Apraxia and motor dysfunction in corticobasal syndrome

Combined non-invasive neuromodulation using transcranial direct current stimulation, motor imagery and action observation for motor, cognitive and functional recovery in cortico-basal degeneration: a single case study

This case report presents a comprehensive assessment and therapeutic intervention using non-invasive motor cortex neuromodulation for a 70-year-old female patient diagnosed with corticobasal degeneration (CBD). The study followed the CARE guidelines. The patient meets the criteria for probable CBD, with neuroimaging evidence of exclusively cortical impairment. The patient underwent a non-invasive neuromodulation protocol involving transcranial direct current stimulation (tDCS) and action observation plus motor imagery (AO+MI). The neuromodulation protocol comprised 20 sessions involving tDCS over the primary motor cortex and combined AO+MI. Anodal tDCS was delivered a 2 mA excitatory current for 20 minutes. AO+MI focused on lower limb movements, progressing over four weeks with video observation and gradual execution, both weekly and monthly. The neuromodulation techniques were delivered online (i.e. applied simultaneously in each session). Outcome measures were obtained at baseline, post-intervention and follow-up (1 month later), and included motor (lower limb), cognitive/neuropsychological and functional assessments. Walking speed improvements were not observed, but balance (Berg Balance Scale) and functional strength (Five Times Sit-to-Stand Test) improved post-treatment. Long-term enhancements in attentional set-shifting, inhibitory control, verbal attentional span, and working memory were found. There was neurophysiological evidence of diminished intracortical inhibition. Functional changes included worsening in Cortico Basal Ganglia Functional Scale score. Emotional well-being and general health (SF-36) increased immediately after treatment but were not sustained, while Falls Efficacy Scale International showed only long-term improvement. The findings suggest potential benefits of the presented neuromodulation protocol for CBD patients, highlighting multifaceted outcomes in motor, cognitive, and functional domains.

Left and right corticobasal syndrome: comparison of cognitive profiles between metabolic imaging - matched groups

BACKGROUND

Corticobasal syndrome (CBS) is typically asymmetric. Case reports suggest that left-hemisphere CBS (lhCBS) is associated with major language impairment, and right-hemisphere CBS (rhCBS) is associated with major visuospatial deficits, but no group study has ever verified these observations. In our study, we enrolled 49 patients with CBS, classified them as lhCBS or rhCBS based on asymmetry of hypometabolism on brain FDG-PET and compared their cognitive and behavioural profiles.

METHODS

We defined asymmetry of hypometabolism upon visual inspection of qualitative PET images and confirmed it through paired comparison of left- and right-hemisphere FDG uptake values. The two groups were also matched for severity of hypometabolism within the more affected and more preserved hemispheres, to unravel differences in the cognitive profiles ascribable specifically to each hemisphere's functional specializations. All patients were assessed for memory, language, executive and visuospatial deficits, apraxia, neglect, dyscalculia, agraphia and behavioural disturbances.

RESULTS

LhCBS (n. 26) and rhCBS (n. 23) patients did not differ for demographics, disease duration and severity of global cognitive impairment. The two cognitive profiles were largely overlapping, with two exceptions: Digit span forward was poorer in lhCBS, and visual neglect was more frequent in rhCBS.

CONCLUSIONS

After balancing out patients for hemispheric hypometabolism, we did not confirm worse language or visuospatial deficits in, respectively, lhCBS and rhCBS. However, verbal short-term memory was more impaired in lhCBS, and spatial attention was more impaired in rhCBS. Both of these functions reflect the functional specialization of the left and right fronto-parietal pathways, i.e. of the main loci of neurodegeneration in CBS.

Localizing apraxia in corticobasal syndrome: a morphometric MRI study

Apraxia localization has relied on voxel-based, lesion-symptom mapping studies in left hemisphere stroke patients. Studies on the neural substrates of different manifestations of apraxia in neurodegenerative disorders are scarce. The primary aim of this study was to look into the neural substrates of different manifestations of apraxia in a cohort of corticobasal syndrome patients (CBS) by use of cortical thickness. Twenty-six CBS patients were included in this cross-sectional study. The Goldenberg apraxia test (GAT) was applied. 3D-T1-weighted images were analyzed via the automated recon-all Freesurfer version 6.0 pipeline. Vertex-based multivariate General Linear Model analysis was applied to correlate GAT scores with cortical thickness. Deficits in imitation of meaningless gestures correlated with bilateral superior parietal atrophy, extending to the angular and supramarginal gyri, particularly on the left. Finger imitation relied predominantly on superior parietal lobes, whereas the left angular and supramarginal gyri, in addition to superior parietal lobes, were critical for hand imitation. The widespread bilateral clusters of atrophy in CBS related to apraxia indicate different pathophysiological mechanisms mediating praxis in neurodegenerative disorders compared to vascular lesions, with implications both for our understanding of praxis and for the rehabilitation approaches of patients with apraxia.

