More frequent Lewy bodies but less frequent Alzheimer-type lesions in multiple system atrophy as compared to age-matched control brains

Limitations and potential strategies of immune checkpoint blockade in age-related neurodegenerative disorders

Neurological disorders such as Alzheimer's disease (AD), and Parkinson's disease (PD) have no disease-modifying treatments, resulting in a global dementia crisis that affects more than 50 million people. Amyloid-beta (Aβ), tau, and alpha-synuclein (α-Syn) are three crucial proteins that are involved in the pathogenesis of these age-related neurodegenerative diseases. Only a few approved AD medications have been used in the clinic up to this point, and their results are only partial symptomatic alleviation for AD patients and cannot stop the progression of AD. Immunotherapies have attracted considerable interest as they target certain protein strains and conformations as well as promote clearance. Immunotherapies also have the potential to be neuroprotective: as they limit synaptic damage and spread of neuroinflammation by neutralizing extracellular protein aggregates. Lately, disease-modifying therapies (DMTs) that can alter the pathophysiology that underlies AD with anti-Aβ monoclonal antibodies (MAbs) (e.g., aducanumab, lecanemab, gantenerumab, donanemab, solanezumab, crenezumab, tilavonemab). Similarly, in Parkinson's disease (PD), DMTs utilizing anti-αSyn (MAbs) (e.g., prasinezumab, cinpanemab,) are progressively being developed and evaluated in clinical trials. These therapies are based on the hypothesis that both AD and PD may involve systemic impairments in cell-dependent clearance mechanisms of amyloid-beta (Aβ) and alpha-synuclein (αSyn), respectively, meaning the body's overall inability to effectively remove Aβ and αSyn due to malfunctioning cellular mechanisms. In this review we will provide possible evidence behind the use of immunotherapy with MAbs in AD and PD and highlight the recent clinical development landscape of anti-Aβ (MAbs) and anti-αSyn (MAbs) from these clinical trials in order to better investigate the therapeutic possibilities and adverse effects of these anti-Aβ and anti-αSyn MAbs on AD and PD.

Pathology of neurodegenerative disease for the general neurologist

Neurodegeneration refers to progressive dysfunction or loss of selectively vulnerable neurones from brain and spinal cord regions. Despite important advances in fluid and imaging biomarkers, the definitive diagnosis of most neurodegenerative diseases still relies on neuropathological examination. Not only has careful clinicopathological correlation shaped current clinical diagnostic criteria and informed our understanding of the natural history of neurodegenerative diseases, but it has also identified conditions with important public health implications, including variant Creutzfeldt-Jakob disease, iatrogenic amyloid-β and chronic traumatic encephalopathy. Neuropathological examination may also point to previously unsuspected genetic diagnoses with potential implications for living relatives. Moreover, detailed neuropathological assessment is crucial for research studies that rely on curated postmortem tissue to investigate the molecular mechanisms responsible for neurodegeneration and for biomarker discovery and validation. This review aims to elucidate the hallmark pathological features of neurodegenerative diseases commonly seen in general neurology clinics, such as Alzheimer's disease and Parkinson's disease; rare but well-known diseases, including progressive supranuclear palsy, corticobasal degeneration and multiple system atrophy and more recently described entities such as chronic traumatic encephalopathy and age-related tau astrogliopathy.

Multiple system atrophy with amyloid-β-predominant Alzheimer's disease neuropathologic change

Multiple system atrophy is a neurodegenerative disease with α-synuclein pathology predominating in the striatonigral and olivopontocerebellar systems. Mixed pathologies are considered to be of low frequency and mostly comprise primary age-related tauopathy or low levels of Alzheimer's disease-related neuropathologic change. Therefore, the concomitant presence of different misfolded proteins in the same brain region is less likely in multiple system atrophy. During the neuropathological evaluation of 21 consecutive multiple system atrophy cases, we identified four cases exhibiting an unusual discrepancy between high Thal amyloid-β phase and low transentorhinal Braak neurofibrillary tangle stage. We mapped α-synuclein pathology, measured the size and number of glial cytoplasmic inclusions and compared the amyloid-β peptides between multiple system atrophy and Alzheimer's disease. In addition, we performed α-synuclein seeding assay from the affected putamen samples. We performed genetic testing for APOE, MAPT, PSEN1, PSEN2 and APP. We refer to the four multiple system atrophy cases with discrepancy between amyloid-β and tau pathology as 'amyloid-β-predominant Alzheimer's disease neuropathologic change-multiple system atrophy' to distinguish these from multiple system atrophy with primary age-related tauopathy or multiple system atrophy with typical Alzheimer's disease neuropathologic change. As most multiple system atrophy cases with mixed pathologies reported in the literature, these cases did not show a peculiar clinical or MRI profile. Three amyloid-β-predominant Alzheimer's disease neuropathologic change-multiple system atrophy cases were available for genetic testing, and all carried the APOE ɛ4 allele. The extent and severity of neuronal loss and α-synuclein pathology were not different compared with typical multiple system atrophy cases. Analysis of amyloid-β peptides revealed more premature amyloid-β plaques in amyloid-β-predominant Alzheimer's disease neuropathologic change-multiple system atrophy compared with Alzheimer's disease. α-Synuclein seeding amplification assay showed differences in the kinetics in two cases. This study highlights a rare mixed pathology variant of multiple system atrophy in which there is an anatomical meeting point of amyloid-β and α-synuclein, i.e. the striatum or cerebellum. Since biomarkers are entering clinical practice, these cases will be recognized, and the clinicians have to be informed that the prognosis is not necessarily different than in pure multiple system atrophy cases but that the effect of potential α-synuclein-based therapies might be influenced by the co-presence of amyloid-β in regions where α-synuclein also aggregates. We propose that mixed pathologies should be interpreted not only based on differences in the clinical phenotype but also on whether protein depositions regionally overlap, potentially leading to a different response to α-synuclein-targeted therapies.

