Distance to thrombus on MR angiography predicts outcome of middle cerebral artery occlusion treated with IV thrombolysis.

Introduction: The distance to thrombus (DT) on CT angiography was recently proposed as a predictor of outcome in patients treated by intravenous thrombolysis (IVT) for stroke due to occlusion of the middle cerebral artery (MCA). The purpose of the present study was to validate its inter-rater reliability and its prognostic value on contrast-enhanced magnetic resonance angiography (CE-MRA). Furthermore, we investigated the relation between DT and FLAIR-vascular hyperintensities (FVH) as a surrogate of collateral circulation and hypoperfusion.
Methods: Patients with acute MCA occlusions treated by IVT and diagnosed with magnetic resonance imaging (MRI) were included. Two readers measured DT. FVH and acute DWI lesion volumes were quantified. Clinical status was determined using the initial NIH stroke scale (NIHSS) and 90-day modified Rankin Scale (90d mRS).
Results: Sixty-one patients showed a lesion on diffusion-weighted magnetic resonance images and an occlusion of the MCA on CE-MRA. We found significant inverse correlations between DT and NIHSS scores at admission (ρ = -0.29; P = 0.02), DT and mRS at 90 days (ρ = -0.29; P = 0.04), and between DT and FVH (ρ = -0.32; P = 0.01). For a DT <22 mm, the likelihood of an unfavorable outcome (90d mRS 3-6 or NIHSS score improvement of ≤10 points at discharge) was >50 %. Initial DWI lesion volumes showed no correlation with the outcome. Excellent inter-rater agreement for DT was observed (Cronbach's α = 0.98; P < 0.001).
Conclusions: DT on CE-MRA is reliably measurable, correlates inversely with FLAIR-vascular hyperintensities, and predicts outcome in patients with acute MCA occlusion treated with IVT.