Alzheimer disease with amygdala Lewy bodies: a distinct form of alpha-synucleinopathy

Different Morphology of Neuritic Plaques in the Archicortex of Alzheimer's Disease with Comorbid Synucleinopathy: A Pilot Study

BACKGROUND

Bulbous neuritic changes in neuritic plaques have already been described, and their possible effect on the clinical course of the disease has been discussed.

OBJECTIVE

In our study, we focused on the location and density of these structures in patients with only Alzheimer's disease (AD) and patients with AD in comorbidity with synucleinopathies.

METHODS

Utilizing immunohistochemistry and confocal microscopy, we evaluated differences of neocortical and archicortical neuritic plaques and the frequency of bulbous changes in the archicortex of 14 subjects with Alzheimer's disease (AD), 10 subjects with the Lewy body variant of Alzheimer's disease (AD/DLB), and 4 subjects with Alzheimer's disease with amygdala Lewy bodies (AD/ALB). Also, the progression and density of neuritic changes over the time course of the disease were evaluated.

RESULTS

We found structural differences in bulbous dystrophic neurites more often in AD/DLB and AD/ALB than in pure AD cases. The bulbous neuritic changes were more prominent in the initial and progressive phases and were reduced in cases with a long clinical course.

CONCLUSION

Our results indicate that there is a prominent difference in the shape and composition of neocortical and archicortical neuritic plaques and, moreover, that bulbous neuritic changes can be observed at a higher rate in AD/DLB and AD/ALB subjects compared to pure AD subjects. This observation probably reflects that these subacute changes are more easily seen in the faster clinical course of AD patients with comorbidities.

Alzheimer's Disease Neuropathological Comorbidities are Common in the Younger-Old

BACKGROUND

Clinicopathological studies have demonstrated that Alzheimer's disease dementia (ADD) is often accompanied by clinically undetectable comorbid neurodegenerative and cerebrovascular disease that alter the rate of cognitive decline. Aside from causing increased variability in clinical response, it is possible that the major ADD comorbidities may not respond to ADD-specific molecular therapeutics.

OBJECTIVE

As most reports have focused on comorbidity in the oldest-old, its extent in younger age groups that are more likely to be involved in clinical trials is largely unknown; our objective is to provide this information.

METHODS

We conducted a survey of neuropathological comorbidities in sporadic ADD using data from the US National Alzheimer's Coordinating Center. Subject data was restricted to those with dementia and meeting National Institute on Aging-Alzheimer's Association intermediate or high AD Neuropathological Change levels, excluding those with known autosomal dominant AD-related mutations.

RESULTS

Highly prevalent ADD comorbidities are not restricted to the oldest-old but are common even in early-onset ADD. The percentage of cases with ADD as the sole major neuropathological diagnosis is highest in the under-60 group, where "pure" ADD cases are still in the minority at 44%. After this AD as a sole major pathology in ADD declines to roughly 20%in the 70s and beyond. Lewy body disease is the most common comorbidity at younger ages but actually is less common at later ages, while for most others, their prevalence increases with age.

CONCLUSION

Alzheimer's disease neuropathological comorbidities are highly prevalent even in the younger-old.

Cerebrovascular and Neurodegenerative Pathologies in Long-Term Stable Mild Cognitive Impairment

BACKGROUND

Mild cognitive impairment (MCI) is considered by some to be a prodromal phase of a progressive disease (i.e., neurodegeneration) resulting in dementia; however, a substantial portion of individuals (ranging from 5-30%) remain cognitively stable over the long term (sMCI). The etiology of sMCI is unclear but may be linked to cerebrovascular disease (CVD), as evidence from longitudinal studies suggest a significant proportion of individuals with vasculopathy remain stable over time.

OBJECTIVE

To quantify the presence of neurodegenerative and vascular pathologies in individuals with long-term (>5-year) sMCI, in a preliminary test of the hypothesis that CVD may be a contributor to non-degenerative cognitive impairment. We expect frequent vasculopathy at autopsy in sMCI relative to neurodegenerative disease, and relative to individuals who convert to dementia.

METHODS

In this retrospective study, using data from the National Alzheimer's Coordinating Center, individuals with sMCI (n = 28) were compared to those with MCI who declined over a 5 to 9-year period (dMCI; n = 139) on measures of neurodegenerative pathology (i.e., Aβ plaques, neurofibrillary tangles, TDP-43, and cerebral amyloid angiopathy) and CVD (infarcts, lacunes, microinfarcts, hemorrhages, and microbleeds).

RESULTS

Alzheimer's disease pathology (Aβ plaques, neurofibrillary tangles, and cerebral amyloid angiopathy) was significantly higher in the dMCI group than the sMCI group. Microinfarcts were the only vasculopathy associated with group membership; these were more frequent in sMCI.

CONCLUSION

The most frequent neuropathology in this sample of long-term sMCI was microinfarcts, tentatively suggesting that silent small vessel disease may characterize non-worsening cognitive impairment.

Mixed Brain Pathology Is the Most Common Cause of Cognitive Impairment in the Elderly

BACKGROUND

Systemic diseases, diabetes mellitus (DM), and cardiovascular disease (CaVD) have been suggested being risk factors for cognitive impairment (CI) and/or influence Alzheimer's disease neuropathologic change (ADNC).

OBJECTIVE

The purpose was to assess the type and the extent of neuropathological alterations in the brain and to assess whether brain pathology was associated with CaVD or DM related alterations in peripheral organs, i.e., vessels, heart, and kidney.

METHODS

119 subjects, 15% with DM and 24% with CI, age range 80 to 89 years, were chosen and neuropathological alterations were assessed applying immunohistochemistry.

RESULTS

Hyperphosphorylated τ (HPτ) was seen in 99%, amyloid-β (Aβ) in 71%, transactive DNA binding protein 43 (TDP43) in 62%, and α-synuclein (αS) in 21% of the subjects. Primary age related tauopathy was diagnosed in 29% (more common in females), limbic predominant age-related TDP encephalopathy in 4% (14% of subjects with CI), and dementia with Lewy bodies in 3% (14% of subjects with CI) of the subjects. High/intermediate level of ADNC was seen in 47% and the extent of HPτ increased with age. The extent of ADNC was not associated with the extent of pathology observed in peripheral organs, i.e., DM or CaVD. Contrary, brain alterations such as pTDP43 and cerebrovascular lesions (CeVL) were influenced by DM, and CeVL correlated significantly with the extent of vessel pathology.

CONCLUSION

In most (66%) subjects with CI, the cause of impairment was "mixed pathology", i.e., ADNC combined with TDP43, αS, or vascular brain lesions. Furthermore, our results suggest that systemic diseases, DM and CaVD, are risk factors for CI but not related to ADNC.

Pharmacological management of dementia with Lewy bodies with a focus on zonisamide for treating parkinsonism

INTRODUCTION

Dementia with Lewy bodies (DLB) has no approved symptomatic or disease-modifying treatments in the US and Europe, despite being the second most common cause of neurodegenerative dementia.

AREAS COVERED

Herein, the authors briefly review the DLB drug development pipeline, providing a summary of the current pharmacological intervention studies. They then focus on the anticonvulsant zonisamide, a benzisoxazole derivative with a sulfonamide group and look at its value for treating parkinsonism in DLB.

EXPERT OPINION

Several new compounds are being tested in DLB, the most innovative being those aimed at decreasing brain accumulation of α-synuclein. Unfortunately, new drug testing is challenging in terms of consistent diagnostic criteria and lack of reliable biomarkers. Few randomized controlled trials (RCTs) are well-designed, with enough power to detect significant drug effects. Levodopa monotherapy can treat the parkinsonism in DLB, but it can cause agitation or visual hallucination worsening. Two Phase II/III RCTs of DLB patients recently reported a statistically significant improvement in motor function in those receiving zonisamide as an adjunctive treatment to levodopa. New biomarker strategies and validated outcome measures for DLB or prodromal DLB may enhance clinical trial design for the development of specific disease-modifying treatments.

Von Economo Neurons in Behavioral Variant Frontotemporal Dementia with Underlying Alzheimer's Disease

The selective loss of von Economo neurons has been linked to the behavioral deficits in behavioral variant frontotemporal dementia (bvFTD) but whether these neurons are affected in bvFTD patients with underlying Alzheimer's disease (AD) has yet to be established. The present study assesses the von Economo neurons in pathological AD cases clinically diagnosed with either AD or bvFTD. Our results demonstrate no significant loss of von Economo neurons in all pathological AD cases, irrespective of clinical diagnosis or co-existing Lewy body pathology. These results suggest that the behavioral deficits in patients with clinical bvFTD and underlying pathological AD are not driven by the loss of von Economo neurons.

