Brain Autopsy Research Articles

Classification of Microglial Morphological Phenotypes Using Machine Learning.

Microglia are the brain’s immunocompetent macrophages with a unique feature that allows surveillance of the surrounding microenvironment and subsequent reactions to tissue damage, infection, or homeostatic perturbations. Thereby, microglia’s striking morphological plasticity is one of their prominent characteristics and the categorization of microglial cell function based on morphology is well established. Frequently, automated classification of microglial morphological phenotypes is performed by using quantitative parameters. As this process is typically limited to a few and especially manually chosen criteria, a relevant selection bias may compromise the resulting classifications. In our study, we describe a novel microglial classification method by morphological evaluation using a convolutional neuronal network on the basis of manually selected cells in addition to classical morphological parameters. We focused on four microglial morphologies, ramified, rod-like, activated and amoeboid microglia within the murine hippocampus and cortex. The developed method for the classification was confirmed in a mouse model of ischemic stroke which is already known to result in microglial activation within affected brain regions. In conclusion, our classification of microglial morphological phenotypes using machine learning can serve as a time-saving and objective method for post-mortem characterization of microglial changes in healthy and disease mouse models, and might also represent a useful tool for human brain autopsy samples.

Polygenic Risk Score for Alzheimer's Disease in Caribbean Hispanics.

Polygenic risk scores (PRSs) assess the individual genetic propensity to a condition by combining sparse information scattered across genetic loci, often displaying small effect sizes. Most PRSs are constructed in European-ancestry populations, limiting their use in other ethnicities. Here we constructed and validated a PRS for late-onset Alzheimer's Disease (LOAD) in Caribbean Hispanics (CH). We used a CH discovery (n=4,312) and independent validation sample (n=1,850) to construct an ancestry-specific PRS ("CH-PRS") and evaluated its performance alone and with other predictors using the area under curve (AUC) and logistic regression (strength of association with LOAD and statistical significance). We tested if CH-PRS predicted conversion to LOAD in a subsample with longitudinal data (n=1,239). We also tested the CH-PRS in an independent replication CH cohort (n=200) and brain autopsy cohort (n=33). Finally, we tested the effect of ancestry on PRS by using European and African American discovery cohorts to construct alternative PRSs ("EUR-PRS", "AA-PRS"). The full model (LOAD ~ CH-PRS + sex + age +APOE-ɛ4), achieved an AUC=74% (ORCH-PRS = 1.51 95%CI=1.36-1.68), raising to >75% in APOE-ɛ4 non-carriers. CH-PRS alone achieved an AUC=72% in the autopsy cohort, raising to AUC=83% in full model. Higher CH-PRS was significantly associated with clinical LOAD in the replication CH cohort (OR=1.61, 95%CI=1.19-2.17) and significantly predicted conversion to LOAD (HR=1.93, CI=1.70-2.20) in the longitudinal subsample. EUR-PRS and AA-PRS reached lower prediction accuracy (AUC=58% and 53%, respectively). Enriching diversity in genetic studies is critical to provide an effective PRS in profiling LOAD risk across populations. ANN NEUROL 2021;90:366-376.

Concurrent axon and myelin destruction differentiates X-linked adrenoleukodystrophy from multiple sclerosis.

Cerebral disease manifestation occurs in about two thirds of males with X-linked adrenoleukodystrophy (CALD) and is fatally progressive if left untreated. Early histopathologic studies categorized CALD as an inflammatory demyelinating disease, which led to repeated comparisons to multiple sclerosis (MS). The aim of this study was to revisit the relationship between axonal damage and myelin loss in CALD. We applied novel immunohistochemical tools to investigate axonal damage, myelin loss and myelin repair in autopsy brain tissue of eight CALD and 25 MS patients. We found extensive and severe acute axonal damage in CALD already in prelesional areas defined by microglia loss and relative myelin preservation. In contrast to MS, we did not observe selective phagocytosis of myelin, but a concomitant decay of the entire axon-myelin unit in all CALD lesion stages. Using a novel marker protein for actively remyelinating oligodendrocytes, breast carcinoma-amplified sequence (BCAS) 1, we show that repair pathways are activated in oligodendrocytes in CALD. Regenerating cells, however, were affected by the ongoing disease process. We provide evidence that-in contrast to MS-selective myelin phagocytosis is not characteristic of CALD. On the contrary, our data indicate that acute axonal injury and permanent axonal loss are thus far underestimated features of the disease that must come into focus in our search for biomarkers and novel therapeutic approaches.