From Synaptic Physiology to Synaptic Pathology: The Enigma of α-Synuclein

Alpha-synuclein (α-syn) has gained significant attention due to its involvement in neurodegenerative diseases, particularly Parkinson's disease. However, its normal function in the human brain is equally fascinating. The α-syn protein is highly dynamic and can adapt to various conformational stages, which differ in their interaction with synaptic elements, their propensity to drive pathological aggregation, and their toxicity. This review will delve into the multifaceted role of α-syn in different types of synapses, shedding light on contributions to neurotransmission and overall brain function. We describe the physiological role of α-syn at central synapses, including the bidirectional interaction between α-syn and neurotransmitter systems.

[Cognitive impairment in multiple system atrophy - exclusion criteria or an integral part of the clinical picture?]

Multiple system atrophy (MSA) is a severe, orphan disease characterized by a steady increase in symptoms of parkinsonism, cerebellar disorders, and autonomic failure. In addition to autonomic failure, which is considered the defining symptom of this type of atypical parkinsonism, there are a range of other non-motor clinical manifestations, such as sleep disorders, pain syndrome, anxiety-depressive disorders, cognitive impairment (CI). CI, especially severe CI, has long been considered as a distinctive feature of MCA. Recently, there have been many clinical studies with pathomorphological or neuroimaging confirmation, indicating a high prevalence of cognitive disorders in MCA. In this article, we discuss the pathogenetic mechanisms of the development of MCA and CI in MCA, as well as the range of clinical manifestations of cognitive dysfunction.

Profiling neuroprotective potential of trehalose in animal models of neurodegenerative diseases: a systematic review

Trehalose, a unique nonreducing crystalline disaccharide, is a potential disease-modifying treatment for neurodegenerative diseases associated with protein misfolding and aggregation due to aging, intrinsic mutations, or autophagy dysregulation. This systematic review summarizes the effects of trehalose on its underlying mechanisms in animal models of selected neurodegenerative disorders (tau pathology, synucleinopathy, polyglutamine tract, and motor neuron diseases). All animal studies on neurodegenerative diseases treated with trehalose published in Medline (accessed via EBSCOhost) and Scopus were considered. Of the 2259 studies screened, 29 met the eligibility criteria. According to the SYstematic Review Center for Laboratory Animal Experiment (SYRCLE) risk of bias tool, we reported 22 out of 29 studies with a high risk of bias. The present findings support the purported role of trehalose in autophagic flux and protein refolding. This review identified several other lesser-known pathways, including modifying amyloid precursor protein processing, inhibition of reactive gliosis, the integrity of the blood-brain barrier, activation of growth factors, upregulation of the downstream antioxidant signaling pathway, and protection against mitochondrial defects. The absence of adverse events and improvements in the outcome parameters were observed in some studies, which supports the transition to human clinical trials. It is possible to conclude that trehalose exerts its neuroprotective effects through both direct and indirect pathways. However, heterogeneous methodologies and outcome measures across the studies rendered it impossible to derive a definitive conclusion. Translational studies on trehalose would need to clarify three important questions: 1) bioavailability with oral administration, 2) optimal time window to confer neuroprotective benefits, and 3) optimal dosage to confer neuroprotection.

The aging immune system in Alzheimer's and Parkinson's diseases

The neurodegenerative diseases Alzheimer's disease (AD) and Parkinson's disease (PD) both have a myriad of risk factors including genetics, environmental exposures, and lifestyle. However, aging is the strongest risk factor for both diseases. Aging also profoundly influences the immune system, with immunosenescence perhaps the most prominent outcome. Through genetics, mouse models, and pathology, there is a growing appreciation of the role the immune system plays in neurodegenerative diseases. In this review, we explore the intersection of aging and the immune system in AD and PD.

Heterogeneity of Multiple System Atrophy: An Update

Multiple system atrophy (MSA) is a fatal, rapidly progressing neurodegenerative disease of uncertain etiology, clinically characterized by various combinations of Levodopa unresponsive parkinsonism, cerebellar, autonomic and motor dysfunctions. The morphological hallmark of this α-synucleinopathy is the deposition of aberrant α-synuclein in both glia, mainly oligodendroglia (glial cytoplasmic inclusions /GCIs/) and neurons, associated with glioneuronal degeneration of the striatonigral, olivopontocerebellar and many other neuronal systems. Typical phenotypes are MSA with predominant parkinsonism (MSA-P) and a cerebellar variant (MSA-C) with olivocerebellar atrophy. However, MSA can present with a wider range of clinical and pathological features than previously thought. In addition to rare combined or "mixed" MSA, there is a broad spectrum of atypical MSA variants, such as those with a different age at onset and disease duration, "minimal change" or prodromal forms, MSA variants with Lewy body disease or severe hippocampal pathology, rare forms with an unusual tau pathology or spinal myoclonus, an increasing number of MSA cases with cognitive impairment/dementia, rare familial forms, and questionable conjugal MSA. These variants that do not fit into the current classification of MSA are a major challenge for the diagnosis of this unique proteinopathy. Although the clinical diagnostic accuracy and differential diagnosis of MSA have improved by using combined biomarkers, its distinction from clinically similar extrapyramidal disorders with other pathologies and etiologies may be difficult. These aspects should be taken into consideration when revising the current diagnostic criteria. This appears important given that disease-modifying treatment strategies for this hitherto incurable disorder are under investigation.

Elderly-Onset Multiple System Atrophy with Lewy Body Pathology: A Case Report

An 81-year-old woman presented with a 2-year history of progressive dysarthria and gait disturbance. Subsequently, she developed orthostatic hypotension, obstructive sleep apnea, right-sided resting tremor, and rigidity. Together with characteristic findings of imaging studies, she was diagnosed with multiple system atrophy (MSA). Despite progressive dysphagia and repeated choking episodes, the patient elected not to use artificial feeding or tracheostomy. She died suddenly at age 91 after 12 years of illness. The autopsy revealed neuropathological features of both MSA and of Parkinson's disease. The peripheral autonomic ganglia revealed both pre- and postganglionic involvement by synucleinopathy, which may have underscored the sudden death of the patient. The patient survived 10 years after onset, despite the presence of multiple poor prognostic factors in MSA including the onset of old age and early appearance of orthostatic hypotension and falls, in addition to the complication of PD pathology found by autopsy. Multidisciplinary team approach and her preserved cognitive function may have been contributory to the long-term survival.