Transcranial magnetic stimulation neurophysiology in patients with non-Alzheimer's neurodegenerative diseases: A systematic review and meta-analysis

Non-Alzheimer's dementia (NAD) accounts for 30% of all neurodegenerative conditions and is characterized by cognitive decline beyond mere memory dysfunction. Diagnosing NAD remains challenging due to the lack of established biomarkers. Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological tool that enables the investigation of cortical excitability in the human brain. Paired-pulse TMS paradigms include short- and long-interval intracortical inhibition (SICI/LICI), intracortical facilitation (ICF), and short-latency afferent inhibition (SAI), which can assess neurophysiological functions of GABAergic, glutamatergic, and cholinergic neural circuits, respectively. We conducted the first systematic review and meta-analysis to compare these TMS indices among patients with NAD and healthy controls. Our meta-analyses indicated that TMS neurophysiological examinations revealed decreased glutamatergic function in patients with frontotemporal dementia (FTD) and decreased GABAergic function in patients with FTD, progressive supranuclear palsy, Huntington's disease, cortico-basal syndrome, and multiple system atrophy-parkinsonian type. In addition, decreased cholinergic function was found in dementia with Lewy body and vascular dementia. These results suggest the potential of TMS as an additional diagnostic tool to differentiate NAD.

Clinical neurophysiology of Parkinson's disease and parkinsonism

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This review is part of the series on the clinical neurophysiology of movement disorders and focuses on Parkinson’s disease and parkinsonism.

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The pathophysiology of cardinal parkinsonian motor symptoms and myoclonus are reviewed.

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The recordings from microelectrode and deep brain stimulation electrodes are reported in detail.

This review is part of the series on the clinical neurophysiology of movement disorders. It focuses on Parkinson’s disease and parkinsonism. The topics covered include the pathophysiology of tremor, rigidity and bradykinesia, balance and gait disturbance and myoclonus in Parkinson’s disease. The use of electroencephalography, electromyography, long latency reflexes, cutaneous silent period, studies of cortical excitability with single and paired transcranial magnetic stimulation, studies of plasticity, intraoperative microelectrode recordings and recording of local field potentials from deep brain stimulation, and electrocorticography are also reviewed. In addition to advancing knowledge of pathophysiology, neurophysiological studies can be useful in refining the diagnosis, localization of surgical targets, and help to develop novel therapies for Parkinson’s disease.

Impaired Affordance Perception as the Basis of Tool Use Deficiency in Alzheimer’s Disease

The present study investigated whether defective affordance perception capacity underpins tool use deficits in patients with Alzheimer’s disease (AD). An affordance, a concept James Gibson introduced, scales environmental objects to an animal’s action capabilities, thus offering opportunities for action. Each man-made artifact carries both a primary affordance (its designed function) and secondary affordances. In Experiment 1, participants identified secondary affordances of objects as a measure of their ability to identify alternative uses of familiar tools. A single response Go/No-Go task was administered to 4 groups: AD, mild cognitive impairment (MCI), Parkinson’s disease (PD), and elderly controls (EC). Groups were matched for age and years of education. The AD group performed poorest, followed by MCI, and PD and EC. EC and PD groups’ results failed to reach statistical significance, and the AD group performed at chance. In Experiment 2, participants judged the physical properties of the same objects used in Experiment 1. Even AD patients performed reliably, ruling out a visual processing deficit as the basis for their poor performance in Experiment 1. Results suggest that degraded affordance detection capacity can differentiate AD from normal aging and other neurodegenerative disorders and could be an affordable marker for AD, even in the early stages of AD.

