Often called 'suicide headaches', around 130,000 people in the UK suffer from the debilitating condition, cluster headaches. They are excruciating attacks of pain on one side of the head. The pain can be so bad that sufferers sometimes harm themselves to distract themselves from the pain.
Now, a new study has been launched to try and discover what causes these headaches.
Tim Muffett has been to find out more…A warning that some viewers might find some images in this film distressing.