Neuropathology of multiple system atrophy: Kurt Jellinger`s legacy

Multiple System Atrophy (MSA) is a rare, fatal neurodegenerative disorder. Its etiology and exact pathogenesis still remain poorly understood and currently no disease-modifying therapy is available to halt or slow down this detrimental neurodegenerative process. Hallmarks of the disease are α-synuclein rich glial cytoplasmic inclusions (GCIs). Neuropathologically, various degrees of striatonigral degeneration (SND) and olivopontocerebellar atrophy (OPCA) can be observed. Since the original descriptions of this multifaceted disorder, several steps forward have been made to clarify its neuropathological hallmarks and key pathophysiological mechanisms. The Austrian neuropathologist Kurt Jellinger substantially contributed to the understanding of the underlying neuropathology of this disease, to its standardized assessment and to a broad systematical clinic-pathological correlation. On the occasion of his 90th birthday, we reviewed the current state of the art in the field of MSA neuropathology, highlighting Prof. Jellinger’s substantial contribution.

Identification of multiple system atrophy mimicking Parkinson's disease or progressive supranuclear palsy

We studied a subset of patients with autopsy-confirmed multiple system atrophy who presented a clinical picture that closely resembled either Parkinson's disease or progressive supranuclear palsy. These mimics are not captured by the current diagnostic criteria for multiple system atrophy. Among 218 autopsy-proven multiple system atrophy cases reviewed, 177 (81.2%) were clinically diagnosed and pathologically confirmed as multiple system atrophy (i.e. typical cases), while the remaining 41 (18.8%) had received an alternative clinical diagnosis, including Parkinson's disease (i.e. Parkinson's disease mimics; n = 16) and progressive supranuclear palsy (i.e. progressive supranuclear palsy mimics; n = 17). We also reviewed the clinical records of another 105 patients with pathologically confirmed Parkinson's disease or progressive supranuclear palsy, who had received a correct final clinical diagnosis (i.e. Parkinson's disease, n = 35; progressive supranuclear palsy-Richardson syndrome, n = 35; and progressive supranuclear palsy-parkinsonism, n = 35). We investigated 12 red flag features that would support a diagnosis of multiple system atrophy according to the current diagnostic criteria. Compared with typical multiple system atrophy, Parkinson's disease mimics more frequently had a good levodopa response and visual hallucinations. Vertical gaze palsy and apraxia of eyelid opening were more commonly observed in progressive supranuclear palsy mimics. Multiple logistic regression analysis revealed an increased likelihood of having multiple system atrophy [Parkinson's disease mimic versus typical Parkinson's disease, odds ratio (OR): 8.1; progressive supranuclear palsy mimic versus typical progressive supranuclear palsy, OR: 2.3] if a patient developed any one of seven selected red flag features in the first 10 years of disease. Severe autonomic dysfunction (orthostatic hypotension and/or urinary incontinence with the need for a urinary catheter) was more frequent in clinically atypical multiple system atrophy than other parkinsonian disorders (Parkinson's disease mimic versus typical Parkinson's disease, OR: 4.1; progressive supranuclear palsy mimic versus typical progressive supranuclear palsy, OR: 8.8). The atypical multiple system atrophy cases more frequently had autonomic dysfunction within 3 years of symptom onset than the pathologically confirmed patients with Parkinson's disease or progressive supranuclear palsy (Parkinson's disease mimic versus typical Parkinson's disease, OR: 4.7; progressive supranuclear palsy mimic versus typical progressive supranuclear palsy, OR: 2.7). Using all included clinical features and 21 early clinical features within 3 years of symptom onset, we developed decision tree algorithms with combinations of clinical pointers to differentiate clinically atypical cases of multiple system atrophy from Parkinson's disease or progressive supranuclear palsy.

Sacral Reflex Characteristics of Patients with Multiple System Atrophy

Objectives

To observe and analyze the parameters of the sacral reflex and pudendal nerve somatosensory evoked potential (SSEP) in patients with multiple system atrophy (MSA) with respect to factors such as age, disease course, and subtype and provide evidence for the clinical diagnosis of MSA.

Materials and Methods

A total of 51 MSA patients and 30 healthy controls were selected from the First Affiliated Hospital of Wenzhou Medical University from May 2013 to November 2015. Electrophysiological sacral reflex detection and SSEP detection were performed using the Keypoint EMG/EP system. The extraction rate, latency, and amplitude of the sacral reflex and SSEP in the MSA group and control group were compared.

Results

The sacral reflex latency and amplitude in patients with MSA were statistically different from those of the healthy controls. The latency of sacral reflex increases with the prolongation of the disease course, and the amplitude and initiation rate decrease with the prolongation of the disease course. There was no significant difference in sacral reflex latency and amplitude between MSA patients of different ages and subtypes. There was no significant difference in the latency or amplitude of SSEP between the MSA group and healthy control group.

Conclusions

The latency of sacral reflex increases with the prolongation of the disease course, and the amplitude and extraction rate decrease with the prolongation of the disease course. There was no significant difference in the parameters of sacral reflex between young MSA patients and elderly patients. And there was no statistically significant difference between MSA-P subtypes and MSA-C subtypes. This trial is registered with ISRCTNCR2009041.

