Evaluation of ischemic lesions after carotid artery stenting with diffusion-weighted imaging.

Background: Almost 90% of cerebral thromboembolism cases are caused by atherosclerosis. Craniocervical atherosclerosis is often observed at the carotid bifurcation and is responsible for 20%-30% of all stroke cases. The course of atherosclerotic carotid artery stenosis varies depending on the grade of stenosis and characteristics of the plaque. Carotid artery stenting (CAS) can be used as a less invasive method in patients with symptomatic and asymptomatic high-grade carotid artery stenosis. Diffusion-weighted imaging (DWI) is an effective method for detection of silent or symptomatic acute ischemic lesions that may arise due to CAS or carotid endarterectomy. The number and volume of new ischemic lesions are determined using DWI.

Aim: To evaluate the number and volume of ischemic lesions and their cerebral parenchymal and vascular distribution after CAS using DWI.

Methods: Forty-seven male (73.4%) and seventeen female (26.6%) patients (total, = 64) aged 42-84 years (mean 67.96 ± 8.03 years) diagnosed with carotid stenosis between October 2006 and July 2012 were included in this retrospective study. Twelve of the cases (18.8%) were asymptomatic, while fifty-two (81.2%) were symptomatic. The area where the stenosis was highest was measured, and the stenosis rate was determined using the North American Symptomatic Carotid Endarterectomy Trial method. DWI of the cases was evaluated by two radiologists experienced in neuroradiology (B.A. with more than 15 years of experience, E.G. with more than 10 years of experience). Routine DWI examinations were carried out by a 1.5 T MR device 1 h before and after the operation. Since the ischemic lesions that developed in the first hour and in the follow-up period of 5-24 h were assumed to be due to CAS, all lesions within the first 24 h were considered as new ischemias.

Results: In the present study, 39 new ischemic lesions were detected in 20 cases. The average number of new lesions after all CAS operations was 0.62. They were mostly located in the occipital lobes, followed by the frontal and parietal lobes. These new ischemic lesions were most common in the middle cerebral artery territory, followed by the posterior cerebral artery territory and middle cerebral artery-posterior cerebral artery watershed areas. New lesions were found in 31.2% (20/64) of patients, including 17 (26.5%) in ipsilateral and three (4.6%) in contralateral hemispheres. New bilateral lesions were detected in one case (1.5%). The average volume of the new ischemic lesions detected by the two observers was 1.10 cm³. The numbers of newly appearing ischemic lesions in DWI after CAS were significantly higher in cases where stenting was applied on the left side of the carotid artery and in cases where longer plaques (> 1 cm) were responsible for the narrowing in symptomatic patients. The stenosis rate was low in the group with ulcerated plaques.

Conclusion: New ischemic lesions due to CAS appear mostly in the main arterial territory but they may also occur in watershed areas.