Brain Morphological Changes in COVID-19

The aim of the study was to identify the pathomorphology of brain damage in patients who died of COVID-19.Material and methods. Autopsy reports and autopsy brain material of 17 deceased patients with pre-mortem confirmed COVID-19 infection were analyzed. Fatal cases in which COVID19 was the major cause of death were included in the study. Five people were diagnosed with cerebral infarction. Organ samples were taken for histological examination during autopsy. Sections were stained with hematoxylin and eosin and by Nissl to assess brain histopathology. To study the vascular basal membranes the PAS reaction was used, to detect fibrin in vessels phosphotungstic acid-hematoxylin (PTAH) staining was used, to determine DNA in nuclei sections were stained according to Feulgen, to detect RNA in neuronal nuclei and cytoplasm sections were stained with methyl green-pyronin. Immunohistochemical study of a neuronal marker, nuclear protein NeuN, was performed to assess neuronal damage.Results. The signs of neuronal damage found in patients who died of COVID-19 included nonspecific changes of nerve cells (acute swelling, retrograde degeneration, karyolysis and cytolysis, ‘ghost' cells, neuronophagia and satellitosis) and signs of circulatory disorders (perivascular and pericellular edema, diapedesis, congested and engorged microvasculature).Conclusion. Brain histopathological data indicate damage to the central nervous system in COVID-19 patients. Ischemic stroke in patients with COVID-19 is mostly caused by a combination of hypoxia resulting from respiratory failure and individual risk factors, including cerebrovascular atherosclerosis and hypertension.

Abnormal brain cholesterol homeostasis in Alzheimer\u2019s disease\u2014a targeted metabolomic and transcriptomic study

The role of brain cholesterol metabolism in Alzheimer’s disease (AD) remains unclear. Peripheral and brain cholesterol levels are largely independent due to the impermeability of the blood brain barrier (BBB), highlighting the importance of studying the role of brain cholesterol homeostasis in AD. We first tested whether metabolite markers of brain cholesterol biosynthesis and catabolism were altered in AD and associated with AD pathology using linear mixed-effects models in two brain autopsy samples from the Baltimore Longitudinal Study of Aging (BLSA) and the Religious Orders Study (ROS). We next tested whether genetic regulators of brain cholesterol biosynthesis and catabolism were altered in AD using the ANOVA test in publicly available brain tissue transcriptomic datasets. Finally, using regional brain transcriptomic data, we performed genome-scale metabolic network modeling to assess alterations in cholesterol biosynthesis and catabolism reactions in AD. We show that AD is associated with pervasive abnormalities in cholesterol biosynthesis and catabolism. Using transcriptomic data from Parkinson’s disease (PD) brain tissue samples, we found that gene expression alterations identified in AD were not observed in PD, suggesting that these changes may be specific to AD. Our results suggest that reduced de novo cholesterol biosynthesis may occur in response to impaired enzymatic cholesterol catabolism and efflux to maintain brain cholesterol levels in AD. This is accompanied by the accumulation of nonenzymatically generated cytotoxic oxysterols. Our results set the stage for experimental studies to address whether abnormalities in cholesterol metabolism are plausible therapeutic targets in AD.

Autoimmune Global Amnesia as Manifestation of AMPAR Encephalitis and Neuropathologic Findings.

