Cluster headache

Cluster headache is a neurological disorder
characterized by recurrent, severe headaches on one side of the head, typically around
the eye. There are often accompanying autonomic symptoms
during the headache such as eye watering, nasal congestion and swelling of and around
the eye, all confined to the side of the head with the pain. Cluster headache belongs to a group of primary
headache disorders, classified as trigeminal autonomic cephalalgias or. The condition is named for the demonstrated
grouping of headache attacks occurring together. Individuals typically experience repeated
attacks of excruciatingly severe unilateral headache pain. CH attacks often occur periodically; spontaneous
remissions may interrupt active periods of pain, though about 10–15% of chronic CH
never remit. The cause has not been identified. While there is no cure, cluster headaches
can sometimes be prevented and acute attacks treated. Recommended treatments for acute attack includes
oxygen or a fast acting triptan. Primary recommended prevention is verapamil. Steroids may be used to prevent a recurrence
until verapamil takes effect. The condition affects approximately 0.2% of
the general population, and men are more commonly affected than women, by a ratio of about 2.5:1
to 3.5:1. Signs and symptoms
Cluster headaches are recurring bouts of excruciating unilateral headache attacks of extreme intensity. The duration of a typical CH attack ranges
from about 15 to 180 minutes. Most untreated attacks last less than 60 minutes. The onset of an attack is rapid and most often
without preliminary signs that are characteristic in migraine. Preliminary sensations of pain in the general
area of attack, referred to as “shadows”, may signal an imminent CH, or these symptoms
may linger after an attack has passed, or even between attacks. Though a CH is strictly unilateral, there
are some documented cases of “side-shift” between cluster periods, extremely rare, simultaneously
bilateral headache. Pain
The pain occurs on one side only, around the eye, particularly above the eye, in the temple,
in any combination. The pain of CH is remarkably greater than
in other headache conditions, including severe migraine. The term “headache” does not adequately convey
the severity of the condition; the disease may be the most painful condition known to
medical science. The pain is described as stabbing, burning
or squeezing and may be located near or behind the eye and at the back of the head or neck. Other symptoms
The typical symptoms of cluster headache are grouping of recurring headache attacks of
severe or very severe unilateral orbital, supraorbital and/or temporal pain. If left untreated, attack frequency will range
from one attack every two days to eight attacks a day. The headache attack is accompanied by at least
one of the following autonomic symptoms: drooping eyelid, pupil constriction, redness of the
conjunctiva, tearing, runny nose, and, less commonly, facial blushing, swelling, or sweating,
commonly but not always appearing on the same side of the head as the pain. Restlessness, photosensitivity, aversion to
light or sensitivity to noise may occur during a CH. Nausea is a rare symptom, although it has
been reported. Secondary effects may include inability to
organize thoughts and plans, physical exhaustion, confusion, agitation, aggressiveness, depression
and anxiety. People with CH may dread facing another headache
and adjust their physical or social activities around a possible future occurrence. Likewise they may seek assistance to accomplish
what would otherwise be normal tasks. They may hesitate to make plans because of
the regularity, or conversely, the unpredictability of the pain schedule. These factors can lead to generalized anxiety
disorders, panic disorder, serious depressive disorders, social withdrawal and isolation. Recurrence
Cluster headaches are occasionally referred to as “alarm clock headaches” because of the
regularity of their timing and they may awaken individuals from sleep. Both individual attacks and the cluster grouping
can have a metronomic regularity; attacks striking at a precise time of day each morning
or night is typical. The grouping of headache clusters can occur
more often around solstices, or spring and autumn equinoxes, sometimes showing circannual
periodicity. This has prompted researchers to speculate
involvement, or dysfunction of the brain’s hypothalamus, which controls the body’s “biological
clock” and circadian rhythm. Conversely, attack frequency may be highly
unpredictable, showing no periodicity at all. In episodic cluster headaches, attacks occur
once or more daily, often at the same time each day, for a period of several weeks, followed
by a headache-free period lasting weeks, months, or years. Approximately 10–15% of cluster headaches
chronic, with multiple headaches occurring every day for years, sometimes without any
remission. In accordance with the International Headache
Society diagnostic criteria, 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 may be classified as episodic. If attacks occur for more than a year without
pain-free remission of at least one month, the condition is classified chronic. Chronic CH occurs continuously without any
