Abstract TP118: New Markers for Basilar Artery Atherosclerotic Plaque on Conventional T2-weighted MR Imaging

Abstract

Backgrounds and purpose: In vivo visualization of intracranial atherosclerotic plaque has been studied with high-resolution wall MRI (HRMRI). However, HRMRI is not widely available in routine clinical practice. We hypothesized that increased outer wall and partial loss of flow-void of basilar artery (BA) in conventional T2 axial imaging might be suggestive of positive remodeling and atherosclerotic plaque. Methods: Using a consecutive stroke registry, patients with basilar artery atherosclerotic steno-occlusion were identified. Subjects with same range of age who were negative for abnormal wall thickening of the BA in HRMRI served as controls. Using conventional T2 axial images, maximal diameter and T2 plaque sign (an eccentric or complete obscuration of normal flow-related T2 signal void) within the BA were measured. We tested the diagnostic value of T2 plaque sign and maximal diameter to distinguish patients from controls. Results: Seventy-five patients (age range, 51-81) and 36 controls (50-81) were identified. Maximal diameter was significantly larger in patients than controls (3.87 ± 0.868 mm vs 2.68 ± 0.447 mm, p<0.001). Positivity of T2 plaque sign were 61.3% in patients with BA atherosclerosis, 71.2% in patients with >30% BA stenosis, 77.5% in >50% BA stenosis, and 96.3% in patients with >70% BA stenosis. Receiver operating characteristic curve showed high predictive power (the area under the curve 0.921, 95% CI 0.872 - 0.970, p<0.001) of maximal BA diameter to distinguish patients and controls with an optimal cutoff of 3.185 mm, (sensitivity, 78.7%; specificity, 94.4%). Sensitivity and specificity of T2 plaque sign were 61.3% and 100.0% for BA atherosclerosis of any degree. Increasing sensitivity and decreasing specificity were noted for the diagnosis of higher degree stenosis. Conclusion: Our data suggest that increased BA diameter and plaque sign on conventional T2 imaging are markers of basilar artery atherosclerosis. This would be helpful for earlier identification of causative stroke mechanism. Further study is needed for validation of these findings among different stroke etiologies.