Note on "Transformation": Approximately 2.5% of patients with Episodic Migraine progress to Chronic Migraine each year. Risk factors include overuse of acute medication (medication-overuse headache), obesity, depression, and high baseline headache frequency.
15 or more headache days per month for at least three months, where at least 8 of those days meet full migraine criteria. Episodic Migraine Chronic Migraine Frequency < 15 days per month 15+ days per month Persistence Intermittent attacks with clear breaks More persistent and often more intense Prevalence More common form of migraine Affects a smaller percentage of migraineurs Progression Can progress to chronic (approx. 3% annually) Can revert to episodic with treatment Source: Healthline , American Migraine Foundation Phases of an Episodic Migraine Attack episodic migraine definition
Patients with HFEM are considered to have a disability burden nearly identical to patients with Chronic Migraine. The 15-day threshold is a diagnostic boundary, but disability often escalates linearly as days increase. Note on "Transformation": Approximately 2
The primary differentiator for "episodic" status is frequency. | Feature | Episodic Migraine (EM) | Chronic
| Feature | Episodic Migraine (EM) | Chronic Migraine (CM) | | :--- | :--- | :--- | | | < 15 headache days per month | ≥ 15 headache days per month | | Duration | 3 months of observation required | Must have lasted > 3 months | | Nature | Discrete attacks with pain-free intervals in between | Often constant or near-constant pain; distinct attacks may blur | | Transition | Prodromal Stage | Complication of Migraine | | Risk of Progression | Can progress to Chronic Migraine | May remit back to Episodic Migraine |