Development of severe, unilateral and sudden headache marks the onset of cluster headaches. Individuals usually experience headaches 2 to 3 hours after they fall asleep. Attacks can occur almost every day and can continue for several months. Headaches typically occur at the same time of the day, every day and last for about 15 to 180 minutes. Affected individuals experience the following signs and symptoms [8]:

• Burning, stabbing and sharp pain on one side of the head
• Pain gets worse within 5 to 10 minutes, and strong pain continues for half an hour to 2 hours
• Nasal stuffiness
• Lacrimation
• Flushing and sweating
• Edema of the eyelid 
• Miosis
• Ptosis

• Severe Pain

  All six included studies used a single dose of triptan to treat an attack of moderate to severe pain intensity. [ncbi.nlm.nih.gov]

  This headache syndrome involves what is described as “attacks” of severe pain on one side of the head lasting 15-180 minutes and occurring as little as once every day or as often as 8 times a day. [coloradoheadache.com]

  In an attack: You'll have very severe pain around one eye and that side of your head The pain is strongest within minutes and usually lasts half an hour to an hour The pain may wake you up from sleep and may make you want to pace around You may also have [merckmanuals.com]

• Swelling

  Other substances that cause blood vessel swelling, such as nitroglycerin or histamine, also can provoke an acute attack during a series. Smoking can increase the severity of cluster headaches during a cluster period. [columbianeurology.org]

  Attacks are associated with eye redness, tearing from the eye, runny nose, nasal congestion, facial sweating, or sometimes eyelid swelling all occuring on one side. [coloradoheadache.com]

  […] forehead that last from 15 minutes to three hours if not treated Headache has at least one of the following: Ipsilateral conjunctival injection and/or lacrimation—which is pink eye, swollen eyelid and/or tearing Nasal congestion and/or runny nose Eyelid swelling [migraine.com]

  Sufferers will also experience swelling of the eye and congestion of the nasal passage on the affected side. Some people also experience facial sweating and agitation. Cluster headaches are named from their pattern of occurrence. [physioworks.com.au]

  Facial sweating, nasal congestion, drooping eyelids (ptosis), and eyelid swelling (edema) are also common. Rarely before an attack patients will report seeing an aura or having other visual disturbances. [rarediseases.org]

• Episodic Pain

  There are videos documenting the severe bouts of episodic pain that capture the intensity of the condition, which can last anywhere from a few minutes to three hours at a time. [medicaldaily.com]

  However, with a prevalence of approximately 0.1% and a lengthy history of disabling and distressing episodic pain, cluster headache is an important neurologic problem. [neurology.org]

  Different personality profiles might be explained as a response to continued exposure to pain, as it would occur in chronic forms, or to the risk of sudden intense pain, as would happen in episodic pains [ 46 ]. [thejournalofheadacheandpain.biomedcentral.com]

• Nocturnal Awakening

  Patients with poorly defined nocturnal or awakening headaches should undergo polysomnography to exclude a treatable sleep disturbance, especially in the absence of an underlying psychological disorder or analgesic overuse syndrome. [doi.org]

• Nasal Congestion

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis, eyelid oedema. [healthcentral.com]

  Attacks are associated with eye redness, tearing from the eye, runny nose, nasal congestion, facial sweating, or sometimes eyelid swelling all occuring on one side. [coloradoheadache.com]

  We report the case of an 11-year-old boy who suffered from sudden attacks of shock-like, intense pain, localized in the right orbital region, with associated photophobia, phonophobia, conjunctival injection, lacrimation, nasal congestion, rhinorrhoea [ncbi.nlm.nih.gov]

  The pain is associated with ipsilateral conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis and/or eyelid oedema, and/or with restlessness or agitation. [ichd-3.org]

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, facial sweating, eyelid edema, and miosis. [icd9data.com]

• Rhinorrhea

  Abstract Cluster headache (CH) is characterized by a series of sudden attacks of short-lasting severe headache pain with ipsilateral autonomic features, including lacrimation, rhinorrhea, localized sweating, eyelid edema, and partial or complete Horner's [ncbi.nlm.nih.gov]

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, facial sweating, eyelid edema, and miosis. [icd9data.com]

