Diagnosis and treatment of corticobasal degeneration

Role of Amyloidogenic and Non-Amyloidogenic Protein Spaces in Neurodegenerative Diseases and their Mitigation Using Theranostic Agents

Neurodegenerative diseases (NDDs) refer to a complex heterogeneous group of diseases which are associated with the accumulation of amyloid fibrils or plaques in the brain leading to progressive loss of neuronal functions. Alzheimer's disease is one of the major NDD responsible for 60-80 % of all dementia cases. Currently, there are no curative or disease-reversing/modifying molecules for many of the NDDs except a few such as donepezil, rivastigmine, galantamine, carbidopa and levodopa which treat the disease-associated symptoms. Similarly, there are very few FDA-approved tracers such as flortaucipir (Tauvid) for tau fibril imaging and florbetaben (Neuraceq), flutemetamol (Vizamyl), and florbetapir (Amyvid) for amyloid imaging available for diagnosis. Recent advances in the cryogenic electron microscopy reported distinctly different microstructures for tau fibrils associated with different tauopathies highlighting the possibility to develop tauopathy-specific imaging agents and therapeutics. In addition, it is important to identify the proteins that are associated with disease development and progression to know about their 3D structure to develop various diagnostics, therapeutics and theranostic agents. The current article discusses in detail the disease-associated amyloid and non-amyloid proteins along with their structural insights. We comprehensively discussed various novel proteins associated with NDDs and their implications in disease pathology. In addition, we document various emerging chemical compounds developed for diagnosis and therapy of different NDDs with special emphasis on theranostic agents for better management of NDDs.

A Case of Corticobasal Syndrome and Posterior Cortical Atrophy With Biomarkers of Alzheimer Disease

Corticobasal syndrome is a clinical entity characterized by asymmetric akinetic rigidity and a variety of higher cortical dysfunction. Predicting background pathology of corticobasal syndrome is rather challenging; however, clinical and neuroimaging findings may provide a clue to its etiopathological origin. Visuospatial dysfunction of posterior cortical atrophy and logopenic-type language impairment indicate the presence of Alzheimer's disease-related pathology, and they provide useful information in distinguishing Alzheimer's disease from other types of corticobasal syndrome. Here we describe a case of corticobasal syndrome who showed characteristic visuospatial symptoms with imaging evidence of Alzheimer's disease supported by amyloid-PET and tau/astrogliosis-PET. Early, accurate diagnosis based on clinical features and predictable biomarkers is mandatory to the success of early intervention in corticobasal syndrome associated with Alzheimer's disease.

Role of Tau in Various Tauopathies, Treatment Approaches, and Emerging Role of Nanotechnology in Neurodegenerative Disorders

A few protein kinases and phosphatases regulate tau protein phosphorylation and an imbalance in their enzyme activity results in tau hyper-phosphorylation. Aberrant tau phosphorylation causes tau to dissociate from the microtubules and clump together in the cytosol to form neurofibrillary tangles (NFTs), which lead to the progression of neurodegenerative disorders including Alzheimer's disease (AD) and other tauopathies. Hence, targeting hyperphosphorylated tau protein is a restorative approach for treating neurodegenerative tauopathies. The cyclin-dependent kinase (Cdk5) and the glycogen synthase kinase (GSK3β) have both been implicated in aberrant tau hyperphosphorylation. The limited transport of drugs through the blood-brain barrier (BBB) for reaching the central nervous system (CNS) thus represents a significant problem in the development of drugs. Drug delivery systems based on nanocarriers help solve this problem. In this review, we discuss the tau protein, regulation of tau phosphorylation and abnormal hyperphosphorylation, drugs in use or under clinical trials, and treatment strategies for tauopathies based on the critical role of tau hyperphosphorylation in the pathogenesis of the disease. Pathology of neurodegenerative disease due to hyperphosphorylation and various therapeutic approaches including nanotechnology for its treatment.