remission periods between cycles; there may be high and low variation in cycles, meaning
the frequency and severity of attacks may change without predictability, for a period
of time. The amount of change during these cycles varies
between individuals and does not demonstrate complete remission of the episodic form. The condition may change unpredictably, from
chronic to episodic and from episodic to chronic. Remission periods lasting for decades have
been known to occur. Causes
The cause of cluster headache is unknown. Genetics
Cluster headache may, but rarely, run in some families in an autosomal dominant inheritance
pattern. People with a first degree relative with the
condition are about 14-48 times more likely to develop it themselves, and between 1.9
and 20% of persons with CH have a positive family history. This suggests that genetic factors are important,
but the type and number of genes involved is unclear. Smoking
About 65% of persons with CH are, or have been, tobacco smokers. Stopping smoking does not lead to improvement
of the condition and CH also occurs in those who have never smoked; it is thought unlikely
that smoking is a cause. People with CH may be predisposed to certain
traits, including smoking or other lifestyle habits. Hypothalamus
One theory is that the cause is dysfunction of the hypothalamus, which may explain why
cluster headaches frequently strike around the same time each day, and during a particular
season. One of the functions of the hypothalamus is
regulation of the biological clock. Metabolic abnormalities have also been reported. The positron emission tomography scans indicate
the brain areas which are activated during pain of attack only, compared to pain free
periods. These pictures show brain areas which are
active during pain in yellow/orange color. The area in the center is specifically activated
during CH only. The bottom row voxel-based morphometry shows
structural brain differences between individuals with and without CH; only a portion of the
hypothalamus is different. Pathophysiology
Cluster headache has been historically classified as vascular headaches; for decades, it has
been proposed that intense pain was caused by dilation of blood vessels which was thought
to create pressure on the trigeminal nerve. While this theory was thought to be the immediate
cause of the pain, the etiology is not fully understood and CH pathogenesis is the subject
of ongoing debate. Investigations into the vascular theory of
headache disorders are helping to identify the role of other possible causative mechanisms
in CH. Diagnosis
Cluster headaches are often misdiagnosed, mismanaged, or undiagnosed for many years;
they may be confused with migraine, “cluster-like” headache, CH subtypes, other TACs, or other
types of primary or secondary headache syndrome. Cluster-like head pain may be diagnosed as
secondary headache rather than cluster headache. A detailed oral history aids correct differential
diagnosis, as there are no confirmatory tests for CH. A headache diary can be useful in tracking
when and where pain occurs, how severe it is, and how long the pain lasts. A record of coping strategies used may help
distinguish between headache type; data on frequency, severity and duration of headache
attacks is a necessary tool for initial and correct differential diagnosis in headache
conditions. Correct diagnosis of CH is a challenge for
practitioners, and is especially problematic in hospital emergency departments, where staff
are not trained in the diagnosis of rare or complex chronic disease. Although experienced ER staff are sometimes
trained to detect headache types, CH attacks themselves are not life-threatening. Individuals with CH typically experience a
lengthy delay before correct diagnosis. People are often misdiagnosed due to reported
neck, tooth, jaw, and sinus symptoms and may unnecessarily endure many years of referral
to ear, nose and throat specialists for investigation of sinuses; dentists for tooth assessment;
chiropractors and manipulative therapists for treatment; or psychiatrists, psychologists
and other medical disciplines before their headaches are correctly diagnosed. Often there is a delay of several years before
the correct diagnosis is reached. Medical students receive little training in
differential diagnoses and management of headaches. Differential
Cluster headache may be misdiagnosed as migraine or sinusitis. Other types of headache are sometimes mistaken
for, or may mimic closely, CH. Incorrect terms like “cluster migraine” confuse
headache types for both practitioner and patient, confound differential diagnosis and are often
the cause of unnecessary diagnostic delay, ultimately delaying appropriate specialist
treatment. Headaches that may be confused with CH include:
Chronic paroxysmal hemicrania is a unilateral headache condition, without the male predominance
usually seen in CH. Paroxysmal hemicrania may also be episodic. CPH typically responds “absolutely” to treatment
with the anti-inflammatory drug indomethacin where in most cases CH typically shows no
positive indomethacin response, making “Indomethacin response” an important diagnostic tool for
specialist practitioners seeking correct differential diagnosis between the conditions. Short-lasting unilateral neuralgiform headache