ObjectiveTo report an unusual clinical phenotype of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis and describe associated neuropathologic findings.MethodsWe retrospectively investigated 3 AMPAR encephalitis patients with autoimmune global hippocampal amnesia using comprehensive cognitive and neuropsychologic assessment, antibody testing by in-house tissue-based and cell-based assays, and neuropathologic analysis of brain autopsy tissue including histology and immunohistochemistry.ResultsThree patients presented with acute-to-subacute global amnesia without affection of cognitive performance, attention, concentration, or verbal function. None of the patients had epileptic seizures, change of behavior, personality changes, or psychiatric symptoms. The MRI was normal in 1 patient and showed increased fluid-attenuated inversion recovery/T2 signal in the hippocampus in the other 2 patients. Two patients showed complete remission after immunotherapy. The one patient who did not improve had an underlying adenocarcinoma of the lung and died 3.5 months after disease onset because of tumor progression. Neuropathologic analysis of the brain autopsy revealed unilateral hippocampal sclerosis accompanied by mild inflammatory infiltrates, predominantly composed of T lymphocytes, and decrease of AMPAR immunoreactivity.ConclusionAMPAR antibodies usually associate with limbic encephalitis but may also present with immune responsive, acute-to-subacute, isolated hippocampal dysfunction without overt inflammatory CSF or MRI changes.

Further Delineation of the Clinical and Pathologic Features of HIKESHI-Related Hypomyelinating Leukodystrophy

BackgroundA recurrent homozygous missense variant, c.160G>C;p.(Val54Leu) in HIKESHI, was found to cause a hypomyelinating leukodystrophy with high frequency in the Ashkenazi Jewish population. We provide extended phenotypic classification of this disorder based on clinical history of a further seven affected individuals, assess carrier frequency in the Ashkenazi Jewish population, and provide a neuropathological study. MethodsClinical information, neuroimaging, and biosamples were collected. Brain autopsy was performed for one case. ResultsIndividuals with HIKESHI-related disease share common clinical features: early axial hypotonia evolving to dystonia or with progressive spasticity, hyperreflexia and clonus, feeding difficulties with poor growth, and nystagmus. Severe morbidity or death during febrile illness occurred in five of the nine affected individuals. Magnetic resonance images of seven patients were analyzed and demonstrated diffuse hypomyelination and thin corpus callosum. Genotyping data of more than 125,000 Ashkenazi Jewish individuals revealed a carrier frequency of 1 in 216. Gross pathology examination in one case revealed abnormal white matter. Microscopically, there was a near-total absence of myelin with a relative preservation of axons. The cerebral white matter showed several reactive astrocytes and microglia. ConclusionsWe provide pathologic evidence for a primary disorder of the myelin in HIKESHI-related leukodystrophy. These findings are consistent with the hypomyelination seen in brain magnetic resonance imaging and with the clinical features of early-onset spastic/dystonic quadriplegia and nystagmus. The high carrier rate of the recurrent variant seen in the Ashkenazi Jewish population requires increased attention to screening and diagnosis of this condition, particularly in this population.

Two cases of non-fluent variant primary progressive aphasia with different pathological diagnoses

Non-fluent variant primary progressive aphasia (nfvPPA), a subtype of frontotemporal lobar dementia syndrome, has been proven to have various pathological diagnoses. A 63-year-old woman and 71-year-old man separately visited our clinic for language dysfunction. Both patients showed non-fluent speech. The female patient showed personality change accompanied by language dysfunction, while the male patient had parkinsonian symptoms such as bradykinesia and cogwheel rigidity. Both patients were clinically diagnosed with nfvPPA. Several years after the first visit, the patients died, and a brain autopsy was performed. On postmortem examination, the female patient was pathologically diagnosed with Pick’s disease, while the male patient was diagnosed with progressive supranuclear palsy. Our report suggests that nfvPPA patients might show distinct clinical features depending on underlying pathologies.

Neurologic Manifestations of COVID-19 in Children: Emerging Pathophysiologic Insights.

The COVID-19 pandemic has affected mortality and morbidity across all ages, including children. Neurologic manifestations of coronavirus disease 2019, ranging from headaches to cerebrovascular stroke, may involve the CNS or peripheral nervous system. Neurologic involvement is also noted in the multisystem inflammatory syndrome in children, a pediatric condition that occurs weeks after infection with severe acute respiratory syndrome coronavirus 2, the virus that causes COVID-19. Knowledge about mechanisms of neurologic disease and immunologic response to severe acute respiratory syndrome coronavirus 2 is scarce but rapidly growing. Here, we concisely review experimental and clinical data relevant to pathophysiologic hypotheses regarding neurologic manifestations of coronavirus disease 2019. We highlight important knowledge gaps in differences between adults and children in their response to coronavirus disease 2019.