Defining and predicting transdiagnostic categories of neurodegenerative disease

The prevalence of concomitant proteinopathies and heterogeneous clinical symptoms in neurodegenerative diseases hinders the identification of individuals who might be candidates for a particular intervention. Here, by applying an unsupervised clustering algorithm to post-mortem histopathological data from 895 patients with degeneration in the central nervous system, we show that six non-overlapping disease clusters can simultaneously account for tau neurofibrillary tangles, α-synuclein inclusions, neuritic plaques, inclusions of the transcriptional repressor TDP-43, angiopathy, neuron loss and gliosis. We also show that membership to the six transdiagnostic disease clusters, which explains more variance in cognitive phenotypes than can be explained by individual diagnoses, can be accurately predicted from scores of the Mini-Mental Status Exam, protein levels in cerebrospinal fluid, and genotype at the APOE and MAPT loci, via cross-validated multiple logistic regression. This combination of unsupervised and supervised data-driven tools provides a framework that could be used to identify latent disease subtypes in other areas of medicine.

The Neuropathological Diagnosis of Alzheimer's Disease-The Challenges of Pathological Mimics and Concomitant Pathology

The definitive diagnosis of Alzheimer's disease (AD) rests with post-mortem neuropathology despite the advent of more sensitive scanning and the search for reliable biomarkers. Even though the classic neuropathological features of AD have been known for many years, it was only relatively recently that more sensitive immunohistochemistry for amyloid beta (Aβ) and hyperphosphorylated tau (HP-tau) replaced silver-staining techniques. However, immunohistochemistry against these and other proteins has not only allowed a more scientific evaluation of the pathology of AD but also revealed some mimics of HP-tau pathological patterns of AD, including age-related changes, argyrophilic grain disease and chronic traumatic encephalopathy. It also highlighted a number of cases of AD with significant additional pathology including Lewy bodies, phosphorylated TDP-43 (p-TDP-43) positive neuronal cytoplasmic inclusions and vascular pathology. This concomitant pathology can cause a number of challenges including the evaluation of the significance of each pathological entity in the make-up of the clinical symptoms, and the threshold of each individual pathology to cause dementia. It also raises the possibility of underlying common aetiologies. Furthermore, the concomitant pathologies could provide explanations as to the relative failure of clinical trials of anti-Aβ therapy in AD patients.

Testing Amyloid Cross-Toxicity in the Vertebrate Brain

While amyloid proteins such as amyloid β (Aβ),α-synuclein, tau, and lysozyme are known to be prion-like; emerging data have revealed that they are also able to seed the misfolding of prion-like proteins differing in sequence. In the present study, we have developed a tool designed to test neurohistochemical outcomes associated with the entry of an amyloid protein into heterotypic neurons, i.e., neurons that do not express the invading amyloid and, instead, endogenously express amyloids differing in sequence. The stereotaxic introduction of Aβ into the rodent tegmental area of the mid-brain revealed that the foreign amyloid had infiltrated into nigral neurons. Furthermore, Aβ was found colocalized with α-synuclein, an amyloid endogenous to the substantia nigra and differing in sequence relative to Aβ. Disruption of α-synuclein status in the substantia nigra is associated with Parkinson's disease onset and progress. In addition to the study findings, a significant inroad to future neurodegenerative research was made via the stereotaxic introduction of the foreign amyloid. This technique limits the presence of confounding neurometabolic variables that may be prevalent in transgenic animal models of cross-toxicity and, thereby, better addresses the role of individual neuronal factors in cross-toxicity. Finally, the data from this work may help reconcile the high frequency of clinical comorbidity seen in neurodegenerative diseases.

Neuropathological Findings of Dementia Associated With Subjective Hearing Loss

OBJECTIVE

The relationship between hearing loss and cognitive decline is of great importance with growing evidence of hearing loss as an independent modifiable risk factor for dementia. Our goal was to evaluate for differences in dementia neuropathology between subjective normal hearing and hearing loss subjects, as well as subjects who wore hearing aids.

STUDY DESIGN

Retrospective database.

SETTING

Tertiary academic center.

PATIENTS

Brain tissue analyzed from our Center on Aging. Demographics, subjective hearing status, hearing aid use, cognitive status, and dementia neuropathology documented.

INTERVENTIONS

Dementia neuropathology analyzed in brains of normal hearing and hearing loss subjects.

MAIN OUTCOME MEASURES

Differences in dementia neuropathology between hearing groups. Groups were compared using logistic regression and analysis of covariance (ANCOVA).

RESULTS

Two-hundred and seventy-three subjects were included, 189 normal hearing and 84 subjective hearing loss subjects. No significant difference demonstrated in Alzheimer's disease neuropathology (p > 0.05) or pathologic stage (p = 0.2471). No significant difference observed in neuropathology of other major dementia types, specifically, presence of Lewy bodies (p > 0.05), Lewy body disease pathologic stage (p = 0.9778), or presence of micro-infarcts, macro-infarcts, or arteriosclerosis (p > 0.05). Hearing aid-wearing subjects had a lower prevalence of clinical dementia (39.1% versus 57.9%; p = 0.0208) with no significant difference in dementia neuropathology (p > 0.05).

CONCLUSION

Subjective hearing loss was not found to be associated with significantly different dementia neuropathology, which counters hypotheses on hearing loss causing permanent neurodegeneration and cognitive decline. Hearing aid users were found to have a lower prevalence of dementia for similar levels of neurodegeneration, suggesting a potential neuroprotective effect of hearing aids.

Abnormal Sleep Behaviours Across the Spectrum of Alzheimer's Disease Severity: Influence of APOE Genotypes and Lewy Bodies

BACKGROUND

The Apolipoprotein (APOE) ε4 allele is a well-known risk factor for Alzheimer's Disease (AD), and sleep disturbances are commonly associated with AD. However, few studies have investigated the relationship between APOE ε4 and abnormal sleep patterns (N+) in AD.

OBJECTIVE

To examine the relationship between APOE genotype, Lewy body pathology, and abnormal sleep patterns in a large group of subjects with known AD load evaluated upon autopsy.

METHOD

Data from 2,368 cases obtained from the National Alzheimer's Coordinating Centre database were categorized as follows: Braak Stage V/VI and CERAD frequent neuritic plaques as high load AD, Braak Stage III/IV and moderate CERAD as intermediate load AD, and Braak Stage 0/I/II and infrequent CERAD as no to low load AD. Cases discrepant between the two measures were discarded.

RESULTS

Disrupted sleep was more frequent in males (42.4%) compared to females (35.1%), and in carriers (42.3%) as opposed to non-carriers (36.5%) of ε4. Amongst female subjects with high AD load and Lewy body pathology, homozygous (ε4/ε4) carriers experienced disrupted sleep more often compared with heterozygous (ε4/x) or non-carriers of ε4. Such recessive, gender-specific, and Lewy body association is reminiscent of the ε4 effect on psychosis in AD. However, such association was lost after adjusting for covariates. In subjects with no to low AD pathology, female ε4 carriers had significantly more nighttime disturbances than non-carriers; this effect is independent of the presence of Lewy body pathology.

CONCLUSION

The influence of APOE ε4 on sleep disturbances is dependent on gender and severity of AD load.

Neuroprotective Effect of Brazilin on Amyloid β (25-35)-Induced Pathology in a Human Neuroblastoma Model

Until the recent past, the sole exemplar of proteins as infectious agents leading to neurodegenerative disorders remained the prion protein. Since then, the self-seeding mechanism characteristic of the prion protein has also been attributed to other neurodegenerative-disease-associated proteins, including amyloid-β (Aβ), tau, and α-synuclein (α-Syn). In model cell line studies, truncated Aβ, viz. amyloid beta (25-35), has been found to influence cellular homeostasis through its interactions with, and via, the disruption of key housekeeping machinery. Here, we demonstrate that the incubation of human neuroblastoma (SH-SY5Y) cell line with Brazilin ((6aS,11bR)-7,11b-dihydro-6H-indeno[2,1-c]chromene-3,6a,9,10-tetrol) prior to Aβ (25-35)-insult protected the cells from oxidative stress and apoptotic cell death. Furthermore, Brazilin mitigated Aβ-induced alterations in protein disulfide isomerase (PDI) and α-synuclein status, both of which are important biomarkers that report on Parkinson's pathogenesis. The results obtained in this study suggest that the tetrol is neuroprotective and helps resist Aβ-induced cross-pathology and amyloidogenic onset.

