Bar graph displays the rates of any hemorrhage (black) and significant hemorrhage (hemorrhage volume > 25ml) (gray) following intra-arterial thrombolysis based on pial collateral score.
Pial collateral score
Pial collateral score
Pial collateral formation identified  on angiography can be predictive of infarct volume following acute ischemic stroke treated with intra-arterial thrombolysis.