Neuropathological findings in multiple system atrophy with cognitive impairment

Cognitive impairment (CI), previously considered an exclusion criterium for the diagnosis of multiple system atrophy (MSA) according to the second consensus criteria, is not uncommon in MSA. Mild cognitive impairment (MCI) has been reported in up to 47% of MSA patients, while severe dementia is rare. We related clinical CI with neuropathological findings in 48 autopsy-proven cases of MSA. This retrospective study included 33 parkinsonism predominant MSA (MSA-P), and 15 cerebellar ataxia-predominant MSA (MSA-C) cases (mean age at death 60.5 ± 7.8; range 46-82 years). Cognitive state was assessed from hospital charts, however, without comprehensive neuropsychological testing. Neuropathological examination, in addition to grading of the MSA pathologies, included semiquantitative assessment of Lewy and Alzheimer-related co-pathologies. Their incidence was compared with 143 age-matched controls (mean age 60.5 ± 7.6 years). MCI reported in ten cases (20.8%) was associated with moderate cortical tau pathology in only three; moderate CI in seven patients (14.5%) was associated with cortical amyloid plaques and moderate cortical tau pathology in six each, and one with probable primary age-related tauopathy (PART); a female aged 82 years with severe dementia showed fully developed Alzheimer disease. Cortical amyloid plaques, observed in eight cases, three of them without tau pathology, were associated with clinical MCI, as was cortical Lewy pathology in five. Two cases with cortical Lewy pathology and neuritic Braak stages II and III, and three with Braak stage IV, without cortical Lewy bodies, had shown moderate CI. Cortical Lewy pathology observed in four cases was not associated with clinical CI. 77.1% of the MSA cases were free of Alzheimer-type lesions, compared to 42% of controls; while Lewy pathology in the MSA cohort (22.9%) was significantly higher than in the control group (8.4%) both p < 0.001. Mild-to-moderate CI, reported in 35.3% of MSA patients, being significantly older than those without CI, were frequently associated with cortical Alzheimer (Braak stages III and IV) and Lewy pathologies, while only one with severe dementia had fully developed Alzheimer disease. In view of these findings in a limited series of MSA patients, further studies to elucidate the pathological basis of cognitive impairment in MSA are warranted.

Clinicopathologic and genetic features of multiple system atrophy with Lewy body disease

Background: Abnormal aggregates of α‐synuclein are pathologic hallmarks of multiple system atrophy (MSA) and Lewy body disease (LBD). LBD sometimes coexists with MSA, but the impact of co‐pathology, particularly diffuse LBD, on presentation of MSA has not been studied. We aimed to determine the frequency and clinicopathologic features of MSA with LBD (MSA+LBD). Methods: Using hematoxylin & eosin and α‐synuclein‐immunostained slides, we assessed the distribution and severity of LBD in 230 autopsy‐confirmed MSA patients collected from 1998 to 2018. Alzheimer‐type pathology was assessed to assign the likelihood of clinical presentations of dementia with Lewy body (DLB) using the consensus criteria for DLB. We reviewed medical records to characterize clinicopathologic features of MSA+LBD. Genetic risk factors for LBD, including APOE ε4 allele and mutations in GBA, SNCA, LRRK2, and VPS35, were analyzed. Results: LBD was observed in 11 MSA patients (5%); seven were brainstem type, three were transitional type, and one was diffuse type. The latter four had an intermediate or high likelihood of DLB. Three of the four had an antemortem diagnosis of Parkinson’s disease with dementia (PDD) or clinically probable DLB. Two patients had neuronal loss in the substantia nigra, but not in striatal or olivocerebellar systems with widespread glial cytoplasmic inclusions, consistent with minimal change MSA. In these cases, LBD was considered the primary pathology, and MSA was considered coincidental. APOE ε4 allele frequency was not different between MSA+LBD and MSA without LBD. Two of nine MSA+LBD patients had a risk variant of GBA (p.T408M and p.E365K). Conclusions: Although rare, MSA with transitional or diffuse LBD can develop clinical features of PDD or DLB. Minimal change MSA can be interpreted as a coincidental, but distinct, α‐synucleinopathy in a subset of patients with diffuse LBD.

Neuropathological correlates of parkinsonian disorders in a large Dutch autopsy series

The clinical diagnosis in patients with parkinsonian disorders can be challenging, and a definite diagnosis requires neuropathological confirmation. The aim of this study was to examine whether a clinical diagnosis of Parkinson’s disease (PD) and atypical parkinsonian disorders predict the presence of Lewy pathology (LP) and concomitant neuropathological lesions.

We included 293 donors with a history of parkinsonism without dementia at disease onset, collected by the Netherlands Brain Bank (NBB) from 1989 to 2015. We retrospectively categorized donors according the International Parkinson and Movement Disorder Society clinical diagnostic criteria for PD (MDS-PD criteria) as ‘not PD’, ‘probable PD’ or ‘established PD’. We compared the final clinical diagnosis to presence of neuropathological lesions as defined by BrainNet Europe and National Institute on Aging – Alzheimer's Association guidelines.

LP was present in 150 out of 176 donors (85%) with a clinical diagnosis of PD, in 8 out of 101 donors (8%) with atypical parkinsonian disorders and in 4 out of 16 donors (25%) without a definite clinical diagnosis. Independent from age at death, stages of amyloid-β, but not neurofibrillary tau or neuritic plaques, were higher in donors with LP compared to other types of pathology (p = 0.009). The MDS-PD criteria at a certainty level of ‘probable PD’ predicted presence of LP with a diagnostic accuracy of 89.3%. Among donors with LP, ‘established PD’ donors showed similar Braak α-synuclein stages and stages of amyloid-β, neurofibrillary tau and neuritic plaques compared to ‘not PD’ or ‘probable PD’ donors.

In conclusion, both a clinical diagnosis of PD as well as MDS-PD criteria accurately predicted presence of LP in NBB donors. LP was associated with more widespread amyloid-β pathology, suggesting a link between amyloid-β accumulation and LP formation.