Diffuse Lewy Body Disease and Alzheimer Disease: Neuropathologic Phenotype Associated With the PSEN1 p.A396T Mutation

In sporadic and dominantly inherited Alzheimer disease (AD), aggregation of both tau and α-synuclein may occur in neurons. Aggregates of either protein occur separately or coexist in the same neuron. It is not known whether the coaggregation of tau and α-synuclein in dominantly inherited AD occurs in association with specific mutations of the APP, PSEN1, or PSEN2 genes. The aim of this study was to provide the first characterization of the neuropathologic phenotype associated with the PSEN1 p.A396T mutation in a man who was clinically diagnosed as having AD, but for whom the PSEN1 mutation was found postmortem. The proband, who was 56 years old when cognitive impairment first manifested, died at 67 years of age. Neuropathologically, 3 proteinopathies were present in the brain. Widespread α-synuclein-immunopositive neuronal inclusions suggested a diagnosis of diffuse Lewy body disease (DLBD), while severe and widespread tau and amyloid-β pathologies confirmed the clinical diagnosis of AD. Immunohistochemistry revealed the coexistence of tau and α-synuclein aggregates in the same neuron. Neuropathologic and molecular studies in brains of carriers of the PSEN1 p.A396T mutation or other PSEN1 or PSEN2 mutations associated with the coexistence of DLBD and AD are needed to clarify whether tau and α-synuclein proteinopathies occur independently or whether a relationship exists between α-synuclein and tau that might explain the mechanisms of coaggregation.

Factors associated with development and distribution of granular/fuzzy astrocytes in neurodegenerative diseases

Granular/fuzzy astrocytes (GFAs), a subtype of “aging‐related tau astrogliopathy,” are noted in cases bearing various neurodegenerative diseases. However, the pathogenic significance of GFAs remains unclear. We immunohistochemically examined the frontal cortex, caudate nucleus, putamen and amygdala in 105 cases composed of argyrophilic grain disease cases (AGD, N = 26), and progressive supranuclear palsy (PSP, N = 10), Alzheimer’s disease (AD, N = 20) and primary age‐related tauopathy cases (PART, N = 18) lacking AGD, as well as 31 cases bearing other various neurodegenerative diseases to clarify (i) the distribution patterns of GFAs in AGD, and PSP, AD and PART lacking AGD, (ii) the impacts of major pathological factors and age on GFA formation and (iii) immunohistochemical features useful to understand the formation process of GFAs. In AGD cases, GFAs consistently occurred in the amygdala (100%), followed by the putamen (69.2%) and caudate nucleus and frontal cortex (57.7%, respectively). In PSP cases without AGD, GFAs were almost consistently noted in all regions examined (90–100%). In AD cases without AGD, GFAs were less frequent, developing preferably in the putamen (35.0%) and caudate nucleus (30.0%). PART cases without AGD had GFAs most frequently in the amygdala (35.3%), being more similar to AGD than to AD cases. Ordered logistic regression analyses using all cases demonstrated that the strongest independent factor of GFA formation in the frontal cortex and striatum was the diagnosis of PSP, while that in the amygdala was AGD. The age was not significantly associated with GFA formation in any region. In GFAs in AGD cases, phosphorylation and conformational change of tau, Gallyas‐positive glial threads indistinguishable from those in tufted astrocytes, and the activation of autophagy occurred sequentially. Given these findings, AGD, PSP, AD and PART cases may show distinct distributions of GFAs, which may provide clues to predict the underlying processes of primary tauopathies.

Severe hyposmia distinguishes neuropathologically confirmed dementia with Lewy bodies from Alzheimer's disease dementia

Many subjects with neuropathologically-confirmed dementia with Lewy bodies (DLB) are never diagnosed during life, instead being categorized as Alzheimer's disease dementia (ADD) or unspecified dementia. Unrecognized DLB therefore is a critical impediment to clinical studies and treatment trials of both ADD and DLB. There are studies that suggest that olfactory function tests may be able to distinguish DLB from ADD, but few of these had neuropathological confirmation of diagnosis. We compared University of Pennsylvania Smell Identification Test (UPSIT) results in 257 subjects that went on to autopsy and neuropathological examination. Consensus clinicopathological diagnostic criteria were used to define ADD and DLB, as well as Parkinson's disease with dementia (PDD), with (PDD+AD) or without (PDD-AD) concurrent AD; a group with ADD and Lewy body disease (LBD) not meeting criteria for DLB (ADLB) and a clinically normal control group were also included. The subjects with DLB, PDD+AD and PDD-AD all had lower (one-way ANOVA p < 0.0001, pairwise Bonferroni p < 0.05) first and mean UPSIT scores than the ADD, ADLB or control groups. For DLB subjects with first and mean UPSIT scores less than 20 and 17, respectively, Firth logistic regression analysis, adjusted for age, gender and mean MMSE score, conferred statistically significant odds ratios of 17.5 and 18.0 for the diagnosis, vs ADD. For other group comparisons (PDD+AD and PDD-AD vs ADD) and UPSIT cutoffs of 17, the same analyses resulted in odds ratios ranging from 16.3 to 31.6 (p < 0.0001). To our knowledge, this is the largest study to date comparing olfactory function in subjects with neuropathologically-confirmed LBD and ADD. Olfactory function testing may be a convenient and inexpensive strategy for enriching dementia studies or clinical trials with DLB subjects, or conversely, reducing the inclusion of DLB subjects in ADD studies or trials.

Non-polyphenolic natural inhibitors of amyloid aggregation

Protein misfolding diseases (PMDs) are chronic and progressive, with no effective therapy so far. Aggregation and misfolding of amyloidogenic proteins are closely associated with the onset and progression of PMDs, such as amyloid-β (Aβ) in Alzheimer's disease, α-Synuclein (α-Syn) in Parkinson's disease and human islet amyloid polypeptide (hIAPP) in type 2 diabetes. Inhibiting toxic aggregation of amyloidogenic proteins is regarded as a promising therapeutic approach in PMDs. The past decade has witnessed the rapid progresses of this field, dozens of inhibitors have been screened and verified in vitro and in vivo, demonstrating inhibitory effects against the aggregation and misfolding of amyloidogenic proteins, together with beneficial effects. Natural products are major sources of small molecule amyloid inhibitors, a number of natural derived compounds have been identified with great bioactivities and translational prospects. Here, we review the non-polyphenolic natural inhibitors that potentially applicable for PMDs treatment, along with their working mechanisms. Future directions are proposed for the development and clinical applications of these inhibitors.

Cardiac sympathetic denervation and synucleinopathy in Alzheimer's disease with brain Lewy body disease

Comorbid Lewy body pathology is very common in Alzheimer’s disease and may confound clinical trial design, yet there is no in vivo test to identify patients with this. Tissue (and/or radioligand imaging) studies have shown cardiac sympathetic denervation in Parkinson’s disease and dementia with Lewy bodies, but this has not been explored in Alzheimer’s subjects with Lewy bodies not meeting dementia with Lewy bodies clinicopathological criteria. To determine if Alzheimer’s disease with Lewy bodies subjects show sympathetic cardiac denervation, we analysed epicardial and myocardial tissue from autopsy-confirmed cases using tyrosine hydroxylase and neurofilament immunostaining. Comparison of tyrosine hydroxylase fibre density in 19 subjects with Alzheimer’s disease/dementia with Lewy bodies, 20 Alzheimer’s disease with Lewy bodies, 12 Alzheimer’s disease subjects without Lewy body disease, 19 Parkinson’s disease, 30 incidental Lewy body disease and 22 cognitively normal without Alzheimer’s disease or Lewy body disease indicated a significant group difference (P < 0.01; Kruskal–Wallis analysis of variance) and subsequent pair-wise Mann–Whitney U tests showed that Parkinson’s disease (P < 0.05) and Alzheimer’s disease/dementia with Lewy bodies (P < 0.01) subjects, but not Alzheimer’s disease with Lewy bodies subjects, had significantly reduced tyrosine hydroxylase fibre density as compared with cognitively normal. Both Parkinson’s disease and Alzheimer’s disease/dementia with Lewy bodies subjects also showed significant epicardial losses of neurofilament protein-immunoreactive nerve fibre densities within the fibre bundles as compared with cognitively normal subjects (P < 0.01) and both groups showed high pathologic alpha-synuclein densities (P < 0.0001). Cardiac alpha-synuclein densities correlated significantly with brain alpha-synuclein (P < 0.001), while cardiac tyrosine hydroxylase and neurofilament immunoreactive nerve fibre densities were negatively correlated with the densities of both brain and cardiac alpha-synuclein, as well as Unified Parkinson’s Disease Rating Scale scores (P < 0.05). The clear separation of Alzheimer’s disease/dementia with Lewy bodies subjects from Alzheimer’s disease and cognitively normal, based on cardiac tyrosine hydroxylase fibre density, is the first report of a statistically significant difference between these groups. Our data do not show significant sympathetic cardiac denervation in Alzheimer’s disease with Lewy bodies, but strongly confirm that cardiac nuclear imaging with a noradrenergic radioligand is worthy of further study as a potential means to separate Alzheimer’s disease from Alzheimer’s disease/dementia with Lewy bodies during life.

