Abnormal Frontal Brain Activation in Patients With Asymptomatic Carotid Artery Stenosis


Background Emerging evidence suggests that asymptomatic carotid artery stenosis (ACAS) is associated with cognitive and mobility dysfunction, and that this may be secondary to cerebral hemodynamic changes. Functional near-infrared spectroscopy (fNIRS) is a noninvasive imaging technology that measures cerebral hemodynamic responses using the absorption of near-infrared light to identify changes in hemoglobin concentrations evoked by neural activity. In this study, we evaluated the changes in oxygenated hemoglobin concentration (HbO2) in healthy control subjects and subjects with bilateral ACAS during two tasks: regular walking and during a dual task assessment involving mobility and executive function (walking while talking [WWT]). Methods fNIRS measures were obtained in twenty-three healthy subjects (mean 41 ± 14 years, 14 males) and eight subjects with bilateral moderate-grade (50%-69%) ACAS (mean 66.75 ± 8.5 years, 3 males) using the Brite 23 Artinis fNIRS system. Measures were obtained with subjects walking at their normal pace and then while performing the WWT complex task (reciting alternate letters while walking). Each task was preceded by 30 seconds of rest to establish a baseline oxyhemoglobin level. The HbO2 tracings from each task were generated using OxySoft software and analyzed using a self-script in MATLAB. The MATLAB script filtered out any physiologically irrelevant signals and bad quality data. Bifrontal brain activation was assessed by averaging the signals from the left and right frontal lobes. Results Subjects with bilateral moderate-grade ACAS demonstrated significantly higher mean HbO2 concentrations while walking (controls 0.24 μmol/L and bilateral ACAS 0.69 μmol/L, P = .006) and during the WWT complex task (controls 0.62 μmol/L and bilateral 1.3 μmol/L, P = .007). The bilateral ACAS subjects required higher HbO2 recruitment compared with controls (Figure) during both tasks. Both groups demonstrated a higher mean HbO2 recruitment during the WWT task as compared with regular walking. Conclusions Using fNIRS, we found that subjects with bilateral moderate-grade ACAS required higher oxyhemoglobin recruitment, indicating a greater degree of frontal neural activity, to accomplish the same mobility task as healthy controls. This pilot study indicates that patients with ACAS may exhibit compensatory brain activation patterns with increased HbO2 recruitment required to complete tasks compared with healthy controls.

Journal of Vascular Surgery