The corticobasal syndrome-Alzheimer's disease conundrum

Boundary-based registration improves sensitivity for detecting hypoperfusion in sporadic frontotemporal lobar degeneration

Introduction

Frontotemporal lobar degeneration (FTLD) is associated with FTLD due to tau (FTLD-tau) or TDP (FTLD-TDP) inclusions found at autopsy. Arterial Spin Labeling (ASL) MRI is often acquired in the same session as a structural T1-weighted image (T1w), enabling detection of regional changes in cerebral blood flow (CBF). We hypothesize that ASL-T1w registration with more degrees of freedom using boundary-based registration (BBR) will better align ASL and T1w images and show increased sensitivity to regional hypoperfusion differences compared to manual registration in patient participants. We hypothesize that hypoperfusion will be associated with a clinical measure of disease severity, the FTLD-modified clinical dementia rating scale sum-of-boxes (FTLD-CDR).

Materials and methods

Patients with sporadic likely FTLD-tau (sFTLD-tau; N = 21), with sporadic likely FTLD-TDP (sFTLD-TDP; N = 14), and controls (N = 50) were recruited from the Connectomic Imaging in Familial and Sporadic Frontotemporal Degeneration project (FTDHCP). Pearson's Correlation Coefficients (CC) were calculated on cortical vertex-wise CBF between each participant for each of 3 registration methods: (1) manual registration, (2) BBR initialized with manual registration (manual+BBR), (3) and BBR initialized using FLIRT (FLIRT+BBR). Mean CBF was calculated in the same regions of interest (ROIs) for each registration method after image alignment. Paired t-tests of CC values for each registration method were performed to compare alignment. Mean CBF in each ROI was compared between groups using t-tests. Differences were considered significant at p < 0.05 (Bonferroni-corrected). We performed linear regression to relate FTLD-CDR to mean CBF in patients with sFTLD-tau and sFTLD-TDP, separately (p < 0.05, uncorrected).

Results

All registration methods demonstrated significant hypoperfusion in frontal and temporal regions in each patient group relative to controls. All registration methods detected hypoperfusion in the left insular cortex, middle temporal gyrus, and temporal pole in sFTLD-TDP relative to sFTLD-tau. FTLD-CDR had an inverse association with CBF in right temporal and orbitofrontal ROIs in sFTLD-TDP. Manual+BBR performed similarly to FLIRT+BBR.

Discussion

ASL is sensitive to distinct regions of hypoperfusion in patient participants relative to controls, and in patients with sFTLD-TDP relative to sFTLD-tau, and decreasing perfusion is associated with increasing disease severity, at least in sFTLD-TDP. BBR can register ASL-T1w images adequately for controls and patients.

Evaluating the Effect of Alzheimer's Disease-Related Biomarker Change in Corticobasal Syndrome and Progressive Supranuclear Palsy

OBJECTIVES

To evaluate the effect of Alzheimer's disease (AD) -related biomarker change on clinical features, brain atrophy and functional connectivity of patients with corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP).

METHODS

Data from patients with a clinical diagnosis of CBS, PSP, and AD and healthy controls were obtained from the 4-R-Tauopathy Neuroimaging Initiative 1 and 2, the Alzheimer's Disease Neuroimaging Initiative, and a local cohort from the Toronto Western Hospital. Patients with CBS and PSP were divided into AD-positive (CBS/PSP-AD) and AD-negative (CBS/PSP-noAD) groups based on fluid biomarkers and amyloid PET scans. Cognitive, motor, and depression scores; AD fluid biomarkers (cerebrospinal p-tau, t-tau, and amyloid-beta, and plasma ptau-217); and neuroimaging data (amyloid PET, MRI and fMRI) were collected. Clinical features, whole-brain gray matter volume and functional networks connectivity were compared across groups.

RESULTS

Data were analyzed from 87 CBS/PSP-noAD and 23 CBS/PSP-AD, 18 AD, and 30 healthy controls. CBS/PSP-noAD showed worse performance in comparison to CBS/PSP-AD in the PSPRS [mean(SD): 34.8(15.8) vs 23.3(11.6)] and the UPDRS scores [mean(SD): 34.2(17.0) vs 21.8(13.3)]. CBS/PSP-AD demonstrated atrophy in AD signature areas and brainstem, while CBS/PSP-noAD patients displayed atrophy in frontal and temporal areas, globus pallidus, and brainstem compared to healthy controls. The default mode network showed greatest disconnection in CBS/PSP-AD compared with CBS/PSP-no AD and controls. The thalamic network connectivity was most affected in CBS/PSP-noAD.

INTERPRETATION

AD biomarker positivity may modulate the clinical presentation of CBS/PSP, with evidence of distinctive structural and functional brain changes associated with the AD pathology/co-pathology. ANN NEUROL 2024;96:99-109.

Diagnosis and Management of Progressive Corticobasal Syndrome

Purpose of review

The purpose of this review is to discuss the clinical, radiological, and neuropathological heterogeneity of corticobasal syndrome (CBS), which can complicate the determination of underlying etiology and lead to inaccurate treatment decisions. Though the most common diagnosis is corticobasal degeneration (CBD), the spectrum of underlying pathologies expands beyond CBD and can overlap with other neurodegenerative diseases and even the neuroimmunology field. We will review possible clinical presentations and cues that can point towards the etiology. We will also discuss the most recent available biomarkers to facilitate a more accurate diagnosis. Additionally, we will examine current and future potential therapeutic options.

Recent findings

The range of available fluid and neuroimaging biomarkers is increasing and some are already being used in clinical practice. While the treatment of neurodegenerative diseases is largely aimed at managing symptoms, early detection and accurate diagnosis are crucial for initiating early management and enrollment in clinical trials. The recent approval of a disease-modifying therapy for Alzheimer's disease (AD) has raised hopes for the development of more therapeutic options for other proteinopathies. Several candidates are currently being studied in clinical trial pipelines, particularly those targeting tau pathology.

Summary

Recent advancements in understanding the genetic and neuropathological diversity of CBS, along with the promising development of fluid and imaging biomarkers, are driving clinical trial research forward, instilling optimism for creating more effective disease-modifying treatments for brain proteinopathies.

Neuropathological hints from CSF and serum biomarkers in corticobasal syndrome (CBS): a systematic review

Corticobasal syndrome (CBS) is a clinical syndrome determined by various underlying neurodegenerative disorders requiring a pathological assessment for a definitive diagnosis. A literature review was performed following the methodology described in the Cochrane Handbook for Systematic Reviews to investigate the additional value of traditional and cutting-edge cerebrospinal fluid (CSF) and serum/plasma biomarkers in profiling CBS. Four databases were screened applying predefined inclusion criteria: (1) recruiting patients with CBS; (2) analyzing CSF/plasma biomarkers in CBS. The review highlights the potential role of the association of fluid biomarkers in diagnostic workup of CBS, since they may contribute to a more accurate diagnosis and patient selection for future disease-modifying agent; for example, future trial designs should consider baseline CSF Neurofilament Light Chains (NfL) or progranulin dosage to stratify treatment arms according to neuropathological substrates, and serum NfL dosage might be used to monitor the evolution of CBS. In this scenario, prospective cohort studies, starting with neurological examination and neuropsychological tests, should be considered to assess the correlations of clinical profiles and various biomarkers.