Behavioral defects associated with amygdala and cortical dysfunction in mice with seeded α-synuclein inclusions

Parkinson’s disease (PD) is defined by motor symptoms such as tremor at rest, bradykinesia, postural instability, and stiffness. In addition to the classical motor defects that define PD, up to 80% of patients experience cognitive changes and psychiatric disturbances, referred to as PD dementia (PDD). Pathologically, PD is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and intracellular inclusions, called Lewy bodies and Lewy neurites, composed mostly of α-synuclein. Much of PD research has focused on the role of α-synuclein aggregates in degeneration of SNpc dopamine neurons because of the impact of loss of striatal dopamine on the classical motor phenotypes. However, abundant Lewy pathology is also found in other brain regions including the cortex and limbic brain regions such as the amygdala, which may contribute to non-motor phenotypes. Little is known about the consequences of α-synuclein inclusions in these brain regions, or in neuronal subtypes other than dopamine neurons. This project expands knowledge on how α-synuclein inclusions disrupt behavior, specifically non-motor symptoms of synucleinopathies. We show that bilateral injections of fibrils into the striatum results in robust bilateral α-synuclein inclusion formation in the cortex and amygdala. Inclusions in the amygdala and prefrontal cortex primarily localize to excitatory neurons, but unbiased stereology shows no significant loss of neurons in the amygdala or cortex. Fibril injected mice show defects in a social dominance behavioral task and fear conditioning, tasks that are associated with prefrontal cortex and amygdala function. Together, these observations suggest that seeded α-synuclein inclusion formation impairs behaviors associated with cortical and amygdala function, without causing cell loss, in brain areas that may play important roles in the complex cognitive features of PDD

Lewy-related pathology exhibits two anatomically and genetically distinct progression patterns: a population-based study of Finns aged 85

According to a generally accepted concept Lewy-related pathology (LRP) follows hierarchical caudo-rostral progression. LRP is also frequently present concomitantly with Alzheimer’s disease (AD), and it has been hypothesized that AD-associated LRP forms a distinct type of α-synucleinopathy, where LRP originates in the amygdala. The frequency of distinct forms of LRP progression types has not been studied in a population-based setting. We investigated the distribution and progression of LRP and its relation to AD pathology and apolipoprotein (APOE) ε4 in a population-based sample of Finns aged over 85 years (N = 304). Samples from spinal cord to neocortical areas representing 11 anatomical sites without any hierarchical selection were analyzed immunohistochemically (α-synuclein antibody clone 5G4). LRP was present in 124 individuals (41%) and according to DLB Consortium guidelines 19 of them were categorized as brainstem, 10 amygdala-predominant, 41 limbic, and 43 diffuse neocortical type, whereas 11 could not be classified. To determine the LRP progression patterns, a systematic anatomical scoring was carried out by taking into account the densities of the semiquantitative LRP scores in each anatomic site. With this scoring 123 (99%) subjects could be classified into two progression pattern types: 67% showed caudo-rostral and 32% amygdala-based progression. The unsupervised statistical K-means cluster analysis was used as a supplementary test and supported the presence of two progression patterns and had a 90% overall concordance with the systematic anatomical scoring method. Severe Braak NFT stage, high CERAD score and APOE ε4 were significantly (all p < 0.00001) associated with amygdala-based, but not with caudo-rostral progression type (all p > 0.2). This population-based study demonstrates two distinct common LRP progression patterns in the very elderly population. The amygdala-based pattern was associated with APOE ε4 and AD pathology. The results confirm the previous progression hypotheses but also widen the concept of the AD-associated LRP.

Aβ Seeding as a Tool to Study Cerebral Amyloidosis and Associated Pathology

Misfolded proteins can form aggregates and induce a self-perpetuating process leading to the amplification and spreading of pathological protein assemblies. These misfolded protein assemblies act as seeds of aggregation. In an in vivo exogenous seeding model, both the features of seeds and the position at which seeding originates are precisely defined. Ample evidence from studies on intracerebal injection of amyloid-beta (Aβ)-rich brain extracts suggests that Aβ aggregation can be initiated by prion-like seeding. In this mini-review article, we will summarize the past and current literature on Aβ seeding in mouse models of AD and discuss its implementation as a tool to study cerebral amyloidosis and associated pathology.

Unique α-synuclein pathology within the amygdala in Lewy body dementia: implications for disease initiation and progression

The protein α-synuclein (αsyn) forms pathologic aggregates in a number of neurodegenerative diseases including Lewy body dementia (LBD) and Parkinson's disease (PD). It is unclear why diseases such as LBD may develop widespread αsyn pathology, while in Alzheimer's disease with amygdala restricted Lewy bodies (AD/ALB) the αsyn aggregates remain localized. The amygdala contains αsyn aggregates in both LBD and in AD/ALB; to understand why αsyn pathology continues to progress in LBD but not in AD/ALB, tissue from the amygdala and other regions were obtained from 14 cases of LBD, 9 cases of AD/ALB, and 4 controls for immunohistochemical and biochemical characterization. Utilizing a panel of previously characterized αsyn antibodies, numerous unique pathologies differentiating LBD and AD/ALB were revealed; particularly the presence of dense neuropil αsyn aggregates, astrocytic αsyn, and αsyn-containing dystrophic neurites within senile plaques. Within LBD, these unique pathologies were predominantly present within the amygdala. Biochemically, the amygdala in LBD prominently contained specific carboxy-truncated forms of αsyn which are highly prone to aggregate, suggesting that the amygdala may be prone to initiate development of αsyn pathology. Similar to carboxy-truncated αsyn, it was demonstrated herein that the presence of aggregation prone A53T αsyn is sufficient to drive misfolding of wild-type αsyn in human disease. Overall, this study identifies within the amygdala in LBD the presence of unique strain-like variation in αsyn pathology that may be a determinant of disease progression.

Intriguing Mixed Pathologic Features in a Case of Dementia With Lewy Bodies

Neuropathologic confirmation of dementia with Lewy bodies (DLB) involves labeling cytoplasmic Lewy body inclusions for α-synuclein in cortical and subcortical neurons. The authors studied the postmortem brain of a 78-year-old man who had a diagnosis of DLB by exclusion. The patient had symptoms ascribed to DLB that included fluctuating cognitive changes in attention and executive function with progression to dementia, visual hallucinations, and parkinsonism. Sections from the olfactory bulbs and cortical and subcortical regions were stained with periodic acid-Schiff, as well as immunolabeled with antibodies specific for α-synuclein, tau protein, β-amyloid 1-42, and Chlamydia pneumoniae. Most regions demonstrated mixed neuropathologic features, and α-synuclein was notable in Lewy bodies in the amygdala and hippocampus. Periodic acid-Schiff-positive staining was noted in bodies in the amygdala and olfactory bulbs. In this case of DLB, neuropathologic inclusions were consistent with the disease diagnosis, but also with Alzheimer disease and other neurodegenerative diseases, such as polyglucosan body disease.

Molecular pathology of neurodegenerative diseases: principles and practice

Neurodegenerative diseases are characterised by selective dysfunction and progressive loss of synapses and neurons associated with pathologically altered proteins that deposit primarily in the human brain and spinal cord. Recent discoveries have identified a spectrum of distinct immunohistochemically and biochemically detectable proteins, which serve as a basis for protein-based disease classification. Diagnostic criteria have been updated and disease staging procedures have been proposed. These are based on novel concepts which recognise that (1) most of these proteins follow a sequential distribution pattern in the brain suggesting a seeding mechanism and cell-to-cell propagation; (2) some of the neurodegeneration-associated proteins can be detected in peripheral organs; and (3) concomitant presence of neurodegeneration-associated proteins is more the rule than the exception. These concepts, together with the fact that the clinical symptoms do not unequivocally reflect the molecular pathological background, place the neuropathological examination at the centre of requirements for an accurate diagnosis. The need for quality control in biomarker development, clinical and neuroimaging studies, and evaluation of therapy trials, as well as an increasing demand for the general public to better understand human brain disorders, underlines the importance for a renaissance of postmortem neuropathological studies at this time. This review summarises recent advances in neuropathological diagnosis and reports novel aspects of relevance for general pathological practice.

