Cluster headaches are excruciating attacks of pain in one side of the head, often felt behind the eye.
Sufferers often call them 'suicidal headaches' because they're so severe.
Cluster headache attacks
Cluster headaches begin unexpectedly. They're much more painful than migraines or any other type of headache.
They're called cluster headaches because sufferers usually get one to three of these attacks every day, for several weeks or months, before they subside. A pain-free period will follow, which sometimes lasts months or years, before the headache attacks start again.
Because of the intensity of the pain, some people will pace the room, rock, or bang their head against the wall out of frustration, restlessness and despair.
Types of cluster headache
There are two types of cluster headache, episodic or chronic (long-term).
episodic – headache clusters are separated by headache-free periods of one month or more
chronic – headache clusters are separated by headache-free periods of less than one month, or are not separated at all
About 10% of cluster headache cases are chronic.
Causes of cluster headaches
Research suggests that when a cluster headache happens, there's a lot more activity in an area of the brain called the hypothalamus. It's thought the hypothalamus releases chemicals that trigger the cluster headaches, possibly by causing blood vessels to widen, causing an increase in bloodflow to the brain.
It's not known what causes the hypothalamus to act in this way. However, in some people, cluster headaches are triggered by certain things, such as:
drinking alcohol during the period that headaches occur – during headache-free periods, alcohol doesn't appear to trigger attacks
an extreme increase in temperature (such as from exercising in hot weather)
taking inhaled nitroglycerin – a medication that causes the blood vessels to enlarge
They are also more common in autumn and spring.
Who is affected
Cluster headaches are rare and affect around one in 1,000 people. Anyone can be affected, but approximately eight out of 10 people who have them are men and most are smokers.
Treatment and support
Cluster headaches can severely affect quality of life, so it's important that sufferers are referred to a specialist clinic for treatments to relieve and prevent the attacks.
Organisations such as Ouch UK and the Worldwide Cluster Headache Support Group offer advice and support.
Although cluster headaches can cause great suffering, they're not life-threatening. They can often be relieved with a medication calledsumatriptan or with oxygen therapy. In some cases, preventative treatment may also be necessary.
These treatments may vary in effectiveness from person to person. A few treatments may need to be tried before the attacks are under control.
Symptoms of cluster headaches
The pain of a cluster headache starts quickly, without warning, and is described as excruciating.
The headache always affects one side of the head and is usually felt around the eye. Sometimes it affects the temples (forehead) and cheeks.
Most people feel restless and frustrated during an attack as the pain is so intense. They may react by rocking, pacing or banging their head against the wall.
An attack is relatively short, lasting between 15 minutes and three hours (but often less than an hour).
Pattern of attacks
Headache attacks occur in groups or clusters, which usually happen one to three (and up to eight) times a day. They occur every day for several weeks or months and are followed by a period of no headaches, which lasts for months or years (the average is one year).
Cluster headaches usually affect the same side of the head, although they can sometimes move to the opposite side.
One in 10 people have chronic cluster headaches, where the attacks occur regularly without significant pain-free intervals.
During a period of cluster headaches, the headaches often occur at the same time each day. For example, people often wake up with a cluster headache within around two hours of going to sleep, at the same time each night or early in the morning.
Cluster headaches are associated with one or more of the following symptoms:
inflammation (redness and swelling) of the eye
drooping and swelling of the eyelid
a smaller pupil during the attack
watering from the eye
sweating of the face
a blocked or runny nose on the affected side of the face
Treating cluster headaches
Cluster headaches can't be treated with over-the-counter painkillers, such as paracetamol, as they're too slow to take effect. You'll need to be treated at a specialist clinic.
There are two main types of treatment:
those that relieve cluster headaches
those that prevent cluster headaches
Relieving cluster headaches
A drug called sumatriptan (Imigran) is commonly used to treat cluster headaches. It works in a similar way to a brain chemical called 5HT. It causes your blood vessels to narrow, reducing bloodflow to the brain.
Sumatriptan is usually given as an injection, which you can give yourself as soon as the headache starts. It works very quickly (within about 10 minutes).
The adult dose in an injection is 6mg and you can take a maximum of two injections in 24 hours, as long as they're at least an hour apart.
If an injection is unsuitable, sumatriptan or zolmitriptan nasal spray may be used.
Some people have mild side effects, such as nausea, dizziness, tiredness and a dry mouth. If you have any side effects, talk to your GP. You shouldn't take it if you have heart disease or peripheral vascular disease.
Your doctor may prescribe oxygen cylinders to use at home. You breathe a high flow of pure oxygen through a mask for about 15 minutes, up to five times a day. It's a safe treatment and there's evidence it is effective in relieving cluster headaches.
Preventing cluster headaches
If attacks of cluster headaches happen often or last more than three weeks, preventative treatments are usually necessary. This involves starting treatment as soon as the headaches begin, and continuing every day throughout the period of headaches until they end.
The National Institute for Health and Care Excellence (NICE) recommends that verapamil may be considered as a preventative treatment for cluster headaches.
Verapamil tablets are usually used to treat heart problems but are also effective at preventing cluster headaches. The heart must be closely monitored with ECGs (electrocardiograms) when the dose of verapamil is increased.
Alternative treatments may be considered if verapamil is not effective. Preventative treatments must only be administered under the guidance and close monitoring of a specialist. Some of these treatments are outlined below.
Lithium tablets are normally used to treat mood disorders, but can help cluster headaches. The level of lithium in your blood may need to be carefully monitored to avoid side effects.
Occipital nerve anaesthetic block
The occipital nerve runs from the top of the spine to the scalp and is involved in the pain of cluster headaches. Occipital nerve block is the injection of a local anaesthetic, such as lidocaine, into the back of the head to relieve the pain of cluster headaches for a period of time (usually several weeks). Although there's a lack of research evidence on this treatment, it appears to provide relief for some patients.