Abstract
BackgroundCarotid artery stenosis is a frequent cause of ischemic stroke. While any degree of stenosis can cause embolic stroke, a higher degree of stenosis can also cause hemodynamic infarction. The hemodynamic effect of a stenosis can be assessed via perfusion weighted MRI (PWI). Our aim was to investigate the ability of PWI-derived parameters such as TTP (time-to-peak) and Tmax (time to the peak of the residue curve) to predict outcome in patients with unilateral acute symptomatic internal carotid artery (sICA) stenosis.MethodsPatients with unilateral acute sICA stenosis (≥50 % according to NASCET), without intracranial stenosis or occlusion, who underwent PWI, were included. Clinical characteristics, volume of restricted diffusion, volume of prolonged TTP and Tmax were retrospectively analyzed and correlated with outcome represented by the modified Rankin Scale (mRS) score at discharge. TTP and Tmax volumes were dichotomized using a ROC curve analysis. Multivariate analysis was performed to determine which PWI-parameter was an independent predictor of outcome.ResultsThirty-two patients were included. Degree of stenosis, volume of visually assessed TTP and volume of TTP ≥2 s did not distinguish patients with favorable (mRS 0–2) and unfavorable (mRS 3–6) outcome. In contrast, patients with unfavorable outcome had higher volumes of TTP ≥4 s (9.12 vs. 0.87 ml; p = 0.043), TTP ≥6 s (6.70 vs. 0.20 ml; p = 0.017), Tmax ≥4 s (25.27 vs. 0.00 ml; p = 0.043), Tmax ≥6 s (9.21 vs. 0.00 ml; p = 0.017), Tmax ≥8 s (6.86 vs. 0.00 ml; p = 0.011) and Tmax ≥10s (5.94 vs. 0.00 ml; p = 0.025) in univariate analysis. Multivariate logistic regression showed that NIHSS score on admission (Odds Ratio (OR) 0.466, confidence interval (CI) [0.224;0.971], p = 0.041), Tmax ≥8 s (OR 0.025, CI [0.001;0.898] p = 0.043) and TTP ≥6 s (OR 0.025, CI [0.001;0.898] p = 0.043) were independent predictors of clinical outcome.ConclusionAs they stood out in multivariate regression and are objective and reproducible parameters, PWI-derived volumes of Tmax ≥8 s and TTP ≥6 s might be superior to degree of stenosis and visually assessed TTP maps in predicting short term patient outcome. Future studies should assess if perfusion weighted imaging might guide the selection of patients for recanalization procedures.Electronic supplementary materialThe online version of this article (doi:10.1186/s12883-016-0576-5) contains supplementary material, which is available to authorized users.
Highlights
Carotid artery stenosis is a frequent cause of ischemic stroke
Even though it seems obvious that Tmax or TTP are superior to the degree of stenosis in depicting clinically relevant hypoperfusion in patients with carotid artery stenosis, it has not been demonstrated in detail yet and patients with higher degree of stenosis are commonly suspected to have higher degrees of hypoperfusion
All other perfusion weighted MRI (PWI)-derived parameters were significantly different in patients with favorable and unfavorable outcome in the receiver operating characteristic (ROC)-analysis (Additional file 2: Table S1) and in univariate analysis that included other clinical parameters as well
Summary
Carotid artery stenosis is a frequent cause of ischemic stroke. While any degree of stenosis can cause embolic stroke, a higher degree of stenosis can cause hemodynamic infarction. A hemodynamically relevant stenosis usually has a degree of at least 70 % with a decrease of the poststenotic peak systolic velocity, increased pulsatility of the prestenotic common carotid artery and a decrease of the slope to peak systolic velocity in the transcranial Doppler sonography [4]. This type of stenosis can cause, in addition to embolic strokes, hemodynamic strokes of the watershed areas [5]. Even though it seems obvious that Tmax or TTP are superior to the degree of stenosis in depicting clinically relevant hypoperfusion in patients with carotid artery stenosis, it has not been demonstrated in detail yet and patients with higher degree of stenosis are commonly suspected to have higher degrees of hypoperfusion
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