Characteristic distributions of intracerebral hemorrhage–associated diffusion-weighted lesions

Abstract

Objectives: To determine whether small diffusion-weighted imaging (DWI) lesions occur beyond the acute posthemorrhage time window in patients with intracerebral hemorrhage (ICH) and to characterize their spatial distribution in patients with lobar and deep cerebral hemorrhages. Methods:In this cross-sectional study, we retrospectively analyzed 458 MRI scans obtained in the acute (#7 days after ICH) or nonacute (.14 days after ICH) phases from 392 subjects with strictly lobar (n 5 276) and deep (n 5 116) ICH (48.7% women; mean age 72.8 6 11.7 years). DWI, apparent diffusion coefficient maps, fluid-attenuated inversion recovery, and T2* MRIs were reviewed for the presence and location of DWI lesions. Results:We identified 103 DWI hyperintense lesions on scans from 62 subjects, located mostly in lobar brain regions (90 of 103, 87.4%). The lesions were not uniformly distributed throughout the brain lobes; patients with strictly lobar ICH had relative overrepresentation of lesions in frontal lobe, and patients with deep ICH in parietal lobe (p 5 0.002). Although the frequency of DWI lesions tended to be greater on scans performed within 7 days after ICH (39 of 214, 18.2%), they continued at high frequency in the nonacute period as well (23 of 178, 12.9%, odds ratio 1.5, 95% confidence interval 0.86-2.6 for acute vs nonacute). There was also no difference in frequency of lesions on acute and nonacute scans among 66 subjects with MRIs in both time periods (8 of 66 acute, 10 of 66 nonacute, odds ratio 0.77, 95% confidence interval 0.25-2.4). Conclusions:The high frequency of DWI lesions beyond the acute post-ICH period and their characteristic distributions suggest that they are products of the small vessel diseases that underlie ICH. Recent analyses of patients with primary intracerebral hemorrhage (ICH) have identified a surprisingly high incidence of small hyperintense lesions on diffusion-weighted imaging (DWI) sequences. 1-6Although the neuropathologic basis of these clinically asymptomatic DWI hyperintense lesions has not been determined, their imaging properties are suggestive of small cerebral infarcts. One possibility is that these neuroimaging lesions represent a subset of acute, relatively large cerebral microinfarcts (CMI), a widespread form of ischemic brain injury associated with advanced small vessel disease (SVD). 7-10Given the brief time window (7-14 days 11 ) during which small incident infarcts remain detectable by DWI, the high frequency of ICH-associated lesions suggests that small DWI lesions may occur frequently in patients with SVD. Most reports have focused on the early post-ICH period, however, raising the question of whether these DWI lesions represent an ongoing process occurring throughout the course of SVD rather than a byproduct of the acute ICH. Specific ties between the From the J. Philip

Ischemic brain injury in cerebral amyloid angiopathy

“…Focal DWI lesions have shown to be more common in patients with CAA-related ICH (15% to 23%) than in patients with Alzheimer's disease and controls 59,60 and continue to occur in high frequency beyond the post-ICH period. 61 Importantly, DWI lesions have been found to be associated with other imaging markers of CAA (i.e., WMH volume and lobar microbleeds), but not with traditional vascular risk factors such as hypertension. 59,60 Furthermore, DWI lesions in the white matter have found to cause chronic local microstructural injury.…”

“…59,60 Furthermore, DWI lesions in the white matter have found to cause chronic local microstructural injury. 62 The fact that these DWI lesions are a frequent finding in CAA despite the short time window in which they remain visible has led to the belief that they are the most prevalent of all infarct types 10,61,63 and therefore may have a substantial impact on cognitive functioning. 12,[64][65][66] The hypothesis that microinfarcts occur in large numbers in patients with CAA is supported by a recently developed mathematical model used to estimate the total microinfarct burden based on the number of microinfarcts found on routine postmortem examination.…”

“…149 A similar two-way interaction is suggested for hemorrhagic and ischemic lesions. 150,151 Studies have found that the incidence of ischemic infarcts is relatively high in the period immediately after an ICH [59][60][61]96 and associated with worse clinical outcome. 152 Alterations in local hemodynamics, bloodbrain barrier permeability, and release of inflammatory cytokines after an ICH might contribute to the pathogenesis of ischemic insults.…”

Microinfarct disruption of white matter structure

“…The study also benefited from the temporal information provided by DWI, allowing us to identify the timing of incident lesions. The main limitation was our small sample size noted above, a function of the relatively low frequency (approximately 10%-15%) [11][12][13] of DWI lesions even among subjects with advanced CAA. Interpretation of our data is also limited by the absence of neuropathologic correlation for the asymptomatic DWI lesions, another important goal for future studies.…”

“…To do so, we took advantage of the unique opportunity provided by our ongoing serial high-resolution MRI study of patients with cerebral amyloid angiopathy (CAA), a small-vessel disease associated with relatively frequent DWI lesions. [11][12][13] Postlesional changes were assessed by measuring alterations in magnitude and directionality of water diffusion with diffusion tensor imaging (DTI) 14,15 as well as by high-resolution T1-and T2-weighted MRI. To determine the extent of the lesions' structural impact, we analyzed both the lesions themselves and their surrounding fiber tracts.…”