The tauopathies: Neuroimaging characteristics and emerging experimental therapies

The tauopathies are a heterogeneous group of neurodegenerative disorders in which the prevailing underlying disease process is intracellular deposition of abnormal misfolded tau protein. Diseases often categorized as tauopathies include progressive supranuclear palsy, chronic traumatic encephalopathy, corticobasal degeneration, and frontotemporal lobar degeneration. Tauopathies can be classified through clinical assessment, imaging findings, histologic validation, or molecular biomarkers tied to the underlying disease mechanism. Many tauopathies vary in their clinical presentation and overlap substantially in presentation, making clinical diagnosis of a specific primary tauopathy difficult. Anatomic imaging findings are also rarely specific to a single tauopathy, and when present may not manifest until well after the point at which therapy may be most impactful. Molecular biomarkers hold the most promise for patient care and form a platform upon which emerging diagnostic and therapeutic applications could be developed. One of the most exciting developments utilizing these molecular biomarkers for assessment of tau deposition within the brain is tau‐PET imaging utilizing novel ligands that specifically target tau protein. This review will discuss the background, significance, and clinical presentation of each tauopathy with additional attention to the pathologic mechanisms at the protein level. The imaging characteristics will be outlined with select examples of emerging imaging techniques. Finally, current treatment options and emerging therapies will be discussed. This is by no means a comprehensive review of the literature but is instead intended for the practicing radiologist as an overview of a rapidly evolving topic.

Cerebrospinal Fluid Biomarkers in Autopsy-Confirmed Alzheimer Disease and Frontotemporal Lobar Degeneration

BACKGROUND AND OBJECTIVES

To determine how fully automated Elecsys CSF immunoassays for β-amyloid (Aβ) and tau biomarkers and an ultrasensitive Simoa assay for neurofilament light chain (NFL) correlate with neuropathologic changes of Alzheimer disease (AD) and frontotemporal lobar degeneration (FTLD).

METHODS

We studied 101 patients with antemortem CSF and neuropathology data. CSF samples were collected a mean of 2.9 years before death (range 0.2-7.5 years). CSF was analyzed for Aβ40, Aβ42, total tau (T-tau), tau phosphorylated at amino acid residue 181 (P-tau), P-tau/Aβ42 and Aβ42/Aβ40 ratios, and NFL. Neuropathology measures included Thal phases, Braak stages, Consortium to Establish a Registry for Alzheimer's Disease (CERAD) scores, AD neuropathologic change (ADNC), and primary and contributory pathologic diagnoses. Associations between CSF biomarkers and neuropathologic features were tested in regression models adjusted for age, sex, and time from sampling to death.

RESULTS

CSF biomarkers were associated with neuropathologic measures of Aβ (Thal, CERAD score), tau (Braak stage), and overall ADNC. The CSF P-tau/Aβ42 and Aβ42/Aβ40 ratios had high sensitivity, specificity, and overall diagnostic performance for intermediate-high ADNC (area under the curve range 0.95-0.96). Distinct biomarker patterns were seen in different FTLD subtypes, with increased NFL and reduced P-tau/T-tau in FTLD-TAR DNA-binding protein 43 and reduced T-tau in progressive supranuclear palsy compared to other FTLD variants.

DISCUSSION

CSF biomarkers, including P-tau, T-tau, Aβ42, Aβ40, and NFL, support in vivo identification of AD neuropathology and correlate with FTLD neuropathology.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that distinct CSF biomarker patterns, including for P-tau, T-tau, Aβ42, Aβ40, and NFL, are associated with AD and FTLD neuropathology.