Virtual brain simulations reveal network-specific parameters in neurodegenerative dementias

Introduction

Neural circuit alterations lay at the core of brain physiopathology, and yet are hard to unveil in living subjects. The Virtual Brain (TVB) modeling, by exploiting structural and functional magnetic resonance imaging (MRI), yields mesoscopic parameters of connectivity and synaptic transmission.

Methods

We used TVB to simulate brain networks, which are key for human brain function, in Alzheimer's disease (AD) and frontotemporal dementia (FTD) patients, whose connectivity and synaptic parameters remain largely unknown; we then compared them to healthy controls, to reveal novel in vivo pathological hallmarks.

Results

The pattern of simulated parameter differed between AD and FTD, shedding light on disease-specific alterations in brain networks. Individual subjects displayed subtle differences in network parameter patterns that significantly correlated with their individual neuropsychological, clinical, and pharmacological profiles.

Discussion

These TVB simulations, by informing about a new personalized set of networks parameters, open new perspectives for understanding dementias mechanisms and design personalized therapeutic approaches.

Evaluation of Plasma Phosphorylated Tau217 for Differentiation Between Alzheimer Disease and Frontotemporal Lobar Degeneration Subtypes Among Patients With Corticobasal Syndrome

Importance

Plasma phosphorylated tau217 (p-tau217), a biomarker of Alzheimer disease (AD), is of special interest in corticobasal syndrome (CBS) because autopsy studies have revealed AD is the driving neuropathology in up to 40% of cases. This differentiates CBS from other 4-repeat tauopathy (4RT)-associated syndromes, such as progressive supranuclear palsy Richardson syndrome (PSP-RS) and nonfluent primary progressive aphasia (nfvPPA), where underlying frontotemporal lobar degeneration (FTLD) is typically the primary neuropathology.

Objective

To validate plasma p-tau217 against positron emission tomography (PET) in 4RT-associated syndromes, especially CBS.

Design, Setting, and Participants

This multicohort study with 6, 12, and 24-month follow-up recruited adult participants between January 2011 and September 2020 from 8 tertiary care centers in the 4RT Neuroimaging Initiative (4RTNI). All participants with CBS (n = 113), PSP-RS (n = 121), and nfvPPA (n = 39) were included; other diagnoses were excluded due to rarity (n = 29). Individuals with PET-confirmed AD (n = 54) and PET-negative cognitively normal control individuals (n = 59) were evaluated at University of California San Francisco. Operators were blinded to the cohort.

Main Outcome and Measures

Plasma p-tau217, measured by Meso Scale Discovery electrochemiluminescence, was validated against amyloid-β (Aβ) and flortaucipir (FTP) PET. Imaging analyses used voxel-based morphometry and bayesian linear mixed-effects modeling. Clinical biomarker associations were evaluated using longitudinal mixed-effect modeling.

Results

Of 386 participants, 199 (52%) were female, and the mean (SD) age was 68 (8) years. Plasma p-tau217 was elevated in patients with CBS with positive Aβ PET results (mean [SD], 0.57 [0.43] pg/mL) or FTP PET (mean [SD], 0.75 [0.30] pg/mL) to concentrations comparable to control individuals with AD (mean [SD], 0.72 [0.37]), whereas PSP-RS and nfvPPA showed no increase relative to control. Within CBS, p-tau217 had excellent diagnostic performance with area under the receiver operating characteristic curve (AUC) for Aβ PET of 0.87 (95% CI, 0.76-0.98; P < .001) and FTP PET of 0.93 (95% CI, 0.83-1.00; P < .001). At baseline, individuals with CBS-AD (n = 12), defined by a PET-validated plasma p-tau217 cutoff 0.25 pg/mL or greater, had increased temporoparietal atrophy at baseline compared to individuals with CBS-FTLD (n = 39), whereas longitudinally, individuals with CBS-FTLD had faster brainstem atrophy rates. Individuals with CBS-FTLD also progressed more rapidly on a modified version of the PSP Rating Scale than those with CBS-AD (mean [SD], 3.5 [0.5] vs 0.8 [0.8] points/year; P = .005).

Conclusions and Relevance

In this cohort study, plasma p-tau217 had excellent diagnostic performance for identifying Aβ or FTP PET positivity within CBS with likely underlying AD pathology. Plasma P-tau217 may be a useful and inexpensive biomarker to select patients for CBS clinical trials.

Is the pathology of posterior cortical atrophy clinically predictable?

Posterior cortical atrophy (PCA) is a neurodegenerative disorder characterized by an early prominent deficit of visual functions associated with signs and symptoms that are the expression of dysfunction of posterior brain regions. Although PCA is commonly associated with Alzheimer's disease (AD), in recent years new pathological substrates have emerged. Among them, frontotemporal lobar degeneration (FTLD) is the most commonly reported but, to date, little is known about the clinical features of PCA due to FTLD. We conducted a systematic search in the main biomedical database MEDLINE. We searched for all clinical PCA reports that assessed the pathological basis of such syndrome with at least one of the following: (1) neuropathological examination, (2) cerebrospinal fluid biomarkers, (3) amyloid-PET imaging and (4) genetic testing. Of 369 potentially eligible studies, 40 fulfilled the inclusion criteria with an overall number of 144 patients (127 PCA-AD vs. 17 PCA-FTD/non-AD). We found that hallucinations/illusions were present in none of the probable PCA-FTD/non-AD subjects while were reported in 15 out of 97 PCA-AD individuals. Optic ataxia and Parkinsonism showed a significantly greater prevalence in probable PCA FTD/non-AD than in PCA-AD whereas myoclonus and disorientation in time and space were significantly more frequent in PCA-AD than in probable PCA FTD/non-AD. We also found a predominance of a left-side pattern of atrophy/hypometabolism in the probable PCA FTD/non-AD. Clinical features such as optic ataxia, Parkinsonism, myoclonus, hallucinations and disorientation in time and space suggest the underlying pathological basis of PCA and help in leading the diagnostic protocol consequently.

TREM2 risk variants are associated with atypical Alzheimer's disease

Alzheimer's disease (AD) has multiple clinically and pathologically defined subtypes where the underlying causes of such heterogeneity are not well established. Rare TREM2 variants confer significantly increased risk for clinical AD in addition to other neurodegenerative disease clinical phenotypes. Whether TREM2 variants are associated with atypical clinical or pathologically defined subtypes of AD is not known. We studied here the clinical and pathological features associated with TREM2 risk variants in an autopsy-confirmed cohort. TREM2 variant cases were more frequently associated with non-amnestic clinical syndromes. Pathologically, TREM2 variant cases were associated with an atypical distribution of neurofibrillary tangle density with significantly lower hippocampal NFT burden relative to neocortical NFT accumulation. In addition, NFT density but not amyloid burden was associated with an increase of dystrophic microglia. TREM2 variant cases were not associated with an increased prevalence, extent, or severity of co-pathologies. These clinicopathological features suggest that TREM2 variants contribute to clinical and pathologic AD heterogeneity by altering the distribution of neurofibrillary degeneration and tau-dependent microglial dystrophy, resulting in hippocampal-sparing and non-amnestic AD phenotypes.

