Episodic vs. Chronic Migraine
According to the International Classification of Headache Disorders (ICHD) an episode of migraine can last 4-72 hours. Anything longer than 3 days is not, by definition “a migraine.” It is commonly short term medication overuse headache. Things get sticky here because the ICHD defines medication overuse headache as occurring after over treatment with pain medication over a period of 2 months. In the neurologic practice of headache many patients present with daily or very frequent headache times lasting less than 2 months. What to call this? Well, first of all the patient should have a positive check list for migraine (see article on migraine without aura). I call it short term medication overuse headache and it makes sense to me, although it is not a universally accepted term. So, 4 days of headache is not “a migraine” but could be considered short term medication overuse headache if there is a clinical history of over treatment with medication.
Thus, an “episode” of migraine can last 3 days and usually to call migraine episodic, there have to be no more than two 3 day episodes of headache in a week, because three 3 day episodes of headache is 9 days and that is too much headache. That many headache days mergers into chronic migraine.
Chronic migraine is defined by ICHD as fifteen headache days a month, 8 of which have migraine features. Many patients with chronic migraine that I see have daily headache for a year or more. I saw a patient several years ago who told me that she took 6 Advil a day from the time she was 6 years old until I met her at 60. She reported daily headache the whole time with frequent occurrences of more severe migraine headaches. Her headaches improved markedly and she converted back to episodic migraine in about a month after stopping Advil.
Cluster headache is a special type of headache different from migraine but the word “cluster” is commonly attached many times erroneously to patients who don’t have cluster headache merely because they have very frequent headaches. Patients with cluster headache usually have headaches that come the same time every year and last 6-8 weeks and during that time they may have 1-8 headaches per day. Some persons and doctors erroneously mix-up medication overuse headache caused chronic migraine which is daily headache with cluster headache. Read my article on cluster headache to better understand that syndrome.
One can’t cure migraine and the treatment is doing the migraine lifestyle, using preventive medication, and acute migraine treatment no more than 2 days a week. Episodic migraine is a much more benign and less disabling condition and I try to keep my patients there, knowing that migraine may occasionally mysteriously vanish and that in general migraine gets better with age.