Carotid Plaque Inflammation Is Associated With Cerebral Microembolism in Patients With Recent Transient Ischemic Attack or Stroke

Background— Cerebral infarcts distal to carotid stenoses are thought to be caused by emboli from inflamed, destabilized plaques. We hypothesized that microembolic signals (MES) on transcranial Doppler will be associated with carotid plaque inflammation on 18 F fluorodeoxyglucose positron-emission tomography (FDG PET) in recently symptomatic patients. Methods and Results— Sixteen patients presenting with recent (47±31 days) anterior circulation transient ischemic attack or minor stroke and 50% to 99% stenosis of the ipsilateral carotid bifurcation underwent FDG PET, high-resolution black-blood carotid MRI, and transcranial Doppler for detection of MES. Patients with potential cardiac sources of emboli or contralateral MES were excluded. Regions of interest defined on the coregistered MRI were used to measure FDG standardized uptake values (with Rousset partial volume correction) from the index and contralateral carotid plaques and artery. Ipsilateral MES were detected in 7 patients (MES+ group) and absent in 8 (MES− group). There was a significant difference in index-to-contralateral plaque standardized uptake value ratio between MES+ (median, 1.05; first to third quartile, 0.96 to 1.32) and MES− (median, 0.76; first to third quartile, 0.62 to 0.94) patients ( P =0.005). The interval from symptom onset to PET and percent index carotid stenosis were not different between the 2 groups ( P =0.68 and P =0.48, respectively). Conclusions— In this sample of recently symptomatic patients with carotid stenosis, an association was found between in vivo measures of plaque inflammation detected by FDG PET and the presence of transcranial Doppler MES. These findings strengthen the notion that embolic events distal to carotid stenoses are related to plaque inflammation, and FDG PET may be useful in the investigation of culprit carotid lesions.