IV tPA (IVT) for ischemic stroke is associated with a 3% to 4% increase in the risk of symptomatic intracranial hemorrhage (sICH), often leading to poor outcomes. Although this represents a considerable hazard, the benefits of tPA are robust and warrant careful consideration of the risk/benefit profile in all patients with possible ischemic stroke. Clinical models to predict which patients will be at higher risk for sICH have had mixed results and researchers have begun to utilize high resolution gradient echo T2* MRI sequences to examine if their increased sensitivity can better predict risk of hemorrhage and prognosis.

Pascal Gratz et al. examined a cohort of 392 ischemic stroke patients treated with with IVT, endovascular therapy (EVT) or IVT followed by EVT, who also had a pre-treatment MRI with susceptibility-weighted imaging (SWI). Several radiologists retrospectively reviewed the MRIs to identify cerebral microbleeds (CMBs), which were characterized as consistent with hypertension if they were deep and as amyloid angiopathy if more superficial in older patients. CMB were detected in 20.2% and sICH was present in 5.4% and asymptomatic in 19.4%. The presence of CMB within the stroke did not increase the risk for ICH or worsen outcome, even if CMB burden, predominant location or presumed etiology were taken into account. There was a small increase in the risk of ICH outside the infarct with increasing CMB burden, but the effect was marginal and barely reached significance.

This data argues against the use of SWI for ICH risk stratification prior to IVT, EVT, or IVT/EVT. We should not delay the administration of IVT, the most effective therapy for acute ischemic stroke, for advanced imaging unless it clearly indicates that the patient will not benefit from tPA. A recent article showed a statistically significant association between the gradient echo T2* “brush sign” in patients with ischemic stroke treated with IVT and subsequent hemorrhagic transformation. While this was a small trial, and not measuring sICH, the results suggest that there may be utility for gradient echo T2* advanced imaging and further study is warranted. The debate surrounding the effectiveness of EVT is ongoing and SWI may be more important in this population, whose morbidity is often related to sICH. These results should again encourage physicians to give tPA when patients meet criteria, and not defer based on concerns about prior CMBs.