Therapeutic Application of rTMS in Atypical Parkinsonian Disorders

The terms atypical parkinsonian disorders (APDs) and Parkinson plus syndromes are mainly used to describe the four major entities of sporadic neuronal multisystem degeneration: progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), multiple system atrophy (MSA), and dementia with Lewy bodies (LBD). APDs are characterized by a variety of symptoms and a lack of disease modifying therapies; their treatment thus remains mainly symptomatic. Brain stimulation via repetitive transcranial magnetic stimulation (rTMS) is a safe and noninvasive intervention using a magnetic coil, and it is considered an alternative therapy in various neuropsychiatric pathologies. In this paper, we review the available studies that investigate the efficacy of rTMS in the treatment of these APDs and Parkinson plus syndromes. Τhe majority of the studies have shown beneficial effects on motor and nonmotor symptoms, but research is still at a preliminary phase, with large, double-blind studies lacking in the literature.

Evolving concepts in progressive supranuclear palsy and other 4-repeat tauopathies

Tauopathies are classified according to whether tau deposits predominantly contain tau isoforms with three or four repeats of the microtubule-binding domain. Those in which four-repeat (4R) tau predominates are known as 4R-tauopathies, and include progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease, globular glial tauopathies and conditions associated with specific MAPT mutations. In these diseases, 4R-tau deposits are found in various cell types and anatomical regions of the brain and the conditions share pathological, pathophysiological and clinical characteristics. Despite being considered 'prototype' tauopathies and, therefore, ideal for studying neuroprotective agents, 4R-tauopathies are still severe and untreatable diseases for which no validated biomarkers exist. However, advances in research have addressed the issues of phenotypic overlap, early clinical diagnosis, pathophysiology and identification of biomarkers, setting a road map towards development of treatments. New clinical criteria have been developed and large cohorts with early disease are being followed up in prospective studies. New clinical trial readouts are emerging and biomarker research is focused on molecular pathways that have been identified. Lessons learned from failed trials of neuroprotective drugs are being used to design new trials. In this Review, we present an overview of the latest research in 4R-tauopathies, with a focus on progressive supranuclear palsy, and discuss how current evidence dictates ongoing and future research goals.

Towards clinical application of tau PET tracers for diagnosing dementia due to Alzheimer's disease

The recent development of several tau positron emission tomography (PET) tracers represents a major milestone for the Alzheimer's disease (AD) field. These tau PET tracers bind tau neurofibrillary tangles, a key neuropathological characteristic of AD that is tightly linked to synaptic loss, brain atrophy, and cognitive decline. It is notable that these tau PET tracers show low uptake in most non-AD tauopathies and other neurodegenerative disorders, resulting in a diagnostic specificity that is superior to that of amyloid beta (Aβ) PET and biofluid markers, especially at an older age when incidental Aβ pathology is common. Furthermore, tau PET tracers diagnostically outperform widely used MRI markers. Given its excellent diagnostic performance due to the combination of high sensitivity and specificity for detecting tau pathology in AD dementia, we hypothesize that tau PET can become an important diagnostic tool in specialized clinics for the differential diagnosis of dementia syndromes where AD is among the major possible underlying diseases.

Palliative Care for Parkinson's Spectrum Disorders: an Emerging Approach

Parkinson's spectrum disorders (PSD) are neurodegenerative parkinsonian conditions that carry a tremendous symptom burden. Palliative care is an interdisciplinary medical specialty that focuses on improving quality of life for patients and caregivers affected by serious life-limiting illnesses, at any stage of disease. Research and clinical programs into this emerging therapeutic approach remain limited. This review focuses on the role of palliative care in the treatment of patients with PSD. Gaps in knowledge and recommendations for future research are discussed.

Four-Repeat Tauopathies: Current Management and Future Treatments

Four-repeat tauopathies are a neurodegenerative disease characterized by brain parenchymal accumulation of a specific isoform of the protein tau, which gives rise to a wide breadth of clinical syndromes encompassing diverse symptomatology, with the most common syndromes being progressive supranuclear palsy-Richardson's and corticobasal syndrome. Despite the lack of effective disease-modifying therapies, targeted treatment of symptoms can improve quality of life for patients with 4-repeat tauopathies. However, managing these symptoms can be a daunting task, even for those familiar with the diseases, as they span motor, sensory, cognitive, affective, autonomic, and behavioral domains. This review describes current approaches to symptomatic management of common clinical symptoms in 4-repeat tauopathies with a focus on practical patient management, including pharmacologic and nonpharmacologic strategies, and concludes with a discussion of the history and future of disease-modifying therapeutics and clinical trials in this population.