Clinical and Imaging Features of Multiple System Atrophy: Challenges for an Early and Clinically Definitive Diagnosis

Multiple system atrophy (MSA) is an adult-onset, progressive neurodegenerative disorder. Patients with MSA show various phenotypes during the course of their illness, including parkinsonism, cerebellar ataxia, autonomic failure, and pyramidal signs. Patients with MSA sometimes present with isolated autonomic failure or motor symptoms/ signs. The median duration from onset to the concomitant appearance of motor and autonomic symptoms is approximately 2 years but can range up to 14 years. As the presence of both motor and autonomic symptoms is essential for the current diagnostic criteria, early diagnosis is difficult when patients present with isolated autonomic failure or motor symptoms/signs. In contrast, patients with MSA may show severe autonomic failure and die before the presentation of motor symptoms/signs, which are currently required for the diagnosis of MSA. Recent studies have also revealed that patients with MSA may show nonsupporting features of MSA such as dementia, hallucinations, and vertical gaze palsy. To establish early diagnostic criteria and clinically definitive categorization for the successful development of disease-modifying therapy or symptomatic interventions for MSA, research should focus on the isolated phase and atypical symptoms to develop specific clinical, imaging, and fluid biomarkers that satisfy the requirements for objectivity, for semi- or quantitative measurements, and for uncomplicated, worldwide availability. Several novel techniques, such as automated compartmentalization of the brain into multiple parcels for the quantification of gray and white matter volumes on an individual basis and the visualization of α-synuclein and other candidate serum and cerebrospinal fluid biomarkers, may be promising for the early and clinically definitive diagnosis of MSA.

Very old onset parkinsonism: A clinical-pathological study

BACKGROUND

With increasing age of the world population, the number of parkinsonian patients with disease onset in very old age is expected to increase. Information about the clinical and morphological phenotype of very old age onset parkinsonism is poor, and only three autopsy-confirmed studies of parkinsonian patients of 80 years and older onset are available.

METHODS

A retrospective autopsy study of 345 patients clinically diagnosed as Parkinson disease (PD) included 90 cases with disease onset ≥80 years).

RESULTS

Clinically, the majority (60%) presented with a rigid-akinetic phenotype, 13.3% with mixed tremor, akinesia and rigidity, 8.9% tremor-dominant type, 7.8% with tremor + rigidity, 5.6% with tremor-akinesia, and 4.4% with pure akinesia or gait disorder. Additional 8.9% developed hemiparesis, and 80% were demented. In only about 49% of the patients, positive reaction to l-dopa therapy was reported. The progress of disease was accelerated, and survival time (4.34 ± 2.95 SD) was significantly shorter than in younger onset groups. At post mortem examination, only 21 cases (23.3%) revealed Lewy body disease of brainstem type (PD) alone, 44 cases (48.9%) had PD plus Alzheimer disease (AD) (including 6 cases of Lewy body variant of AD). 11% had PD plus cerebrovascular lesions, 6 cases (6.7%) were cerebrovascular disorders and 8 cases (8.9%) were other neurodegenerative diseases (AD, single cases of multiple system atrophy, progressive supranuclear palsy).

CONCLUSION

The present and other data confirm the clinical and morphological heterogeneity of parkinsonism with shorter survival in the octogenarian population.

Deep brain stimulation does not enhance neuroinflammation in multiple system atrophy

Slowly progressive, levodopa-responsive multiple system atrophy (MSA) may be misdiagnosed as Parkinson's disease (PD). Deep brain stimulation (DBS) is mostly ineffective in these patients and may even worsen the clinical course. Here we assessed whether neuropathological differences between patients with MSA who were treated with DBS of the subthalamic nucleus because of a misleading clinical presentation and typical disease cases may explain the more benign disease course of the former, and also the rapid clinical decline after surgery. The post-mortem assessment included the subthalamic nucleus, the globus pallidus, the thalamus and the putamen in five patients with MSA who received DBS and nine typical disease cases. There was no evidence for distinct neuroinflammatory profiles between both groups that could be related to the surgical procedure or that could explain the rapid clinical progression during DBS. Patients who received deep brain stimulation displayed a higher proportion of α-synuclein bearing neuronal cytoplasmic inclusions in the putamen compared with typical cases, while the number of surviving neurons was not different between groups. Our findings suggest that DBS does not induce neuroinflammatory changes in patients with MSA, at least several years after the surgery. We further hypothesize that the peculiar pattern of α-synuclein pathology may contribute to differences in the clinical phenotype, with a greater proportion of neuronal inclusions in the putamen being associated to a milder, "PD-like" phenotype with sustained levodopa response and slower disease progression.

α-Synuclein: Multiple System Atrophy Prions

Multiple system atrophy (MSA) is a rapidly progressive neurodegenerative disease arising from the misfolding and accumulation of the protein α-synuclein in oligodendrocytes, where it forms glial cytoplasmic inclusions (GCIs). Several years of studying synthetic α-synuclein fibrils has provided critical insight into the ability of α-synuclein to template endogenous protein misfolding, giving rise to fibrillar structures capable of propagating from cell to cell. However, more recent studies with MSA-derived α-synuclein aggregates have shown that they have a similar ability to undergo template-directed propagation, like PrP prions. Almost 20 years after α-synuclein was discovered as the primary component of GCIs, α-synuclein aggregates isolated from MSA patient samples were shown to infect cultured mammalian cells and also to transmit neurological disease to transgenic mice. These findings argue that α-synuclein becomes a prion in MSA patients. In this review, we discuss the in vitro and in vivo data supporting the recent classification of MSA as a prion disease.

Mitochondrial dysfunction and altered ribostasis in hippocampal neurons with cytoplasmic inclusions of multiple system atrophy

Multiple system atrophy (MSA) is a sporadic adult-onset neurodegenerative disease. It has recently been shown that patients with MSA accompanied by cognitive decline display numerous neuronal cytoplasmic inclusions (NCIs) in the limbic neurons. We examined potential mechanisms underlying the formation of these NCIs by determining of mitochondrial function and statuses of RNA processing by analyzing 12 pathologically confirmed cases of MSA. Among them, four had cognitive impairment Semiquantitative evaluation using immunohistochemistry analyses revealed a significantly greater NCI burden in the hippocampal cornu ammonis 1 (CA1) subfield, subiculum, and amygdala in the cases with cognitive impairments compared with those without cognitive impairment. Immunofluorescent staining revealed that limbic neurons with NCIs often accelerated production of reactive oxygen species (ROS) and degraded mitochondrial quality control. Immunofluorescent staining also revealed that neurons with these NCIs translocated heterogeneous nuclear ribonucleoprotein A1 (HNRNPA1) from the nucleus and aggregated abnormally at the perinuclear rim. Since the NCIs in the hippocampal neurons of MSA with cognitive impairments were more numerous, the neuronal mitochondrial dysfunction and altered ribostasis observed in NCI formation may be involved in the hippocampal degeneration of MSA.

