Episodic status migrainosus: A novel migraine subtype.

Objective To report a case series of a novel migraine subtype, which we term as episodic status migrainosus (ESM), characterized by attacks of migraine exclusively lasting more than 72 hours. We hypothesized that this would represent a novel nosologic entity, possibly an unstable migraine phenotype with a high conversion rate to chronic migraine (CM). Methods We conducted a retrospective review of patients diagnosed with status migrainosus at the Mayo Clinic, Rochester, between January 2005 and December 2015. All the records were then manually reviewed for patients with migraine headaches exclusively lasting more than 72 hours. Results We identified 18 patients with ESM, with a female predominance (15(83.3%)) and a median age of onset of 16.5 (IQR 13-19) years. The median monthly attack frequency was two (IQR 1-3), with each attack lasting a median duration of seven (IQR 4-12.5) days. Stress was the most commonly reported precipitant (11 (61.1%)). Migraine with aura was common (10 (55.6%)), as was comorbid depression (10 (55.6%)). Fifteen (83.3%) patients developed CM at a median of 7.8 (IQR 2.6-21.9) years from their first attack. There was no significant association between the time to the development of chronic migraine with either attack frequency or duration. Conclusions and relevance We report the existence of a novel migraine subtype, episodic status migrainosus. This migraine subtype appears to have similar clinical characteristics to episodic migraine with or without aura, except for a notably high tendency to progress to chronic migraine.