Pharmacological interventions in corticobasal degeneration: a review

Corticobasal degeneration (CBD) is a sporadic tauopathy that presents with a varied combination of motor, cognitive, and behavioral features, making its diagnosis difficult. CBD has high morbidity and poor prognosis, with no effective therapy at present. We searched the PubMed/MEDLINE database for articles published from 1990 to 2019, using the keywords “corticobasal degeneration” AND “treatment.” The PRISMA method was adopted. Retrieved articles were characterized as having one of two methodological approaches: (1) studies aimed at primary tauopathy treatment and (2) symptomatic management. Review articles (based on CBD expert groups), case reports, case series, and pilot clinical trials were selected. Few attempts have been made to study drug options and drug efficacy in CBD systematically, and an effective treatment is not yet available. Treatment is symptomatic and based on similarity with other diseases due to the scarcity of studies specifically addressing CBD. CBD seems not to spark interest in more clinical trials for its low prevalence and reliability in clinical diagnosis.

Improved Mobility, Cognition, and Disease Severity in Corticobasal Degeneration of an African American Man After 12 Weeks of Adapted Tango: A Case Study

Corticobasal degeneration (CBD) has no available treatment to slow disease progression and generally resists drug therapy. Corticobasal degeneration has symptoms and decreased quality of life similar to Parkinson disease. Adapted Tango, a successful rehabilitation for Parkinson, may address CBD. A 63-yr-old African American man with CBD (alias: YD; CBD duration = 2 yrs) was evaluated for motor, cognitive, and psychosocial function before, immediately after, 1 mo after, and 6 mos after 12 wks of 20, biweekly 90-min adapted-tango lessons. After intervention, disease-related motor symptoms improved and YD reported fewer problems in nonmotor experiences of daily living, which include mood, cognition, pain, fatigue, etc. Motor symptoms remained above baseline at 6-mo posttest. YD's balance confidence improved after intervention but declined below baseline at 6-mo posttest. Quality of life was maintained despite worsened depression. YD improved or maintained executive function, and visuospatial function and attention at posttest and 1-mo posttest. At posttest, YD maintained mobility and improved on dynamic balance. At 1-mo posttest, most mobility measures had improved relative to baseline. However, YD showed executive function and overall motor decline 6 mos after intervention. Adapted tango may have temporarily slowed disease progression and improved or maintained mobility and cognition. Gains were poorly maintained after 6 mos. Further study is warranted.

Corticobasal degeneration

Corticobasal degeneration (CBD) is a rare neurodegenerative disease characterized by the predominance of pathological 4 repeat tau deposition in various cell types and anatomical regions. Corticobasal syndrome (CBS) is one of the clinical phenotypes associated with CBD pathology, manifesting as a progressive asymmetric akinetic-rigid, poorly levodopa-responsive parkinsonism, with cerebral cortical dysfunction. CBD can manifest as several clinical phenotypes, and similarly, CBS can also have a pathologic diagnosis other than CBD. This chapter discusses the clinical manifestations of pathologically confirmed CBD cases, the current diagnostic criteria, as well as the pathologic and neuroimaging findings of CBD/CBS. At present, therapeutic options for CBD remain symptomatic. Further research is needed to improve the clinical diagnosis of CBD, as well as studies on disease-modifying therapies for this relentlessly progressive neurodegenerative disorder.