246 Maintenance of Circadian/Daily Activity Patterns and Cognitive Resilience to Alzheimer’s Pathology in Late Life

Abstract Introduction Many individuals remain free from dementia despite substantial plaque and tangle deposits, the hallmarks of Alzheimer’s disease (AD). Understanding of this cognitive resilience is poor. Evidence suggests that circadian disturbances predict increased risk of incident AD, and that circadian regulation deteriorates as clinical AD progresses. We hypothesize that circadian robustness protects against dementia, and the effect is stronger in individuals with AD pathology than those without. Methods We studied 575 deceased participants (age at death: 91.1□6.2; female: 414) in the Rush Memory and Aging Project who underwent brain autopsy at death, had clinical diagnostic opinion of dementia and motor activity assessments with actigraphy of ~10 days before death. Using actigraphy proximate to death, we calculated four circadian metrics: amplitude, acrophase, interdaily stability, and intradaily variability. Logistic regressions, stratified by postmortem pathologic AD diagnosis, were used to examine associations of circadian metrics with odds of dementia, and separately cognitive impairment (CI, including both dementia and mild cognitive impairment [MCI]), adjusting for age at death, sex, education, and time-lag between actigraphy and death. Results Based on postmortem assessment, 378 participants met the NIA-Reagan criteria for high/intermediate likelihood AD (AD group), including 197 clinically diagnosed with dementia, 86 MCI, and 85 cognitively intact. Non-AD group consisted of the remaining 197 participants, including 36 with clinical dementia, 47 MCI, and 114 cognitively intact. In the AD group, greater amplitude, greater interdaily stability, and lower intradaily variability were associated with lower odds of CI and dementia, i.e., odds ratios [OR] for CI corresponding to 1-SD changes were 0.54 (95% CI: 0.40-0.71), 0.70 (0.54-0.91), and 0.63 (0.47-0.84), and were 0.46 (0.35-0.60), 0.55 (0.43-0.70), and 0.61 (0.48-0.78) for dementia. In the non-AD group, only amplitude was associated with the odds of CI or dementia, i.e., the ORs corresponding to 1-SD increase was 0.61 (0.42-0.88) and 0.50 (0.31-0.82), respectively. Conclusion Better preserved circadian function, as characterized by more pronounced, more stable and less fragmented rest-activity rhythms, links to lower risk of CI or dementia in older people, especially those with pathological AD. Support (if any) NIH RF1AG064312, RF1AG059867, R01AG017917, R01AG56352; and the BrightFocus Foundation A2020886S.

Pathomorphological Changes in the Brain in Dynamics of Long-Term Dust Exposure.

Histological and morphometric studies of brain autopsy material showed that the development of hypoxic changes in miners starts at the early stages of working in the dusty atmosphere. Edema of the pericellular and perivascular zones and the pia mater, degenerative changes in some nerve cells and even their loss and formation of gliosis foci were identified. The revealed changes in neurons progressed with increasing the duration of working under hazardous conditions.

3D Analysis of the Synaptic Organization in the Entorhinal Cortex in Alzheimer's Disease.

The entorhinal cortex (EC) is especially vulnerable in the early stages of Alzheimer’s disease (AD). In particular, cognitive deficits have been linked to alterations in the upper layers of EC. In the present report, we examined Layers II and III from eight human brain autopsies (four subjects with no recorded neurologic alterations and four AD cases). We used stereological methods to assess cortical atrophy of the EC and possible changes in the volume occupied by different cortical elements (neuronal and glial cell bodies; blood vessels; and neuropil). We performed 3D ultrastructural analyses of synapses using focused ion beam/scanning electron microscopy (FIB/SEM) to examine possible alterations related to AD. At the light microscope level, we found a significantly lower volume fraction occupied by neuronal bodies in Layer III and a higher volume fraction occupied by glial cell bodies in Layer II in AD cases. At the ultrastructural level, we observed that (1) there was a significantly lower synaptic density in both layers in AD cases; (2) synapses were larger and more complex in Layer II in AD cases; and (3) there was a greater proportion of small and simple synapses in Layer III in AD cases than in control individuals. These structural differences may play a role in the anatomic basis for the impairment of cognitive functions in AD.

