Cerebral microbleeds in CADASIL: a gradient-echo magnetic resonance imaging and autopsy study

An increased frequency of clinically silent microbleeds (MB) has recently been observed in patients with sporadic small-vessel disease related to vascular amyloid deposition or hypertension. In this study, we searched for cerebral MBs in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a unique type of small-vessel disease caused by mutations in the Notch3 gene. Our purposes were (1) to determine the frequency, extent, and pattern of MBs in CADASIL; (2) to analyze the relationship between MBs and T2-hyperintense lesions; and (3) to evaluate the histopathology of brain tissue affected by MBs.

Gradient-echo, T2/PD-weighted dual-echo, and T1-weighted MRI scans of the brain were obtained from 16 consecutive CADASIL subjects and 16 age-matched control subjects. T2-lesion volume measurements were made with a semiautomated segmentation technique based on local thresholding. Postmortem examinations were performed on the brains of 7 additional CADASIL subjects.

Focal areas of signal loss on gradient-echo images suggesting past MBs were found in 11 CADASIL individuals (69%) and no control subjects (P<0.001). The average number of MBs was 5.9+/-7.3 (range, 0 to 22) in individual CADASIL patients. MBs were associated with age (r=0.71, P=0.002) and total lesion volume (r=0.75, P=0.001). However, after correction for age, the correlation with lesion volume was no longer significant. MBs were located simultaneously in various parts of the brain with a preference for cortical-subcortical regions (38%), white matter (20%), thalamus (13%), and brainstem (14%). Eighty-two percent of the MBs were located outside areas appearing hyperintense on T2-weighted images. Postmortem examination revealed focal accumulations of hemosiderin-containing macrophages in 6 of the 7 brains (86%). They were always found outside ischemic lesions.

This study shows a high frequency and multiplicity of MBs in individuals with CADASIL. Our results suggest that MBs and ischemic lesions are largely independent manifestations of the underlying angiopathy. The pattern of MBs shows a significant overlap with that reported in other types of small-vessel disease.