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. Patients often describe them as pressure and bilateral, and in contrast to migraines they are not typically aggravated by activity.
If the patient’s symptoms don’t meet the diagnostic criteria listed above for one of the other category of headaches, they are usually classified as migrainous.
Secondary headaches are brought on by an underlying medical condition. The largest categories are meningitis, subarachnoid hemorrhage, vascular disease, toothache, and sinusitis. There is a long list of etiologies (See excellent DDx on Life in the Fast Lane).
The diagnosis of a primary headache is made by ruling out an organic disorder through the history, physical, or findings. It can also be suggested when an organic disorder was suggested and then ruled out. It is important to note that sometimes an organic disorder is present but the headache is not related to it.
Many secondary headaches are actually migraine headaches triggered by a malignant stimulus.
There is a spectrum of headaches upon which all primary headaches lie, the effectiveness of the medication is not related to its defined nature. Treatment options can include triptans, dopamine antagonists, NSAIDs, sleep. For those with recurrent headaches prophylactic medications can be used such as depakote or dexamethasone. An important principal is to never use opiods for primary headache. It is not supported by any guideline.