What is a Cluster Headache?

Cluster Headache

Cluster Headache

The eponymous characteristic of the cluster headache is the periodically accumulated incidence of headache attacks. These periods with headache attacks are interrupted by phases of complete relief of headache pain.

Often Used Terms

Terms used in the past for this headache condition, which should no longer be used today, are Erythroprosopalgia (of Bing), Ciliary or migrainous neuralgia (of Harris), erythromelalgia of the head, Horton’s headache, Bing-Horton headache, histaminic cephalalgia, Petrosus neuralgia (of Gardner), sphenopalatine neuralgia (Sluder’s neuralgia), Vidian neuralgia and hemicrania periodica neuralgiformis.

In the episodic cluster headache, cluster periods extend from one week to a maximum of one year – on average lasting between one and two months. As a rule, one to two cluster phases occur every 24 months. By definition, the pain-free phases last at least 14 days. The average duration of the remission phases is between six months and two years. In some patients, constant patterns of these remission phases can be observed. However, there are completely different phase lengths in other patients. In exceptional cases, remission phases lasting more than 20 years can be observed.

If cluster periods last for more than a year without any headache-free remission phase of at least 14 days having occurred, this is referred to as a chronic cluster headache. It is possible that a chronic cluster headache already takes this course from the beginning, i.e. not being separated by pain-free intervals. In such cases, the condition is referred to as a so-called primary chronic cluster headache from the beginning without remission.

If the initial occurrence consists of an episodic cluster headache with headache-free intervals subsequently turning into a chronic cluster headache, this is called a chronic cluster headache after a primary episodic course. If the attacks of a patient fulfill the HIS criteria for the cluster headache with only one exception, it is possible to arrive at a diagnosis of a cluster headache-like disturbance.

Time and Duration of the Attacks

Cluster attacks have a spontaneous duration of 15 to 180 minutes. On average, an attack lasts from 30 to 45 minutes. The duration of the attacks at the beginning of a cluster episode and towards the end of the cluster episode is shorter than in the middle of the cluster episode. The rapid rise of a pain attack is reflected in the fact that in almost all patients, the apex of the pain intensity is already reached after 10 minutes. This plateau is maintained for approx. 30 minutes; afterwards the attack subsides. The frequency of the attacks varies between one attack every second day and up to eight attacks per day. The average attack frequency during the cluster phase amounts to two attacks per day. More than three to four attacks per day are rare. In the majority of the patients, there is a typical association with a specific time of the day when the cluster attacks occur.

Attacks can be observed most frequently at night between 1 a.m. and 2 a.m. A second apex occurs between 1 p.m. and 3 p,m. in the afternoon and a third at 9 p.m. in the evening. However, there is a clear preponderance for the nightly occurrence between 1 a.m. and 3 a.m. In more than 50% of patients, attacks start during sleep.

Pain Characteristics

In almost all patients, cluster headache attacks are strictly constant to one side. The cluster headache occurs practically always on the same side and never (!) simultaneously on both sides. Only in extremely rare exceptions is there a change in the occurrence from one side to the other between different cluster periods. In more than 90% of patients, the pain starts in the eye region, either behind the eye, above the eye, or in the fronto-temporal eye area. The pain can also radiate towards the forehead, the jaw, the throat, the ear, to the back of the head, or, in rare cases, to the neck and to the shoulder. The increase of the intensity of pain is very fast. Out of a state of well-being, an extremely severe pain, often felt as crushing, develops within ten minutes. Patients describe the pain as a hot knife that is stuck into the eye or as a burning spike that is being rammed into the temple.

Attendant Discomforts

The attendant discomforts occur exclusively on the side affected by the pain. The most frequent occurrence – with 80% of the cases – is a flow of tears at the affected eye. Reddened eyes appear as the second-most frequent attendant symptom – with a frequency between 50% and 80%. An incomplete Horner’s syndrome (miosis), drooping upper eyelid (ptosis), and a seemingly sunken eyeball (pseudoenophthalmos) can be observed during the attack in up to almost 70% of patients. In longer courses of the disease, an incomplete Horner’s syndrome can continue to persist in some patients during the remission phase as well. In approx. 60% to 80%, there is an increased running of the nose. Facial sweating and reddening can also be found on the affected side; however, this disturbance occurs with a clearly lower frequency than the aforementioned discomforts. In a few patients, the autonomous attendant discomforts are pronounced to such a small degree that the patients do not realize their occurrence. Such mild autonomous disturbances are to be expected in less than 3% to 5% of the patients.

