Early [C-11]flumazenil/H2O positron emission tomography predicts irreversible ischemic cortical damage in stroke patients receiving acute thrombolytic therapy

Background and Purpose-Central benzodiazepine receptor ligands, such as [C- 11]flumazenil (FMZ), are markers of neuronal integrity and therefore might be useful in the differentiation of functionally and morphologically damage d tissue early ill ischemic stroke. We sought to assess the value of a benz odiazepine receptor ligand for the early identification of irreversible isc hemic damage to cortical areas that cannot benefit from reperfusion. Methods-Eleven patients (7 male, 4 female, aged 52 to 75 years) with acute, hemispheric ischemic stroke were treated with alteplase (recombinant tissu e plasminogen activator, 0.9 mg/kg according to National Institute of Neuro logical Disorders and Stroke protocol) within 3 hours of onset of symptoms. At the beginning of thrombolysis, cortical cerebral blood flow ([O-15]H2O) and FMZ binding were assessed by positron emission tomography (PET). Those early PET findings were related to the change in neurological deficit (Nat ional Institutes of Health Stroke Scale) and to the extent of cortical dama ge on MRI or CT 3 weeks after the stroke. Results-Hypoperfusion was observed in all cases, and in 8 patients the valu es were below critical thresholds estimated at 12 mL/100 g per minute. comp rising 1 to 174 cm(3) of cortical tissue. Substantial reperfusion was seen in most of these regions 24 hours after thrombolysis. In 4 cases, distinct areas of decreased FMZ binding were detected. Those patients suffered perma nent lesions in cortical areas corresponding to their FMZ defects (112, ver sus 146, 3 versus 3, 2 versus 1, and 128 versus 136 cm(3)). In the other pa tients no morphological defects were detected on MRI or CT, although blood flow was critically decreased in areas ranging in size up to 78 cm(3) befor e thrombolysis. Conclusions-These findings suggest that imaging of benzodiazepine receptors by FMZ PET distinguishes between irreversibly damaged and viable penumbra tissue early after acute stroke.