The Relationship between the Change of Brain Perfusion and Neurocognitive Function after Carotid Revascularization in the Patients with Carotid Atherosclerotic disease

Reducing embolic stroke by carotid artery stenting (CAS) and carotid endarterectomy (CEA) in patients with severe internal carotid occlusive disease has been well proven. Neurocognitive function is being increasingly recognized as an important outcome measure. Cognitive impairment and decline were found in patients with asymptomatic high-grade stenosis of the left internal carotid artery (ICA), and hypoperfusion may be a potential cause. It is intuitive that reopening a stenotic vessel and restoring blood flow to the brain would certainly have favorable neurocognitive effects, but previous studies have provided inconsistent results. In this study, we explored the effect of CAS on neurocognitive function in patients with severe carotid artery occlusive disease and tried to find out the specific population who will benefit from the procedure. By using 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) to assess brain metabolism, we would also like to demonstrate the metabolic improvement following successful CAS. First of all, we investigated the cognitive effect of successful CAS in patients with chronic internal carotid artery occlusion (ICAO) and ipsilateral cerebral ischemia. As compared to the failed group (N=7), we found that successful CAS (N=12) improved global cognitive function as well as attention and psychomotor processing speed in patients with chronic ICAO. For further proving the effect of CAS on neurocognitive function in patients with severe carotid artery occlusive disease, we expanded patient cohort to assess the neurocognitive change after CAS in all patients with severe ICA disease, analyzed according to baseline perfusion status of ipsilateral hemisphere and procedure result. We also found that successful CAS can improve global cognitive functions in patients with ICA stenosis/occlusion, but only in patients with baseline objective abnormal cerebral perfusion. The changes of cognitive function are correlated with the change of brain perfusion. The results imply the reversibility of cognitive function in ischemic hemisphere after restoring cerebral perfusion. With the assist of FDG PET, we observed that patients who underwent successful CAS had superior brain metabolism outcomes by comparison to those with failed recanalization. The improvement of brain FDG observed in areas corresponding to the treated ICA territory could be due to the restored perfusion. In summary, successful CAS not only improves neurocognitive outcome but also improves cerebral glucose metabolism in patients with objectively-assessed cerebral ischemia due to severe chronic carotid stenosis or occlusion.