Diagnostic contribution and therapeutic perspectives of transcranial magnetic stimulation in dementia

Transcranial magnetic stimulation (TMS) is a powerful tool to probe in vivo brain circuits, as it allows to assess several cortical properties such asexcitability, plasticity and connectivity in humans. In the last 20 years, TMS has been applied to patients with dementia, enabling the identification of potential markers of thepathophysiology and predictors of cognitive decline; moreover, applied repetitively, TMS holds promise as a potential therapeutic intervention. The objective of this paper is to present a comprehensive review of studies that have employed TMS in dementia and to discuss potential clinical applications, from the diagnosis to the treatment. To provide a technical and theoretical framework, we first present an overview of the basic physiological mechanisms of the application of TMS to assess cortical excitability, excitation and inhibition balance, mechanisms of plasticity and cortico-cortical connectivity in the human brain. We then review the insights gained by TMS techniques into the pathophysiology and predictors of progression and response to treatment in dementias, including Alzheimer's disease (AD)-related dementias and secondary dementias. We show that while a single TMS measure offers low specificity, the use of a panel of measures and/or neurophysiological index can support the clinical diagnosis and predict progression. In the last part of the article, we discuss the therapeutic uses of TMS. So far, only repetitive TMS (rTMS) over the left dorsolateral prefrontal cortex and multisite rTMS associated with cognitive training have been shown to be, respectively, possibly (Level C of evidence) and probably (Level B of evidence) effective to improve cognition, apathy, memory, and language in AD patients, especially at a mild/early stage of the disease. The clinical use of this type of treatment warrants the combination of brain imaging techniques and/or electrophysiological tools to elucidate neurobiological effects of neurostimulation and to optimally tailor rTMS treatment protocols in individual patients or specific patient subgroups with dementia or mild cognitive impairment.

Dentatorubrothalamic tract reduction using fixel-based analysis in corticobasal syndrome

PURPOSE

The word "fixel" refers to the specific fiber population within each voxel, and fixel-based analysis (FBA) is a recently developed technique that facilitates fiber tract-specific statistical analysis. The aim of the paper is to apply FBA to detect impaired fibers for corticobasal syndrome (CBS) especially in regions that contain multiple crossed fibers.

METHODS

FBA was performed in cohorts of participants clinically diagnosed with CBS (n = 10) and Parkinson's disease (n = 15) or in healthy controls (n = 9). The parameters of the diffusion weighted image were echo time, 83 ms; time, 8123.6 ms; flip angle, 90°; section thickness, 2 mm; b = 1000 s/mm²; and 32 axes. Diffusion tensor analysis was conducted using tract-based spatial statistics (TBSS), and white matter volume was estimated via voxel-based morphometry.

RESULTS

A comparison of PD or HC to CBS revealed a significant difference in the dentatorubrothalamic tract of the brainstem in FBA in addition to the affected regions in voxel-based morphometry and TBSS (family-wise error-corrected p < 0.05). Reduction of the white matter fibers crossing the brainstem could not be detected via microstructural changes identified using TBSS, but it was detected using FBA.

CONCLUSION

FBA has some advantages in determining the distribution of corticobasal syndrome lesions.

Corticobasal syndrome: neuroimaging and neurophysiological advances

Corticobasal degeneration (CBD) is a neurodegenerative condition characterized by 4R tau protein deposition in several brain regions that clinically manifests itself as a heterogeneous atypical parkinsonism typically expressed in adulthood. The prototypical clinical phenotype of CBD is corticobasal syndrome (CBS). Important insights into the pathophysiological mechanisms underlying motor and higher cortical symptoms in CBS have been gained by using advanced neuroimaging and neurophysiological techniques. Structural and functional neuroimaging studies often show asymmetric cortical and subcortical abnormalities, mainly involving perirolandic and parietal regions and basal ganglia structures. Neurophysiological investigations including electroencephalography and somatosensory evoked potentials provide useful information on the origin of myoclonus and on cortical sensory loss. Transcranial magnetic stimulation demonstrates heterogeneous and asymmetric changes in the excitability and plasticity of primary motor cortex and abnormal hemispheric connectivity. Neuroimaging and neurophysiological abnormalities in multiple brain areas reflect asymmetric neurodegeneration, leading to asymmetric motor and higher cortical symptoms in CBS.

Reduced capacity for empathy in corticobasal syndrome and its impact on carer burden

Corticobasal syndrome (CBS) is clinically characterised by a wide range of motor, cognitive, and behavioural features but remains challenging to diagnose accurately. Despite recent evidence supporting the presence of social cognition and emotion processing disturbances, few studies have explored the nature of empathic ability in CBS. This study aimed to (a) investigate the extent to which cognitive and affective dimensions of empathy are affected in CBS and (b) to determine the impact of such changes on carer burden. Empathic capacity was assessed in 29 CBS patients and 28 matched healthy controls. We employed the Interpersonal Reactivity Index (IRI), an instrument measuring: (a) perspective taking, (b) fantasy, (c) empathic concern, and (d) personal distress. A significant change in both perspective taking and empathic concern was observed in CBS following disease onset. Furthermore, affective empathy deficits in CBS patients predicted higher levels of carer burden. Disturbances in both cognitive and affective empathy are present in CBS and lead to increased levels of carer burden.

