Silent Microembolism on Diffusion-Weighted MRI after Coil Embolization of Cerebral Aneurysms

PURPOSE: The purpose of this study was to investigate the frequency and risk factors of procedure-related thromboembolism on diffusion-weighted imaging (DWI) associated with aneurysmal coil embolization. MATERIALS AND METHODS: We prospectively evaluated 39 consecutive patients with a cerebral aneurysm with DWI after coil embolization. All hyperintense lesions on DWI with a drop of apparent diffusion coefficient values were classified into acute thromboembolic infarction (larger than 5 mm in maximal diameters, and located in the vascular territory of the parent artery) and silent microembolism (single or multiple tiny dot-like lesion, less than 5 mm, usually 1-2 mm in size). Possible risk factors for thromboembolic events included vascular risk factors, aneurysmal factors, and procedure-related factors. RESULTS: Hyperintense lesions on DWI were seen in 17 (43.6%) patients and symptomatic DWI positive lesions were four (10.3%). Acute thromboembolic infarction was observed in seven (17.9%) patients and silent microembolism in 14 (35.9%) patients. Numbers of silent microembolism ranged from 1 to 15 (mean: 2.86, standard deviation: 3.74). Silent microembolisms were located at ipsilateral (n=3, 21.4%), contralateral (n=5, 35.7%), bilateral (n=4, 28.6%), and not related (n=2, 14.3%) to the procedure site. There were no statistical significant risk factors in acute thromboembolic infarction. However, incidence of silent microembolisms was significantly correlated with left side approach (odds ratio, 4.44, 95% confidence interval, 1.08-18.36; P=0.03). CONCLUSION: Left side approach may have increased the likelihood of asymptomatic multiple scattered microemboli after aneurysmal coiling procedures. Particular care must be taken in the handling of guiding catheters, especially when proving left side great vessels.