PET Imaging of Dementia: Update 2022

ABSTRACT

PET imaging plays an essential role in achieving earlier and more specific diagnoses of dementia syndromes, important for clinical prognostication and optimal medical management. This has become especially vital with the recent development of pathology-specific disease-modifying therapy for Alzheimer disease, which will continue to evolve and require methods to select appropriate treatment candidates. Techniques that began as research tools such as amyloid and tau PET have now entered clinical use, making nuclear medicine physicians and radiologists essential members of the care team. This review discusses recent changes in the understanding of dementia and examines the roles of nuclear medicine imaging in clinical practice. Within this framework, multiple cases will be shown to illustrate a systematic approach of FDG PET interpretation and integration of PET imaging of specific molecular pathology including dopamine transporters, amyloid, and tau. The approach presented here incorporates contemporary understanding of both common and uncommon dementia syndromes, intended as an updated practical guide to assist with the sophisticated interpretation of nuclear medicine examinations in the context of this rapidly and continually developing area of imaging.

Clinical Spectrum of Tauopathies

Tauopathies are both clinical and pathological heterogeneous disorders characterized by neuronal and/or glial accumulation of misfolded tau protein. It is now well understood that every pathologic tauopathy may present with various clinical phenotypes based on the primary site of involvement and the spread and distribution of the pathology in the nervous system making clinicopathological correlation more and more challenging. The clinical spectrum of tauopathies includes syndromes with a strong association with an underlying primary tauopathy, including Richardson syndrome (RS), corticobasal syndrome (CBS), non-fluent agrammatic primary progressive aphasia (nfaPPA)/apraxia of speech, pure akinesia with gait freezing (PAGF), and behavioral variant frontotemporal dementia (bvFTD), or weak association with an underlying primary tauopathy, including Parkinsonian syndrome, late-onset cerebellar ataxia, primary lateral sclerosis, semantic variant PPA (svPPA), and amnestic syndrome. Here, we discuss clinical syndromes associated with various primary tauopathies and their distinguishing clinical features and new biomarkers becoming available to improve in vivo diagnosis. Although the typical phenotypic clinical presentations lead us to suspect specific underlying pathologies, it is still challenging to differentiate pathology accurately based on clinical findings due to large phenotypic overlaps. Larger pathology-confirmed studies to validate the use of different biomarkers and prospective longitudinal cohorts evaluating detailed clinical, biofluid, and imaging protocols in subjects presenting with heterogenous phenotypes reflecting a variety of suspected underlying pathologies are fundamental for a better understanding of the clinicopathological correlations.

The Significance of Asymmetry in the Assessment of Brain Perfusion in Atypical Tauopathic Parkinsonian Syndromes

Progressive supranuclear palsy syndrome (PSPS) and corticobasal syndrome (CBS) are clinical manifestations of tauopathic Parkinsonian syndromes. Due to their overlapping symptomatology, the differential diagnosis of these entities may be difficult when bounded to clinical assessment. The manifestations are commonly associated with pathological entities—corticobasal degeneration and progressive supranuclear palsy, which are four-repeat tauopathies. In this study, the authors attempted to find whether the asymmetry typically associated with CBS may be feasible in the interpretation of perfusion single-photon computed tomography. The analysis based on the examination of patients with progressive supranuclear palsy—Richardson syndrome (PSP-RS), progressive supranuclear palsy—Parkinsonism predominant (PSP-P), and corticobasal syndrome (CBS) revealed significant asymmetry of perfusion of the amygdala in corticobasal syndrome. The more pronounced abnormalities of perfusion were observed in the left amygdala among patients with more severe Parkinsonian syndromes in CBS on the right. This study shows that the comparison of the perfusion of tauopathic Parkinsonian syndromes should be extended by asymmetry analysis. Interestingly, the differentiating potential of brain perfusion is present in the comparison of CBS and PSP-RS, but not in CBS and PSP-P. This phenomenon could be explained by more distinct asymmetry in the perfusion observed in PSP-P, which diminishes the differentiating potential of this parameter when it comes to the comparison of PSP-P and CBS. To the best of our knowledge, this is the first study evaluating which structures can be interpreted as significantly asymmetrical in the context of perfusion in CBS.

Atypical Alzheimer Disease Variants

PURPOSE OF REVIEW

This article discusses the clinical, neuroimaging, and biomarker profiles of sporadic atypical Alzheimer disease (AD) variants, including early-onset AD, posterior cortical atrophy, logopenic variant primary progressive aphasia, dysexecutive variant and behavioral variant AD, and corticobasal syndrome.

RECENT FINDINGS

Significant advances are being made in the recognition and characterization of the syndromically diverse AD variants. These variants are identified by the predominant cognitive and clinical features: early-onset amnestic syndrome, aphasia, visuospatial impairments, dysexecutive and behavioral disturbance, or motor symptoms. Although understanding of regional susceptibility to disease remains in its infancy, visualizing amyloid and tau pathology in vivo and CSF examination of amyloid-β and tau proteins are particularly useful in atypical AD, which can be otherwise prone to misdiagnosis. Large-scale research efforts, such as LEADS (the Longitudinal Early-Onset Alzheimer Disease Study), are currently ongoing and will continue to shed light on our understanding of these diverse presentations.

SUMMARY

Understanding the clinical, neuroimaging, and biomarker profiles of the heterogeneous group of atypical AD syndromes improves diagnostic accuracy in patients who are at increased risk of misdiagnosis. Earlier accurate identification facilitates access to important interventions, social services and disability assistance, and crucial patient and family education.

Differential Diagnosis of Rare Subtypes of Progressive Supranuclear Palsy and PSP-Like Syndromes—Infrequent Manifestations of the Most Common Form of Atypical Parkinsonism

Presently, there is increasing interest in rare PSP (progressive supranuclear palsy) variants, including PSP-PGF (PSP-progressive gait freezing), PSP-PI (PSP-postural instability), PSP-OM (PSP-ocular motor dysfunction), PSP-C (PSP-predominant cerebellar ataxia), PSP-CBS (PSP-corticobasal syndrome), PSP-SL (PSP-speech/language disorders), and PSP-PLS (PSP-primary lateral sclerosis). Diagnosis of these subtypes is usually based on clinical symptoms, thus thorough examination with anamnesis remains a major challenge for clinicians. The individual phenotypes often show great similarity to various neurodegenerative diseases and other genetic, autoimmune, or infectious disorders, manifesting as PSP-mimicking syndromes. At the current stage of knowledge, it is not possible to isolate a specific marker to make a definite ante-mortem diagnosis. The purpose of this review is to discuss recent developments in rare PSP phenotypes and PSP-like syndromes.

An autopsy case of corticobasal syndrome with pure diffuse Lewy Body Disease

Corticobasal syndrome (CBS) is associated with diverse pathological substrates such as tau, prion protein, transactive response and, rarely, alpha synuclein. We report the case of a54-year-old man, who presented with asymmetric levodopa-poor-responsive parkinsonism, frontal lobe signs and behavioral changes. He was diagnosed with CBS, and postmortem analyses revealed Lewy body disease Braak stage VI without comorbid pathologies. Retrospectively, the clinical course of our patient and previous reports indicate that CBS plus mood changes and autonomic dysfunction, including reduced uptake of metaiodobenzylguanidine, are predictive factors of Lewy body pathology, even if the clinical picture is atypical.