  Cluster headaches cause excruciating, unilateral periorbital or temporal pain, with ipsilateral autonomic symptoms (ptosis, lacrimation, rhinorrhea, nasal congestion). Diagnosis is clinical. [merckmanuals.com]

• Nasal Discharge

  It is available in injectable, nasal spray and tablet forms, although the latter is the least effective because of the time it takes before the onset of action. [headaches.org]

  The trigeminal nerve also stimulates the parasympathetic autonomic system, which causes the eye tearing and redness, nasal congestion and discharge with cluster attacks. [my.clevelandclinic.org]

  […] congestion, rhinorrhea (nasal discharge/”runny nose”), forehead and facial sweating, miosis (excessive constriction/tightening of the eye’s pupil), ptosis (drooping of the upper eyelid), eyelid edema (swelling/”puffiness” of the eyelid from excessive [clusterbusters.org]

• Nausea

  Our female cluster headache population had more nausea and significantly more vomiting than our men. Manzoni et al 12 also found that nausea was more common in women than men. They did not find any other sex differences in cluster headache symptoms. [dx.doi.org]

  Photophobia or phonophobia and nausea were in part responsible for this delay, and should be recognised as part of the clinical spectrum of CH. [ncbi.nlm.nih.gov]

  Confusion, dizziness, blurry vision, diabetes insipidus, headache, nausea, polyuria In a double-blind crossover study 33 of 30 patients, 50 percent of patients responded in two weeks. [aafp.org]

• Vomiting

  Nausea has been reported in 10% to 54% of patients, whereas vomiting has been noted in 1% to 15% (data from mainly male cluster headache populations). [dx.doi.org]

  Anti-nausea drugs are commonly used as well, since many sufferers experience nausea or vomiting during a migraine. [diffen.com]

  Erythroprosopalgia of Bing Migrainous neuralgia Difference between cluster headache and migraines Migraines are typically made worse by physical activity, cause throbbing pain and occurs with at least one of the following migraine symptoms : nausea, vomiting [migraine.com]

• Conjunctival Injection

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis, eyelid oedema. [healthcentral.com]

  METHODS/RESULTS: Ophthalmic features such as conjunctival injection, lacrimation, ptosis and miosis occur in the vast majority of patients with cluster headache, whereas co-existent ocular movement disorders are rare. [ncbi.nlm.nih.gov]

• Lacrimation

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis, eyelid oedema. [healthcentral.com]

  METHODS/RESULTS: Ophthalmic features such as conjunctival injection, lacrimation, ptosis and miosis occur in the vast majority of patients with cluster headache, whereas co-existent ocular movement disorders are rare. [ncbi.nlm.nih.gov]

• Miosis

  It is a neurological disorder, wherein the affected individuals would also experience associated symptoms such as conjunctival injection, nasal congestion, rhinorrhea, miosis or ptosis. [symptoma.com]

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis, eyelid oedema. [healthcentral.com]

  METHODS/RESULTS: Ophthalmic features such as conjunctival injection, lacrimation, ptosis and miosis occur in the vast majority of patients with cluster headache, whereas co-existent ocular movement disorders are rare. [ncbi.nlm.nih.gov]

  The pain is associated with ipsilateral conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis and/or eyelid oedema, and/or with restlessness or agitation. [ichd-3.org]

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, facial sweating, eyelid edema, and miosis. [icd9data.com]

• Photophobia

  Both men and women have frequent photophobia and phonophobia with cluster headache attacks. [dx.doi.org]

  Photophobia or phonophobia and nausea were in part responsible for this delay, and should be recognised as part of the clinical spectrum of CH. [ncbi.nlm.nih.gov]

  Interictal headache or concomitant symptoms, such as photophobia or nausea during episodes, may distract from the appropriate diagnosis. [doi.org]

• Eye Pain

  July 2013 Article – “Cluster Headaches – a Medical Enigma” Symptoms Symptoms may include Excruciating, boring, burning pain (much more severe than migraine) localized around one eye pain very pronounced behind one eye, commonly radiating to forehead, [headacheaustralia.org.au]

