[Imaging-based patient selection for mechanical thrombectomy based on time since symptom onset]

In ischemic stroke due to large vessel occlusion (LVO), the indications for patient selection for endovascular mechanical thrombectomy (MT) are based on findings from brain imaging. Several imaging protocols from computed tomography (CT) or magnetic resonance imaging (MRI) are available to guide treatment decisions.

To recommend the optimal choice of imaging modalities and protocols for MT with respect to time windows from symptom onset.

Evaluation of the results of large randomized placebo-controlled trials regarding imaging-based patient selection in MT categorized by time intervals since symptom onset. We discuss methodological aspects, advantages and caveats of individual stroke imaging protocols. Summary of recommendations for the practice.

In MT trials CT was mostly used for patient selection. Plain CT combined with CT angiography or additional perfusion imaging is the preferred option. In early time windows CT with CTA is adequate (≤ 6 h for MT, ≤ 4.5 h in cases of accompanying thrombolysis according to exclusion criteria). In later or unknown time windows perfusion imaging is needed for patient selection. Patients presenting with unknown time windows should be examined by MRI as a first-line choice in mild to moderate deficits, in cases of severe deficits CT imaging with perfusion imaging.