Recent advances in neuropathology, biomarkers and therapeutic approach of multiple system atrophy

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterised by a variable combination of autonomic failure, levodopa-unresponsive parkinsonism, cerebellar ataxia and pyramidal symptoms. The pathological hallmark is the oligodendrocytic glial cytoplasmic inclusion (GCI) consisting of α-synuclein; therefore, MSA is included in the category of α-synucleinopathies. MSA has been divided into two clinicopathological subtypes: MSA with predominant parkinsonism and MSA with predominant cerebellar ataxia, which generally correlate with striatonigral degeneration and olivopontocerebellar atrophy, respectively. It is increasingly recognised, however, that clinical and pathological features of MSA are broader than previously considered.In this review, we aim to describe recent advances in neuropathology of MSA from a review of the literature and from information derived from review of nearly 200 definite MSA cases in the Mayo Clinic Brain Bank. In light of these new neuropathological findings, GCIs and neuronal cytoplasmic inclusions play an important role in clinicopathological correlates of MSA. We also focus on clinical diagnostic accuracy and differential diagnosis of MSA as well as candidate biomarkers. We also review some controversial topics in MSA. Cognitive impairment, which has been a non-supporting feature of MSA, is considered from both clinical and pathological perspectives. The cellular origin of α-synuclein in GCI and a 'prion hypothesis' are discussed. Finally, completed and ongoing clinical trials targeting disease modification, including immunotherapy, are summarised.

Multiple System Atrophy: An Oligodendroglioneural Synucleinopathy1

Multiple system atrophy (MSA) is an orphan, fatal, adult-onset neurodegenerative disorder of uncertain etiology that is clinically characterized by various combinations of parkinsonism, cerebellar, autonomic, and motor dysfunction. MSA is an α-synucleinopathy with specific glioneuronal degeneration involving striatonigral, olivopontocerebellar, and autonomic nervous systems but also other parts of the central and peripheral nervous systems. The major clinical variants correlate with the morphologic phenotypes of striatonigral degeneration (MSA-P) and olivopontocerebellar atrophy (MSA-C). While our knowledge of the molecular pathogenesis of this devastating disease is still incomplete, updated consensus criteria and combined fluid and imaging biomarkers have increased its diagnostic accuracy. The neuropathologic hallmark of this unique proteinopathy is the deposition of aberrant α-synuclein in both glia (mainly oligodendroglia) and neurons forming glial and neuronal cytoplasmic inclusions that cause cell dysfunction and demise. In addition, there is widespread demyelination, the pathogenesis of which is not fully understood. The pathogenesis of MSA is characterized by propagation of misfolded α-synuclein from neurons to oligodendroglia and cell-to-cell spreading in a "prion-like" manner, oxidative stress, proteasomal and mitochondrial dysfunction, dysregulation of myelin lipids, decreased neurotrophic factors, neuroinflammation, and energy failure. The combination of these mechanisms finally results in a system-specific pattern of neurodegeneration and a multisystem involvement that are specific for MSA. Despite several pharmacological approaches in MSA models, addressing these pathogenic mechanisms, no effective neuroprotective nor disease-modifying therapeutic strategies are currently available. Multidisciplinary research to elucidate the genetic and molecular background of the deleterious cycle of noxious processes, to develop reliable biomarkers and targets for effective treatment of this hitherto incurable disorder is urgently needed.

Multiple system atrophy: pathogenic mechanisms and biomarkers

Multiple system atrophy (MSA) is a unique proteinopathy that differs from other α-synucleinopathies since the pathological process resulting from accumulation of aberrant α-synuclein (αSyn) involves the oligodendroglia rather than neurons, although both pathologies affect multiple parts of the brain, spinal cord, autonomic and peripheral nervous system. Both the etiology and pathogenesis of MSA are unknown, although animal models have provided insight into the basic molecular changes of this disorder. Accumulation of aberrant αSyn in oligodendroglial cells and preceded by relocation of p25α protein from myelin to oligodendroglia results in the formation of insoluble glial cytoplasmic inclusions that cause cell dysfunction and demise. These changes are associated with proteasomal, mitochondrial and lipid transport dysfunction, oxidative stress, reduced trophic transport, neuroinflammation and other noxious factors. Their complex interaction induces dysfunction of the oligodendroglial-myelin-axon-neuron complex, resulting in the system-specific pattern of neurodegeneration characterizing MSA as a synucleinopathy with oligodendroglio-neuronopathy. Propagation of modified toxic αSyn species from neurons to oligodendroglia by "prion-like" transfer and its spreading associated with neuronal pathways result in a multi-system involvement. No reliable biomarkers are currently available for the clinical diagnosis and prognosis of MSA. Multidisciplinary research to elucidate the genetic and molecular background of the deleterious cycle of noxious processes, to develop reliable diagnostic biomarkers and to deliver targets for effective treatment of this hitherto incurable disorder is urgently needed.