Clinical Phenotypes in Corticobasal Syndrome with or without Amyloidosis Biomarkers

Corticobasal syndrome (CBS) is a neuropathologically heterogeneous entity. The use of cerebrospinal fluid and amyloid biomarkers enables detection of underlying Alzheimer's disease (AD) pathology. We thus compared clinical, eye movement, and 18FDG-PET imaging characteristics in CBS in two groups of patients divided according to their amyloid biomarkers profile. Fourteen patients presenting with CBS and amyloidosis (CBS-A+) were compared with 16 CBS patients without amyloidosis (CBS-A-). The two groups showed similar motor abnormalities (parkinsonism, dystonia) and global cognitive functions. Unlike CBS-A+ patients who displayed more posterior cortical abnormalities, CBS-A- patients demonstrated more anterior cortical and brain stem dysfunctions on the basis of neuropsychological testing, study of saccade velocities and brain hypometabolism areas on 18FDG-PET. Interestingly, Dopamine Transporter SPECT imaging showed similar levels of dopaminergic degeneration in both groups. These findings confirm common and distinct brain abnormalities between the different neurodegenerative diseases that result in CBS. We demonstrate the importance of a multidisciplinary approach to improve diagnosis in vivo in particular on oculomotor examination.

Longitudinal Amyloid-β PET in Atypical Alzheimer's Disease and Frontotemporal Lobar Degeneration

BACKGROUND

Rates of amyloid-β (Aβ) accumulation have been characterized across the cognitively normal to typical Alzheimer's dementia spectrum, but little is known about Aβ accumulation in atypical Alzheimer's disease (AD) and other neurodegenerative diseases, such as frontotemporal lobar degeneration (FTLD).

OBJECTIVE

We aimed tocharacterize longitudinal Aβ accumulation anddetermine the influence of age, apolipoprotein E (APOE) genotype, disease duration, and sexin atypical AD and FTLD.

METHODS

322 patients (138 atypical AD, 184 FTLD) underwent Pittsburgh compound B PET scanning, with 73 having serialPiB-PET scans (42 atypical AD, 31 FTLD). Global Aβ standard uptake value ratios were calculated for every scan. Mixed effects models were used to assess the effect of age, APOE genotype, disease duration, and sex on baseline and change measures of Aβ.

RESULTS

Atypical AD showed higher baseline Aβ than FTLD. Rate of Aβ accumulation was not associated with baseline Aβ in either group. Older age was associated with greater baseline Aβ and faster rates of accumulation in FTLD. In patients under age 70, atypical AD showed faster rates of accumulation than FTLD. APOEɛ4 genotype was associated with greater baseline Aβ in FTLD but did not influence rates of accumulation. Rates of Aβ accumulation were faster in FTLD patents with time from onset-to-PET≤4 years. Female sex was associated with faster rates of accumulation in atypical AD.

CONCLUSION

Accumulation of Aβ is observed in atypical AD and FTLD, although different demographic factors influence accumulation in these diseases providing insight into potentially different biological mechanisms of Aβ deposition.

Individual Brain Metabolic Signatures in Corticobasal Syndrome

BACKGROUND

Corticobasal syndrome (CBS) is the usual clinical presentation of patients with corticobasal degeneration pathology. Nevertheless, there are CBS individuals with postmortem neuropathology typical of Alzheimer's disease (AD).

OBJECTIVE

In this study, we aim to detect FDG-PET metabolic signatures at the single-subject level in a CBS sample, also evaluated with cerebrospinal fluid (CSF) markers for AD pathology.

METHODS

21 patients (68.9±6.4 years; MMSE score = 21.7±6.3) fulfilling current criteria for CBS were enrolled. All underwent a clinical-neuropsychological assessment and an instrumental evaluation for biomarkers of neurodegeneration, amyloid and tau pathology (i.e., FDG-PET imaging and CSF Aβ42 and tau levels) at close intervals. CBS subjects were classified according to the presence or absence of CSF markers of AD pathology (i.e., low Aβ42 and high phosphorylated tau levels). Optimized voxel-based SPM procedures provided FDG-PET metabolic patterns at the single-subject and group levels.

RESULTS

Eight CBS had an AD-like CSF profile (CBS-AD), while thirteen were negative (CBS-noAD). The two subgroups did not differ in demographic characteristics or global cognitive impairment. FDG-PET SPM t-maps identified different metabolic signatures. Namely, all CBS-AD patients showed the typical AD-like hypometabolic pattern involving posterior cingulate cortex, precuneus and temporo-parietal cortex, whereas CBS-noAD cases showed bilateral hypometabolism in fronto-insular cortex and basal ganglia that is typical of the frontotemporal lobar degeneration spectrum.

DISCUSSION

These results strongly suggest the inclusion of FDG-PET imaging in the diagnostic algorithm of individuals with CBS clinical phenotype in order to early identify functional metabolic signatures due to different neuropathological substrates, thus improving the diagnostic accuracy.

A systematic review of atypical Alzheimer's disease including behavioural and psychological symptoms

Alzheimer's disease (AD) is the commonest cause of dementia, characterized by the clinical presentation of progressive anterograde episodic memory impairment. However, atypical presentation of patients is increasingly recognized. These atypical AD include logopenic aphasia, behavioural variant AD, posterior cortical atrophy, and corticobasal syndrome. These atypical AD are more common in patients with young onset AD before the age of 65 years old. Since medical needs (including the behavioural and psychological symptoms of dementia) of atypical AD patients could be different from typical AD patients, it is important for clinicians to be aware of these atypical forms of AD. In addition, disease modifying treatment may be available in the future. This review aims at providing an update on various important subtypes of atypical AD including behavioural and psychological symptoms.

An autopsy case of corticobasal syndrome due to asymmetric degeneration of the motor cortex and substantia nigra with TDP-43 proteinopathy, associated with Alzheimer's disease pathology

We herein report a case of corticobasal syndrome (CBS) due to asymmetric degeneration of the motor cortex and substantia nigra with transactivation response DNA-binding protein of 43 kDa (TDP-43) proteinopathy, associated with Alzheimer's disease (AD) pathology. An 85-year-old man initially noticed that he had difficulty in walking and had trouble in moving his right hand and lower limb one year later. His gait disturbance was aggravated, and at the age of 87 years, his neurological examination revealed parkinsonism and positive frontal lobe signs. Brain magnetic resonance imaging (MRI) revealed atrophy of the left frontotemporal lobe and cerebral peduncle, and cerebral blood flow scintigraphy revealed hypoperfusion of the left frontotemporal lobe, leading to a possible diagnosis of CBS. At the age of 89 years, he was bedridden, and rarely spoke. He died of aspiration pneumonia five years after the onset of initial symptoms. At the autopsy, the brain weighed 1280 g and showed left-sided hemiatrophy of the cerebrum and cerebral peduncle. Neuropathological examination revealed AD pathology (Braak AT8 stage V, Braak stage C, CERAD B, Thal classification 5). Phosphorylated TDP-43 (p-TDP-43) immunohistochemistry revealed widespread deposits of dystrophic neurites (DNs), glial cytoplasmic inclusions (GCIs), and neuronal cytoplasmic inclusions (NCIs), which were most remarkable in layers II/III of the motor cortex and predominant on the left hemisphere of the frontal cortex, these neuropathology being consistent with frontotemporal lobar degeneration with TDP-43 (FTLD-TDP) type A. Interestingly, neuronal loss in the substantia nigra was more severe on the left than the right side, with a few phosphorylated tau (p-tau) and p-TDP-43 deposits. It is highly likely that asymmetric TDP-43 pathology rather than symmetric tau pathology contributed to the laterality of degeneration of the cerebral cortex, substantia nigra, and pyramidal tract, which led us to suggest that TDP-43 proteinopathy might be a primary cause.

