Cerebral cortical microinfarcts in patients with internal carotid artery occlusion

Abstract

Cerebral cortical microinfarcts (CMI) are small ischemic lesions that are associated with cognitive impairment and probably have multiple etiologies. Cerebral hypoperfusion has been proposed as a causal factor. We studied CMI in patients with internal carotid artery (ICA) occlusion, as a model for cerebral hemodynamic compromise. We included 95 patients with a complete ICA occlusion (age 66.2 ± 8.3, 22% female) and 125 reference participants (age 65.5 ± 7.4, 47% female). Participants underwent clinical, neuropsychological, and 3 T brain MRI assessment. CMI were more common in patients with an ICA occlusion (54%, median 2, range 1-33) than in the reference group (6%, median 0; range 1-7; OR 14.3; 95% CI 6.2-33.1; p<.001). CMI were more common ipsilateral to the occlusion than in the contralateral hemisphere (median 2 and 0 respectively; p<.001). In patients with CMI compared to patients without CMI, the number of additional occluded or stenosed cervical arteries was higher (p=.038), and cerebral blood flow was lower (B -6.2 ml/min/100 ml; 95% CI -12.0:-0.41; p=.036). In conclusion, CMI are common in patients with an ICA occlusion, particularly in the hemisphere of the occluded ICA. CMI burden was related to the severity of cervical arterial compromise, supporting a role of hemodynamics in CMI etiology.

Keywords: Cerebral blood flow; cerebral hemodynamic compromise; cerebrovascular disease; internal carotid artery occlusion; microinfarct.

Figure 1.

3D distribution across the cortex on an MNI-standard brain of all CMI in 40 patients with a unilateral ICA occlusion and CMI. For patients with a right ICA occlusion the CMI distribution was flipped to create this image where CMI are presented ipsilateral (red) and contralateral (yellow) to the occlusion. An atlas based representation of the watershed areas is included in blue. CMI burden is higher in the hemisphere ipsilateral to the occlusion (p=.001). From visual inspection CMI appear to have a predilection for watershed areas. This distribution was not evaluated by formal statistical testing, because sensitivity of CMI detection may vary by brain region and because the actual watershed region varies between individuals. Note: for visualization of both the CMI and the watershed areas, the cortex was shrunk and made translucent. This may give the false impression that some CMI were located outside of the brain.

Figure 2.

CMI presence in patients with 1-3 occluded or >50% stenosed cervical arteries (i.e. left and right internal carotid arteries and left and right vertebral arteries). None of the patients had occlusions or >50% stenosis in all 4 cervical arteries. ^aNumber of patients with 1, 2 or 3 occluded or >50% stenosed cervical arteries. N = 90 because of 5 missings.

Figure 3.

Total cerebral blood flow (mean ± SD, ml/min/100 ml) to the brain and blood flow through the non-occluded ICA and basilar artery (mean ± SD, ml/min). ^aTotal cerebral blood flow was significantly lower in patients with CMI than in patients without CMI. ^bThis difference was attributable to a lower flow in the contralateral ICA ^cnot in the basilar artery. N=75 (CMI present N=38, CMI absent N=37) because of 5 missings and because 15 patients were excluded from this analysis due to a double-sided ICA occlusion.