuralgia, Erythromelagia of the head, Horton's headache, Histaminic cephalalgia, Petrosal neuralgia, sphenopalatine neuralgia, Vidian neuralgia, Sluder's neuralgia, and Hemicrania angioparalyticia.^[8] Sluder's neuralgia(syndrome) and cluster pain can often be temporarily stopped with nasal lidocaine spray. If successful, outpatient nasal septoplasty and splinting can resolve the condition.^{citation needed]}

Prevalence

While migraines 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. [1]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.^[9] Latitude plays a role in the occurrence of cluster headaches, which are more common as one moves away from the equator towards the poles. It is believed that greater changes in day length are responsible for the increase. ^{citation needed]}

Pathophysiology

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.

Hypothalamus

Among the most widely accepted theories is that cluster headaches are due to an abnormality in the hypothalamus. 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. Metabolic 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.

Genetics

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.^[10] However, genetics appears to play a much smaller role in cluster headache than in some other types of headaches.

Triggers

Nitroglycerin (glyceryl trinitrate) can sometimes induce cluster headaches in sufferers in a manner similar to spontaneous attacks. Ingestion of alcohol 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. The role of diet and specific foods in triggering cluster headaches is controversial and not well understood.

Treatment

Cluster headaches often go undiagnosed for many years, being confused with migraine or other causes of headache.^[11]

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.

Some have reported partial relief from narcotic pain killers, but the frequency of their use in a cluster cycle (1–8 or more times a day) often disqualifies them from use and they are mostly ineffective due to the intensity of the pain involved in cluster attacks. Anecdotal evidence indicates that cluster headaches can be so excruciating that even morphine does little to ease the pain. However, some newer medications like fentanyl have shown promise in early studies and use.

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.

In many cases, some doctors have tried the use of beta blockers as a treatment.

Abortive treatment

During the onset of a cluster headache, the most rapid abortive treatment is the inhalation of pure oxygen (12-15 litres per minute in a non-rebreathing apparatus).^[12] When used at the onset this can abort the attack in as little as 5 minutes. Once an attack is at its peak, using oxygen therapy appears to have little effect. Alternative first-line treatment is subcutaneous administration of triptan drugs, like sumatriptan and zolmitriptan.^[12]. 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.

Lidocaine and other topical anesthetics sprayed into the nasal cavity may relieve or stop the pain,^[13] 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.

Sometimes, laying in a dark room will help a person if the pain is a side effect of Horner's Syndrome.

Cool showers have helped about 15% of people who try them; while not aborting the attack, they allow the body to cool and thus help to reduce the level of pain.^{citation needed]} 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.^[14][15]

Prophylactic treatment

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 240mg daily. Steroids, such as prednisolone, are also effective, with a high dose given for the first five days before tapering down. Methysergide, lithium and the anticonvulsant topiramate are recommended as alternative treatments.^[12]

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.

Non-established and research approaches

Feverfew, an herb used to treat migraine, is not clearly beneficial according to anecdotes from web forums. A large proportion of those trying kudzu have reported suppression of the symptoms.

There is substantial anecdotal evidence that serotonergic psychedelics such as psilocybin (mushrooms) and LSD and LSA d-Lysergic acid amide (Rivea corymbosa seeds) abort cluster periods and extend remission periods.^[16][17] Melatonin, psilocybin, serotonin, 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.^[18] A clinical study of these treatments under the auspices of MAPS is being developed by researchers at Harvard Medical School, McLean Hospital.^[19]

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.^[20]

• 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.^[21]

• It is also possible to have two or more different types of headaches, complicating diagnosis and treatment.