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

• Pain

  Pain from cluster headache is typically on one side of the head and in the worst attacks the pain can be excruciating. Pain may also be bilateral and non-throbbing. There are two types of cluster headaches, episodic and chronic. [migraine.com]

  A headache diary can be useful in tracking when and where pain occurs, how severe it is, and how long the pain lasts. [en.wikipedia.org]

  Women have even compared cluster headache pain to be equivalent to labor pain, while men express that it’s the worst pain they’ve ever felt. Cluster headaches involve intense and relentless pain in or around one eye on one side of the head. [draxe.com]

• 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 [msdmanuals.com]

• Falling

  The headaches can also be seasonal, with the spring or fall signaling the onset of attacks. 3. You need a doctor who 100% gets it. [prevention.com]

  In the late 1990s Goadsby and his colleagues linked cluster headaches to heightened synaptic activity falling in or near the hypothalamus, a brain region that mediates hunger, thirst, sleep, sex drive and more. [scientificamerican.com]

  Often, an individual has such headaches every spring, fall, winter or summer, for decades on end. The pain is debilitating. Like a Pencil in Your Eyeball Cluster headaches are both rare and uncommonly painful. [psychcentral.com]

  For example, cluster periods can occur seasonally, such as every spring or every fall. Most people have episodic cluster headaches. [mayoclinic.org]

  And they usually happen at the same time every year, usually spring or fall. "In most cases, this kind of headache is very treatable once it is correctly diagnosed," Bryson said. [sciencedaily.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]

• Episodic Course

  The distinctive features of this case are: a close temporal relation between head trauma and headache onset; pain ipsilateral to the side of trauma; mild severity of trauma; episodic course well-responsive to low doses of verapamil. [ncbi.nlm.nih.gov]

• 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]

• Constipation

  Common side effects include injection site reactions and constipation. Here we present a patient with hemicrania continua (HC) who responded well to erenumab, while the medication additionally treated her debilitating diarrhea. [jpain.org]

  Side effects are rare, but constipation is common. Other side effects include dizziness, nausea, edema, bradycardia, fatigue, and hypotension. [migraine.ie]

  Like all medicines, verapamil has side-effects: constipation flushing dizziness ankle swelling Other preventive medicines If verapamil doesn’t work for you, there are other medicines that can help. [bupa.co.uk]

  Prophylaxis of Episodic Cluster Headache Drug Dosage and route of administration Adverse effects Comments Verapamil Minimum of 240 mg orally per day, insingle or divided doses Abdominal discomfort,bradycardia, constipation,edema, gum hyperplasia,hypotension [aafp.org]

• Failure to Thrive

  Clinical description Homocystinuria without methylmalonic aciduria manifests mainly in early childhood with failure to thrive, megaloblastic anemia, developmental delay, hypotonia, seizures and cerebral atrophy with white matter abnormalities. [orpha.net]

  When the condition begins early in life, affected individuals typically have an inability to grow and gain weight at the expected rate (failure to thrive), which is sometimes recognized before birth (intrauterine growth retardation). [ghr.nlm.nih.gov]

• Gagging

  (19; 16–22) Itching — — — 1 (3%) 1 (3%) 1 (100%) (102) Dry nose — — — 1 (3%) 1 (3%) 1 (100%) (134) Dry skin — — — 1 (3%) 1 (3%) 1 (100%) ( 49 ) Taste alterations — — — 1 (3%) 1 (3%) 1 (100%) (149) Sensation of implant — — — 1 (3%) 1 (3%) — Depressed gag [ncbi.nlm.nih.gov]

• Hypertension

  The high prevalence of hypertension among patients with headache was not due to overweight. The data indicate that headache is significantly associated with hypertension, but not with other cardiovascular risk factors. [dx.doi.org]

  The mainstay is verapamil, a calcium channel blocker which is often well tolerated and is also used to treat hypertension and angina. [painmanagement.org.au]

  Methylergonovine, probably the active metabolite of methysergide, decreased cluster headache frequency by more than 50 percent in 19 of 20 patients in a pilot study. 32 Contraindications include hypertension and pregnancy. [aafp.org]

