['Thrombotic thrombocytopenic purpura (TTP) is a rare hematologic disorder that frequently presents with neurologic involvement. However, the yield and prognostic value of acute brain neuroimaging in patients with TTP has not been studied. Our aim was to evaluate brain imaging findings in consecutive patients with TTP and assess their impact on prognosis.', 'We retrospectively collected clinical, laboratory, and neuroradiologic information in 47 episodes of acute TTP studied with brain imaging at our medical center between 1997 and 2007. Head CT and brain MRI were evaluated independently by 2 investigators. We then performed statistical analysis to determine whether the presence of acute lesions on brain imaging was associated with worse functional outcome as assessed by the modified Rankin score upon discharge and long-term follow-up.', 'Ten patients (25%) of those who had a head CT had acute changes, half of them indicating posterior reversible encephalopathy syndrome (PRES). Most cases studied with brain MRI had acute changes (82%). More than half of those had evidence of PRES (48%). Atypical variants of PRES were seen in 2 patients with isolated basal ganglia involvement. Acute ischemia and hemorrhage were uncommon. Most patients with acute changes on brain imaging recovered favorably, and radiologic lesions were not associated with worse functional outcome.'] Are brain lesions most often reversible in acute thrombotic thrombocytopenic purpura?