Efficient RT-QuIC seeding activity for α-synuclein in olfactory mucosa samples of patients with Parkinson's disease and multiple system atrophy

Background

Parkinson’s disease (PD) is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms. PD is characterized by intraneuronal accumulation of abnormal α-synuclein in brainstem while neurodegenerative parkinsonisms might be associated with accumulation of either α-synuclein, as in the case of Multiple System Atrophy (MSA) or tau, as in the case of Corticobasal Degeneration (CBD) and Progressive Supranuclear Palsy (PSP), in other disease-specific brain regions. Definite diagnosis of all these diseases can be formulated only neuropathologically by detection and localization of α-synuclein or tau aggregates in the brain. Compelling evidence suggests that trace-amount of these proteins can appear in peripheral tissues, including receptor neurons of the olfactory mucosa (OM).

Methods

We have set and standardized the experimental conditions to extend the ultrasensitive Real Time Quaking Induced Conversion (RT-QuIC) assay for OM analysis. In particular, by using human recombinant α-synuclein as substrate of reaction, we have assessed the ability of OM collected from patients with clinical diagnoses of PD and MSA to induce α-synuclein aggregation, and compared their seeding ability to that of OM samples collected from patients with clinical diagnoses of CBD and PSP.

Results

Our results showed that a significant percentage of MSA and PD samples induced α-synuclein aggregation with high efficiency, but also few samples of patients with the clinical diagnosis of CBD and PSP caused the same effect. Notably, the final RT-QuIC aggregates obtained from MSA and PD samples owned peculiar biochemical and morphological features potentially enabling their discrimination.

Conclusions

Our study provide the proof-of-concept that olfactory mucosa samples collected from patients with PD and MSA possess important seeding activities for α-synuclein. Additional studies are required for (i) estimating sensitivity and specificity of the technique and for (ii) evaluating its application for the diagnosis of PD and neurodegenerative parkinsonisms. RT-QuIC analyses of OM and cerebrospinal fluid (CSF) can be combined with the aim of increasing the overall diagnostic accuracy of these diseases, especially in the early stages.

Electronic supplementary material

The online version of this article (10.1186/s40035-019-0164-x) contains supplementary material, which is available to authorized users.

Alzheimer's disease and other neurodegenerative dementias in comorbidity: A clinical and neuropathological overview

Neuropathological diagnostic criteria of neurodegenerative disorders are based on the presence of specific inclusions in a specific area of brain tissue that correlate with clinical manifestations. Concomitant neurodegenerative disorders correspond to a combination of two (or more) different fully developed diseases in the same patient. Concomitant neurodegenerative pathology represents the presence of definite neurodegeneration and deposits of pathological proteins specific for another disease, which is not, however, fully developed. Very frequent overlaps include Alzheimer's disease and alpha-synuclein inclusions. Nevertheless, careful neuropathological investigations reveal an increasing frequency of different co-pathologies in examined brains. In Alzheimer's disease, protein TDP-43 may co-aggregate, but it is not clear whether this is atypical isolated Alzheimer's disease or overlap of Alzheimer's disease with early frontotemporal lobar degeneration. Comorbidities of Alzheimer's disease and tauopathies are relatively rare. A combination of vascular pathology with primary neurodegeneration (mostly Alzheimer's disease or dementia with Lewy bodies) is historically called mixed dementia. Overlap of different neuropathologically confirmed neurodegenerations could lead to atypical and unusual clinical presentations and may be responsible for faster disease progression. Several CSF biomarkers have been evaluated for their utility in diagnostic processes in different neurodegenerative dementias; however, evidence regarding their role in neurodegenerative overlaps is still limited.

Clinicopathologic subtype of Alzheimer's disease presenting as corticobasal syndrome

INTRODUCTION

The corticobasal syndrome (CBS) is associated with several neuropathologic disorders, including corticobasal degeneration and Alzheimer's disease (AD).

METHOD

In this report, we studied 43 AD patients with CBS (AD-CBS) and compared them with 42 AD patients with typical amnestic syndrome (AD-AS), as well as 15 cases of corticobasal degeneration and CBS pathology.

RESULTS

Unlike AD-AS, AD-CBS had prominent motor problems, including limb apraxia (90%), myoclonus (81%), and gait disorders (70%). Alien limb phenomenon was reported in 26% and cortical sensory loss in 14%. Language problems were also more frequent in AD-CBS, and memory impairment was less frequent. AD-CBS had more tau pathology in perirolandic cortices but less in superior temporal cortex than AD-AS. In addition, AD-CBS had greater neuronal loss in the substantia nigra.

DISCUSSION

AD-CBS is a clinicopathological subtype of AD with an atypical distribution of Alzheimer-type tau pathology. Greater neuronal loss in the substantia nigra may contribute to Parkinsonism which is not a feature of typical AD.

Most cases with Lewy pathology in a population-based cohort adhere to the Braak progression pattern but 'failure to fit' is highly dependent on staging system applied

Braak et al.'s 2003 paper detailing the caudo-rostral progression of Lewy body pathology (LP) formed the foundation of current understanding of disease spread in Parkinson's disease (PD); however, its methods are difficult to recreate and consequently multiple new staging systems emerged to recapitulate Braak's staging system using standard neuropathological methods and to account for other patterns of LP. Studies using these systems have documented widely variable rates of cases that 'fail to fit' expected patterns of LP spread. This could be due to population differences, features of individual systems, or may constitute under-recognized patterns of disease. We examined 324 neuropathological cases from the Honolulu Asia Aging Study and applied four different LP staging systems to determine the proportion of cases adhering to different staging methodologies and those that 'fail to fit' expected patterns of LP. Of 141 cases with LP (24: PD, 8: Dementia with Lewy bodies (DLB), 109: Incidental Lewy body disease (ILBD)), our application of Braak et al., 2003 classified 83.7%, Müller et al., 2005 classified 87.9%, Beach et al., 2009 classified 100%, and Leverenz et al., 2008 classified 98.6%. There were significant differences in the cases classifiable by the Leverenz and Beach systems versus the Braak and Müller systems (p < 0.001 for each). In this population-based autopsy cohort with a high prevalence of ILBD, the majority of cases were consistent with the progression characterized by the Braak et al. however, the determination of cases as atypical is highly dependent on the staging system applied.

Manganese-Induced Neurotoxicity: New Insights Into the Triad of Protein Misfolding, Mitochondrial Impairment, and Neuroinflammation

Occupational or environmental exposure to manganese (Mn) can lead to the development of "Manganism," a neurological condition showing certain motor symptoms similar to Parkinson's disease (PD). Like PD, Mn toxicity is seen in the central nervous system mainly affecting nigrostriatal neuronal circuitry and subsequent behavioral and motor impairments. Since the first report of Mn-induced toxicity in 1837, various experimental and epidemiological studies have been conducted to understand this disorder. While early investigations focused on the impact of high concentrations of Mn on the mitochondria and subsequent oxidative stress, current studies have attempted to elucidate the cellular and molecular pathways involved in Mn toxicity. In fact, recent reports suggest the involvement of Mn in the misfolding of proteins such as α-synuclein and amyloid, thus providing credence to the theory that environmental exposure to toxicants can either initiate or propagate neurodegenerative processes by interfering with disease-specific proteins. Besides manganism and PD, Mn has also been implicated in other neurological diseases such as Huntington's and prion diseases. While many reviews have focused on Mn homeostasis, the aim of this review is to concisely synthesize what we know about its effect primarily on the nervous system with respect to its role in protein misfolding, mitochondrial dysfunction, and consequently, neuroinflammation and neurodegeneration. Based on the current evidence, we propose a 'Mn Mechanistic Neurotoxic Triad' comprising (1) mitochondrial dysfunction and oxidative stress, (2) protein trafficking and misfolding, and (3) neuroinflammation.