How to approach a patient with parkinsonism - red flags for atypical parkinsonism

Parkinsonism is a clinical syndrome defined by bradykinesia plus rigidity or tremor. Though most commonly encountered in the setting of idiopathic Parkinson's disease, a number of neurodegenerative, structural, metabolic and toxic neurological disorders can result in parkinsonism. Accurately diagnosing the underlying cause of parkinsonism is of both therapeutic and prognostic relevance, especially as we enter the era of disease-modifying treatment trials for neurodegenerative disorders. Being aware of the wide array of potential causes of parkinsonism is of paramount importance for clinicians. In this chapter, we present a pragmatic clinical approach to patients with parkinsonism, specifically focusing on 'red flags', which should alert one to consider diagnoses other than idiopathic Parkinson's disease.

Therapeutic Management of the Overlapping Syndromes of Atypical Parkinsonism

Progressive supranuclear palsy, corticobasal degeneration and multiple system atrophy account for approximately 10% of neurodegenerative parkinsonism. Considerable clinical overlap exists between these disorders that extends to features considered characteristic of each disease. Clinical diagnostic criteria have attempted to increase the accuracy of clinical diagnosis as accurate diagnosis is necessary to inform prognosis and to facilitate the recognition of disease-modifying treatments. Currently no such treatment exists. Nevertheless, many clinical trials aiming to change the natural history of these diseases are ongoing. The spread and accumulation of abnormal proteins are among the pathophysiological mechanisms targeted. For the time being, however, only symptomatic treatment is available. Levodopa is used to treat parkinsonism, but patients usually show a poor or transient response. Amantadine is also used in practice for the same indication. Botulinum toxin can alleviate focal dystonic manifestations. Addressing non-motor manifestations is limited by the potential of available drugs to impact on other aspects of the disease. Most of the new symptomatic formulations under study are focused on orthostatic hypotension in multiple system atrophy. Exercise, occupational, physical, and speech therapy and psychotherapy should always accompany pharmacological approaches.

Long-Term Non-Invasive Treatment via Intranasal Administration of Nerve Growth Factor Protects the Human Brain in Frontotemporal Dementia associated with Corticobasal Syndrome: A Pilot Study

Background:

Nerve growth factor (NGF) is known for playing a critical protective role on a number of brain neurons in mammals, including humans. NGF can be delivered to the CNS via nasal route and has a neuroprotective action in case of neurodegenerative diseases.

Objective:

The aim of this study is to investigate for the first time whether purified NGF can play a neuroprotective role on human brain neurons affected by neurodegenerative diseases when administered via nasal route.

Methods:

Two female patients, both affected by frontotemporal dementia (FTD) associated with corticobasal syndrome (CBS) at different stages of disease progression, received a daily intranasal NGF spray for one year. Clinical/neurological aspects were observed over time. The follow-up study was performed using 18 FDG PET.

Results:

This case study seems to demonstrate that IN-NGF slows down the common decline caused by FTD/CBS.

Conclusions:

These findings suggest the potential neuroprotective role of IN-NGF administered in case of neurodegenerative diseases.

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.

Visual signs and symptoms of corticobasal degeneration

Corticobasal degeneration is a rare, progressive neurodegenerative disease and a member of the 'parkinsonian' group of disorders, which also includes Parkinson's disease, progressive supranuclear palsy, dementia with Lewy bodies and multiple system atrophy. The most common initial symptom is limb clumsiness, usually affecting one side of the body, with or without accompanying rigidity or tremor. Subsequently, the disease affects gait and there is a slow progression to influence ipsilateral arms and legs. Apraxia and dementia are the most common cortical signs. Corticobasal degeneration can be difficult to distinguish from other parkinsonian syndromes but if ocular signs and symptoms are present, they may aid clinical diagnosis. Typical ocular features include increased latency of saccadic eye movements ipsilateral to the side exhibiting apraxia, impaired smooth pursuit movements and visuo-spatial dysfunction, especially involving spatial rather than object-based tasks. Less typical features include reduction in saccadic velocity, vertical gaze palsy, visual hallucinations, sleep disturbance and an impaired electroretinogram. Aspects of primary vision such as visual acuity and colour vision are usually unaffected. Management of the condition to deal with problems of walking, movement, daily tasks and speech problems is an important aspect of the disease.