Astrocytic Tau Deposition Is Frequent in Typical and Atypical Alzheimer Disease Presentations

Typical Alzheimer disease (AD) features an amnestic syndrome that reflects the progression of pathology through specific neural networks. However, a subset of patients exhibits atypical onset with prominent language, behavioral, or visuospatial deficits that are not explained by current neuropathological staging schemes. Astrogliopathy featuring tau inclusions with thorn-shaped and granular fuzzy morphologies is common in the aging brain and collectively known as aging-related tau astrogliopathy (ARTAG). Prior studies have identified tau-positive thorn-shaped astrocytes in the white matter that associate with a primary progressive aphasia phenotype in an AD cohort. However, a possible contribution of ARTAG copathology to AD clinical heterogeneity has yet to be systematically examined. To investigate whether ARTAG pathology contributes to atypical presentations, we mapped the presence and density of ARTAG subtypes throughout cortical and subcortical regions in a well-characterized cohort of AD cases enriched for atypical presentations. In our cohort, ARTAG pathology is frequent and correlates with older age and higher Braak stage. ARTAG subtypes exhibit distinct distribution patterns with subpial and subependymal deposition occurring in the amygdala, while white and grey matter astrocytic deposition are distributed throughout cortical regions. However, ARTAG pathology is equally prevalent in cases with typical and atypical clinical presentations.

Primary Tau Pathology, Not Copathology, Correlates With Clinical Symptoms in PSP and CBD

Distinct neuronal and glial tau pathologies define corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). Additional Alzheimer disease, TDP-43, and Lewy body copathologies are also common. The interplay of these pathologies with clinical symptoms remains unclear as individuals can present with corticobasal syndrome, frontotemporal dementia, PSP, or atypical Parkinsonism and may have additional secondary impairments. We report clinical, pathological, and genetic interactions in a cohort of CBD and PSP cases. Neurofibrillary tangles and plaques were common. Apolipoprotein E (APOE)ε4 carriers had more plaques while PSP APOEε2 carriers had fewer plaques. TDP-43 copathology was present and age-associated in 14% of PSP, and age-independent in 33% of CBD. Lewy body copathology varied from 9% to 15% and was not age-associated. The primary FTD-Tau burden-a sum of the neuronal, astrocytic and oligodendrocytic tau-was not age-, APOE-, or MAPT-related. In PSP, FTD-Tau, independent of copathology, associated with executive, language, motor, and visuospatial impairments, while PSP with Parkinsonism had a lower FTD-Tau burden, but this was not the case in CBD. Taken together, our results indicate that the primary tauopathy burden is the strongest correlate of clinical PSP, while copathologies are principally determined by age and genetic risk factors.

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.

The Progressive Acalculia Presentation of Parietal Variant Alzheimer's Disease

BACKGROUND

Many patients with early-onset Alzheimer's disease (EOAD; age of onset <65 years) have non-amnestic presentations involving language (logopenic primary progressive aphasia, lvPPA), visuospatial abilities (posterior cortical atrophy, PCA), and even asymmetric symptoms consistent with corticobasal syndrome (CBS). An inferior parietal lobule variant of EOAD commonly presents with progressive difficulty with calculations.

METHODS

We reviewed 276 EOAD patients for presentations with predominant acalculia. These patients were diagnosed with clinically probable Alzheimer's disease (AD) verified by positron emission tomography (PET) or cerebrospinal fluid amyloid-β or tau biomarkers.

RESULTS

We identified 18 (9M/9F) (6.5%) EOAD patients with progressive acalculia that did not meet most criteria for lvPPA, visual PCA, or CBS. Their ages of onset and presentation were 56.6 (5.0) and 59.4 (6.5), respectively. Their acalculia was consistent with a primary acalculia ("anarithmetia") not explained by language or visuospatial impairments. Many also had anomia (14/18), ideomotor apraxia (13/18), and the complete Gerstmann's syndrome (7/18). Visual analysis of their diverse magnetic resonance imaging disclosed biparietal atrophy, disproportionately worse on the left.

CONCLUSIONS

Primary acalculia may be the most common manifestation of an inferior parietal presentation of EOAD affecting the left intraparietal sulcus. This parietal variant also commonly involves progressive anomia, ideomotor apraxia, and other elements of Gerstmann's syndrome. The early recognition of patients with this variant, which is distinguishable from lvPPA, visual PCA, or CBS, would be facilitated by its recognition as a unique subtype of EOAD.

Difficulties in the diagnosis of four repeats (4R) tauopathic parkinsonian syndromes

Corticobasal Degeneration Degeneration (CBD) and Progressive Supranuclear Palsy (PSP) are types of four repeats (4R) tauopathies, which are associated to parkinsonian syndromes. The aim of the work is to analyze cases of patients of the Department of Neurology, overlapping of syndromes related to both pathologies and to show that most likely CBS and PSP are not lineary related to their commonly associated syndromes i.e. adequately corticobasal syndromes and progressive supranuclear palsy syndromes. In the context of each patient factors in favor of most likely CBS, PSP or both diseases are discussed and analyzed using contemporary criteria. This work discusses multidimensional aspect of the examination of five patient aged 64 to 83 - 4 females and 1 male with 4R tauopathies and difficulties in distinguishing both diseases. The duration of the disease varied from 1 to 5 years. Each patient after neurological examination was assessed using magnetic resonance imaging (MRI) and psychological test. Examination of all patients was extended using single photon emission computer tomography (SPECT) to reveal the usefulness of this tool in differentiation of diseases was done. The outcome of this examination was verified with prior clinical manifestation of patients and morphological abnormalities in magnetic resonance imaging. Autopsies were not conducted.

Early stage memory impairment, visual hallucinations, and myoclonus combined with temporal lobe atrophy predict Alzheimer's disease pathology in corticobasal syndrome

Corticobasal syndrome (CBS) is a typical phenotype of corticobasal degeneration (CBD). However, autopsy series have shown that many CBS cases emerge from various types of non-CBD pathology. We report a 73-year-old Korean man who was clinically diagnosed with CBS whose underlying pathology was Alzheimer's disease (AD) at autopsy (CBS-AD). This case suggests that early developing memory impairment and myoclonus, severe temporoparietal atrophy, and visual hallucinations may support a more specific prediction of CBS-AD.

Diagnosing Corticobasal Syndrome Based on the Presence of Visual Hallucinations and Imaging with Amyloid Positron Emission Tomography

A 61-year-old woman was admitted to our hospital due to memory difficulties, visual hallucinations, and slowly progressing motor difficulties in the limbs. A clinical examination revealed bradykinesia, gait disturbance, left-side-dominant rigidity, ideomotor apraxia, dressing apraxia, left-sided spatial agnosia, impaired visuospatial ability, and executive dysfunction. Her symptoms were unresponsive to levodopa, and corticobasal syndrome (CBS) was diagnosed. One year later, amyloid positron emission tomography revealed amyloid beta accumulation in the bilateral cerebral cortices; at this point, CBS with underlying Alzheimer's disease pathology (CBS-AD) was diagnosed. Visual hallucinations may help differentiate CBS with corticobasal degeneration (CBS-CBD) from other pathologies, including CBS-AD.