Physical Activity

In contrast to the migraine, a differentially-diagnostically important characteristic of the cluster headache is the urge of the patient to move during the attack. Typically, patients describe that they walk around restlessly during the pain attacks; suffering in pain, they bang their fists on the table or with the head against the wall. Bed rest is rarely kept.

Trigger Factors

A row of trigger factors may trigger cluster attacks during the cluster period; while patients in the remission phase can expose themselves to the same conditions without consequences. The best-known trigger factor for cluster headaches is alcohol. The important fact is that it is not the alcohol per se triggering the individual cluster attacks, but on the amount of alcohol consumed. During the cluster period, small amounts of alcohol may generate cluster attacks in a very potent and reliable manner, while larger amounts of alcohol may, in part, even prevent cluster attacks. A list of other substances may trigger cluster attacks. Among these are, in particular, histamine, nitroglycerin, and calcium antagonists such as, e.g., nifedipine. Blinding light is also mentioned as a trigger factor. The temporary wearing of sunglass lenses during the cluster episode may have a preventive effect.


No characteristic course of cluster headaches can be specified for individual cases. There are no epidemiological long-term studies. An active cluster headache production after the age of 75 is virtually never observed. It is possible to observe both transitions from an episodic to a chronic cluster headache as well as vice versa. The influence of preventive medications on the spontaneous course of the disease is still unknown. 80% of patients with a primary episodic cluster headache still suffer from an episodic cluster headache 10 years later, while in 12% of patients, a chronic cluster headache develops after a primary episodic course. In more than half of the people affected by a primary chronic cluster headache, this chronic form of the disease course continues to exist even after 10 years without any longer-lasting remission phases. A longer-lasting remission phase of more than three years can only be expected in approx. 10% of patients.


The median age for the initial occurrence of a cluster headache is 28 to 30 years. However, initial cluster headaches can also be observed in significantly higher ages. In children and adolescents, however, cluster headaches are a rare exception. The incidence of the cluster headache is 15.6 in 100,000 persons per year for men and 4.0 in 100,000 persons per year for women. The average incidence is 9.8 in 100,000 persons per year. According to various studies, the prevalence of the cluster headache is approx. 0.9%. As the only form of primary headache diseases, the cluster headache shows a clear preponderance of men. The share of men among patients with chronic and episodic cluster headaches is between 70% and 90%.


Generally, patients suffering from cluster headaches are able to describe the occurrence of their attacks in great detail. Recording the duration of the cluster headache attack is sometimes problematic. If two, three, or four cluster headache attacks occur, the patients are unsure whether they constitute a single attack lasting for eight hours with interruptions, or whether they are several attacks. In some cases, the maintenance of a headache calendar can yield more detailed information. As long as patients have not been under medical treatment, they will usually have taken all kinds of analgesics.

Since a cluster headache attack subsides after one hour in most cases, patients are under the impression that the remission is caused by the medication. It is only due to the long duration of the cluster periods and based on the neurological attendant disturbances that patients finally seek help. In order to arrive at a diagnosis, the characteristics of the headache attack must be enquired in detail. Among them are primarily the duration, the one-sidedness, the severity of the attack, the typical attendant symptoms, the localization in the eye area, and also the behavior of the patient during the attack.

Objective Diagnostic Tests

Since patients often do not notice attendant neurological disturbances themselves (such as incomplete Horner’s syndrome in particular), it is recommended to ask the patient to look into the mirror during the attack. Should there nevertheless be doubts as whether it is a cluster headache, a cluster attack could be triggered by the administration of nitroglycerin during a cluster period during consulting hours. For a successful provocation of such a triggered attack, it is necessary that no attack was spontaneously generated within the last eight hours, that no vasoconstrictive substances were taken within the last 24 hours, and that no medicinal prophylaxis is being performed.

Clinical Examinations

A diagnosis requires a regular neurological and general examination report. Additional equipment-based findings are not currently able to make a specific contribution to the diagnosis. However, there are situations, in which doubts exist as to whether it constitutes a primary headache condition. Such doubts specifically arise in cases when the following conditions are present:

  • The initial occurrence of the cluster headache is in a very young patient (under the age of 20) or in patients over the age of 60
  • A particular necessity for a thorough neurological examination – with additional imaging methods – is given if the headache runs a gradually increasing course, or if additional uncharacteristic attendant disturbances occur – in particular, disturbances regarding concentration, disturbances of memory, nausea, vomiting, clouding of consciousness, epileptic seizures, etc.

First and foremost, in the above-mentioned prerequisites, a magnetic resonance tomogram of the brain and a computer tomogram of the osseous base of the skull are arranged as an imaging procedure. In particular, one should pay attention to a possible pituitary tumor or a space occupation in the area of the skull basis (e.g. metastasis). Nose and paranasal sinus processes must also be captured.


