A Pilot Study on the Perioperative Change in Cognitive Function and Underlying Magnetoencephalography (MEG) Markers on Recently Symptomatic Patients Undergoing Carotid Endarterectomy

Abstract

Introduction - Carotid endarterectomy (CEA) is performed for stroke risk reduction but it may also impact cognitive function. Findings on cognitive outcomes after CEA are inconsistent1: deterioration, no change or improvement have been reported. CEA may lead to cognitive decline caused by procedural emboli, general anesthesia or temporal carotid flow interruption during clamping. On the other hand, opening of a stenotic artery and restoring blood flow to the brain may improve cognitive function following chronic hypoperfusion and by preventing additional ischemic lesions in the brain caused by emboli arising from atherosclerotic lesions. Different methods have been used to measure this change in cognition (including MMSE, specific neuropsychological examinations (NPEs)) and the underlying structural and functional changes in the brain (e.g. EEG, MRI). Magnetoencephalography (MEG) measures the magnetic fields produced by the electric activity of the brain withpotential of comparing both spatial and temporal characteristics of neural activation during rest or cognitive tasks. In this pilot study we aimed at establishing a) possible change in cognitive function and b) feasibility of using MEG to detect change in neuronal activity in recently symptomatic carotid patients undergoing CEA. Methods - Three recently symptomatic CEA patients (Table 1) were prospectively enrolled to this study, which included head MRI, NPE and MEG (rest, eyes open/close) prior to surgery. CEAs were performed under locoregional anesthesia using NIRS-monitoring. MRI was performed postoperatively to detect potential lesions associated with CEA. Follow-up MEG and NPE were conducted after 3 months. For MEG data, we report the peak amplitude and frequency of the well documented 10 Hz oscillation (alpha), which is generally considered to have a marked role in cognitive function. This study was approved by local ethics committee. Statistics: Mean, median and range are reported when appropriate. A paired samples t-test was used to compare pre- and postoperative NPE scores.Table 1Patient characteristics.Patient characteristicsN (%)n= /male sex3/100 %Age (mean, median, range)73, 72, 71-77 yrsIndication: minor stroke/TIA1(33) / 2(67)DM II, HTA, MCC, FA1(33),3(100),2(67),1(33) Open table in a new tab Results - Table 2 shows operative details. There was a significant difference in pre- vs. postoperative auditory working memory (WAIS-IV Digit Span, p<0.01) and information processing efficiency (SDMT, p=0.04) (Figure 1). MEGs were performed without problems for all patients, but one dataset had to be discarded due to strong magnetic artefacts in the data. In the preliminary analysis of MEG data (n=2), changes either in peak amplitude or peak frequency of the alpha oscillation were visible postoperatively. Two out of three patients showed Fazekas 3 -level white matter atrophy on preoperative MRI. There were no major 30-day complications.Table 2Operative details.Stenosis (NASCET) (mean, median, range)65, 70, 55-70 %Locoregional anesthesia3 (100 %)Patch3 (100 %)Shunt1 (33 %) Open table in a new tab Conclusion - MEG is technically feasible in pre- and postoperative evaluation of recently symptomatic CEA-patients. Observed MEG changes in resting state alpha may associate to the cognitive test results, which showed improvement in measures of working memory and information processing efficiency. Additional analyses in bigger populations with age-matched healthy controls are required to confirm the cognitive effects and to further evaluate the utility of MEG in this setting. References1)Naylor AR et al. Management of atherosclerotic carotid and vertebral artery disease: 2017 clinical practice guidelines of the European society for vascular surgery. Eur J Vasc Endovasc Surg. 2018 Jan;55(1):3-81.