Attacks often come in the early morning hours, and will waken the patient from sleep. The pain of cluster headaches usually is centered around one eye, and is almost always on one side of the head. There can be nasal stuffiness and tearing with the headache. The pain is excruciating for most people, often described as a knife or nail being driven into the head. Unlike migraine headache, lying down often makes cluster headaches worse.
Some people pace the floor and move about, unable to find any relief.
Causes Precisely what causes cluster headaches is unknown, but the condition has several well-recognized triggers, including alcohol, particularly if a person is going through a cluster period, and nitroglycerine or similar drugs. The fact that some of these triggers also cause blood vessels to dilate or open up to increase blood flow, or involve medications which make blood vessels constrict or narrow to reduce blood flow, suggests that changes in the vascular structure of the head may be partly responsible. There are other causes of headache as well. Many people with brain tumors have headaches. Their pain may be worse in the morning as a result of pressure buildup in the brain after lying flat all night.