Nonmotor Features in Atypical Parkinsonism

Atypical parkinsonism (AP) comprises mainly multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD), which are distinct pathological entities, presenting with a wide phenotypic spectrum. The classic syndromes are now called MSA-parkinsonism (MSA-P), MSA-cerebellar type (MSA-C), Richardson's syndrome, and corticobasal syndrome. Nonmotor features in AP have been recognized almost since the initial description of these disorders; however, research has been limited. Autonomic dysfunction is the most prominent nonmotor feature of MSA, but also gastrointestinal symptoms, sleep dysfunction, and pain, can be a feature. In PSP and CBD, the most prominent nonmotor symptoms comprise those deriving from the cognitive/neuropsychiatric domain. Apart from assisting the clinician in the differential diagnosis with Parkinson's disease, nonmotor features in AP have a big impact on quality of life and prognosis of AP and their treatment poses a major challenge for clinicians.

Selective vulnerability in neurodegeneration: insights from clinical variants of Alzheimer's disease

Selective vulnerability in the nervous system refers to the fact that subpopulations of neurons in different brain systems may be more or less prone to abnormal function or death in response to specific types of pathological states or injury. The concept has been used extensively as a potential way of explaining differences in degeneration patterns and the clinical presentation of different neurodegenerative diseases. Yet the increasing complexity of molecular histopathology at the cellular level in neurodegenerative disorders frequently appears at odds with phenotyping based on clinically-directed, macroscopic regional brain involvement. While cross-disease comparisons can provide insights into the differential vulnerability of networks and neuronal populations, we focus here on what is known about selective vulnerability-related factors that might explain the differential phenotypic expressions of the same disease-in this case, typical and atypical forms of Alzheimer's disease. Whereas considerable progress has been made in this area, much is yet to be elucidated; further studies comparing different phenotypic variants aimed at identifying both vulnerability and resilience factors may provide valuable insights into disease pathogenesis, and suggest novel targets for therapy.

Progressive Supranuclear Palsy and Corticobasal Degeneration: Pathophysiology and Treatment Options

OPINION STATEMENT

There are currently no disease-modifying treatments for progressive supranuclear palsy (PSP) or corticobasal degeneration (CBD), and no approved pharmacological or therapeutic treatments that are effective in controlling their symptoms. The use of most pharmacological treatment options are based on experience in other disorders or from non-randomized historical controls, case series, or expert opinion. Levodopa may provide some improvement in symptoms of Parkinsonism (specifically bradykinesia and rigidity) in PSP and CBD; however, evidence is conflicting and where present, benefits are often negligible and short lived. In fact, "poor" response to levodopa forms part of the NINDS-SPSP criteria for the diagnosis of PSP and consensus criteria for the diagnosis of CBD (Lang Mov Disord. 20 Suppl 1:S83-91, 2005; Litvan et al. Neurology. 48:119-25, 1997; Armstrong et al. Neurology. 80(5):496-503, 2013). There is some evidence that intrasalivery gland botulinum toxin is useful in managing problematic sialorrhea and that intramuscular botulinum toxin and baclofen are helpful in reducing dystonia, including blepharospasm. Benzodiazepines may also be useful in managing dystonia. Myoclonus may be managed using levetiracetam and benzodiazepines. Pharmacological agents licensed for Alzheimer's disease (such as acetylcholinesterase inhibitors and N-Methyl-D-aspartate receptor antagonists) have been used off-label in PSP, CBD, and other tauopathies with the aim of improving cognition; however, there is limited evidence that they are effective and risk of adverse effects may outweigh benefits. The use of atypical antipsychotics for behavioural symptoms is not recommended in the elderly or those with demetia associated conditions and most antipsychotics will worsen Parkinsonism. Antidepressants may be useful for behavioral symptoms and depression but are often poorly tolerated due to adverse effects. In the absence of an effective drug treatment to target the underlying cause of CBD and PSP, management should focus on optimizing quality of life, relieving symptoms and assisting patients with their activities of daily living (ADL). Patients should be managed by a multidisciplinary team consisting of neurologists, physiotherapists (PT), occupational therapists (OT), speech and language therapists (SALT), dieticians, ophthalmologists, psychologists, and palliative care specialists.

Malignant progression in parietal-dominant atrophy subtype of Alzheimer's disease occurs independent of onset age

Recently, we reported that earlier stages of Alzheimer's disease (AD) can be categorized into 3 following anatomical subtypes using a hierarchical cluster analysis of cortical thickness across the entire brain: medial temporal-dominant (MT), parietal-dominant (P), and diffuse atrophy (D). The goal of this study was to investigate the rates of cognitive decline in these anatomical subtypes. Of the patients included in the prior study, 100 AD patients (MT, n = 36; P, n = 20; D, n = 44) who underwent follow-up neuropsychological assessments over a 3-year period were included. A linear mixed model analysis was performed to compare the longitudinal changes in neuropsychological test scores. The P subtype exhibited the most rapid cognitive decline in attention, language, visuospatial, memory, and frontal executive function, whereas MT and D subtypes did not differ in their longitudinal decline. When repeating the analyses with early-onset AD, which is known to progress faster than late-onset AD, only the P subtype showed such rapid progression. The P subtype appears to be a unique subtype of AD characterized by an aggressive rate of progression.

Corticobasal Syndrome in a Family with Early-Onset Alzheimer's Disease Linked to a Presenilin-1 Gene Mutation

BACKGROUND

Alzheimer's disease (AD) is the second-most frequent cause underlying corticobasal syndrome (CBS). However, a reliable diagnosis using clinical, neuropsychological, or neuroimaging approaches has not yet been achieved.

METHODS

Clinical, neuropsychological, imaging, and neuropathology studies were undertaken in a large Spanish family with early-onset familial AD (EOFAD) carrying a Met233Leu mutation linked to presenilin-1 gene (PSEN-1).

RESULTS

Two of three examined members of this family presented with the usual amnestic pattern. At the age of 47 years, a third family member, in whom pathology was later confirmed, developed prominent CBS combined with severe neuropsychiatric and behavioral disturbances resembling those often found in EOFAD.

CONCLUSION

Although CBS in EOFAD appears to be rare, demonstration of a linkage to PSEN-1 gene mutations may permit in vivo diagnosis.

Atypical parkinsonism: diagnosis and treatment

Atypical parkinsonism comprises typically progressive supranuclear palsy, corticobasal degeneration, and mutilple system atrophy, which are distinct pathologic entities; despite ongoing research, their cause and pathophysiology are still unknown, and there are no biomarkers or effective treatments available. The expanding phenotypic spectrum of these disorders as well as the expanding pathologic spectrum of their classic phenotypes makes the early differential diagnosis challenging for the clinician. Here, clinical features and investigations that may help to diagnose these conditions and the existing limited treatment options are discussed.

Anodal transcranial direct current stimulation of parietal cortex enhances action naming in Corticobasal Syndrome

Background: Corticobasal Syndrome (CBS) is a neurodegenerative disorder that overlaps both clinically and neuropathologically with Frontotemporal dementia (FTD) and is characterized by apraxia, alien limb phenomena, cortical sensory loss, cognitive impairment, behavioral changes and aphasia. It has been recently demonstrated that transcranial direct current stimulation (tDCS) improves naming in healthy subjects and in subjects with language deficits.