Faster cognitive decline in dementia due to Alzheimer disease with clinically undiagnosed Lewy body disease

Background

Neuropathology has demonstrated a high rate of comorbid pathology in dementia due to Alzheimer’s disease (ADD). The most common major comorbidity is Lewy body disease (LBD), either as dementia with Lewy bodies (AD-DLB) or Alzheimer’s disease with Lewy bodies (AD-LB), the latter representing subjects with ADD and LBD not meeting neuropathological distribution and density thresholds for DLB. Although it has been established that ADD subjects with undifferentiated LBD have a more rapid cognitive decline than those with ADD alone, it is still unknown whether AD-LB subjects, who represent the majority of LBD and approximately one-third of all those with ADD, have a different clinical course.

Methods

Subjects with dementia included those with “pure” ADD (n = 137), AD-DLB (n = 64) and AD-LB (n = 114), all with two or more complete Mini Mental State Examinations (MMSE) and a full neuropathological examination.

Results

Linear mixed models assessing MMSE change showed that the AD-LB group had significantly greater decline compared to the ADD group (β = -0.69, 95% CI: -1.05, -0.33, p<0.001) while the AD-DLB group did not (β = -0.30, 95% CI: -0.73, 0.14, p = 0.18). Of those with AD-DLB and AD-LB, only 66% and 2.1%, respectively, had been diagnosed with LBD at any point during their clinical course. Compared with clinically-diagnosed AD-DLB subjects, those that were clinically undetected had significantly lower prevalences of parkinsonism (p = 0.046), visual hallucinations (p = 0.0008) and dream enactment behavior (0.013).

Conclusions

The probable cause of LBD clinical detection failure is the lack of a sufficient set of characteristic core clinical features. Core DLB clinical features were not more common in AD-LB as compared to ADD. Clinical identification of ADD with LBD would allow stratified analyses of ADD clinical trials, potentially improving the probability of trial success.

Neuropathology and pathogenesis of extrapyramidal movement disorders: a critical update-I. Hypokinetic-rigid movement disorders

Extrapyramidal movement disorders include hypokinetic rigid and hyperkinetic or mixed forms, most of them originating from dysfunction of the basal ganglia (BG) and their information circuits. The functional anatomy of the BG, the cortico-BG-thalamocortical, and BG-cerebellar circuit connections are briefly reviewed. Pathophysiologic classification of extrapyramidal movement disorder mechanisms distinguish (1) parkinsonian syndromes, (2) chorea and related syndromes, (3) dystonias, (4) myoclonic syndromes, (5) ballism, (6) tics, and (7) tremor syndromes. Recent genetic and molecular-biologic classifications distinguish (1) synucleinopathies (Parkinson's disease, dementia with Lewy bodies, Parkinson's disease-dementia, and multiple system atrophy); (2) tauopathies (progressive supranuclear palsy, corticobasal degeneration, FTLD-17; Guamian Parkinson-dementia; Pick's disease, and others); (3) polyglutamine disorders (Huntington's disease and related disorders); (4) pantothenate kinase-associated neurodegeneration; (5) Wilson's disease; and (6) other hereditary neurodegenerations without hitherto detected genetic or specific markers. The diversity of phenotypes is related to the deposition of pathologic proteins in distinct cell populations, causing neurodegeneration due to genetic and environmental factors, but there is frequent overlap between various disorders. Their etiopathogenesis is still poorly understood, but is suggested to result from an interaction between genetic and environmental factors. Multiple etiologies and noxious factors (protein mishandling, mitochondrial dysfunction, oxidative stress, excitotoxicity, energy failure, and chronic neuroinflammation) are more likely than a single factor. Current clinical consensus criteria have increased the diagnostic accuracy of most neurodegenerative movement disorders, but for their definite diagnosis, histopathological confirmation is required. We present a timely overview of the neuropathology and pathogenesis of the major extrapyramidal movement disorders in two parts, the first one dedicated to hypokinetic-rigid forms and the second to hyperkinetic disorders.

α-synuclein in the pathophysiology of Alzheimer's disease

The Alzheimer’s disease (AD) afflicted brain is neuropathologically defined by extracellular amyloid-β (Aβ) plaques and intraneuronal neurofibrillary tangles composed of hyperphosphorylated tau protein. However, accumulating evidence suggests that the presynaptic protein α-synuclein (αSyn), mainly associated with synucleinopathies like Parkinson’s disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA), is involved in the pathophysiology of AD. Lewy-related pathology (LRP), primarily comprised of αSyn, is present in a majority of autopsied AD brains, and higher levels of αSyn in the cerebrospinal fluid (CSF) of patients with mild cognitive impairment (MCI) and AD have been linked to cognitive decline. Recent studies also suggest that the asymptomatic accumulation of Aβ plaques is associated with higher CSF αSyn levels in subjects at risk of sporadic AD and in individuals carrying autosomal dominant AD mutations. Experimental evidence has further linked αSyn mainly to tau hyperphosphorylation, but also to the pathological actions of Aβ and the APOEε4 allele, the latter being a major genetic risk factor for both AD and DLB. In this review, we provide a summary of the current evidence proposing an involvement of αSyn either as an active or passive player in the pathophysiological ensemble of AD, and furthermore describe in detail the current knowledge of αSyn structure and inferred function.

Influence of Lewy Pathology on Alzheimer's Disease Phenotype: A Retrospective Clinico-Pathological Study

Background:

Studies have shown the frequent coexistence of Lewy pathology (LP) in Alzheimer’s Disease (AD).

Objective:

The aim of this study was to determine the influence of LP on the clinical and cognitive phenotype in a cohort of patients with a neuropathological diagnosis of AD.

Methods:

We reviewed neuropathologically proven AD cases, reaching Braak stages V and VI in the brain banks of Lille and Paris between 1993 and 2016, and classified them according to LP extension (amygdala, brainstem, limbic, or neocortical). We then searched patient files for all available clinical and neuropsychiatric features and neuropsychological data.

Results:

Thirty-three subjects were selected for this study, among which 16 were devoid of LP and 17 presented AD with concomitant LP. The latter were stratified into two subgroups according to LP distribution: 7 were AD with amygdala LP and 10 were AD with ‘classical’ (brainstem, limbic or neocortical) LP. When analyzing the incidence of each clinical feature at any point during the disease course, we found no significant difference in symptom frequency between the three groups. However, fluctuations appeared significantly earlier in patients with classical LP (2±3.5 years) than in patients without LP (7±1.7 years) or with amygdala LP (8±2.8 years; p < 0.01). There was no significant difference in cognitive profiles.

Conclusion:

Our findings suggest that the influence of LP on the clinical phenotype of AD is subtle. Core features of dementia with Lewy bodies do not allow clinical diagnosis of a concomitant LP on a patient-to-patient basis.

The standardization of cerebrospinal fluid markers and neuropathological diagnoses brings to light the frequent complexity of concomitant pathology in Alzheimer's disease: The next challenge for biochemical markers?

During the last two decades, neuropathological examination of the brain has evolved both technically and scientifically. The increasing use of immunohistochemistry to detect protein aggregates paralleled a better understanding of neuroanatomical progression of protein deposition. As a consequence, an international effort was achieved to standardize hyperphosphorylated-Tau (phospho-TAU), ßAmyloid (Aß), alpha syncuclein (alpha-syn), phosphorylated transactive response DNA-binding protein 43 (phospho-TDP43) and vascular pathology detection. Meanwhile harmonized staging systems emerged in order to increase inter rater reproducibility. Therefore, a refined definition of Alzheimer's disease was recommended., a clearer picture of the neuropathological lesions diversity emerged secondarily to the systematic assessment of concomitant pathology highlighting finally a low rate of pure AD pathology. This brings new challenges to laboratory medicine in the field of cerebrospinal fluid (CSF) markers of Alzheimer's disease: how to further validate total Tau, phospho-TAU, Aß40 and Aß42 and new marker level cut-offs while autopsy rates are declining?

Rare histotype of sporadic Creutzfeldt-Jakob disease, clinically suspected as corticobasal degeneration

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rare neurodegenerative disease that can mimic other neurological disorders. We present a case of sCJD in a 64-year-old man that presented with corticobasal syndrome and survived for 3 years. He presented initially with dementia, hemiparkinsonism and alien limb phenomenon and was diagnosed with corticobasal degeneration, ultimately progressing to immobility and akinetic mutism. With a normal MRI 1 year before onset, his neuroimaging 1 year later revealed abnormal DaTscan, cortical and hippocampal atrophy with ventricular dilatation on MRI, and diffusion-weighted cortical ribboning and thalamic hyperintensity. Postmortem, the patient's brain was collected by the Parkinson's UK Tissue Bank. Prion protein immunohistochemistry revealed widespread diffuse microvacuolar staining without kuru-type plaques. Hyperphosphorylated tau was only found in the entorhinal cortex and hippocampus. This case highlights the clinical heterogeneity of sCJD presentation and the important inclusion of CJD in the differential diagnosis of atypical presentations of neurodegenerative disease.

