Cluster headaches are excruciating attacks of pain in one side of the head, often felt around the eye.
They're estimated to affect around 1 in 500-1,000 people. Anyone of any age can be affected, but they're more common in men and tend to develop in people over the age of 20.
It's not clear exactly what causes cluster headaches, but they've been linked to activity in part of the brain called the hypothalamus. People who smoke seem to be at a higher risk. Some cases also appear to run in families, which suggests there may be a genetic link.
For most people, cluster headaches occur in recurrent "bouts" over several weeks (typically 4-12 weeks) followed by headache-free periods (remission) that often last for months, or sometimes years.
Cluster headache bouts may occur every year over many years and may be lifelong. In general, they become less frequent over time. Treatment is available to control them.
Cluster headaches begin suddenly and without warning. The pain is very severe and is often described as a sharp, burning or piercing sensation on one side of the head.
The headaches can't be treated with over-the-counter painkillers such as paracetamol, as these are too slow to take effect. You'll need to have one or more specialist treatments instead.
Alternative treatments may be considered if verapamil is not effective. These may include corticosteroids , lithium medication and occipital nerve blocks (injections of a local anaesthetic into the back of the head).
The first time you experience what you think may be a cluster headache, then you should see a doctor as soon as possible. The doctor will ask you about your symptoms and may refer you for tests.
Cluster headaches are excruciating attacks of pain in one side of the head, often felt around the eye. It's not clear exactly what causes cluster headaches, but they've been linked to activity in part of the brain called the hypothalamus.