• Motor Restlessness

  A recent review that focuses mostly on the behavior of motor restlessness during the CH attack, it also addresses the issue of suicidality. PubMed Google Scholar 20. Mitsikostas DD, Thomas AM: Comorbidity of headache and depressive disorders. [doi.org]

• 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]

• 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]

• Excessive Tearing

  Affected individuals also experience excessive tearing along with stuffed nose. Diagnosis: A preliminary physical examination would be done at the initial level. [symptoma.com]

  Common signs and symptoms during a headache include: Excruciating pain, generally situated in or around one eye, but may radiate to other areas of your face, head, neck and shoulders One-sided pain Restlessness Excessive tearing Redness in your eye on [mayoclinic.org]

  Symptoms can include: Swelling under or around the eye (may affect both eyes) Excessive tearing Red eye Rhinorrhea (runny nose) or one-sided stuffy nose (same side as the head pain) Red, flushed face Cluster headaches may occur daily for months, alternating [web.archive.org]

  Other signs and symptoms may be evident on the painful side of the head, including: a droopy eyelid a constricted pupil excessive tearing from your eye eye redness sensitivity to light swelling under or around one or both of your eyes a runny nose or [healthline.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]

• 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]

• 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]

• Seizure

  Anti-seizure Medications — Medications used to control seizures in conditions such as epilepsy may be prescribed to help control cluster headaches. These include divalproex topiramate and gabapentin. [ucsfhealth.org]

  Some of these symptoms include: Changes in alertness Changes in movement or sensation Drowsiness Nausea or vomiting Seizures Vision changes Prevention If prone to cluster headache, stop smoking. [web.archive.org]

  These include beta blockers (propranolol or timolol), anti-seizure drugs (topirmate), and some types of antidepressants. [everydayhealth.com]

• Dizziness

  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]

• Insomnia

  Ramelteon, a selective melatonin receptor agonist and a member of a new class of insomnia therapies, completely suppressed the attacks during sleep and provided rapid relief from insomnia. [ncbi.nlm.nih.gov]

  Side effects include insomnia, restlessness, hyponatremia, edema, hyperglycemia, osteoporosis, myopathy, and gastric ulcers. [migraine.ie]

  Sahota PK, Dexter JD: Transient recurrent situational insomnia associated with cluster headache. Sleep 1993, 16 :255–257. PubMed Google Scholar 27. [link.springer.com]

  Considerations Some people are particularly sensitive to caffeine and even small doses can cause symptoms of heart palpitations, irritability and insomnia. The amount of caffeine in analgesics may be enough to create these symptoms. [livestrong.com]

  Patients may feel nervous, or insomnia can become a porblem. The euphoric effects of cocaine may occur, but these are not common. [chicagoheadacheclinic.com]

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.

1. Mendizabal JE, Umana E, Zweifler RM. Cluster headache: Horton's cephalalgia revisited. South Med J. Jul 1998;91(7):606-17.
2. Manzoni GC. Cluster headache and lifestyle: remarks on a population of 374 male patients. Cephalalgia 1999; 19:88.
3. Evers S, Frese A, Majewski A, et al. Age of onset in cluster headache: the clinical spectrum (three case reports). Cephalalgia 2002; 22:160.
4. Rozen TD, Fishman RS. Female cluster headache in the United States of America: what are the gender differences? Results from the United States Cluster Headache Survey. J Neurol Sci. Jun 15 2012;317(1-2):17-28.
5. Lodi R, Pierangeli G, Tonon C, et al. Study of hypothalamic metabolism in cluster headache by proton MR spectroscopy. Neurology. 2006;66(8):1624-6.
6. Favier I, van Vliet JA, Roon KI, et al. Trigeminal autonomic cephalgias due to structural lesions: a review of 31 cases. Arch Neurol 2007; 64:25.
7. May A. Cluster headache: pathogenesis, diagnosis, and management. Lancet 2005; 366:843.
8. Sjaastad, O (Ed). Cluster Headache Syndrome. W B Saunders Company Ltd, London 1992.
9. Petersen AS, Barloese MC, Jensen RH. Oxygen treatment of cluster headache: a review. Cephalalgia 2014; 34:1079.
10. Tfelt-Hansen P. Acute pharmacotherapy of migraine, tension-type headache, and cluster headache. J Headache Pain. Apr 2007;8(2):127-34.