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Article, Annals of clinical and translational neurology. 6(12): 2595-2600 (2019)

Background: Since the advent of magnetic resonance imaging technology, cerebral microbleeds can be diagnosed in vivo. However, the underlying mechanism of cerebral microbleed formation is not fully understood. Objectives: This study aimed to identify the factors associated with cerebral microbleeds after carotid artery stenting (CAS). Method: We retrospectively examined 125 patients who underwent CAS for carotid stenosis. Cerebral microbleeds were investigated using T2*-weighted gradient-echo (GRE) imaging before and after CAS. We analyzed the possible association of new microbleeds with the following risk factors: the number of baseline microbleeds and ischemic cerebral lesions, the occurrence of cerebral hyperperfusion syndrome, and new ischemic cerebral lesions after CAS. Results: Baseline cerebral microbleeds were detected in 53 patients (42.4%). New cerebral microbleeds after CAS were observed in 13 of 125 patients (10.4%) and were exclusively associated with new ischemic lesions but not with other risk factors. No patient showed a merged image of a new cerebral microbleed on GRE imaging or a new ischemic lesion on diffusion-weighted imaging. Lobar and deep microbleeds were noted in 12/13 (92.3%) and 1 patient (7.7%), respectively. Of 12 patients with new microbleeds, 10 (76.9%) and 2 (15.4%) had a new microbleed in the ipsilateral and contralateral hemispheres, respectively. Conclusions: We found that new cerebral microbleeds developed after CAS and that these might be associated with new ischemic lesions, mostly in the territory of the treated carotid artery. We speculate that these microbleeds result from the deoxygenation of hemoglobin in the embolus or, alternatively, small hemorrhagic transformation of ischemic lesions.

Cerebral microbleeds (MBs) have been often observed due to the development of imaging devices, and are classified to deep and lobar MBs. Lobar MBs are strongly associated with cerebral amyloid angiopathy. Here, we report 3 cases of lobar MBs that developed after small cortical ischemic stroke. One case underwent carotid artery stenting for severe carotid stenosis, one was diagnosed with artery-to-artery embolism, and the other was embolic stroke of undetermined source. New small cortical infarctions were detected with diffusion-weighted magnetic resonance imaging (MRI). Initial MRI revealed no hemorrhage around the ischemic lesion on T2*-weighted gradient-recalled echo or susceptibility-weighted imaging (SWI) at the onset of stroke. Follow-up SWI after 12-20 months revealed lobar MBs in the previously detected ischemic lesions, and high-intensity lesions remained around the MBs on fluid-attenuated inversion recovery imaging. These cases revealed that cerebral MBs developed through the transformation of small cortical infarctions. All cases showed lobar MBs, and these MBs existed in the previously detected ischemic lesions at a chronic stage. Lobar MBs present around ischemic lesions may predict embolic infarcts.