  These are common symptoms of a cluster headache: Sudden onset of pain, generally around or behind the eye Pain builds to a peak in about 10 to 15 minutes Restlessness or agitation Red or watering eyes Nasal congestion Sweating on the forehead Eyelid drooping [hopkinsmedicine.org]

  The pain is so intense that most cluster headache sufferers cannot sit still and will often pace during an attack. Location of pain The pain is located behind one eye or in the eye region, without changing sides. [my.clevelandclinic.org]

  The pain typically is excruciating and located around or behind one eye. Some patients describe the pain as feeling like a hot poker in the eye. The affected eye may become red, inflamed, and watery. [medicinenet.com]

• Sweating

  The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis, eyelid oedema. [healthcentral.com]

  Six CAS items were surveyed, including: conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, eyelid oedema and forehead/facial sweating. [dx.doi.org]

  Attacks are associated with eye redness, tearing from the eye, runny nose, nasal congestion, facial sweating, or sometimes eyelid swelling all occuring on one side. [coloradoheadache.com]

  Abstract Cluster headache (CH) is characterized by a series of sudden attacks of short-lasting severe headache pain with ipsilateral autonomic features, including lacrimation, rhinorrhea, localized sweating, eyelid edema, and partial or complete Horner's [ncbi.nlm.nih.gov]

• Flushing

  Symptoms: Symptoms of cluster headaches include sudden and severe headache, followed by flushing and redness of face. Affected individuals also experience excessive tearing along with stuffed nose. [symptoma.com]

  The face may be flushed. Nausea may accompany the headaches. Headache attacks may occur several times a day, often at the same time of day or night. [msdmanuals.com]

  Explicitly, they asked about lacrimation, conjunctival injection, nasal congestion, rhinorrhoea, eyelid oedema and forehead/facial flushing. [doi.org]

• Hyperhidrosis

  Labor, DR, Mohr, JP, Nichols, FT, Tatemichi, TK Unilateral hyperhidrosis after cerebral infarction. Neurology 1988 ; 38: 1679 – 82 Google Scholar | Crossref | Medline 12. [dx.doi.org]

• Facial Pain

  Abstract BACKGROUND: Chronic cluster headache (CCH) is characterized by recurrent bouts of facial pain lasting up to 180 minutes in the absence of a long remission period. [ncbi.nlm.nih.gov]

  Headache and facial pain. Stuttgart : G. Thieme Verlag, 1981 : 1 – 274. Google Scholar 11. D’Alessandro, R, Gamerini, G, Benassi, G, Morganti, G, Cortelli, P, Lugaresi, E. Cluster headache in the Republic of San Marino. [oadoi.org]

  Four patients presented with “facial pain”, one with “toothache” and one with “jaw pain”. All were female with mean age 55 ± 10.5 years (range = 41–69). [experts.umn.edu]

• Episodic Headache

  There is debate whether cutaneous allodynia may also occur in cluster headache, another episodic headache disorder. [ncbi.nlm.nih.gov]

  The episodic type is more common, experienced by about 80 percent of sufferers. These are characterized by pain episodes or headaches that occur together in periods known as “a cluster.” [psychcentral.com]

  Abstract Background and purpose: Cluster headache (CH) is an episodic headache disorder characterized by recurrent, unilateral attacks of excruciating pain in the temporal/orbital region. [doi.org]

  Like other headaches, there are two main classifications: Episodic Headaches – Clusters that present themselves from one week to a year with long periods of remission Chronic Headaches – Clusters that occur for longer than a year, or with very short remission [ihateheadaches.org]

  If you have episodic headaches, your doctor will ask you to try coming off your preventive medicine slowly once you have been headache-free for two weeks. You won’t need to take it again until another bout starts. [bupa.co.uk]

• Unilateral Facial Pain

  Patients presenting with unilateral facial pain present a unique diagnostic challenge for dental practitioners. [oooojournal.net]

• Cheek Pain

  People who suffer from cluster headaches--especially people who have tooth or cheek pain with the cluster attacks--have an increased risk of developing a stomach ulcer. [my.clevelandclinic.org]

