Diameter of fluorescent microspheres determines their distribution throughout the cortical watershed area in mice.

•Fluorescent microspheres with different diameters were injected into the ICA of mice.•Ligation of the CCA induced a greater reduction in CBF in the watershed area.•The 24-μm microspheres were distributed in the watershed area most frequently.•Ligation of the CCA did not alter pial vessel diameter or microspheric distribution.•The diameters of micro-emboli mainly determine the watershed pattern of infarction.•Preventing embolus formation seems to be important for patients with carotid stenosis.