“…Data on these issues are scarce and contradictory, as studies so far have been rather small, [8][9][10][11] were restricted to patients from clinical trials, 12,13 were retrospective, 5,14 were not able to fully pursue ascertainment of recurrent stroke subtype, 3,[15][16][17][18] were restricted to lacunar stroke, 10,[19][20][21][22][23][24][25] did not use patients with first-ever stroke, 8,15,18,20,[26][27][28][29][30][31][32][33] or included stroke subtyping that was not clear. 11,[27][28][29][30][31][34][35][36] Some of these studies, especially the early ones, had insufficient computed tomography (CT) validation of index and/or recurrent stroke, included hemorrhage or transient ischemic attack in index stroke, or used restricted age populations. Frequency, stroke type, and risk factors may tell something about heterogeneity of the underlying vascular pathology, and how this develops over time.…”