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Original Contribution
July 2002

Brain Damage After Coronary Artery Bypass Grafting

Author Affiliations

From the Departments of Neuroradiology (Drs Bendszus, Warmuth-Metz, and Solymosi), Cardiothoracic Surgery (Drs Reents and Babin-Ebell), and Neurology (Drs Franke, Müllges, and Koltzenburg), University of Würzburg, Würzburg, Germany. Dr Koltzenburg is now with the Institute of Child Health and the Institute of Neurology, University College London, London, England.

Arch Neurol. 2002;59(7):1090-1095. doi:10.1001/archneur.59.7.1090

Background  Coronary artery bypass grafting (CABG) is associated with a risk for focal neurological deficits and neuropsychological impairment postoperatively.

Objectives  To examine the brain damage after CABG using diffusion-weighted magnetic resonance imaging and 1H-magnetic resonance spectroscopy (MRS) and to correlate the results with neurological and neuropsychological findings.

Patients and Methods  Thirty-five consecutive patients undergoing elective CABG were included. Patients underwent a neurological and neuropsychological examination before and after CABG. The magnetic resonance protocol was applied before and after (mean, 3 days) surgery and included a diffusion-weighted sequence and single-voxel MRS measurements in the frontal lobes.

Results  None of the patients revealed a new focal neurological deficit after surgery. Diffusion-weighted magnetic resonance imaging demonstrated new ischemic lesions in 9 (26%) of the patients. The presence of an ischemic lesion was not related to impaired postoperative test performance (P>.50). The apparent diffusion coefficient values in the cerebellum and the centrum semiovale exhibited an increase after surgery (P<.01), consistent with vasogenic edema. Following surgery, MRS revealed a significant decrease in the metabolite ratio of N-acetylaspartate–creatine (mean ± SD, 1.69 ± 0.20 vs 1.52 ± 0.19; P<.001). The extent of deterioration in neuropsychological test performance after surgery was closely related to the degree of the N-acetylaspartate–creatine ratio decrease (P<.01). A follow-up MRS scan revealed a normalization of the N-acetylaspartate–creatine ratio, which accompanied the recovery in psychological test performance.

Conclusions  Postoperative impairment in neuropsychological test performance is associated with a transient metabolic neuronal disturbance. Focal ischemic lesions after CABG are more frequent than the apparent neurological complication rate; however, they are not related to the diffuse postoperative encephalopathy.