Expanding the spectrum of neuronal pathology in multiple system atrophy

Multiple system atrophy is a sporadic alpha-synucleinopathy that typically affects patients in their sixth decade of life and beyond. The defining clinical features of the disease include progressive autonomic failure, parkinsonism, and cerebellar ataxia leading to significant disability. Pathologically, multiple system atrophy is characterized by glial cytoplasmic inclusions containing filamentous alpha-synuclein. Neuronal inclusions also have been reported but remain less well defined. This study aimed to further define the spectrum of neuronal pathology in 35 patients with multiple system atrophy (20 male, 15 female; mean age at death 64.7 years; median disease duration 6.5 years, range 2.2 to 15.6 years). The morphologic type, topography, and frequencies of neuronal inclusions, including globular cytoplasmic (Lewy body-like) neuronal inclusions, were determined across a wide spectrum of brain regions. A correlation matrix of pathologic severity also was calculated between distinct anatomic regions of involvement (striatum, substantia nigra, olivary and pontine nuclei, hippocampus, forebrain and thalamus, anterior cingulate and neocortex, and white matter of cerebrum, cerebellum, and corpus callosum). The major finding was the identification of widespread neuronal inclusions in the majority of patients, not only in typical disease-associated regions (striatum, substantia nigra), but also within anterior cingulate cortex, amygdala, entorhinal cortex, basal forebrain and hypothalamus. Neuronal inclusion pathology appeared to follow a hierarchy of region-specific susceptibility, independent of the clinical phenotype, and the severity of pathology was duration-dependent. Neuronal inclusions also were identified in regions not previously implicated in the disease, such as within cerebellar roof nuclei. Lewy body-like inclusions in multiple system atrophy followed the stepwise anatomic progression of Lewy body-spectrum disease inclusion pathology in 25.7% of patients with multiple system atrophy, including a patient with visual hallucinations. Further, the presence of Lewy body-like inclusions in neocortex, but not hippocampal alpha-synuclein pathology, was associated with cognitive impairment (P = 0.002). However, several cases had the presence of isolated Lewy body-like inclusions at atypical sites (e.g. thalamus, deep cerebellar nuclei) that are not typical for Lewy body-spectrum disease. Finally, interregional correlations (rho ≥ 0.6) in pathologic glial and neuronal lesion burden suggest shared mechanisms of disease progression between both discrete anatomic regions (e.g. basal forebrain and hippocampus) and cell types (neuronal and glial inclusions in frontal cortex and white matter, respectively). These findings suggest that in addition to glial inclusions, neuronal pathology plays an important role in the developmental and progression of multiple system atrophy.

Diagnosis and differential diagnosis of MSA: boundary issues

Because the progression of multiple system atrophy (MSA) is usually rapid and there still is no effective cause-related therapy, early and accurate diagnosis is important for the proper management of patients as well as the development of neuroprotective agents. However, despite the progression in the field of MSA research in the past few years, the diagnosis of MSA in clinical practice still relies largely on clinical features and there are limitations in terms of sensitivity and specificity, especially in the early course of the disease. Furthermore, recent pathological, clinical, and neuroimaging studies have shown that (1) MSA can present with a wider range of clinical and pathological features than previously thought, including features considered atypical for MSA; thus, MSA can be misdiagnosed as other diseases, and conversely, disorders with other etiologies and pathologies can be clinically misdiagnosed as MSA; and (2) several investigations may help to improve the diagnosis of MSA in clinical practice. These aspects should be taken into consideration when revising the current diagnostic criteria. This is especially true given that disease-modifying treatments for MSA are under investigation.

Amyloid PET imaging: applications beyond Alzheimer's disease

As a biomarker of beta-amyloid, positron emission tomography (PET) amyloid imaging offers a unique opportunity to detect the presence of this protein in the human body during life. Besides Alzheimer's disease (AD), deposits of beta-amyloid in the brain are also present in other neurodegenerative diseases associated to dementia, such as Parkinson's disease and dementia with Lewy bodies, as well as in other processes affecting brain function, such as cerebral amyloid angiopathy, brain trauma, Down's syndrome and meningiomas, as shown by post-mortem pathology studies. Furthermore, in systemic amyloidosis other organs besides the brain are affected, and amyloid PET imaging may be suitable for the identification of these extra-cerebral amyloid depositions. Finally, the potential use of amyloid PET tracer accumulation in cerebral white matter (WM) as a marker of myelin is being investigated, leading to some promising results in patients with WM lesions and multiple sclerosis. In this article, a review of the ongoing research pointing to a broader application of amyloid PET imaging in clinical practice beyond AD is provided.

Multiple system atrophy as emerging template for accelerated drug discovery in α-synucleinopathies

There is evidence that the α-synucleinopathies Parkinson's disease (PD) and the Parkinson variant of multiple system atrophy (MSA-P) overlap at multiple levels. Both disorders are characterized by deposition of abnormally phosphorylated fibrillar α-synuclein within the central nervous system suggesting shared pathophysiological mechanisms. Despite the considerable clinical overlap in the early disease stages, MSA-P, in contrast to PD, is fatal and rapidly progressive. Moreover recent clinical studies have shown that surrogate markers of disease progression can be quantified easily and may reliably depict the rapid course of MSA. We therefore posit that, MSA-P may be exploited as a filter barrier in the development of disease-modifying therapeutic strategies targeting common pathophysiological mechanisms of α-synucleinopathies. This approach might reduce the number of negative phase III clinical trials, and, in turn, shift the available resources to earlier development stages, thereby increasing the number of candidate compounds validated.

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α-synucleinopathies overlap at multiple levels.

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α-synucleinopathies are characterized by an abnormal deposition of α-synuclein.

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Validated surrogate markers in MSA reliably monitor disease progression.

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MSA may serve as a template disease for other α-synucleinopathies.

[Cellular pathology of neurodegenerative disorders]

Common cellular and molecular mechanisms including protein aggregation and inclusion body formation are involved in many neurodegenerative diseases. α-Synuclein is a major component of Lewy bodies in Parkinson's disease (PD) as well as in glial cytoplasmic inclusions in multiple system atrophy (MSA). Tau is a principal component of neurofibrillary and glial tangles in tauopathies. Recently, TDP-43 was identified as a component of ubiquitinated inclusions in amyotrophic lateral sclerosis and frontotemporal lobar degeneration. PD is traditionally considered a movement disorder with hallmark lesions in the brainstem pigmented nuclei. However, pathological changes occur in widespread regions of the central and peripheral nervous systems in this disease. Furthermore, primary glial involvement ("gliodegeneration") can be observed in PD and MSA as well as in tauopathy. The present article reviews abnormal protein accumulation and inclusion body formation inside and outside the central nervous system.

