In vivo visualization of vascular leakage in photochemically induced cortical infarction.

The photothrombotic model for stroke was originally described as a focal cortical infarction resulting from occlusive thrombosis. However, subsequent studies have shown evidence for extravasation of water and proteins using ex vivo techniques. The aim of the present study was to determine the role of vascular leakage in the pathophysiology of photochemically induced infarction in vivo. At several times points after infarct induction, analysis of blood flow and vascular leakage was performed using intravital microscopy and fluorescent labelling of blood plasma. In the first hour following infarct induction, massive vascular leakage of the plasma label occurred inside the lesion core that was destined to become infarcted. Flow had stopped completely in this area at 4h after illumination. On the day following infarct induction substantial leakage was still present in the penumbral area, defined as the area immediately surrounding the lesion core where reduced flow velocities were observed. Thus, together with the formation of occlusive thrombi, vascular leakage is an important factor in the pathophysiology of photothrombotic stroke.