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 or=60 microm. 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 microm and a mean of eight fragments (range, 2 to 21) sized >500 microm. 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.