There is very little known about the difference between the various types of headaches. In the ED the primary concern is to separate primary from secondary causes of headache. Primary headaches are those that are not caused by a secondary medical condition, and are usually divided into migraine, tension, and cluster headaches.

Migraine headaches usually last 4-72 hours, are unilateral and pulsating in character. Almost always aggravated by routine activity, and can be associated with nausea or photophobia. The can sometimes be preceded by an aura or scotoma. Five separate attacks are required to receive a formal diagnosis.

The etiology of migraine headaches involve cortical spreading of depressed electrical activity. This leads to abnormal thalamic pain modulation. This cascade is activated by various factors and various levels related to a genetic predisposition.

Tension headaches are shorter duration lasting between 30 minutes to 7 days.