Tau PET patterns mirror clinical and neuroanatomical variability in Alzheimer's disease

SEE SARAZIN ET AL DOI101093/BRAIN/AWW041 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: The advent of the positron emission tomography tracer (18)F-AV1451 provides the unique opportunity to visualize the regional distribution of tau pathology in the living human brain. In this study, we tested the hypothesis that tau pathology is closely linked to symptomatology and patterns of glucose hypometabolism in Alzheimer's disease, in contrast to the more diffuse distribution of amyloid-β pathology. We included 20 patients meeting criteria for probable Alzheimer's disease dementia or mild cognitive impairment due to Alzheimer's disease, presenting with a variety of clinical phenotypes, and 15 amyloid-β-negative cognitively normal individuals, who underwent (18)F-AV1451 (tau), (11)C-PiB (amyloid-β) and (18)F-FDG (glucose metabolism) positron emission tomography, apolipoprotein E (APOE) genotyping and neuropsychological testing. Voxel-wise contrasts against controls (at P < 0.05 family-wise error corrected) showed that (18)F-AV1451 and (18)F-FDG patterns in patients with posterior cortical atrophy ('visual variant of Alzheimer's disease', n = 7) specifically targeted the clinically affected posterior brain regions, while (11)C-PiB bound diffusely throughout the neocortex. Patients with an amnestic-predominant presentation (n = 5) showed highest (18)F-AV1451 retention in medial temporal and lateral temporoparietal regions. Patients with logopenic variant primary progressive aphasia ('language variant of Alzheimer's disease', n = 5) demonstrated asymmetric left greater than right hemisphere (18)F-AV1451 uptake in three of five patients. Across 30 FreeSurfer-defined regions of interest in 16 Alzheimer's disease patients with all three positron emission tomography scans available, there was a strong negative association between (18)F-AV1451 and (18)F-FDG uptake (Pearson's r = -0.49 ± 0.07, P < 0.001) and less pronounced positive associations between (11)C-PiB and (18)F-FDG (Pearson's r = 0.16 ± 0.09, P < 0.001) and (18)F-AV1451 and (11)C-PiB (Pearson's r = 0.18 ± 0.09, P < 0.001). Voxel-wise linear regressions thresholded at P < 0.05 (uncorrected) showed that, across all patients, younger age was associated with greater (18)F-AV1451 uptake in wide regions of the neocortex, while older age was associated with increased (18)F-AV1451 in the medial temporal lobe. APOE ϵ4 carriers showed greater temporal and parietal (18)F-AV1451 uptake than non-carriers. Finally, worse performance on domain-specific neuropsychological tests was associated with greater (18)F-AV1451 uptake in key regions implicated in memory (medial temporal lobes), visuospatial function (occipital, right temporoparietal cortex) and language (left > right temporoparietal cortex). In conclusion, tau imaging-contrary to amyloid-β imaging-shows a strong regional association with clinical and anatomical heterogeneity in Alzheimer's disease. Although preliminary, these results are consistent with and expand upon findings from post-mortem, animal and cerebrospinal fluid studies, and suggest that the pathological aggregation of tau is closely linked to patterns of neurodegeneration and clinical manifestations of Alzheimer's disease.

Persistent pain as a non-motor symptom in corticobasal syndrome

While a number of studies have investigated pain in Parkinson's disease, pain in corticobasal syndrome (CBS) remains understudied. This study evaluated the presence of persistent pain in CBS to determine whether it is a common non-motor symptom. We retrospectively evaluated the records of patients who were clinically diagnosed with CBS and re-examined or interviewed the patients for evaluation. There were 27 patients with clinically diagnosed CBS, of whom nine had persistent pain of unknown origin in addition to their disease. Seven patients had pain in their affected limbs, and the others had chest or neck pain. One patient's limb pain responded to levodopa treatment, but her parkinsonism responded poorly to the treatment. Pain could be a common non-motor symptom in CBS. Levodopa treatment should be considered because it might be beneficial in some patients.

