An MRI Hyperintense Acute Reperfusion Marker Is Related to Elevated Peripheral Monocyte Count in Acute Ischemic Stroke

BACKGROUND AND PURPOSE: Blood–brain barrier (BBB) disruption detected on magnetic resonance imaging (MRI) in acute ischemic stroke as a hyperintense acute reperfusion marker (HARM) is associated with upregulation of matrix metalloproteinase-9 (MMP-9). Although activated leukocytes, including monocytes, are the main source of MMPs, limited data exist to support relationship between leukocyte activation and BBB disruption in patients with acute ischemic stroke. The goal of this study is to investigate the relationship between neutrophils, lymphocytes, and monocytes with BBB disruption detected as HARM (+) in patients with acute ischemic stroke. METHODS: We conducted a retrospective analysis of prospectively collected data in patients who did not receive any reperfusion therapy with acute (<12 hours) ischemic stroke. MRI scans were obtained at baseline, 24 hours, and 5 days. HARM was evaluated on the 24-hour follow-up scan. RESULTS: Thirty-three patients were studied. HARM was detected in 27% of patients. Median volumes of baseline perfusion (mean transit time [MTT]) deficit (219.4 mL vs. 158.4 mL, P =.029) and DWI infarct growth at 24 hours (18.50 mL vs.14 mL, P =.017), as well as the median absolute numbers (1 × 10³/mm³) of monocytes, were significantly higher in HARM (+) versus HARM (−) patients (0.9 vs. 0.6, p = 0.011). CONCLUSION: Increased monocyte count associated with HARM supports importance of systemic inflammation in BBB disruption in acute ischemic stroke.