• Headache

  Abstract Cluster headache is a rare disorder that is more common in adult male patients. It has a unique phenotype of unilateral, severe, to very severe headaches lasting 15 to 180 min with ipsilateral autonomic symptoms. [ncbi.nlm.nih.gov]

  Cluster headaches are named for the occurrence of groups of headache attacks (clusters). They have also been referred to as "suicide headaches". Cluster headaches are recurring bouts of severe unilateral headache attacks. [en.wikipedia.org]

  Facts about Cluster Headaches Cluster headaches last a short period of time, but cause severe pain Men suffer from cluster headaches three to six times more often than women Less than one adult in 1,000 suffers from cluster headaches The disorder surfaces [migraine.com]

  […] intractable cluster headaches. [draxe.com]

• Neuralgia

  Trigeminal neuralgia: its history and treatment. Springfield, IL : Charles C. Thomas, 1959. Google Scholar 14. Penman, J. Trigeminal neuralgia. In: Vinken, PJ, Bruyn, GW, eds. Handbook of clinical neurology, Vol. 5, Headaches and cranial neuralgias. [doi.org]

  neuralgia, pterygopalatine neuralgia, Sluder disease, Sluder headache, Sluder neuralgia, Sluder sphenopalatine neuralgia, Sluder syndrome, Sluder's disease, Sluder's headache, Sluder's neuralgia, Sluder's sphenopalatine neuralgia, Sluder's syndrome, sphenopalatine [synonyms.com]

  […] histamine headache, Horton, ciliary; neuralgia, cluster; headache, headache; cluster, headache; histamine, histamine; headache, migrainous; neuralgia, neuralgia; ciliary, neuralgia; migrainous, syndrome; cluster headache, Cluster headache (disorder) [ [fpnotebook.com]

• Agitation

  Most patients are restless or agitated during an attack." [healthcentral.com]

  Cluster headache is a trigeminal autonomic cephalalgia characterised by extremely painful, strictly unilateral, short-lasting headache attacks accompanied by ipsilateral autonomic symptoms or the sense of restlessness and agitation, or both. [ncbi.nlm.nih.gov]

  The pain is associated with ipsilateral conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis and/or eyelid oedema, and/or with restlessness or agitation. [ichd-3.org]

• Trigeminal Neuralgia

  Trigeminal neuralgia: its history and treatment. Springfield, IL : Charles C. Thomas, 1959. Google Scholar 14. Penman, J. Trigeminal neuralgia. In: Vinken, PJ, Bruyn, GW, eds. Handbook of clinical neurology, Vol. 5, Headaches and cranial neuralgias. [doi.org]

  In fact, cluster headache is classed as a trigeminal autonomic cephalgia. In this case report, episodic cluster headache is treated in the same way as has been shown effective for trigeminal neuralgia. [ncbi.nlm.nih.gov]

• Stroke

  Author information 1 Department of Psychiatry, VA Connecticut Healthcare/Yale University School of Medicine, West Haven, CT 06516, USA. [email protected] Abstract A 34-year-old man with right-sided cluster headache presented with a stroke from right-sided [ncbi.nlm.nih.gov]

  Association, Singapore National Stroke Association, World Stroke Organization Disclosure: Nothing to disclose. [medscape.com]

  Cluster headaches are a series of relatively short but extremely painful headaches that occur in clusters, usually at the same time of the day and night for several weeks, according to the National Institute of Neurological Disorders and Stroke. [sciencedaily.com]

  Field, A Narrative Review of Persistent Post‐Stroke Headache – A New Entry in the International Classification of Headache Disorders, 3rd Edition, Headache: The Journal of Head and Face Pain, 58, 9, (1442-1453), (2018). [dx.doi.org]

The following procedures are employed for diagnosing cluster headaches:

• Neurological exam: This would be done to detect the physical signs of cluster headaches. The examination would reveal ptosis and miosis and other associated sign.
• Imaging: Imaging studies such as CT scan of the brain and MRI of the blood vessels and brain would help in diagnosing the cause of cluster headaches. These tests would also help in ruling out conditions of tumor and aneurysm.

