Introduction: Bilateral ischemic strokes are often attributed to central or cardiac embolic sources, especially in the absence of severe bilateral carotid stenosis. Carotid MRI detects carotid intraplaque hemorrhage (IPH), a marker of stroke risk independent of stenosis.
Hypothesis: MRI-detected carotid IPH better identifies bilateral carotid source strokes compared to stenosis alone.
Methods: In this retrospective cross sectional study, patients undergoing stroke workup were imaged with carotid and brain MRI. Stroke was determined by the AHA definition of CNS infarction. Patients with non-carotid stroke sources (e.g. cardiac sources), occluded or near-occluded carotids were excluded. A total of 425 patients were analyzed. Carotid imaging findings were recorded, including IPH and NASCET stenosis along with clinical cerebrovascular risk factors and medications. Receiver operating characteristic (ROC) analysis was performed to determine the predictive value (area under the curve, AUC) of carotid imaging findings.
Results: Carotid IPH was present in 89/425 of cases, and was bilateral in 24/89 (27.0%). Bilateral carotid IPH was a good predictor of bilateral stroke (AUC=.808), performing better than bilateral stenosis with ≥50%, ≥60% or ≥70% cutoffs (AUC=.565 p=.001, AUC=.550 p<.001, AUC=.523 p<.001, respectively) but not significantly better than average bilateral stenosis (AUC=.800 p=.90). The combined predictive value of bilateral IPH and average bilateral stenosis was excellent (AUC=.891) and performed better than bilateral IPH alone (p=.07) or average bilateral stenosis alone (p=.002).
Conclusions: Bilateral carotid IPH is associated with bilateral stroke, and adds significant discrimination of bilateral carotid stroke sources compared to stenosis. In the setting of bilateral stroke, carotid MRI may help uncover potential stroke sources undetected by lumen imaging alone.