Inflammation and adaptive immunity in Parkinson's disease

The immune system is designed to protect the host from infection and injury. However, when an adaptive immune response continues unchecked in the brain, the proinflammatory innate microglial response leads to the accumulation of neurotoxins and eventual neurodegeneration. What drives such responses are misfolded and nitrated proteins. Indeed, the antigen in Parkinson's disease (PD) is an aberrant self-protein, although the adaptive immune responses are remarkably similar in a range of diseases. Ingress of lymphocytes and chronic activation of glial cells directly affect neurodegeneration. With this understanding, new therapies aimed at modulating the immune system's response during PD could lead to decreased neuronal loss and improved clinical outcomes for disease.

Parkinson's disease: from genetics to treatments

Parkinson's disease (PD) is a common neurodegenerative disease and typically presents with tremor, rigidity, bradykinesia, and postural instability. The hallmark pathological features of PD are loss of dopaminergic neurons in the substantia nigra (SN) and the presence of neuronal intracellular Lewy body (LB) inclusions. In general, PD is sporadic; however, familial PD, while uncommon, can be inherited in an autosomal dominant (AD) or autosomal recessive (AR) manner. The molecular investigations of proteins encoded by PD-linked genes have clarified that ADPD is associated with α-synuclein and LRRK2, while ARPD is linked to Parkin, PINK1, DJ1, and ATP13A2. Understanding these genes can bring insights into this disease and create possible genetic tests for early diagnosis. Long-term pharmacological treatment is so far disappointing, probably due to unwanted complications and decreasing drug efficacy. Several strategies have been proposed and tested as alternatives for PD. Cellular transplantation of dopamine-secreting stem cells opens the door to new therapeutic avenues for restoration of the functions of degenerative and/or damaged neurons in PD.

Amyloid and glucose imaging in dementia with Lewy bodies and multiple systems atrophy

BACKGROUND

Multiple Systems Atrophy (MSA) and Dementia with Lewy bodies (DLB) can present with both REM behavior disorder and severe autonomic dysfunction. In rare occasions, patients with MSA progress to cognitive impairment and even dementia. Positron emission topography (PET) imaging using both the amyloid ligand Pittsburgh Compound B (11C-PiB) and 18 flurodeoxyglucose (18F-FDG) was used to ascertain the presence of amyloid and pattern of glucose metabolic derangement in both disorders.

METHODS

Patients diagnosed with probable DLB or MSA, with clinical symptoms of either REM Behavior Disorder (RBD), Parkinsonism, or dysautonomia were prospectively identified. All underwent both 11C-PiB and 18F-FDG PET imaging. Statistical comparison between DLB, MSA, and normal controls was performed.

RESULTS

Six patients, 3 with DLB, 2 with Parkinson predominant MSA (MSA-P), and 1 with cerebellar predominant MSA (MSA-C) were identified. Increased level of PiB retention was noted in all patients diagnosed with DLB, but was absent in MSA. In those with DLB, glucose hypometabolism corresponded with regions of amyloid presence, and included prefrontal, parietotemporal, occipital and primary visual cortex regions. MSA patients were distinguished by cerebellar glucose hypometabolism.

CONCLUSIONS

These findings emphasize the distinguishing characteristics between the alpha-synuclein related disorders of DLB and MSA. The absence of amyloid in the cases of MSA is a possible distinguishing characteristic of the disorder.

Protein coding of neurodegenerative dementias: the neuropathological basis of biomarker diagnostics

Neuropathological diagnosis of neurodegenerative dementias evolved by adapting the results of neuroanatomy, biochemistry, and cellular and molecular biology. Milestone findings of intra- and extracellular argyrophilic structures, visualizing protein deposition, initiated a protein-based classification. Widespread application of immunohistochemical and biochemical investigations revealed that (1) there are modifications of proteins intrinsic to disease (species that are phosphorylated, nitrated, oligomers, proteinase-resistant, with or without amyloid characteristics; cleavage products), (2) disease forms characterized by the accumulation of a single protein only are rather the exception than the rule, and (3) some modifications of proteins elude present neuropathological diagnostic procedures. In this review, we summarize how neuropathology, together with biochemistry, contributes to disease typing, by demonstrating a spectrum of disorders characterized by the deposition of various modifications of various proteins in various locations. Neuropathology may help to elucidate how brain pathologies alter the detectability of proteins in body fluids by upregulation of physiological forms or entrapment of different proteins. Modifications of at least the five most relevant proteins (amyloid-beta, prion protein, tau, alpha-synuclein, and TDP-43), aided by analysis of further "attracted" proteins, are pivotal to be evaluated simultaneously with different methods. This should complement the detection of biomarkers associated with pathogenetic processes, and also neuroimaging and genetic analysis, in order to obtain a highly personalized diagnostic profile. Defining clusters of patients based on the patterns of protein deposition and immunohistochemically or biochemically detectable modifications of proteins ("codes") may have higher prognostic predictive value, may be useful for monitoring therapy, and may open new avenues for research on pathogenesis.

Absence of alpha-synuclein pathology in postencephalitic parkinsonism

Postencephalitic parkinsonism (PEP), a chronic complication of encephalitis lethargica, is a tauopathy characterized by multisystem neuronal loss and gliosis with widespread neurofibrillary lesions composed of both 3- and 4-repeat (3R and 4R) tau isoforms. Previous immunohistochemical studies in a small number of PEP cases demonstrated absence of Lewy bodies as well as the lack of other alpha-synuclein pathology, classifying PEP as a "pure" tauopathy. Neuropathologic examination of 10 brains with clinico-pathologically verified PEP confirmed widespread neurodegeneration in subcortical and brainstem areas associated with multifocal neurofibrillary pathology comprising both 3R and 4R tau. Very rare beta-amyloid deposits were observed in two elderly patients, while Lewy bodies and neurites or any other alpha-synuclein deposits were completely absent. The causes and molecular background of total absence of alpha-synuclein pathology in PEP, in contrast to most other tauopathies, remain as unknown as the pathogenesis of PEP.