Autopsied centenarian case of Alzheimer's disease combined with hippocampal sclerosis, TDP-43, and α-synuclein pathologies

A Japanese woman showed slowly progressive memory disturbance starting at the age of 84 years, and disorientation gradually appeared. Head computed tomography revealed severe hippocampal atrophy, whereas the atrophy of the frontal lobe was considerably mild for her age. Behavioral and psychological symptoms of dementia were relatively inconspicuous during the disease course. Apolipoprotein E gene analysis showed ε3/ε4 heterozygosity. She died at the age of 100 years and she was clinically diagnosed as having Alzheimer's disease (AD). Autopsy revealed numerous neurofibrillary tangles, particularly in the hippocampal region, and extensively distributed senile plaques in the brain. Although the findings were compatible with the pathological criteria for AD, combined pathologies of hippocampal sclerosis, trans-activation response DNA-binding protein 43 kDa, and α-synuclein were also revealed. We believe that the clinicopathological findings of the present case are of significance for the diagnosis of elderly dementia and pathogenesis of AD.

Protein misfolding, aggregation, and conformational strains in neurodegenerative diseases

A hallmark event in neurodegenerative diseases (NDs) is the misfolding, aggregation, and accumulation of proteins, leading to cellular dysfunction, loss of synaptic connections, and brain damage. Despite the involvement of distinct proteins in different NDs, the process of protein misfolding and aggregation is remarkably similar. A recent breakthrough in the field was the discovery that misfolded protein aggregates can self-propagate through seeding and spread the pathological abnormalities between cells and tissues in a manner akin to the behavior of infectious prions in prion diseases. This discovery has vast implications for understanding the mechanisms involved in the initiation and progression of NDs, as well as for the design of novel strategies for treatment and diagnosis. In this Review, we provide a critical discussion of the role of protein misfolding and aggregation in NDs. Commonalities and differences between distinct protein aggregates will be highlighted, in addition to evidence supporting the hypothesis that misfolded aggregates can be transmissible by the prion principle. We will also describe the molecular basis and implications for prion-like conformational strains, cross-interaction between different misfolded proteins in the brain, and how these concepts can be applied to the development of novel strategies for therapy and diagnosis.

Lewy Body Pathology and Chronic Traumatic Encephalopathy Associated With Contact Sports

Traumatic brain injury has been associated with increased risk of Parkinson disease and parkinsonism, and parkinsonism and Lewy body disease (LBD) can occur with chronic traumatic encephalopathy (CTE). To test whether contact sports and CTE are associated with LBD, we compared deceased contact sports athletes (n = 269) to cohorts from the community (n = 164) and the Boston University Alzheimer disease (AD) Center (n = 261). Participants with CTE and LBD were more likely to have β-amyloid deposition, dementia, and parkinsonism than CTE alone (p < 0.05). Traditional and hierarchical clustering showed a similar pattern of LBD distribution in CTE compared to LBD alone that was most frequently neocortical, limbic, or brainstem. In the community-based cohort, years of contact sports play were associated with neocortical LBD (OR = 1.30 per year, p = 0.012), and in a pooled analysis a threshold of >8 years of play best predicted neocortical LBD (ROC analysis, OR = 6.24, 95% CI = 1.5-25, p = 0.011), adjusting for age, sex, and APOE ɛ4 allele status. Clinically, dementia was significantly associated with neocortical LBD, CTE stage, and AD; parkinsonism was associated with LBD pathology but not CTE stage. Contact sports participation may increase risk of developing neocortical LBD, and increased LBD frequency may partially explain extrapyramidal motor symptoms sometimes observed in CTE.

APOE ε4 is associated with severity of Lewy body pathology independent of Alzheimer pathology

OBJECTIVE

To evaluate whether APOE ε4 is associated with severity of Lewy body (LB) pathology, independently of Alzheimer disease (AD) pathology.

METHODS

Six hundred fifty-two autopsy-confirmed LB disease (LBD) cases and 660 clinical controls were genotyped for APOE. In case-control analysis, LBD cases were classified into 9 different groups according to severity of both LB pathology (brainstem, transitional, diffuse) and AD pathology (low, moderate, high) to assess associations between APOE ε4 and risk of different neuropathologically defined LBD subgroups in comparison to controls. In LBD cases only, we also measured LB counts from 5 cortical regions and evaluated associations with ε4 according to severity of AD pathology.

RESULTS

As expected, APOE ε4 was associated with an increased risk of transitional and diffuse LBD in cases with moderate or high AD pathology (all odds ratios ≥3.42, all p ≤ 0.004). Of note, ε4 was also associated with an increased risk of diffuse LBD with low AD pathology (odds ratio = 3.46, p = 0.001). In the low AD pathology LBD subgroup, ε4 was associated with significantly more LB counts in the 5 cortical regions, independently of Braak stage and Thal phase (all p ≤ 0.002).

CONCLUSIONS

Our results indicate that APOE ε4 is independently associated with a greater severity of LB pathology. These findings increase our understanding of the mechanism behind reported associations of ε4 with risk of dementia with Lewy bodies and Parkinson disease with dementia, and suggest that ε4 may function as a modifier of processes that favor LB spread rather than acting directly to initiate LB pathology.

Lewy Body Dementia

Dementia with Lewy bodies (DLB) is the second most common neurodegenerative dementia following Alzheimer disease. It stems from the formation of Lewy bodies, which contain aggregates of the misfolded protein, α-synuclein. These deposit in areas of the nervous system and brain, leading to neuronal cell death and causing clinically apparent symptoms. Because of its clinical overlap with other forms of dementia, DLB is often underdiagnosed and misdiagnosed. There is currently no cure for DLB and treatments are aimed at ameliorating specific symptoms.

How early can we diagnose Alzheimer disease (and is it sufficient)? The 2017 Wartenberg lecture

A seismic shift in our understanding of the ability to diagnose Alzheimer disease (AD) is occurring. For the last several decades, AD has been a clinical–pathologic diagnosis, and this conceptualization of the disease has served the field well. Typically, the clinician would identify a syndrome such as mild cognitive impairment or dementia, and label the condition as “probable AD” since the diagnosis of definite AD could not be made until an autopsy revealed the presence of amyloid plaques and tau-based neurofibrillary tangles. However, with the advent of biomarkers for AD including neuroimaging and CSF, the identification of AD pathology can be made in life, which greatly enhances the ability of clinicians to be precise about the underlying etiology of a clinical syndrome. Hypothetical models of the temporal relation among the pathologic elements and the clinical symptoms have been proposed and have influenced the field enormously. This has enabled clinicians to be specific about the underlying cause of a given clinical syndrome. As such, the diagnostic capability of the clinician is evolving. However, AD pathology is only a component of the puzzle describing the causes of cognitive changes in aging. Most often, there is a multitude of pathologic entities contributing to the neuropathologic explanation of cognitive changes in aging. AD changes contribute important elements to the diagnosis, but the final answer is more complex. The field of aging and dementia will have to incorporate these additional elements.

Spinal Lewy body pathology in older adults without an antemortem diagnosis of Parkinson's disease

To test the hypothesis that Lewy body pathology (LBs) is present in the spinal cord of older community-dwelling adults without a clinical diagnosis of Parkinson's disease (PD). We studied 162 prospective autopsies from older adults with PD (N = 6) and without PD (N = 156). We documented the presence of LBs in cerebrum and brainstem structures from each of the six regions used for Braak PD staging and four spinal cord levels (C5/6, T7, L4/5 and S4/5). Parkinsonism proximate to death was based on a previously validated measure present if two or more of the four signs of parkinsonism were present based on a modified version of the Unified Parkinson's Disease Rating Scale (UPDRS). Fifty-three of 156 individuals without PD (34%) had LBs in a least one site within the CNS. About half of cases with LBs in the cerebrum or brainstem, (25/53, 47%) also had spinal LBs. Almost 90% (22/25, 88%) of cases with spinal LBs had LBs in the cerebrum (Braak stages 4-6) and about 10% (3/25, 12%) had only brainstem LBs (Braak stages 1-3). Four of six cases with PD showed LBs in cerebrum, brainstem and spinal cord. Individuals with LBs in the spinal cord were more likely to have clinical parkinsonism proximate to death compared to individuals with LBs in brainstem and cerebrum alone (52% vs. 32%; Chi-Square x2  = 5.368, d.f. = 1, P = 0.0.021) and more severe nigral neuronal loss (48% vs. 11%; Chi-Square x2  = 9.049, d.f. = 1, P = 0.003). These findings were unchanged when we included cases with a history of PD. Older community-dwelling adults without a clinical diagnosis of PD have evidence of LBs throughout the CNS including the spinal cord which is associated with parkinsonism and more severe nigral neuronal loss.