Similar Diseases – Differentiation of the Cluster Headache

  • Migraine; 4 - 72 hours of nausea, vomiting, phonophobia, photophobia, no firm side localization, spreading tendency of the pain
  • Chronic paroxysmal hemicrania; 15 - 30 minutes; medium attack frequency – 14 per day, same neurological autonomous attendant disturbances as in the cluster headache, but a certain response to indometacin
  • Trigeminal neuralgia; Fractions of a second up to a maximum of 2 minutes, neurological attendant disturbances – as in the cluster headache – are not observed. Triggered by external stimulations such as chewing, talking, etc.
  • SUNCT Syndrome; Short-lasting Unilateral Neuralgiform headache attacks with conjunctival injection, tearing, sweating, and rhinorrhea, pain episodes lasting from 15 to 60 seconds; high attack frequency of 5 to 30 attacks per hour
  • Paranasal sinus processes, as a rule – constant pain, neurological attendant disturbances as in the cluster headache are not observed. No attack-wise occurrence and provocation through nitroglycerin or alcohol
  • Eye lesions; No temporal occurrence pattern of the cluster headache, reddening of the eyes is present, typical attendant disturbances as in the cluster headache lacking, anamnesis and ophthalmic findings, reduced vision (normal in cluster headaches)


Development Mechanism (Pathophysiology)

The imaging view of the eye veins, which had been performed in cluster headache patients during active cluster periods, yielded clues for an infection of unclear cause in a special vein network not caused by pathogens – the cavernous sinus and in the area of the ophthalmica superior vein. In a very small space bounded by bones in the area of the cavernous sinus lie the bundled fibers of the ophthalmic nerve, and also sympathetic fibers supplying the eyelid, the eye, the face, the eye socket, and the vessels. Thus, local inflammatory processes can influence both sensory and autonomous nerve fibers as well as venous and arterial vessels. Thereby, an irritation of the nerve fibers is, conceivably, directly due to released inflammatory neurotransmitters as well as the result of a mechanic compression due to vessels that have been expanded and swollen due to inflammation.

This theory can explain the cluster pain and the varied attendant symptoms. The ability to provoke cluster attacks during active cluster periods by means of vasodilatory substances (alcohol, nitroglycerin, histamine, hypoxia) and to end them quickly by means of vasoconstrictive substances (oxygen, Sumatriptan, Ergotamine), is compatible with the model. This also explains the increase of the pain while reclining and why the venous blood flow of the cavernous sinus is worse while sitting or standing.

It is assumed that there is a basically inflammable base reaction during active cluster periods, which goes through phases of attacks. In the chronic cluster headache, this inflammable base reaction is continuously present, while this is only periodically so in the episodic form. The reliable effectiveness of anti-inflammatory acting corticosteroids for the prevention of cluster headaches is also explained this way.


Behavioral and Non-Medicinal Measures; Contrary to other primary headache conditions, the cluster headache is only minimally influenced by psychological mechanisms. Relaxation procedures, stress management techniques, and similar measures, which play an important role in the therapy of migraine and tension-type headaches, are not able to alter the course of the cluster headache to any significant degree. The use of alternative, non-medicinal therapy measures such as acupuncture, neural therapy, biofeedback, massages, manual therapy, transcutaneous electric nerve stimulation (TENS), etc. are of no use in the cluster headache and delay the initiation of an effective therapy.

The information of the patient by the physician is crucially important. As a rule, about 5 years pass until the diagnosis of a cluster headache is made. Therapy attempts prior to the diagnosis are usually bound to fail since the substances and behavioral measures effective in the cluster headache differ from those in other headache conditions. During this long trial and error phase, the patient is left helpless at the mercy of his crushing pain attacks. An understandable loss of trust towards doctors, vis-à-vis, can be the result and drive patients into resignation.

Regarding the possible provocation of attacks through alcohol and vasodilating substances, such a nitrates or histamine, the patient should be urged to avoid such agents. This also requires an exact medicinal anamnesis. In some patients, nicotine may also provoke cluster headache attacks. For this reason, smoking patients should be induced to give up smoking. Nutritional factors do not have any large influence on the course of the cluster headache, which is why dietary measures in cluster headaches are not indicative of success.

Afterwards, the patient should be informed about the possibilities of a medicinal therapy. A therapy pattern both for the therapy of the attacks, as well as for a prophylaxis, should be developed individually and be given to the patient in form of a treatment plan. The patient should receive information as to how long a prophylactic treatment is conducted, at which times he has to administer a certain medication, and what side effects are to be expected.

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