Post-carotid endarterectomy neurocognitive decline is associated with cerebral blood flow asymmetry on post-operative magnetic resonance perfusion brain scans

Abstract

Objective: Up to 25% of patients experience subtle declines in post-operative neurocognitive function following, otherwise uncomplicated, carotid endarterectomy (CEA). We sought to determine if post-CEA neurocognitive deficits are associated with cerebral blood flow (CBF) abnormalities on post-operative MR perfusion brain scans.

Methods: We enrolled 22 CEA patients to undergo a battery of neuropsychometric tests pre-operatively and on post-operative day 1 (POD 1). Neurocognitive dysfunction was defined as a two standard deviation decline in performance in comparison to a similarly aged control group of lumbar laminectomy patients. All patients received MR perfusion brain scans on POD 1 that were analysed for asymmetries in CBF distribution. One patient experienced a transient ischemic attack within 24 hours before the procedure and was excluded from our analysis.

Results: Twenty-nine percent of CEA patients demonstrated neurocognitive dysfunction on POD 1. One hundred percent of those patients with cognitive deficits demonstrated CBF asymmetry, in contrast to only 27% of those patients without cognitive impairment. Post-CEA cognitive dysfunction was significantly associated with CBF abnormalities (RR=3.75, 95% CI: 1.62-8.67, p=0.004).

Conclusion: Post-CEA neurocognitive dysfunction is significantly associated with post-operative CBF asymmetry. These results support the hypothesis that post-CEA cognitive impairment is caused by cerebral hemodynamic changes. Further work exploring the relationship between CBF and post-CEA cognitive dysfunction is needed.

Figure 1

Analysis of MR brain scan of a patient demonstrating post-CEA neurocognitive dysfunction. The original MR perfusion gray-scale image (A) is converted to a color scale and divided into six vascular territories (B). A relative difference map is generated (C). High intensity in the RDM represents regions of relative CBF asymmetry. In this case, CBF asymmetry is pronounced in the MCA territories. Histograms depicting the distribution of RDM intensities are generated (D): the CBF asymmetry being represented by the broad distribution of the MCA histogram

Figure 2

Analysis of MR brain scan of a patient without post-CEA neurocognitive dysfunction. The original MR perfusion gray-scale image (A) is converted to a color scale and divided into six vascular territories (B). A relative difference map is generated (C). The lack of high intensity in the RDM suggests relative CBF symmetry. In this case, CBF symmetry is demonstrated by the narrow downward sloping histograms in each vascular territory (D)