Primary motor cortex LTP/LTD-like plasticity in probable corticobasal syndrome

Whether the primary motor cortex (M1) contributes to the pathophysiology of corticobasal syndrome (CBS) remains unclear. In this study in patients with probable CBS, we tested whether M1 plasticity contributes to the pathophysiology of symptoms in the contralateral “less affected” limb, manifesting only parkinsonism, and in the contralateral “more affected” limb, manifesting parkinsonism plus other motor and nonmotor symptoms. In Experiment 1, we applied intermittent/continuous theta-burst stimulation (iTBS/cTBS) over the M1 contralateral to the less affected limb in 17 patients. In Experiment 2, we applied iTBS/cTBS over the M1 contralateral to the more affected limb in 14 of the 17 patients. We measured iTBS/cTBS-induced plasticity as reflected by motor-evoked potential (MEP) changes. Data were compared with those obtained in 17 healthy subjects (HS). In Experiment 1, TBS over the M1 contralateral to the less affected limb disclosed reduced plasticity in patients than in HS. In Experiment 2, in 5 of 14 patients we recorded abnormally low-amplitude MEPs, preventing the evaluation of plasticity in the M1 contralateral to the more affected limb. In the remaining nine patients, TBS disclosed abnormal plasticity characterized by high intersubject variability. In these nine patients, the response to TBS correlated with specific patients' clinical features. In the present study in patients with probable CBS, we have demonstrated heterogeneous abnormalities of M1 that contribute to the pathophysiology of this condition.

Left parietal cortex transcranial direct current stimulation enhances gesture processing in corticobasal syndrome

BACKGROUND AND PURPOSE

Corticobasal syndrome (CBS) is a clinical entity characterized by higher cortical dysfunctions associated with asymmetric onset of levodopa-resistant parkinsonism, dystonia and myoclonus. One of the most typical and distressful features of CBS is limb apraxia, which affects patients in their everyday life. Transcranial direct current stimulation (tDCS) is a non-invasive procedure of cortical stimulation, which represents a promising tool for cognitive enhancement and neurorehabilitation. The present study investigated whether anodal tDCS over the parietal cortex (PARC), would improve ideomotor upper limb apraxia in CBS patients.

METHODS

Fourteen patients with possible CBS and upper limb apraxia were enrolled. Each patient underwent two sessions of anodal tDCS (left and right PARC) and one session of placebo tDCS. Ideomotor upper limb apraxia was assessed using the De Renzi ideomotor apraxia test that is performed only on imitation.

RESULTS

A significant improvement of the De Renzi ideomotor apraxia test scores (post-stimulation versus pre-stimulation) after active anodal stimulation over the left PARC was observed (χ(2) = 17.6, P = 0.0005), whilst no significant effect was noticed after active anodal stimulation over the right PARC (χ(2) = 7.2, P = 0.07). A post hoc analysis revealed a selective improvement in the De Renzi ideomotor apraxia score after active anodal stimulation over the left PARC compared with placebo stimulation considering both right (P = 0.03) and left upper limbs (P = 0.01).

CONCLUSIONS

These findings indicate that tDCS to the PARC improves the performance of an ideomotor apraxia test in CBS patients and might represent a promising tool for future rehabilitation approaches.

Prevalence of amyloid PET positivity in dementia syndromes: a meta-analysis

IMPORTANCE

Amyloid-β positron emission tomography (PET) imaging allows in vivo detection of fibrillar plaques, a core neuropathological feature of Alzheimer disease (AD). Its diagnostic utility is still unclear because amyloid plaques also occur in patients with non-AD dementia.

OBJECTIVE

To use individual participant data meta-analysis to estimate the prevalence of amyloid positivity on PET in a wide variety of dementia syndromes.

