Spatial relation between microbleeds and amyloid deposits in amyloid angiopathy.

Advanced cerebrovascular ß-amyloid deposition (cerebral amyloid angiopathy, CAA) is associated with cerebral microbleeds, but the precise relationship between CAA burden and microbleeds is undefined. We used T2*-weighted magnetic resonance imaging (MRI) and noninvasive amyloid imaging with Pittsburgh Compound B (PiB) to analyze the spatial relationship between CAA and microbleeds. On coregistered positron emission tomography (PET) and MRI images, PiB retention was increased at microbleed sites compared to simulated control lesions (p = 0.002) and declined with increasing distance from the microbleed (p < 0.0001). These findings indicate that microbleeds occur preferentially in local regions of concentrated amyloid and support therapeutic strategies aimed at reducing vascular amyloid deposition.

Microbleeds versus macrobleeds: evidence for distinct entities.

BACKGROUND AND PURPOSE: Small, asymptomatic microbleeds commonly accompany larger symptomatic macrobleeds. It is unclear whether microbleeds and macrobleeds represent arbitrary categories within a single continuum versus truly distinct events with separate pathophysiologies. METHODS: We performed 2 complementary retrospective analyses. In a radiographic analysis, we measured and plotted the volumes of all hemorrhagic lesions detected by gradient-echo MRI among 46 consecutive patients with symptomatic primary lobar intracerebral hemorrhage diagnosed as probable or possible cerebral amyloid angiopathy. In a second neuropathologic analysis, we performed blinded qualitative and quantitative examinations of amyloid-positive vessel segments in 6 autopsied subjects whose MRI scans demonstrated particularly high microbleed counts (>50 microbleeds on MRI, n=3) or low microbleed counts (<3 microbleeds, n=3). RESULTS: Plotted on a logarithmic scale, the volumes of 163 hemorrhagic lesions identified on scans from the 46 subjects fell in a distinctly bimodal distribution with mean volumes for the 2 modes of 0.009 cm(3) and 27.5 cm(3). The optimal cut point for separating the 2 peaks (determined by receiver operating characteristics) corresponded to a lesion diameter of 0.57 cm. On neuropathologic analysis, the high microbleed-count autopsied subjects showed significantly thicker amyloid-positive vessel walls than the low microbleed-count subjects (proportional wall thickness 0.53+/-0.01 versus 0.37+/-0.01; P<0.0001; n=333 vessel segments analyzed). CONCLUSIONS: These findings suggest that cerebral amyloid angiopathy-associated microbleeds and macrobleeds comprise distinct entities. Increased vessel wall thickness may predispose to formation of microbleeds relative to macrobleeds.

Association of subdural hematoma with increased mortality in lobar intracerebral hemorrhage.

OBJECTIVE: To determine the prevalence of subdural hematoma (SDH) in patients presenting with primary nontraumatic lobar intracerebral hemorrhage (ICH) and characteristics associated with the presence of SDH. DESIGN: Retrospective analysis of data collected in a prospective cohort study. SETTING: Hospital. PATIENTS: Consecutive sample of 200 patients with primary lobar ICH and 75 patients with deep hemispheric ICH. MAIN OUTCOME MEASURES: Presence of SDH and mortality. RESULTS: Subdural hematoma was present in 40 of 200 patients (20%) with primary lobar ICH. By contrast, SDH was not present in any of 75 consecutive patients with deep hemispheric ICH (P < .001 for comparison with lobar ICH). Intracerebral hemorrhage volume higher than 60 cm3 was the only independent predictor of SDH (odds ratio [OR], 2.69; 95% confidence interval [CI], 1.14-6.34; P = .02). Subdural hematoma thickness more than 5 mm was an independent predictor of increased 30-day mortality (OR, 7.60; 95% CI, 1.86-30.99; P = .005) after controlling for other factors including ICH volume. Further analysis showed that the effect of SDH on mortality depended on ICH volume, with larger odds for mortality in those with low ICH volume (OR, 12.85; 95% CI, 2.42-68.23; P = .003 for those with ICH volume <30 cm3). Cerebral amyloid angiopathy was present in 8 of 9 patients with pathological specimens. CONCLUSIONS: Nontraumatic SDH frequently accompanies primary lobar ICH and is associated with higher 30-day mortality, particularly when the ICH volume is relatively low. Rupture of an amyloid-laden leptomeningeal vessel, with extravasation into the brain parenchyma and subdural space, may be the pathogenic mechanism.