with conjunctival injection and tearing is a headache syndrome belonging to the group
of TACs. Trigeminal neuralgia is a unilateral headache
syndrome, or “cluster-like” headache. Prevention
Preventive treatments are used to reduce or elimination cluster headache attacks; they
are generally used in combination with abortive and transitional techniques. Verapamil
The recommended first-line preventative therapy is verapamil, a calcium channel blocker. Verapamil was previously underused in people
with cluster headache. Steroids
There is little evidence to support a long-term benefit from steroids, but they may be used
until other medications take effect as they appear to be effective at three days. They are generally discontinued after 8–10
days of treatment. Surgery
Nerve simulators may be an option in the small number of people who do not improve with medications. Two procedures, deep brain stimulation or
occipital nerve stimulation, may be useful; early experience shows a benefit in about
60% of cases. It typically takes weeks or months for this
benefit to appear. A non-invasive method using transcutaneous
electrical nerve stimulation is being studied. A number of surgical procedures, such as a
rhizotomy or microvascular decompression, may also be considered, but evidence to support
them is limited and there are cases of people ending up worse off. Other
Lithium, methysergide, and topiramate are recommended alternative treatments, although
there is little evidence supporting the use of topiramate or methysergide. This is also true for melatonin and ergotamine. Valproate, sumatriptan and oxygen are not
recommended as preventative measures. Botox injection have shown mixed success. Management
Treatment for cluster headache is divided into three primary categories: abortive, transitional,
and preventative. There are two primary treatments for acute
CH: oxygen and triptans, but they are underused due to misdiagnosis of the syndrome. During bouts of headaches, triggers such as
alcohol, nitroglycerine and naps during the day should be avoided. Oxygen
Oxygen therapy may help people with CH, but it does not help prevent future episodes. Typically it is given via a non-rebreather
mask at 12-15 liters per minute for 15–20 minutes. Around 70% improve within 15 minutes. It is unclear if hyperbaric oxygen therapy
is better than high flow oxygen. Triptans
The other primarily recommended treatment of acute attacks is subcutaneous or intranasal
sumatriptan. Sumatriptan and zolmitriptan have both been
shown to improve symptoms during an attack with sumatriptan being superior. Because of the vasoconstrictive action of
triptans, they are contraindicated in people with ischemic heart disease. Opioids
The use of opioid medication in management of CH is not recommended; they may make headache
syndromes worse and their long-term use is associated with dependency, addiction and
withdrawal syndromes. Prescription of opioid medication may additionally
lead to a delay in diagnosis, undertreatment, and mismanagement. Other
The vasoconstricting ergot compounds may be useful, but have not been well studied in
acute attacks. Epidemiology
Cluster headache effects about 0.2% of the general population, or 56 to 326 people per
100,000. Males are affected more commonly than females,
in a ratio of about 2.5:1 to 3.5:1. The condition usually starts between the ages
of 20 and 50 years, although it can occur at any age. History
The first complete description of cluster headache was given by the London neurologist
Wilfred Harris in 1926, who named the disease migrainous neuralgia. Descriptions of CH date to 1745 and probably
earlier. The condition was originally named Horton’s
cephalalgia after B.T. Horton, a US neurologist 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 attempt or complete
suicide; his 1939 paper said: “Our patients were disabled by the disorder
and suffered from bouts of pain from two to twenty times a week. They had found no relief from the usual methods
of treatment. Their pain was so severe that several of them
had to be constantly watched for fear of suicide. Most of them were willing to submit to any
operation which might bring relief.” CH has alternately been called erythroprosopalgia
of Bing, ciliary neuralgia, erythromelalgia of the head, Horton’s headache, histaminic
cephalalgia, petrosal neuralgia, sphenopalatine neuralgia, vidian neuralgia, Sluder’s neuralgia,
and hemicrania angioparalyticia. Society and culture
Robert Shapiro, a professor of neurology, says that while cluster headaches are about
as common as multiple sclerosis with a similar disability level, as of 2013, the US National
Institutes of Health had spent $1.872 billion on research into multiple sclerosis in one
decade, but less than $2 million on CH research in 25 years. Research directions
Some controversial case reports suggest that ingesting LSD, psilocybin or cannabis can
reduce pain and interrupt cluster headache cycles. A 2006 interview/survey of 53 individuals
with CH said that psilocybin extended remission periods in 10% cases. The survey was not a blinded or controlled
study, and was “limited by recall and selection bias”. References

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