Introduction

Stroke is a leading cause of mortality and disability worldwide, with 15 million people having a stroke annually. Given that it is very difficult to distinguish an ischemic from a hemorrhagic stroke on a clinical basis, neuroimaging—CT or MRI—plays a central role in the evaluation of patients with acute stroke symptoms. Because of significant advances over the last decade, imaging now provides information beyond the mere presence or absence of intracerebral hemorrhage. Comprehensive neurovascular imaging protocols using CT or MRI can be acquired within minutes, helping to distinguish stroke etiology and guide treatment decisions for acute reperfusion therapies. The role of imaging in guiding stroke treatment is such that the concept of ‘time is brain’ is slowly being replaced by that of ‘pathophysiology is brain’ or ‘imaging is brain’.1 Nevertheless, there are a number of uncertainties and controversies around the use of advanced imaging in acute stroke management. In particular, there is still insufficient proof that perfusion imaging-based treatment decisions improve clinical outcome in patients with acute ischemic stroke.

The goal of this article is to review commonly discussed issues about the role of perfusion imaging in acute stroke through a series of questions and to propose arguments to explain why perfusion imaging is useful and may improve diagnosis, triage, treatment decision and, ultimately, outcome of acute stroke.