HIV-1 gp120-Induced Endolysosome de-Acidification Leads to Efflux of Endolysosome Iron, and Increases in Mitochondrial Iron and Reactive Oxygen Species.

The HIV-1 coat protein gp120 continues to be implicated in the pathogenesis of HIV-1 associated neurocognitive disorder (HAND); a condition known to affect ~50% of people living with HIV-1 (PLWH). Autopsy brain tissues of HAND individuals display morphological changes to mitochondria and endolysosomes, and HIV-1 gp120 causes mitochondrial dysfunction including increased levels of reactive oxygen species (ROS) and de-acidification of endolysosomes. Ferrous iron is linked directly to ROS production, ferrous iron is contained in and released from endolysosomes, and PLWH have elevated iron and ROS levels. Based on those findings, we tested the hypothesis that HIV-1 gp120-induced endolysosome de-acidification and subsequent iron efflux from endolysosomes is responsible for increased levels of ROS. In U87MG glioblastoma cells, HIV-1 gp120 de-acidified endolysosomes, reduced endolysosome iron levels, increased levels of cytosolic and mitochondrial iron, and increased levels of cytosolic and mitochondrial ROS. These effects were all attenuated significantly by the endolysosome-specific iron chelator deferoxamine, by inhibitors of endolysosome-resident two-pore channels and divalent metal transporter-1 (DMT-1), and by inhibitors of mitochondria-resident DMT-1 and mitochondrial permeability transition pores. These results suggest that oxidative stress commonly observed with HIV-1 gp120 is downstream of its ability to de-acidify endolysosomes, to increase the release of iron from endolysosomes, and to increase the uptake of iron into mitochondria. Thus, endolysosomes might represent early and upstream targets for therapeutic strategies against HAND.

HIV disease duration, but not active brain infection, predicts cortical amyloid beta deposition.

Abnormal deposition of the antimicrobial peptide amyloid beta (Aβ) is a characteristic of Alzheimer's disease. The objective of this study was to elucidate risk factors for brain Aβ in a cohort enriched for HIV and other neurotropic pathogens. Cross-sectional cohort study. We examined autopsy brains of 257 donors with a mean age of 52.8 years; 62% were men; and 194 were HIV+ and 63 HIV-. Hyperphosphorylated tau (p-tau) and Aβ were identified in frontal and temporal regions by immunohistochemistry. APOE genotyping was performed. Clinical and neuropathological predictors for Aβ were identified in univariate analyses, and then tested in multivariate regressions. Cortical Aβ was identified in 32% of the sample, and active brain infection in 27%. Increased odds of Aβ were seen with increasing age and having an APOE ε4 allele; for the overall sample, HIV+ status was protective and brain infection was not a predictor. Within the HIV+ population, predictors for Aβ were duration of HIV disease and APOE alleles, but not age. When HIV disease duration and other HIV parameters were introduced into models for the entire sample, HIV disease duration was equivalent to age as a predictor of Aβ. We hypothesize that dual aspects of immune suppression and stimulation in HIV, and beneficial survivor effects in older HIV+ individuals, account for HIV+ status decreasing, and HIV duration increasing, odds of Aβ. Importantly, with HIV, disease duration replaces age as an independent risk for Aβ, suggesting HIV-associated accelerated brain senescence.

Does Virtual Brain Autopsy Could be Used as a Clue for Detection of Personal Identity?

Background: virtual autopsy nowdays show great success in human identification. Nowdays singleComputerized tomography of the brain could help answering many questions regarding the identity ofhumans, it could lead us to the gender ,weight and height roughly of the person in question.Patients and Methods: cross- sectional study during the period April 2019 till Mars2020 , One hundredand fifty participant aged between 15 and 29 years old were envolved in the current study after taking theirwritten and verbal consent or their caregiver and doing C T Brain for every one of the studied participant.Results: brain volume is statistically significant with weight , height, gender of the studied participant hencewe could use CT Brain to know the brain volume and then we could suspect weight , height and even genderso we can reach to the identity of the individual.Conclusion: We me be no longer in need of doing autopsy where virtual autopsy could find the answer tomany questions in research, where a correlation was found between brain volume ,gender, weight and height.

