According to the International Classification of Headache Disorders (ICHD), there are four primary types of headaches: migraines, tension-type headaches, cluster headaches, and "other" primary headaches. Secondary causes of headaches include head or neck trauma and injuries, stroke, intracranial hemorrhage, and vascular malformations.
The underlying cause of migraines is unknown. Research indicates that genetic factors play a role in who develops migraine headaches. Hormone levels are also a factor, and migraine headaches are three times more common among women than men. While the cause of migraines is unknown, there are a number of triggers, which are thought to instigate a migraine attack, though the strength and significance of the correlation are uncertain. Commonly reported triggers are stress, hunger and fatigue.
This is the most common type of primary headache, occurring in 30% to 75% of the population. A tension-type headache occurs when muscles in the neck or head become tense, often as a response to stress, injury or activities that result in the head being held in a strenuous position for a prolonged period of time. Other possible triggers for tension-type headaches include alcohol, caffeine, clenching of the jaw or teeth, and fatigue.
While the exact cause of cluster headaches is unknown, it is thought to be related to a sudden release of histamine or serotonin. This occurrence may be triggered by a number of factors including alcohol, cigarette smoking, high altitude, heat, exertion, and bright light. Another theory is that an abnormality in the hypothalamus, the area of the brain that regulates the biological clock, can cause cluster headaches. This theory is supported by the fact that episodic cluster headaches often occur at the same time each day.
Cluster headache attack is accompanied by at least one of the following autonomic symptoms: drooping eyelid, pupil constriction, redness of the conjunctiva, tearing, runny nose, and less commonly, facial blushing, swelling, or sweating, typically appearing on the same side of the head as the pain, and/or they may report agitation with a headache. While the exact causes of most major headache types is largely unknown, headache patients may be able to attain some degree of relief through proper diagnosis and treatment. For example, it's not uncommon that a patient suffering from a cluster headache treats it as a migraine headache due to improper self-diagnosis. Patients do not have to live with the often searing pain of a migraine, tension-type, and cluster headaches, despite the fact that the cause may be unknown.