Objective: The aim of the present study was to explore the extent to which anodal tDCS over the parietal cortex (PARC) could facilitate naming performance in CBS subjects.

Methods: Anodal tDCS was applied to the left and right PARC during object and action naming in seventeen patients with a diagnosis of possible CBS. Participants underwent two sessions of anodal tDCS (left and right) and one session of placebo tDCS. Vocal responses were recorded and analyzed for accuracy and vocal Reaction Times (vRTs).

Results: A shortening of naming latency for actions was observed only after active anodal stimulation over the left PARC, as compared to placebo and right stimulations. No effects have been reported for accuracy.

Conclusions: Our preliminary finding demonstrated that tDCS decreased vocal reaction time during action naming in a sample of patients with CBS. A possible explanation of our results is that anodal tDCS over the left PARC effects the brain network implicated in action observation and representation. Further studies, based on larger patient samples, should be conducted to investigate the usefulness of tDCS as an additional treatment of linguistic deficits in CBS patients.

Motor features in posterior cortical atrophy and their imaging correlates

Posterior cortical atrophy (PCA) is a neurodegenerative syndrome characterized by impaired higher visual processing skills; however, motor features more commonly associated with corticobasal syndrome may also occur. We investigated the frequency and clinical characteristics of motor features in 44 PCA patients and, with 30 controls, conducted voxel-based morphometry, cortical thickness, and subcortical volumetric analyses of their magnetic resonance imaging. Prominent limb rigidity was used to define a PCA-motor subgroup. A total of 30% (13) had PCA-motor; all demonstrating asymmetrical left upper limb rigidity. Limb apraxia was more frequent and asymmetrical in PCA-motor, as was myoclonus. Tremor and alien limb phenomena only occurred in this subgroup. The subgroups did not differ in neuropsychological test performance or apolipoprotein E4 allele frequency. Greater asymmetry of atrophy occurred in PCA-motor, particularly involving right frontoparietal and peri-rolandic cortices, putamen, and thalamus. The 9 patients (including 4 PCA-motor) with pathology or cerebrospinal fluid all showed evidence of Alzheimer's disease. Our data suggest that PCA patients with motor features have greater atrophy of contralateral sensorimotor areas but are still likely to have underlying Alzheimer's disease.

Clinical Utility of Amyloid Imaging in a Complex Case of Corticobasal Syndrome Presenting with Psychiatric Symptoms

Clinical indications of amyloid imaging in atypical dementia remain unclear. We report a 68-year-old female without past psychiatric history who was hospitalized for auditory hallucinations and persecutory delusions associated with cognitive and motor deficits. Although psychotic symptoms resolved with antipsychotic treatment, cognitive and motor impairments remained. She further showed severe visuoconstructive and executive deficits, ideomotor apraxia, elements of Gerstmann’s syndrome, bilateral agraphesthesia and discrete asymmetric motor deficits. Blood tests were unremarkable. Structural brain imaging revealed diffuse fronto-temporo-parietal atrophy, which was most severe in the parietal regions. Meanwhile, FDG-PET suggested asymmetrical fronto-temporo-parietal hypometabolism, with sparing of the posterior cingulate gyrus. A diagnosis of possible corticobasal syndrome (CBS) was made. Amyloid-PET using the novel tracer NAV4694 was ordered, and revealed significant deposition of fibrillar amyloid (SUVR 2.05). The primary diagnosis was CBS with underlying Alzheimer pathology and treatment with a cholinesterase inhibitor was initiated. Determination of underlying pathological CBS subtype is not simple even when based on extensive investigation including clinical presentation, atrophy patterns on MRI, and regional hypometabolism on FDG-PET. By contrast, amyloid imaging quickly confirmed Alzheimer pathology, and allowed rapid initiation of treatment in this complex case with early psychiatric symptoms. This case study illustrates the clinical utility of amyloid imaging in the setting of atypical cases seen in a tertiary memory clinic.

A disease-specific metabolic brain network associated with corticobasal degeneration

Corticobasal degeneration is an uncommon parkinsonian variant condition that is diagnosed mainly on clinical examination. To facilitate the differential diagnosis of this disorder, we used metabolic brain imaging to characterize a specific network that can be used to discriminate corticobasal degeneration from other atypical parkinsonian syndromes. Ten non-demented patients (eight females/two males; age 73.9 ± 5.7 years) underwent metabolic brain imaging with (18)F-fluorodeoxyglucose positron emission tomography for atypical parkinsonism. These individuals were diagnosed clinically with probable corticobasal degeneration. This diagnosis was confirmed in the three subjects who additionally underwent post-mortem examination. Ten age-matched healthy subjects (five females/five males; age 71.7 ± 6.7 years) served as controls for the imaging studies. Spatial covariance analysis was applied to scan data from the combined group to identify a significant corticobasal degeneration-related metabolic pattern that discriminated (P < 0.001) the patients from the healthy control group. This pattern was characterized by bilateral, asymmetric metabolic reductions involving frontal and parietal cortex, thalamus, and caudate nucleus. These pattern-related changes were greater in magnitude in the cerebral hemisphere opposite the more clinically affected body side. The presence of this corticobasal degeneration-related metabolic topography was confirmed in two independent testing sets of patient and control scans, with elevated pattern expression (P < 0.001) in both disease groups relative to corresponding normal values. We next determined whether prospectively computed expression values for this pattern accurately discriminated corticobasal degeneration from multiple system atrophy and progressive supranuclear palsy (the two most common atypical parkinsonian syndromes) on a single case basis. Based upon this measure, corticobasal degeneration was successfully distinguished from multiple system atrophy (P < 0.001) but not progressive supranuclear palsy, presumably because of the overlap (∼ 24%) that existed between the corticobasal degeneration- and the progressive supranuclear palsy-related metabolic topographies. Nonetheless, excellent discrimination between these disease entities was achieved by computing hemispheric asymmetry scores for the corticobasal degeneration-related pattern on a prospective single scan basis. Indeed, a logistic algorithm based on the asymmetry scores combined with separately computed expression values for a previously validated progressive supranuclear palsy-related pattern provided excellent specificity (corticobasal degeneration: 92.7%; progressive supranuclear palsy: 94.1%) in classifying 58 testing subjects. In conclusion, corticobasal degeneration is associated with a reproducible disease-related metabolic covariance pattern that may help to distinguish this disorder from other atypical parkinsonian syndromes.

Visuoperception test predicts pathologic diagnosis of Alzheimer disease in corticobasal syndrome

OBJECTIVE

To use the Visual Object and Space Perception Battery (VOSP) to distinguish Alzheimer disease (AD) from non-AD pathology in corticobasal syndrome (CBS).

METHODS

This clinicopathologic study assessed 36 patients with CBS on the VOSP. All were autopsied. The primary dependent variable was a binary pathologic outcome: patients with CBS who had primary pathologic diagnosis of AD (CBS-AD, n = 10) vs patients with CBS without primary pathologic diagnosis of AD (CBS-nonAD, n = 26). We also determined sensitivity and specificity of individual VOSP subtests.

