The Difference Between Episodic and Chronic Migraine


David Kudrow, MD, defines episodic and chronic migraine and details how symptoms differ.

David Kudrow, MD: What’s the difference between episodic migraine and chronic migraine? We’ve been using these terms separately for the past couple of decades. Chronic migraine is defined as headache frequency of at least 15 days per month, with at least 8 of those being migraine days. Episodic migraine is everything else, so anything up to 14 headache days per month. But I find that 15-day limit between the 2 diagnostic categories to be rather arbitrary.

Three percent of patients who have episodic migraine will become chronic over the course of a year, and about 25% of patients who have chronic migraine may revert to episodic migraine over the course of a year. More recently, a very important paper from the American Headache Society Wolff Award, which is very prestigious recognized research, showed that an examination of a large database of patients with migraine showed that with respect to the degree of disability that patients experience, patients who have 8 to 14 migraine days per month vs patients who have 15 to 23 migraine days per month are virtually the same. Their degree of disability is about the same, and people who have 24 or more headache days per month have the greatest degree of disability.

That traditional arbitrary boundary between chronic and episodic is in flux at this point. Why is that important? Because there are some medications that we use for patients who have chronic migraine that may be beneficial for patients who have less than chronic migraine. It’s important to understand and recognize that those diagnostic categories are relatively fluid.

Let me also add that with respect to the migraine attack itself, there’s no difference between an acute migraine in a patient who has episodic migraine and an acute migraine that occurs in a patient with chronic migraine. As the frequency of migraine increases, conversely, the frequency of headache-free days decreases. Migraine is a long-lasting phenomenon. We recognize the acute attack as the most obvious clinical observation in a patient that has migraine, but there’s a prodrome to the attack that can be several hours to days in duration. There’s also a postdrome to the attack that can be several hours to days in duration, which prolongs the time of the acute migraine attack. The more frequent migraine becomes, the fewer headache-free days a patient has. That’s important to point out in recognizing how increasing frequency of migraine contributes to disability of the patient’s experience and the need for effective acute and preventive therapeutics.

Is there a difference in the symptoms of migraine in patients who have episodic or chronic migraine? No. The migraine attack is defined as moderate to severe headache. It’s usually unilateral and doesn’t have to be associated with nausea, light sensitivity, or sound sensitivity. The patient doesn’t want to move, it worsens with exertion, and it can occur with a visual aura. Those characteristics are the same, whether a patient has episodic or chronic migraine. Chronic migraine is defined clinically as that frequency of over 14 headache days per month.

Transcript edited for clarity.

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