Cluster headache cannot be cured; it can however be effectively managed by reducing the severity of the symptoms. The major objectives for treatment of the condition involve shortening of the duration of attacks, reducing the frequency and decreasing the severity of headaches. Following are the methods which are employed for treating acute attacks of cluster headaches:

• Oxygen therapy: In acute conditions, inhaling 100% oxygen at rate of 12 liters per minute would provide relief within 15 minutes [9]. 
• Triptans: Triptans can be given through injections or nasal spray. It has been observed that the one given through injections is more effective than nasal spray.
• Octreotide: This medication is given through injection and is a synthetic form of the brain chemical somatostatin. 
• Local anesthetics: Local anesthetics given through intranasal route is an effective treatment regime for cluster headaches.
• Dihydroergotamine: This form of medication is given through the intravenous route and is an effective treatment regime for some percentage of individuals suffering from cluster headaches [10].
• Surgery: This is often the last resort when other forms of aggressive treatment do not work. However, this is usually not an effective way of treatment because the surgical procedures employed may cause damage to the neighboring nerve cells.

Cluster headaches can be severe enough to interfere with daily work and also affects the quality of life; however the condition is not life threatening. With appropriate treatment, it can be effectively managed. Cluster headaches do not permanently damage the brain [7].

The exact cause of cluster headache is not known. The disease is sporadic in nature; however some pieces of evidence suggest an autosomal dominant pattern. Abnormalities in the hypothalamus are known to play foul in the development of cluster headache. An increase in the activity of the hypothalamus has been noted in the affected individuals during the course of cluster headaches. The various risk factors for cluster headache include alcohol consumption, smoking and certain medications such as nitroglycerin [2].

The exact incidence rate of cluster headache in the US is unknown. Middle aged individuals are more prone to develop such a type of condition. However, in many instances, cluster headache can even affect small children aged 1 year and adults aged 79 years and above [3]. Cluster headache is a rare phenomenon, with an estimated prevalence rate of 0.4% in men and 0.08% in women. Males are more prone to develop this condition compared to females, with male to female ratio being 6:1 [4].

The pathophysiology of cluster headaches is not properly understood. The periodic attacks suggest the involvement of human biological clock along with increase in activity of the hypothalamus [5]. Diagnostic procedures have revealed that the major area of defect that gives rise to cluster headaches is the posterior hypothalamic grey matter. One of the mechanisms which have been understood, is that the attack is caused due to dilation of blood vessels which in turn exert pressure on the trigeminal nerve. Such a theory is known to give rise to the condition of cluster headaches [6].

Individuals are advised to avoid the various trigger factors such as smoking and alcohol. Maintaining a headache diary would also help in identifying the day and time of attacks which would help in preventing the onset of future bouts. Certain medications have also proved to be effective in preventing the development of cluster headaches. These include allergic medications, seizure medicines and hypertensive medicines.

Cluster headache is often confused with conditions of migraines, tension headache, sinus or the usual headache. Affected individuals may experience regular attacks for a period of 1 week to a year on a regular basis. This type of neurological condition belongs to a group of trigeminal autonomic cephalalgias. So far there is no known cure to treat cluster headaches. However, these can be prevented and the development of acute attacks can be effectively managed [1].

• Definition: Cluster headaches are a type of neurological disorder which involve onset of sudden and severe headaches usually on one side of head. Males are more prone to contract this disease condition in comparison to females.
• Cause: The exact cause of cluster headache is unknown. Certain trigger factors include alcohol consumption, smoking and medications such as nitroglycerin for treating heart disease.
• Symptoms: Symptoms of cluster headaches include sudden and severe headache, followed by flushing and redness of face. Affected individuals also experience excessive tearing along with stuffed nose.
• Diagnosis: A preliminary physical examination would be done at the initial level. In addition, neurological examination would be done followed by imaging studies such as CT scan and MRI of the brain. This would help in ruling out other conditions of tumor and aneurysm.
• Treatment: There is no known cure for cluster headaches. The condition can be effectively managed with appropriate treatment regime. Pharmacologic treatment forms the basis of the treatment regime. Medications such as triptans and steroids are given through the intravenous route. In addition, oxygen therapy has also been proven to be helpful for providing instant relief. Surgery is often the last resort and not always helpful in treating cluster headaches.

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