Cluster headache is a condition where severe attacks of pain affect one side of the head or face, often around the eye.
This condition is called cluster headache as patients are affected by attacks of symptoms over a cluster of weeks or months. These symptoms will then often disappear (remissions) before reappearing in similar clusters again. People may experience up to 8 attacks per day.
In some patients there is no remission period, resulting in chronic cluster headache. Cluster headache affects 1 in 1,000 individuals over their lifetimes.
The predominant symptom is recurrent attacks of extreme one-sided headache. The pain is often described as feeling like a burn or deep pressure. Each episode starts suddenly and can last up to 3 hours. These attacks typically occur between one and eight times per day and classically affect the same side of the head and/or face. The headache characteristically recurs at the same time of day. It often causes significant distress and reduction in quality of life.
In addition to the headache other symptoms may include:
- Redness and watering of the eye;
- Drooping and swelling of one eyelid;
- Constriction of pupil on the affected side;
- Blocked or runny nostril.
Each cluster of headache typically occurs for a few weeks or months. Between these clusters there are normally periods of remission. The symptoms will often return at a similar time of year to previous episodes. For 1 in 10 patients there will are no remission periods between attacks.
The exact cause of cluster headache is unknown. Increased activity and release of chemical messengers in a part of the brain, called the hypothalamus, is thought to be responsible for the attacks. The hypothalamus also plays an important role in regulating the body clock, perhaps explaining why symptoms typically occur at the same time of day.
Whilst the exact cause is unknown, men and those with a family history of cluster headache are more likely to be affected.
Some patients may have specific triggers. These may include:
- Exposure to heat;
- Strong smells – perfume, paint and petrol.
There is no test to diagnose cluster headache. A diagnosis is made by listening to a patient to understand their symptoms in full.
Other conditions may cause similar symptoms to cluster headache and further tests may be required to exclude their presence.