Regional Overlap of Pathologies in Lewy Body Disorders

Lewy body disorders (LBD) are common neurodegenerative diseases characterized by the presence of aggregated α-synuclein in Lewy bodies and Lewy neurites in the central and peripheral nervous systems. The brains of patients with LBD often display other comorbid pathologies, i.e. insoluble tau, β-amyloid aggregates, TAR DNA-binding protein 43 (TDP-43) deposits, and argyrophilic grain disease (AGD). The incidence and physiological relevance of these concurrent pathological findings remain controversial. We performed a semiquantitative detailed mapping of α-synuclein, tau, β-amyloid (Aβ), TDP-43, and AGD pathologies in 17 areas in 63 LBD cases (44 with Parkinson disease [PD], 28 with dementia, and 19 with dementia with Lewy bodies). APOE and MAPT genetic variants were also investigated. A majority of LBD cases had 2 or 3 concomitant findings, particularly Alzheimer disease-related pathology. Pathological stages of tau, β-amyloid and α-synuclein pathologies were increased in cases with dementia. Aβ score was the best correlate of the time to dementia in PD. In addition, β-amyloid deposition correlated with α-synuclein load in all groups. MAPT H1 haplotype did not influence any assessed pathology in PD. These results highlight the common concurrence of pathologies in patients with LBD that may have an impact on the clinical expression of the diseases.

Cerebrospinal fluid β-amyloid and phospho-tau biomarker interactions affecting brain structure in preclinical Alzheimer disease

OBJECTIVE

To assess the relationships between core cerebrospinal fluid (CSF) biomarkers and cortical thickness (CTh) in preclinical Alzheimer disease (AD).

METHODS

In this cross-sectional study, normal controls (n = 145) from the Alzheimer's Disease Neuroimaging Initiative underwent structural 3T magnetic resonance imaging (MRI) and lumbar puncture. CSF β-amyloid1-42 (Aβ) and phospho-tau₁₈₁p (p-tau) levels were measured by Luminex assays. Samples were dichotomized using published cutoffs (Aβ(+) /Aβ(-) and p-tau(+) /ptau(-)). CTh was measured by Freesurfer. CTh difference maps were derived from interaction and correlation analyses. Clusters from the interaction analysis were isolated to analyze the directionality of the interaction by analysis of covariance.

RESULTS

We found a significant biomarker interaction between CSF Aβ and CSF p-tau levels affecting brain structure. Cortical atrophy only occurs in subjects with both Aβ(+) and p-tau(+). The stratified correlation analyses showed that the relationship between p-tau and CTh is modified by Aβ status and the relationship between Aβ and CTh is modified by p-tau status. p-Tau-dependent thinning was found in different cortical regions in Aβ(+) subjects but not in Aβ(-) subjects. Cortical thickening was related to decreasing CSF Aβ values in the absence of abnormal p-tau, but no correlations were found in p-tau(+) subjects.

INTERPRETATION

Our data suggest that interactions between biomarkers in AD result in a 2-phase phenomenon of pathological cortical thickening associated with low CSF Aβ, followed by atrophy once CSF p-tau becomes abnormal. These interactions should be considered in clinical trials in preclinical AD, both when selecting patients and when using MRI as a surrogate marker of efficacy.

Abstract 2276: Microhemorrhage Burden Increases the Risk of Hematoma Growth in Patients with Intracerebral Hemorrhage

Introduction Microhemorrhages (MH) are lesions detected on radiological studies resulting from an underlying small-vessel angiopathy. We assesed the hypothesis that the presence of MH increases the risk of hematoma growth (HG) in patients with acute Intracerebral Hemorrhage (ICH).

Methods We evaluated a series of patients in a prospective and multicentre study. We included patients with a spontaneous supratentorial ICH within the first 6 hours after symptom onset, that also had a follow-up CT 24-72 hours later and a MRI performed after a variable time after ICH. HG was defined as an increase >33% in the volume of hematoma on the follow-up CT, in comparison with the admission CT. The volume was calculated using the formula AxBxC/2. On MR scans we assessed the presence, number and distribution of MH. After differential diagnosis with other radiological lesions, MH were evaluated on echo-gradient sequences and defined as hypointense rounded lesions with a diameter <10mm. Statistical analysis: Bivariate tests with the whole sample and with the subgroup of patients with less than 3 hours from symptom onset.

Results We studied 46 patients, whose mean age was 68.8±11.2 y and 68% were men. Mean baseline volume was 19.1±27.3 cc. We detected MH in 7/15 patients with HG and in 18/31 patients without HG (46.7% vs 58.1%, p=0.53). In the subgroup of patients with 10 MH, the risk of HG was higher than in patients with 0-10 MH (75% vs 28.6%, p=0.067), and this difference was significant when considering only patients with a <3 hours evolution (100% vs 31%, p=0.044). We did not observe any association between risk of HG and distribution of MH. Age and time to CT were equivalent in the two groups (with and without HG), either in the <6 or <3 hours subgroups.

Conclusions In conclusion, in patients with hyperacute ICH, the presence of more than 10 MH increases the risk of HG. This is probably an indirect marker of a more severe underlying angiopathy.