Subclinical embolization after carotid artery stenting: New lesions on diffusion-weighted magnetic resonance imaging occur postprocedure

Objectives: The reported rate of subclinical brain injury after carotid artery stenting (CAS) seen on diffusion-weighted magnetic resonance imaging (DWI) varies from 10% to >40%. Data from transcranial Doppler after CAS indicate that embolization may continue for several days, suggesting that that at least some lesions seen on DWI occur postprocedure. Because DWI lesions appear ≤1 hour of embolization, we used DWI to prospectively study patients before CAS, 1 hour after, and 48 hours after CAS to answer this question. Methods: The study participants were 48 male patients aged 59 to 83. All patients were examined by a neurologist before and after the procedure and had DWI preprocedure and 48 hours postprocedure. In addition, 23 patients had a DWI 1 hour post-CAS. Magnetic resonance imaging exams, including axial and coronal DWI and fluid-attenuated inversion recovery images, were read by two neuroradiologists blinded to the study timing. The embolic protection device was obtained from all patients, washed, and the contents examined under a digital microscope for fragments ≥60 μm. Results: There were two periprocedural strokes and one transient ischemic attack (TIA), but no strokes or TIAs occurred during follow-up. In the 23 patients imaged 1 hour postprocedure, new lesions were found in two (9%), and 18 (78%) had new lesions at 48 hours (P < .001). For the entire study group, the incidence of new lesions at 48 hours was 67% (36/54). The median number of DWI lesions was four (range, 1 to 17). Every protection device examined had atherosclerotic debris, with a mean of 135 ± 73 fragments (range, 18 to 310) sized >60 μm and a mean of eight fragments (range, 2 to 21) sized >500 μm. Findings on postprocedure DWI did not correlate with the degree of stenosis, size of angioplasty balloon, or number of inflations, nor with the number or size of fragments retrieved from the protection device. Conclusions: CAS can be performed with a very low incidence of clinically evident neurologic events; however, it is associated with embolization during and after the procedure. Protection devices effectively prevent clinical and subclinical events during the procedure. Significant embolization continues for at least 48 hours postprocedure, causing lesions on DWI when there is no mechanism for cerebral protection. These data correlate with transcranial Doppler reports of continued embolization after CAS and indicate that DWI should be done as late as possible to accurately assess the rate of subclinical brain injury with CAS procedures.