Clinical and biomarker changes in presymptomatic genetic frontotemporal dementia

Presymptomatic carriers of GRN and C9orf72 mutations, the most frequent genetic causes of frontotemporal lobar degeneration, represent the optimal target population for the development of disease-modifying drugs. Preclinical biomarkers are needed to monitor the effect of therapeutic interventions in this population. We assessed clinical, functional, and neurophysiological measures in 113 GRN or C9orf72 carriers and in 73 noncarrier first-degree relatives. For 73 patients, follow-up longitudinal data were available. Differences between carriers and noncarriers were assessed using linear mixed-effects models. We observed that biological changes and intracortical facilitation transmission abnormalities significantly antecede the emergence of clinical symptoms of at least 3 decades. These are followed by intracortical inhibition transmission deficits, detected approximately 2 decades before expected symptom onset and then followed by an increase of white matter lesions, structural brain atrophy, and cognitive impairment. These results highlight how several biomarkers can show different aspects and rates of decline, possibly correlated with the underlying physiopathological process, that arise decades before the onset of clinical symptoms.

Interrogating cortical function with transcranial magnetic stimulation: insights from neurodegenerative disease and stroke

Transcranial magnetic stimulation (TMS) is an accessible, non-invasive technique to study cortical function in vivo. TMS studies have provided important pathophysiological insights across a range of neurodegenerative disorders and enhanced our understanding of brain reorganisation after stroke. In neurodegenerative disease, TMS has provided novel insights into the function of cortical output cells and the related intracortical interneuronal networks. Characterisation of cortical hyperexcitability in amyotrophic lateral sclerosis and altered motor cortical function in frontotemporal dementia, demonstration of cholinergic deficits in Alzheimer's disease and Parkinson's disease are key examples where TMS has led to advances in understanding of disease pathophysiology and potential mechanisms of propagation, with the potential for diagnostic applications. In stroke, TMS methodology has facilitated the understanding of cortical reorganisation that underlie functional recovery. These insights are critical to the development of effective and targeted rehabilitation strategies in stroke. The present review will provide an overview of cortical function measures obtained using TMS and how such measures may provide insight into brain function. Through an improved understanding of cortical function across a range of neurodegenerative disorders, and identification of changes in neural structure and function associated with stroke that underlie clinical recovery, more targeted therapeutic approaches may now be developed in an evolving era of precision medicine.

Neurophysiology and neurochemistry of corticobasal syndrome

Corticobasal syndrome is a rare neurodegenerative disorder, which presents with a progressive, asymmetrical, akinetic rigid syndrome and early cortical signs. However, clinical, pathological, and electrophysiological heterogeneity makes the understanding of this syndrome challenging. Corticobasal syndrome can have various pathological substrates including corticobasal degeneration, Alzheimer's disease, Fronto-temporal degeneration with TDP inclusions, Creutzfeldt-Jakob disease, and progressive supranuclear palsy (PSP). Furthermore, tools such as transcranial magnetic stimulation (TMS) and functional neuroimaging techniques like PET and SPECT have not been adequately used to supplement the clinico-pathological heterogeneity. TMS studies in CBS have revealed changes in cortical excitability and transcortical inhibition. Despite the availability of more than 2 decades, its potential in CBS has not been fully utilized in studying the cortical plasticity and effect of Levodopa on central neurophysiology. PET and SPECT studies in CBS have shown abnormalities in regional glucose metabolism, asymmetrical involvement of presynaptic dopaminergic system, and ascending cholinergic connections to the cortex. While most studies have shown normal D2 receptor-binding activity in striatum of CBS cases, the results have not been unanimous. Functional neuroimaging and TMS studies in CBS have shown the involvement of GABAergic, muscarinic, and dopaminergic systems. In this review, we aim to provide the current state of understanding of central neurophysiology and neurochemistry of CBS using TMS and functional neuroimaging techniques. We also highlight the heterogeneous nature of this disorder and the existing knowledge gaps.

