Cluster headache (CH), also referred to as Horton’s syndrome is a primary headache of severe intensity. The cluster headache is so-called because the headache attacks occur in clusters or groups – between one to eight times a day.

The headache pain is deep, unbearable, usually non-throbbing and occurs almost always on one side of the head behind the eye.

The area of the head or face involved is always the same but occasionally switches to the other side of the head may occur.

A cluster headache has a cyclical pattern in which the headaches occur in patterns. Bouts of frequent headaches, known as the cluster period, which can last for weeks or months, periodically alternate with periods of remissions.

During periods of remission, there is no headache and this period can last for months or years. However, this headache can come back without any warning signs.

Characteristics of a cluster headache

The cluster headache period has a seasonal pattern and tends to occur during the same time of the year such as during spring or fall.

Cluster headache pain is the worst pain that one can experience, with some women sufferers claiming it to be more severe than the child labor pain.

Fortunately, this headache lasts for a relatively short time – usually about 15 minutes. However, the headache can last up to 3 hours and it is known to occur several times a day (sometimes up to 8 times a day). The patient finds it better to tolerate the pain by pacing to and fro.

It ends as suddenly as it comes, rapidly decreasing in severity.

It is referred to as an “alarm clock headache” because it often awakens you in the night with intense pain typically around the eye on one side of the head.

The pain of a cluster headache usually starts 2 to 3 hours after falling asleep. Night-time attacks can be more severe in intensity than the daytime attacks.

Probable cause

The exact cause of cluster headaches remains a mystery. However, the pattern of its occurrence suggests a disturbance in the body’s biological clock situated in the hypothalamus of the brain, to be a probable cause.

Scientists have recently discovered evidence that links this headache to the part of the brain called the hypothalamus.

Unlike migraine or tension headaches, which are triggered by certain factors, cluster headaches tend to develop without any reason.

Radiological studies such as PET show activation of the posterior hypothalamic gray matter during the headache as the main defect.

However, certain theories regarding the cause of its occurrence have been put forward and discussed in more detail in that post


CH is more common in people who drink alcohol heavily and/or smoke. Additionally, during the cluster period, you are more sensitive to alcohol and nicotine. A little exposure to either can give rise to a cluster attack.

However, during the period of remission, alcohol will not trigger a headache.

Other symptoms

Besides the severe head pain, cluster headache is accompanied by other symptoms on the same side of the head as the pain. These include:

  • a red eye
  • swelling of the eyelid
  • forehead and facial sweating
  • watering of the eye (lacrimation)
  • abnormally small size of the pupil (miosis)
  • nasal congestion and a runny nose (rhinorrhea) and
  • drooping eyelid (ptosis)

Who can suffer from a cluster headache?

Luckily, cluster headache isn’t common with only 0.1% of the population being affected by it (one in a thousand people).

About 5% of people with cluster headaches have a family member who also suffers from this condition. 

As against migraine and tension headaches, cluster headaches are six times more common in men than in women. It can start at any age but usually starts in the late twenties or thirties.

Patients who suffer from these headaches are usually heavy smokers and those with heavy alcohol consumption.

Other names for cluster headache (synonyms)

  • Migrainous neuralgia
  • It is also called a Histamine headache because it is associated with the release of histamine from body tissues.
  • It is called Horton’s headache or Horton’s cephalgia because Dr. B. T. Horton first postulated the theory about its pathogenesis.
  • It is given the nickname Suicide headache because of the intense pain, which does make one want to prefer taking one’s life. 


CH is classified into two types: Episodic and Chronic

  • Episodic: In case of an episodic cluster headache, the patient experiences a series of headaches for about a week followed by a period of remission of months or even a year followed again by the cluster headache week. Ninety percent of people with cluster headaches suffer from the episodic form.  
  • In the case of chronic cluster headaches, the cluster period can last for several months or even a year followed by a short period of remission of one month or so. Ten percent of cluster patients suffer from the chronic form. Patients in whom cluster headaches have set in later on in life are more likely to suffer from the chronic form.

There is no investigation to confirm the diagnosis of the cluster headache. A doctor diagnoses this headache through a thorough examination of the symptoms.

There is no cure for cluster headaches. However, medication is given to reduce the symptoms. Additionally, there are effective steps that can prevent or gradually reduce cluster attacks.