Cluster headache, also called Horton’s headache or cluster headache, is a rare but extremely painful type of headache. It appears as intense, stabbing, or burning pain behind or around one eye, often described as a knife or an awl drilling from the inside. The attacks occur in clusters lasting weeks to months, with 1–8 attacks per day, often at night, about 1–2 hours after falling asleep. Each attack typically lasts 15–180 minutes but can last longer without treatment. Between clusters, most people are symptom-free, but a few have a chronic form with daily attacks throughout the year.

In addition to the pain, symptoms often include tearing or redness in the eye, a runny or congested nose, drooping eyelid, swelling, a small pupil, as well as sweating and redness on the affected side. Unlike migraine, people with cluster headaches typically become restless and agitated during attacks and may pace or press on the painful area.

Cluster headache usually affects people between the ages of 20 and 40 and is 3–7 times more common in men. About 1 in 1,000 people develop the condition, and there is a certain hereditary tendency. The exact cause of cluster headache is still unknown, but it is known that the hypothalamus - the part of the brain that helps regulate circadian rhythm - is active during attacks. This may explain why the pain often occurs at fixed times of day. The cranial sensory nerve (n. trigeminus) and the autonomic nervous system in the face are also involved in the development of symptoms. In addition, certain triggers such as alcohol and the heart medication nitroglycerin can provoke attacks during cluster periods.

Cluster headache is one of the most disabling headache disorders, and the pain can be unbearable. It is therefore important that relatives understand the condition and show consideration, especially because the affected person often becomes restless and irritable. Fortunately, the attacks can often be treated effectively, and the condition tends to improve with age, as the breaks between cluster periods typically become longer.