RESULTS

Patients with CBS-AD had younger onset (54.5 vs 63.6 years, p = 0.001) and lower memory scores on the Mattis Dementia Rating Scale-2 (16 vs 22 points, p = 0.003). Failure on the VOSP subtests Incomplete Letters (odds ratio [OR] 11.5, p = 0.006), Position Discrimination (OR 10.86, p = 0.008), Number Location (OR 12.27, p = 0.026), and Cube Analysis (OR 45.71 p = 0.0001) had significantly greater odds of CBS-AD than CBS-nonAD. These associations remained when adjusting for total Mattis Dementia Rating score, disease laterality, education, age, and sex. Receiver operating characteristic curves demonstrated significant accuracy for Incomplete Letters and all VOSP spatial subtests, with Cube Analysis performing best (area under the curve 0.91, p = 0.0004).

CONCLUSIONS

In patients with CBS, failure on specific VOSP subtests is associated with greater odds of having underlying AD. There may be preferential involvement of the dorsal stream in CBS-AD.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that some subtests of the VOSP accurately distinguish patients with CBS-AD from those without AD pathology (e.g., Cube Analysis sensitivity 100%, specificity 77%).

The power of neuroimaging biomarkers for screening frontotemporal dementia

Frontotemporal dementia (FTD) is a clinically and pathologically heterogeneous neurodegenerative disease that can result from either frontotemporal lobar degeneration (FTLD) or Alzheimer's disease (AD) pathology. It is critical to establish statistically powerful biomarkers that can achieve substantial cost-savings and increase the feasibility of clinical trials. We assessed three broad categories of neuroimaging methods to screen underlying FTLD and AD pathology in a clinical FTD series: global measures (e.g., ventricular volume), anatomical volumes of interest (VOIs) (e.g., hippocampus) using a standard atlas, and data-driven VOIs using Eigenanatomy. We evaluated clinical FTD patients (N = 93) with cerebrospinal fluid, gray matter (GM) magnetic resonance imaging (MRI), and diffusion tensor imaging (DTI) to assess whether they had underlying FTLD or AD pathology. Linear regression was performed to identify the optimal VOIs for each method in a training dataset and then we evaluated classification sensitivity and specificity in an independent test cohort. Power was evaluated by calculating minimum sample sizes required in the test classification analyses for each model. The data-driven VOI analysis using a multimodal combination of GM MRI and DTI achieved the greatest classification accuracy (89% sensitive and 89% specific) and required a lower minimum sample size (N = 26) relative to anatomical VOI and global measures. We conclude that a data-driven VOI approach using Eigenanatomy provides more accurate classification, benefits from increased statistical power in unseen datasets, and therefore provides a robust method for screening underlying pathology in FTD patients for entry into clinical trials.

[An autopsy case of Alzheimer's disease presenting with corticobasal syndrome]

A right-handed Japanese man developed memory loss at 51 years of age. The right side clumsiness developed from 52 years of age and then progressively worsened. Temporal/parietal lobe atrophy was observed predominantly on the left side upon MR imaging. Subsequently, limb-kinetic apraxia and parkinsonism became apparent predominantly on the right side. These symptoms became aggravated along with dementia, ultimately leading to an apallic state. The patient eventually died at the age of 59 due to aspiration pneumonia. An autopsy was carried out and cerebral atrophy was observed predominantly on the left side. Senile plaques were observed on the entire cerebral cortex at a high frequency, along with many cotton wool plaques. Anti-phosphorylated tau-positive neurofibrillary tangles and several neuropil threads were observed upon immunostaining. The tau-positive structures were also positive for both RD3 and RD4 antibodies. The findings of tauopathy of the glia were poor, and the tau lesion of the brainstem was milder than that of the cerebral cortex. These results suggest the possibility that the corticobasal syndrome clinically developed in some type of Alzheimer's disease and a definite diagnosis was made only by pathological examination.

Sparse canonical correlation analysis relates network-level atrophy to multivariate cognitive measures in a neurodegenerative population

This study establishes that sparse canonical correlation analysis (SCCAN) identifies generalizable, structural MRI-derived cortical networks that relate to five distinct categories of cognition. We obtain multivariate psychometrics from the domain-specific sub-scales of the Philadelphia Brief Assessment of Cognition (PBAC). By using a training and separate testing stage, we find that PBAC-defined cognitive domains of language, visuospatial functioning, episodic memory, executive control, and social functioning correlate with unique and distributed areas of gray matter (GM). In contrast, a parallel univariate framework fails to identify, from the training data, regions that are also significant in the left-out test dataset. The cohort includes164 patients with Alzheimer's disease, behavioral-variant frontotemporal dementia, semantic variant primary progressive aphasia, non-fluent/agrammatic primary progressive aphasia, or corticobasal syndrome. The analysis is implemented with open-source software for which we provide examples in the text. In conclusion, we show that multivariate techniques identify biologically-plausible brain regions supporting specific cognitive domains. The findings are identified in training data and confirmed in test data.

Recent advances in structural MRI in Parkinson’s disease and atypical parkinsonian syndromes

SUMMARY In the past 2 years, technical developments in conventional and advanced MRI, such as ultra-high-field MRI or mapping of brain mineralization, has allowed novel insights into the nature of Parkinson’s disease (PD) and atypical parkinsonian syndromes, which may aid diagnostic accuracy and differential diagnosis. In addition, sophisticated post-processing analyses, such as morphometry- and surface-based classifications and automated whole-brain analyses, have become available; in PD, this has led to direct visualization of structural substantia nigra abnormalities, monitoring disease progression or screening for brain atrophy associated with dementia. Based on conventional MRI, new MRI rating scales have been established for progressive supranuclear palsy and multiple system atrophy and have been further assessed with a view to their diagnostic accuracy. Clinicopathological series of patients with tauopathies imply that correlations between clinical syndromes, imaging patterns and underlying histopathology are not always strong. Here, some of the issues related to conventional and advanced MRI for the diagnostic accuracy of PD and atypical parkinsonian syndromes are reviewed.

The genetics and neuropathology of frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD) is a heterogeneous group of disorders characterized by disturbances of behavior and personality and different types of language impairment with or without concomitant features of motor neuron disease or parkinsonism. FTLD is characterized by atrophy of the frontal and anterior temporal brain lobes. Detailed neuropathological studies have elicited proteinopathies defined by inclusions of hyperphosphorylated microtubule-associated protein tau, TAR DNA-binding protein TDP-43, fused-in-sarcoma or yet unidentified proteins in affected brain regions. Rather than the type of proteinopathy, the site of neurodegeneration correlates relatively well with the clinical presentation of FTLD. Molecular genetic studies identified five disease genes, of which the gene encoding the tau protein (MAPT), the growth factor precursor gene granulin (GRN), and C9orf72 with unknown function are most frequently mutated. Rare mutations were also identified in the genes encoding valosin-containing protein (VCP) and charged multivesicular body protein 2B (CHMP2B). These genes are good markers to distinguish underlying neuropathological phenotypes. Due to the complex landscape of FTLD diseases, combined characterization of clinical, imaging, biological and genetic biomarkers is essential to establish a detailed diagnosis. Although major progress has been made in FTLD research in recent years, further studies are needed to completely map out and correlate the clinical, pathological and genetic entities, and to understand the underlying disease mechanisms. In this review, we summarize the current state of the rapidly progressing field of genetic, neuropathological and clinical research of this intriguing condition.