The effect of carotid endarterectomy on cerebral blood flow and cognitive function

Background: The effect of carotid endarterectomy on cognitive function is not fully understood. This study aims to characterize changes in cerebral blood flow after carotid endarterectomy and to determine if patients with improvement in cerebral blood flow have improved cognitive function after endarterectomy. Methods: Cerebral blood flow was measured preoperatively and 1 month postoperatively using phase contrast magnetic resonance angiography. Preoperative flow impairment was defined as ipsilateral flow at least 20% less than contralateral flow. Improvement in flow was defined as an absolute increase of at least 0.10 in flow ratio from pre- to postoperative assessments. Patients underwent cognitive testing preoperatively and at 1, 6, and 12 months postoperatively. Results: Twenty-four patients with unilateral carotid stenosis were enrolled from 3 sites. Preoperative internal carotid artery (ICA) and middle cerebral artery (MCA) flow impairment was observed in 50% and 22% of patients, respectively. Patients with preoperative flow impairment had an average of 0.25 and 0.16 absolute improvement in flow ratio in the ICA and MCA vessels, respectively; this was statistically significant for patients with baseline ICA flow impairment (P <.01). One hundred percent of patients with improvement in MCA flow had a significant improvement in attention compared to 56% of patients without MCA flow improvement (P =.06). Clinically significant improvements in all 4 cognitive domains were observed at 1 year (P <.01). Conclusions: Patients with baseline impairment of MCA blood flow were more likely to experience improvement in flow after revascularization. Improvement in MCA blood flow was associated with greater cognitive improvement in attention and executive functioning.