Cerebral Microbleeds and Thrombolysis for Acute Ischemic Stroke

Abstract

Cerebral microbleeds (CMB) are small MRI signal voids due to tiny hemosiderin deposits derived from red blood cell extravasation. The relationship between CMB and postthrombolysis intracerebral hemorrhage (ICH), the most feared complication of thrombolysis for acute ischemic stroke, has received considerable attention. Individual studies relating CMB and postthrombolysis ICH have generally failed to show a significant association. However, recent meta-analyses indicate that CMB presence or burden on pretreatment MRI is associated with postthrombolysis ICH. The exact nature of the CMB–postthrombolysis ICH relationship is complicated by the heterogeneous nature of CMB and their associated risk factors hypertension, cerebral amyloid angiopathy, and chronic kidney disease. CMB may be due to a primary disruption of the vessel wall (primary CMB) or may be a consequence of ischemic brain injury (secondary CMB). Clinicians making decisions regarding whether or not to offer intravenous thrombolysis to patients with acute ischemic stroke should attempt to distinguish primary from secondary CMB, as it is the former that likely create the greatest risk for postthrombolysis ICH.