Serial changes in cerebral blood flow and flow-metabolism uncoupling in primates with acute thromboembolic stroke

The authors recently developed a primate thromboembolic stroke model. To characterize the primate model, the authors determined serial changes in cerebral blood flow (CBF) and the relation between CBF and cerebral metabolic rate of glucose (CMRglc) using high-resolution positron emission tomography. Thromboembolic stroke was produced in male cynomolgus monkeys (n = 4). Acute obstruction of the left middle cerebral artery was achieved by injecting an autologous blood clot into the left internal carotid artery. Cerebral blood flow was measured with [15O]H2O before and 1, 2, 4, 6, and 24 hours after embolization. CMRglc was measured with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) 24 hours after embolization. Lesion size and location 24 hours after embolization was determined by the 2,3,5-triphenyltetrazolium chloride (TTC) staining method. The results are summarized as follows: (1) 1 hour after embolization, CBF in the temporal cortex and the basal ganglia decreased to < 40% of the contralateral values. In these regions, regarded as an ischemic core, CBF decreased further with time and CMRglc at 24 hours also decreased. Infarcted lesions as indicated by being unstained with TTC were consistently observed in these regions. (2) In the parietal cortex and several regions surrounding the ischemic core, CBF was > 40% of the contralateral values 1 hour after embolization and recovered gradually with time (ischemic penumbra). In these regions, CMRglc at 24 hours increased compared with that in the contralateral regions, indicating an uncoupling of CBF and CMRglc. No obvious TTC-unstained lesions were detected in these regions. The authors demonstrated a gradual recovery of reduced CBF, an elevated CMRglc and a CBF-CMRglc uncoupling in the penumbra regions of the primate model. Positron emission tomography investigations using this model will provide better understanding of the pathophysiology of thromboembolic stroke in humans.