Abstract
Investigation of cerebral circulation and metabolism in stroke patients with PET has given clinicians useful information in interpreting the results of SPECT examinations in clinical practice. In patients with atherothrombotic internal carotid artery (ICA) or middle cerebral artery (MCA) occlusive disease, the chronic reduction in cerebral perfusion pressure (chronic hemodynamic compromise) increases the risk for cerebral ischemic damage. We have shown that severe hemodynamic compromise, demonstrated as increased oxygen extraction fraction (misery perfusion) with PET, is a risk factor for subsequent ischemic stroke. We have also shown that selective neuronal damage demonstrated as a decrease in central benzodiazepine receptor in the normal-appearing cerebral cortex is associated with increased oxygen extraction fraction (misery perfusion). Detection and appropriate treatment of the patients with misery perfusion is important for preventing ischemic damage in patients with atherothrombotic ICA or MCA occlusive disease. Using PET, we have correlated CBF response to acetazolamide with hemodynamic and metabolic parameters in patients with atherothrombotic ICA or MCA occlusive disease, which suggested that evaluation of cerebral vasodilatory capacity using SPECT with acetazolamide could detect patients with hemodynamic compromise including patients with misery perfusion. A Japanese EC/IC bypass trial for patients with severe hemodynamic compromise, demonstrated as decreased CBF and decreased CBF response to acetazolamide with SPECT, showed a benefit of bypass surgery for preventing ischemic stroke. Thus, detection of the patients with severe hemodynamic compromise is crucial for improving the prognosis of patients with atherothrombotic ICA or MCA occlusive disease. Understanding the pathophysiology of hemodynamic cerebral ischemia is essential for the management of patients with atherothrombotic ICA or MCA occlusive disease. Pathophysiology of hemodynamic cerebral ischemia studied with PET has had impact on clinical significance of SPECT examinations for improving prognosis of patients.
