 - MRI evidence of S3: a. Presence of an S3 1.5 and 2 cm in diameter corresponding to the qualifying event on DWI; when TIA, ADC image must confirm lesion or T2FLAIR hyperintense lesions required for all brainstem events OR multiple S3s on FLAIRTI1.5 cm in diameter hypointense lesions b. Absence of cortical stroke and large subcortical stroke recent or remote. 