RCVS: The Rational Approach to Diagnosis and Treatment

Patients 18 years of age or greater meeting the following inclusion criteria adapted from Singhal and colleagues 2 will be included: 1\. presentation consistent with RCVS : * acute thunderclap/severe headache and \*\*supporting clinical features should prompt increased clinical suspicion (eg., potential medication trigger, recent pregnancy, migraine history)\*\* * evidence of beading/elevated velocities on imaging (Transcranial Doppler (TCD), angiogram, Computer Tomography Angiogram (CTA), MRA) and * reversibility (by 90 days)-will not be required for inclusion but will be retrospectively adjudicated Participants will be excluded from the study if they are: * unable to consent AND no family present to consent, or * have presence of aneurysmal, traumatic, or mesencephalic Subarachnoid Hemorrhage (SAH), or * have presence of other supported diagnosis (eg., vasculitis- inflammatory lumbar puncture) or * are currently pregnant or * the use of nimodipine or verapamil is contraindicated for any reason (eg., allergy, breast feeding) or * have limited TCD sonographic window * stroke or ICH/SAH on presentation will not be a contraindication to inclusion in the trial \*\*