DATA SOURCES

The MEDLINE and Web of Science databases were searched from January 2004 to April 2015 for amyloid PET studies.

STUDY SELECTION

Case reports and studies on neurological or psychiatric diseases other than dementia were excluded. Corresponding authors of eligible cohorts were invited to provide individual participant data.

DATA EXTRACTION AND SYNTHESIS

Data were provided for 1359 participants with clinically diagnosed AD and 538 participants with non-AD dementia. The reference groups were 1849 healthy control participants (based on amyloid PET) and an independent sample of 1369 AD participants (based on autopsy).

MAIN OUTCOMES AND MEASURES

Estimated prevalence of positive amyloid PET scans according to diagnosis, age, and apolipoprotein E (APOE) ε4 status, using the generalized estimating equations method.

RESULTS

The likelihood of amyloid positivity was associated with age and APOE ε4 status. In AD dementia, the prevalence of amyloid positivity decreased from age 50 to 90 years in APOE ε4 noncarriers (86% [95% CI, 73%-94%] at 50 years to 68% [95% CI, 57%-77%] at 90 years; n = 377) and to a lesser degree in APOE ε4 carriers (97% [95% CI, 92%-99%] at 50 years to 90% [95% CI, 83%-94%] at 90 years; n = 593; P < .01). Similar associations of age and APOE ε4 with amyloid positivity were observed in participants with AD dementia at autopsy. In most non-AD dementias, amyloid positivity increased with both age (from 60 to 80 years) and APOE ε4 carriership (dementia with Lewy bodies: carriers [n = 16], 63% [95% CI, 48%-80%] at 60 years to 83% [95% CI, 67%-92%] at 80 years; noncarriers [n = 18], 29% [95% CI, 15%-50%] at 60 years to 54% [95% CI, 30%-77%] at 80 years; frontotemporal dementia: carriers [n = 48], 19% [95% CI, 12%-28%] at 60 years to 43% [95% CI, 35%-50%] at 80 years; noncarriers [n = 160], 5% [95% CI, 3%-8%] at 60 years to 14% [95% CI, 11%-18%] at 80 years; vascular dementia: carriers [n = 30], 25% [95% CI, 9%-52%] at 60 years to 64% [95% CI, 49%-77%] at 80 years; noncarriers [n = 77], 7% [95% CI, 3%-18%] at 60 years to 29% [95% CI, 17%-43%] at 80 years.

CONCLUSIONS AND RELEVANCE

Among participants with dementia, the prevalence of amyloid positivity was associated with clinical diagnosis, age, and APOE genotype. These findings indicate the potential clinical utility of amyloid imaging for differential diagnosis in early-onset dementia and to support the clinical diagnosis of participants with AD dementia and noncarrier APOE ε4 status who are older than 70 years.

Corticobasal degeneration: clinical characteristics and multidisciplinary therapeutic approach in 26 patients

Corticobasal syndrome (CBS) is a sporadic tauopathy that manifests by a various combination of motor and cognitive deficits, which makes its diagnosis challenging. Treatment of CBS is symptomatic and based on evidence from other similar disorders due to the lack of studies on CBS. The aim of the study was to investigate low-frequency repetitive transcranial magnetic stimulation (rTMS) as a therapeutic tool in CBS. Twenty-six patients with clinically evident CBS according to Cambridge criteria were followed for 12-18 months while receiving low-frequency rTMS combined with pharmacological, rehabilitation treatment and botulinum toxin injection. The majority of patients are manifested with akinetic-rigid syndrome and cognitive dysfunction. There was improvement of the UPDRS and quality of life after 3 months of therapeutic interventions (P < 0.001 and <0.05, respectively). No significant deterioration in cognitive functions was detected over the study period. There was a significant reduction of caregiver burden after 3 months of interventions (P < 0.01); this improvement was maintained up to 18 months. Cognitive dysfunction is a frequent manifestation of CBS. CBS patients can benefit from multidisciplinary therapeutic approach employing low-frequency rTMS.