Detection of isolated cerebrovascular beta-amyloid with Pittsburgh compound B.

Imaging of cerebrovascular beta-amyloid (cerebral amyloid angiopathy) is complicated by the nearly universal overlap of this pathology with Alzheimer's pathology. We performed positron emission tomographic imaging with Pittsburgh Compound B on 42-year-old man with early manifestations of Iowa-type hereditary cerebral amyloid angiopathy, a form of the disorder with little or no plaque deposits of fibrillar beta-amyloid. The results demonstrated increased Pittsburgh Compound B retention selectively in occipital cortex, sparing regions typically labeled in Alzheimer's disease. These results offer compelling evidence that Pittsburgh Compound B positron emission tomography can noninvasively detect isolated cerebral amyloid angiopathy before overt signs of tissue damage such as hemorrhage or white matter lesions.

Tissue microstructural changes are independently associated with cognitive impairment in cerebral amyloid angiopathy.

BACKGROUND AND PURPOSE: Cerebral amyloid angiopathy (CAA) is a major cause of lobar intracerebral hemorrhage and cognitive impairment and is associated with white matter hyperintensities and cerebral microbleeds. MRI diffusion tensor imaging detects microstructural tissue damage in advanced CAA even in areas that appear normal on conventional MRI. We hypothesized that higher global mean apparent diffusion coefficient (mean ADC), reflecting a higher amount of chronic tissue disruption caused by CAA, would be independently associated with CAA-related cognitive impairment. METHODS: Preintracerebral hemorrhage cognitive impairment was systematically assessed using a standardized questionnaire (IQCODE) in 49 patients. Volume of white matter hyperintensities, number of microbleeds, and mean ADC were determined from MRIs obtained within 14.0+/-22.5 days of intracerebral hemorrhage cognitive impairment. White matter hyperintensities and mean ADC were measured in the hemisphere uninvolved by intracerebral hemorrhage to avoid confounding. RESULTS: Preintracerebral hemorrhage cognitive impairment was identified in 10 of 49 subjects. Mean ADC was the only variable associated with preintracerebral hemorrhage cognitive impairment and was elevated in those with preintracerebral hemorrhage cognitive impairment compared with those without (12.4x10(-4) versus 11.7x10(-4) mm(2)/s; P=0.03). Mean ADC positively correlated with age but not white matter hyperintensities or number of microbleeds. In logistic regression controlling for age and visible cerebral atrophy, mean ADC was independently associated with preintracerebral hemorrhage cognitive impairment (OR per 1x10(-4) mm(2)/s increase=2.45, 95% CI 1.11 to 5.40, P=0.04). CONCLUSIONS: Mean ADC is independently associated with preintracerebral hemorrhage cognitive impairment in CAA. The lack of correlation with other MRI markers of CAA suggests that mean ADC may be sensitive to distinct aspects of CAA pathology and its tissue consequences. These results suggest that global MRI diffusion changes are sensitive to clinically relevant microstructural alterations and may be useful markers of CAA-related tissue damage.

Validation of intracranial area as a surrogate measure of intracranial volume when using clinical MRI.

BACKGROUND AND PURPOSE: We sought to determine whether mid-sagittal intracranial area (ICA) is a valid surrogate of intracranial volume (ICV) when using retrospective data with relatively thick (6-7 mm) sagittal slices. METHODS: Data were retrospectively analyzed from 47 subjects who had two MRI scans taken at least nine months apart. Twenty-three subjects had manual segmentation of ICV on the T2-weighted sequence for comparison. RESULTS: Intraclass correlation coefficient (ICC) for intraobserver, interobserver, and intraobserver scan-rescan comparisons were 0.96, 0.97 and 0.95. Pearson correlation coefficients between ICV and ICA, averaging the cumulative 1, 2, 3, and 4 most midline slices, were 0.89, 0.94, 0.93, and 0.95. There was a significant marginal increase in explained variance of ICV by measuring two, rather than one, slices (P= 0.001). CONCLUSIONS: These data suggest that ICA, even measured without high-resolution imaging, is a reasonable substitute for ICV.