Juxtacortical susceptibility changes in progressive multifocal leukoencephalopathy at the gray–white matter junction correlates with iron-enriched macrophages

Objective: Describe magnetic resonance imaging (MRI) susceptibility changes in progressive multifocal leukoencephalopathy (PML) and identify neuropathological correlates. Methods: PML cases and matched controls with primary central nervous system lymphoma (PCNSL) were retrospectively identified. MRI brain at 3 T and 7 T were reviewed. MRI-pathology correlations in fixed brain autopsy tissue were conducted in three subjects with confirmed PML. Results: With PML (n = 26 total, n = 5 multiple sclerosis natalizumab-associated), juxtacortical changes on susceptibility-weighted imaging (SWI) or gradient echo (GRE) sequences were noted in 3/3 cases on 7 T MRI and 14/22 cases (63.6%) on 1.5 T or 8/22 (36.4%) 3 T MRI. Similar findings were only noted in 3/25 (12.0%) of PCNSL patients (odds ratio (OR) 12.83, 95% confidence interval (CI), 2.9–56.7, p < 0.001) on 1.5 or 3 T MRI. On susceptibility sequences available prior to diagnosis of PML, 7 (87.5%) had changes present on average 2.7 ± 1.8 months (mean ± SD) prior to diagnosis. Postmortem 7 T MRI showed SWI changes corresponded to areas of increased iron density along the gray–white matter (GM-WM) junction predominantly in macrophages. Conclusion: Susceptibility changes in PML along the GM-WM junction can precede noticeable fluid-attenuated inversion recovery (FLAIR) changes and correlates with iron accumulation in macrophages.

To what degree is late life cognitive decline driven by age-related neuropathologies?

The ageing brain is vulnerable to a wide array of neuropathologies. Prior work estimated that the three most studied of these, Alzheimer's disease, infarcts, and Lewy bodies, account for ∼40% of the variation in late life cognitive decline. However, that estimate did not incorporate many other diseases that are now recognized as potent drivers of cognitive decline [e.g. limbic predominant age-related TDP-43 encephalopathy (LATE-NC), hippocampal sclerosis, other cerebrovascular conditions]. We examined the degree to which person-specific cognitive decline in old age is driven by a wide array of neuropathologies. Deceased participants (n = 1164) from two longitudinal clinical-pathological studies, the Rush Memory and Aging Project and Religious Orders Study, completed up to 24 annual evaluations including 17 cognitive performance tests and underwent brain autopsy. Neuropathological examinations provided 11 pathological indices, including markers of Alzheimer's disease, non- Alzheimer's disease neurodegenerative diseases (i.e. LATE-NC, hippocampal sclerosis, Lewy bodies), and cerebrovascular conditions (i.e. macroscopic infarcts, microinfarcts, cerebral amyloid angiopathy, atherosclerosis, and arteriolosclerosis). Mixed effects models examined the linear relation of pathological indices with global cognitive decline, and random change point models examined the relation of the pathological indices with the onset of terminal decline and rates of preterminal and terminal decline. Cognition declined an average of about 0.10 unit per year (estimate = -0.101, SE = 0.003, P < 0.001) with considerable heterogeneity in rates of decline (variance estimate for the person-specific slope of decline was 0.0094, P < 0.001). When considered separately, 10 of 11 pathological indices were associated with faster decline and accounted for between 2% and 34% of the variation in decline, respectively. When considered simultaneously, the 11 pathological indices together accounted for 43% of the variation in decline; Alzheimer's disease-related indices accounted for 30-36% of the variation, non-Alzheimer's disease neurodegenerative indices 4-10%, and cerebrovascular indices 3-8%. Finally, the 11 pathological indices combined accounted for less than a third of the variation in the onset of terminal decline (28%) and rates of preterminal (32%) and terminal decline (19%). Although age-related neuropathologies account for a large proportion of the variation in late life cognitive decline, considerable variation remains unexplained even after considering a wide array of neuropathologies. These findings highlight the complexity of cognitive ageing and have important implications for the ongoing effort to develop effective therapeutics and identify novel treatment targets.

