Significance of hyperintense vessels on FLAIR MRI in acute stroke

Objective: To describe hyperintense vessels sign (HVS) in patients with acu te stroke on fluid-attenuated inversion recovery (FLAIR) MRI and determine its clinical significance and utility. Background: Enhancement of vessels o n postcontrast MRI in patients with acute stroke is considered an indicator of early brain ischemia. Recently, the FLAIR technique has shown promise i n earlier and better detection of ischemic brain parenchymal lesions. Metho ds: Two observers retrospectively reviewed 304 MRI of patients with stroke and identified 30 patients with acute middle cerebral artery stroke and HVS on FLAIR obtained within 24 hours of symptom onset. These patients were ev aluated with contrast-enhanced MRI (n = 9), MR angiography of carotid and i ntracranial circulation (n = 30), cerebral angiography (n = 8), transcrania l Doppler (n = 17), and SPECT (n = 16). The extent of HVS was compared with final infarct size and NIH Stroke Scale score. Results: HVS on FLAIR was s een in 10% of the patients with acute stroke. HVS was associated with large vessel occlusion or severe stenosis (> 90%). Intravascular enhancement on contrast MRI was observed in vessels that were hyperintense on FLAIR. Both cortical and subcortical infarcts demonstrated HVS. MR angiographic and cer ebral angiographic findings of large vessel occlusion or severe stenosis (> 90%), slow flow, low velocities by transcranial Doppler, and hypoperfusion on SPECT correlated with HVS. HVS was the earliest ischemic change in thre e patients scanned within 3 hours of ictus. Final infarct size was smaller than the area showing HVS in all patients. Conclusion: HVS on FLAIR MRI is an indicator of slow flow and early ischemia as a result of large vessel oc clusion or stenosis and inadequacy of collateral circulation. HVS does not mean that infarction has occurred but indicates brain tissue at risk of inf arction. It should prompt consideration of revascularization and flow augme ntation strategies.