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

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.