Relevance of data homogeneity and fetal post-mortem MRI in congenital brain malformations.

MR imaging is of ever-growing interest in the obstetric community and post-mortem confirmation is crucial in the improvement of this technique. Griffiths et al. assessed the concordance between fetal MRI and brain autopsy in fetuses of the MERIDIAN cohort that ended in termination of pregnancy (BJOG 2020 xxxx).

The Delayed Neuropathological Consequences of Traumatic Brain Injury in a Community-Based Sample.

The late neuropathological effects of traumatic brain injury have yet to be fully elucidated, particularly with respect to community-based cohorts. To contribute to this critical gap in knowledge, we designed a multimodal neuropathological study, integrating traditional and quantitative approaches to detect pathologic changes in 532 consecutive brain autopsies from participants in the Adult Changes in Thought (ACT) study. Diagnostic evaluation including assessment for chronic traumatic encephalopathy (CTE) and quantitative immunoassay-based methods were deployed to examine levels of pathological (hyperphosphorylated) tau (pTau) and amyloid (A) β in brains from ACT participants with (n = 107) and without (n = 425) history of remote TBI with loss of consciousness (w/LOC). Further neuropathological assessments included immunohistochemistry for α-synuclein and phospho-TDP-43 pathology and astro- (GFAP) and micro- (Iba1) gliosis, mass spectrometry analysis of free radical injury, and gene expression evaluation (RNA sequencing) in a smaller sub-cohort of matched samples (49 cases with TBI and 49 non-exposed matched controls). Out of 532 cases, only 3 (0.6%–none with TBI w/LOC history) showed evidence of the neuropathologic signature of chronic traumatic encephalopathy (CTE). Across the entire cohort, the levels of pTau and Aβ showed expected differences for brain region (higher levels in temporal cortex), neuropathological diagnosis (higher in participants with Alzheimer's disease), and APOE genotype (higher in participants with one or more APOE ε4 allele). However, no differences in PHF-tau or Aβ1−42 were identified by Histelide with respect to the history of TBI w/LOC. In a subset of TBI cases with more carefully matched control samples and more extensive analysis, those with TBI w/LOC history had higher levels of hippocampal pTau but no significant differences in Aβ, α-synuclein, pTDP-43, GFAP, Iba1, or free radical injury. RNA-sequencing also did not reveal significant gene expression associated with any measure of TBI exposure. Combined, these findings suggest long term neuropathological changes associated with TBI w/LOC may be subtle, involve non-traditional pathways of neurotoxicity and neurodegeneration, and/or differ from those in autopsy cohorts specifically selected for neurotrauma exposure.

Associations of Alzheimer's Disease Neuropathologic Changes with Clinical Presentations of Parkinson's Disease.

Parkinson's disease (PD) and Alzheimer's disease (AD) are the two most prevalent neurodegenerative diseases associated with age. Pathological studies have shown that these two diseases share a certain degree of neuropathological overlap. AD neuropathologic change contributes to cognitive impairment in PD. However, the impact of AD pathology on other clinical phenotypes in PD remains largely unknown. Herein we aimed to assess the impact of co-occurring AD neuropathologic change on the clinical phenotypes of PD. We examined 46 autopsy brains of PD patients and available clinical information to retrospectively assess the effects of comorbid AD pathology on dementia, hallucinations, and dyskinesia commonly seen in advanced PD. AD neuropathology significantly increased the risk of hallucinations and dementia, but not dyskinesia in PD patients. Surprisingly, diffuse Lewy body pathology, but not AD pathology, was associated with the occurrence of dementia and hallucinations. Most importantly, we reported that the severity of neuronal loss in the locus coeruleus (LC), but not the severity of neuronal loss in the substantia nigra (SN), was associated with the occurrence of dyskinesia in advanced PD patients, while neither Lewy body scores in SN nor LC had significant effects. We show for the first time that neuronal loss in LC contributes to dyskinesia. Understanding the relationships between the two distinct pathologies and their relevant clinical phenotypes will be crucial in the development of effective disease-modifying therapies for PD.