Figure 1.

Initiation of inflammation and thrombosis after subarachnoid hemorrhage. Following rupture of an aneurysm, red blood cells spill into the subarachnoid space, activating macrophages which release cytokines. In response, endothelial cells express adhesion molecules to activate circulating leukocytes and platelets. This results in leukocyte infiltration, phagocytosis of red blood cells, and release of more cytokines. Activated platelets develop into thrombi which may travel downstream to occlude distal microvessels or may cross into the brain parenchyma. Platelet activation and aggregation signal for leukocyte activation, and vice versa, such that even when the aneurysm is treated, thromboinflammation continues via feedforward mechanisms.