Case Presentation: A 22-year-old previously healthy male presented to the Emergency Department (ED) with sudden-onset, excruciating headache in bandlike distribution beginning 2 days prior, associated with nausea and photophobia. The patient experienced mild improvement temporarily with over-the-counter ibuprofen. Social history was significant for daily marijuana use. Non-contrast head CT showed a small amount of subarachnoid hemorrhage (SAH) in the left frontal and right parietal sulci; CT angiogram did not reveal any aneurysm; subsequent brain MRI showed minimal amount of SAH, with no interval change. Despite pain control regimen, the patient reported a recurrence of excruciating headache. Repeat head CT was unchanged. Subsequent diagnostic cerebral angiogram showed intraluminal irregularities consistent with reversible cerebral vasoconstrictive syndrome (RCVS). Patient was started on verapamil 40mg every 8 hours, advised only acetaminophen for pain control, and counseled on abstinence from marijuana before discharge. He returned to the ED a few days later for persistent headache; repeat head CT showed previously noted SAHs had completely resolved. Verapamil was increased to 60mg at the same frequency, and symptoms were subsequently well controlled.

Discussion: RCVS and SAH both present with a thunderclap headache (TCH), though RCVS can be importantly differentiated from SAH by recurrence of TCH. SAH develops in over 30% of patients with RCVS, but the SAH is usually small (restricted to 1 to 2 sulcal spaces), convexal, nonaneurysmal, and unlikely to cause diffuse, multifocal vasoconstriction. Initial angiography can be negative as the narrowing and vasodilation begin distally and are poorly visualized. Additional clinical predictors of RCVS-associated SAH in this patient include younger age and exposure to vasoconstrictive drugs, in this case marijuana. TCH recurrence should strongly indicate evaluation and prophylactic management for RCVS in the setting of small, nonaneurysmal SAH. Treatment is currently based on expert opinion and reported case series. Patients should be counseled to avoid exposure to vasoconstrictors and other precipitating factors. Treatment to reduce headache intensity and recurrence may be achieved with calcium channel blockers such as nimodipine, nifedipine, or verapamil.

Conclusions: RCVS is an underrecognized and commonly misdiagnosed cause of TCH, especially with the presence of SAH. TCH recurrence should strongly suggest underlying RCVS, particularly in nonaneurysmal SAH, and in younger patients with history of exposure to vasoconstrictors. Prompt diagnosis may reduce the number of diagnostic tests and improve management in patients presenting with RCVS.