Impact of the biological definition of Alzheimer's disease using amyloid, tau and neurodegeneration (ATN): what about the role of vascular changes, inflammation, Lewy body pathology?

BACKGROUND

The NIA-AA research framework proposes a biological definition of Alzheimer's disease, where asymptomatic persons with amyloid deposition would be considered as having this disease prior to symptoms.

DISCUSSION

Notwithstanding the fact that amyloid deposition in isolation is not associated with dementia, even the combined association of amyloid and tau pathology does not inevitably need to dementia over age 65. Other pathological factors may play a leading or an accelerating role in age-associated cognitive decline, including vascular small vessel disease, neuroinflammation and Lewy Body pathology.

CONCLUSION

Research should aim at understanding the interaction between all these factors, rather than focusing on them individually. Hopefully this will lead to a personalized approach to the prevention of brain aging, based on individual biological, genetic and cognitive profiles.

TDP-43 pathology in multiple system atrophy: colocalization of TDP-43 and α-synuclein in glial cytoplasmic inclusions

AIMS

This study aimed to assess clinicopathologic features of transactive response DNA-binding protein of 43 kDa (TDP-43) pathology and its risk factors in multiple system atrophy (MSA).

METHODS

Paraffin-embedded sections of the amygdala and basal forebrain from 186 autopsy-confirmed MSA cases were screened with immunohistochemistry for phospho-TDP-43. In cases having TDP-43 pathology, additional brain regions were assessed. Immunohistochemical and immunofluorescence double-staining and immunogold electron microscopy (IEM) were performed to evaluate colocalization of TDP-43 and α-synuclein. Genetic risk factors for TDP-43 pathology were also analysed.

RESULTS

Immunohistochemistry showed various morphologies of TDP-43 pathology in 13 cases (7%), such as subpial astrocytic inclusions, neuronal inclusions, dystrophic neurites, perivascular inclusions and glial cytoplasmic inclusions (GCIs). Multivariable logistic regression models revealed that only advanced age, but not concurrent Alzheimer's disease, argyrophilic grain disease or hippocampal sclerosis, was an independent risk factor for TDP-43 pathology in MSA (OR: 1.11, 95% CI: 1.04-1.19, P = 0.002). TDP-43 pathology was restricted to the amygdala in eight cases and extended to the hippocampus in two cases. The remaining three cases had widespread TDP-43 pathology. Immunohistochemical and immunofluorescence double-staining and IEM revealed colocalization of α-synuclein and TDP-43 in GCIs with granule-coated filaments. Pilot genetic studies failed to show associations between risk variants of TMEM106B or GRN and TDP-43 pathology.

CONCLUSIONS

TDP-43 pathology is rare in MSA and occurs mainly in the medial temporal lobe. Advanced age is a risk factor for TDP-43 pathology in MSA. Colocalization of TDP-43 and α-synuclein in GCIs suggests possible direct interaction between the two molecules.

Amygdala α-Synuclein Pathology in the Population-Based Vantaa 85+ Study

We investigated the frequency of Lewy-related pathology (LRP) in the amygdala among the population-based Vantaa 85+ study. Data of amygdala samples (N = 304) immunostained with two α-synuclein antibodies (clone 42 and clone 5G4) was compared with the previously analyzed LRP and AD pathologies from other brain regions. The amygdala LRP was present in one third (33%) of subjects. Only 5% of pure AD subjects, but 85% of pure DLB subjects had LRP in the amygdala. The amygdala LRP was associated with dementia; however, the association was dependent on LRP on other brain regions, and thus was not an independent risk factor. The amygdala-predominant category was a rare (4%) and heterogeneous group.

Global quantitative analysis of the human brain proteome in Alzheimer's and Parkinson's Disease

Patients with Alzheimer's disease (AD) and Parkinson's disease (PD) often have overlap in clinical presentation and brain neuropathology suggesting that these two diseases share common underlying mechanisms. Currently, the molecular pathways linking AD and PD are incompletely understood. Utilizing Tandem Mass Tag (TMT) isobaric labeling and synchronous precursor selection-based MS3 (SPS-MS3) mass spectrometry, we performed an unbiased quantitative proteomic analysis of post-mortem human brain tissues (n=80) from four different groups defined as controls, AD, PD, and co-morbid AD/PD cases across two brain regions (frontal cortex and anterior cingulate gyrus). In total, we identified 11 840 protein groups representing 10 230 gene symbols, which map to ~65% of the protein coding genes in brain. The utility of including two reference standards in each TMT 10-plex assay to assess intra- and inter-batch variance is also described. Ultimately, this comprehensive human brain proteomic dataset serves as a valuable resource for various research endeavors including, but not limited to, the identification of disease-specific protein signatures and molecular pathways that are common in AD and PD.

Aberrant accumulation of ErbB4 in progressive supranuclear palsy

AIMS

The human epidermal growth factor receptor family consists of four members that belong to the ErbB lineage of proteins (ErbB1-4). Neuregulin-1 (NRG1)/ErbB signalling regulates brain development and function. Abnormalities in this signalling have been implicated in the aetiology or development of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. So, we aimed at investigating whether the expression of NRG1 or ErbB proteins are altered in progressive supranuclear palsy (PSP).

METHODS

The brains of 10 PSP and six control patients were investigated by immunohistochemical analysis.

RESULTS

Whereas C-terminal ErbB4 immunoreacitivity was partially but distinctly present in the cytoplasm and/or in the nucleus of neurons in control patients, it was rarely observed in the neuronal nuclei in PSP patients. In contrast, neurofibrillary tangles, coiled bodies and threads were robustly immunoreactive for C-terminal ErbB4 in PSP. Double immunofluorescence for C-terminal ErbB4 and phospho-tau revealed co-localization of these proteins within neuronal and glial inclusions. To the contrary, there was no difference in the subcellular localization of NRG1, ErbB1, ErbB2, and N-terminal ErbB4 between control and PSP patients. These proteins were localized in the cytoplasm of neurons.

CONCLUSIONS

Our present results suggest that NRG1/ErbB4 signalling could be an important event in the pathogenesis of PSP.

Multiproteinopathy, neurodegeneration and old age: a case study

A complex spectrum of mixed brain pathologies is common in older people. This clinical pathologic conference case study illustrates the challenges of formulating clinicopathologic correlations in late-onset neurodegenerative diseases featuring cognitive-behavioral syndromes with underlying multiple proteinopathy. Studies on the co-existence and interactions of Alzheimer's disease (AD) with neurodegenerative non-AD pathologies in the aging brain are needed to understand the pathogenesis of neurodegeneration and to support the development of diagnostic biomarkers and therapies.

The Amygdala as a Locus of Pathologic Misfolding in Neurodegenerative Diseases

Over the course of most common neurodegenerative diseases the amygdala accumulates pathologically misfolded proteins. Misfolding of 1 protein in aged brains often is accompanied by the misfolding of other proteins, suggesting synergistic mechanisms. The multiplicity of pathogenic processes in human amygdalae has potentially important implications for the pathogenesis of Alzheimer disease, Lewy body diseases, chronic traumatic encephalopathy, primary age-related tauopathy, and hippocampal sclerosis, and for the biomarkers used to diagnose those diseases. Converging data indicate that the amygdala may represent a preferential locus for a pivotal transition from a relatively benign clinical condition to a more aggressive disease wherein multiple protein species are misfolded. Thus, understanding of amygdalar pathobiology may yield insights relevant to diagnoses and therapies; it is, however, a complex and imperfectly defined brain region. Here, we review aspects of amygdalar anatomy, connectivity, vasculature, and pathologic involvement in neurodegenerative diseases with supporting data from the University of Kentucky Alzheimer's Disease Center autopsy cohort. Immunohistochemical staining of amygdalae for Aβ, Tau, α-synuclein, and TDP-43 highlight the often-coexisting pathologies. We suggest that the amygdala may represent an "incubator" for misfolded proteins and that it is possible that misfolded amygdalar protein species are yet to be discovered.