Detection of clinically silent infarcts after carotid endarterectomy by use of diffusion-weighted imaging.

BACKGROUND AND PURPOSE Intraprocedural transcranial Doppler sonography has identified multiple microembolic events during and immediately after carotid endarterectomy (CEA) or angioplasty, yet the rate of clinically evident stroke is small. To determine the significance of the transcranial Doppler sonography findings, we examined patients by use of diffusion-weighted imaging and fluid-attenuated inversion recovery MR imaging before and immediately after CEA for evidence of clinically silent ischemic events. METHODS Twenty-five patients with atherosclerotic disease of the carotid arteries underwent diffusion-weighted imaging and fluid-attenuated inversion recovery MR imaging performed, on average, 3 days before and 12 hours after CEA. Diffusion-weighted images were acquired in three orthogonal directions at b = 900. Pre- and postoperative neurologic examinations were performed by the same physician. RESULTS After endarterectomy, 4.0% of the patients (one of 25 patients) showed a single, cortical focus of restricted diffusion and new fluid-attenuated inversion recovery hyperintensity, measuring <1 cm in diameter, ipsilateral to the CEA. The postoperative neurologic examination showed no change in status from the preoperative baseline state. This patient had an intraoperative course complicated by the development of a large luminal thrombus, necessitating thrombectomy. CONCLUSION The use of diffusion-weighted imaging may serve to improve conspicuity of clinically silent infarcts after CEA. An important next step is to determine the risk factors that predispose to detectable parenchymal ischemic events.