Transcranial Magnetic Stimulation for the Assessment of Neurodegenerative Disease

Transcranial magnetic stimulation (TMS) is a noninvasive technique that has provided important information about cortical function across an array of neurodegenerative disorders, including Alzheimer's disease, frontotemporal dementia, Parkinson's disease, and related extrapyramidal disorders. Application of TMS techniques in neurodegenerative diseases has provided important pathophysiological insights, leading to the development of pathogenic and diagnostic biomarkers that could be used in the clinical setting and therapeutic trials. Abnormalities of TMS outcome measures heralding cortical hyperexcitability, as evidenced by a reduction of short-interval intracortical inhibition and increased in motor-evoked potential amplitude, have been consistently identified as early and intrinsic features of amyotrophic lateral sclerosis (ALS), preceding and correlating with the ensuing neurodegeneration. Cortical hyperexcitability appears to form the pathogenic basis of ALS, mediated by trans-synaptic glutamate-mediated excitotoxic mechanisms. As a consequence of these research findings, TMS has been developed as a potential diagnostic biomarker, capable of identifying upper motor neuronal pathology, at earlier stages of the disease process, and thereby aiding in ALS diagnosis. Of further relevance, marked TMS abnormalities have been reported in other neurodegenerative diseases, which have varied from findings in ALS. With time and greater utilization by clinicians, TMS outcome measures may prove to be of utility in future therapeutic trial settings across the neurodegenerative disease spectrum, including the monitoring of neuroprotective, stem-cell, and genetic-based strategies, thereby enabling assessment of biological effectiveness at early stages of drug development.

Apraxia: Review and Update

Praxis, the ability to perform skilled or learned movements is essential for daily living. Inability to perform such praxis movements is defined as apraxia. Apraxia can be further classified into subtypes such as ideomotor, ideational and limb-kinetic apraxia. Relevant brain regions have been found to include the motor, premotor, temporal and parietal cortices. Apraxia is found in a variety of highly prevalent neurological disorders including dementia, stroke and Parkinsonism. Furthermore, apraxia has been shown to negatively affect quality of life. Therefore, recognition and treatment of this disorder is critical. This article provides an overview of apraxia and highlights studies dealing with the neurophysiology of this disorder, opening up novel perspectives for the use of motor training and noninvasive brain stimulation as treatment.

Laterality of motor cortical function measured by transcranial magnetic stimulation threshold tracking

INTRODUCTION

Threshold tracking paired-pulse transcranial magnetic stimulation (TTTMS) examines cortical function and is useful for diagnosis of motor neuron disorders. Differences in cortical function have been identified between dominant and non-dominant limbs using constant stimulus methods, but they remain unclear, potentially due to methodological differences. In this study we aimed to clarify differences in cortical function between dominant and non-dominant limbs using TTTMS.

METHODS

Single-pulse TMS, TTTMS, and nerve conduction studies were performed in 25 healthy, right-handed participants by recording from the abductor pollicis brevis muscle.

RESULTS

There were no side-to-side differences observed in resting motor threshold, motor evoked potential (MEP) amplitude, MEP latency, central motor conduction time, cortical silent period, short-interval intracortical inhibition and facilitation, compound muscle action potential (CMAP) amplitude, CMAP latency, F-wave latency, or neurophysiological index.

CONCLUSIONS

These findings suggest that, when using TTTMS, there are no differences in cortical function between dominant and non-dominant hemispheres. Muscle Nerve 55: 424-427, 2017.

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.

Lifting the veil: how to use clinical neuropsychology to assess dementia

Neurologists often struggle to interpret the results of neuropsychological testing, even though cognitive assessments are an integral component of the diagnostic process in dementia syndromes. This article reviews the principles underlying clinical neuropsychology, background on common neuropsychological tests, and tips on how to interpret the results when assessing patients with dementia. General cognitive screening tools, appropriate for use by general neurologists and psychiatrists, as well as specific cognitive tests examining the main cognitive domains (attention and orientation, memory, visuospatial function, language and executive function) in patients with dementia are considered. Finally, the pattern of deficits, helpful in defining clinical dementia phenotypes and sometimes in predicting the underlying molecular pathology, are outlined. Such clinicopathological associations will become invaluable as disease-modifying treatments for dementia are developed and implemented.

Therapeutic interventions in parkinsonism: Corticobasal degeneration

Corticobasal degeneration (CBD) is a progressive neurodegenerative disorder resulting from pathological accumulation of tau protein and is included in the spectrum of Atypical Parkinsonism. The typical clinical phenotype of CBD is characterized by the Corticobasal syndrome (CBS). In recent years it has become clear that the clinical picture of CBS may be caused by different pathological conditions, resulting in frequent misdiagnosis. CBD has high morbidity and poor prognosis with no effective therapies. In this review, we will discuss the symptomatic treatment, the palliative care and the disease modifying strategies currently in use. Symptomatic treatment in patients with CBD may sometimes be useful for improving motor (parkinsonism, dystonia and myoclonus) and non-motor (cognitive-behavioral) symptoms, but the effects are often unsatisfactory. In addition, non-pharmacological strategies and palliative care are useful integrating components of the multidisciplinary therapeutic approach for patients with CBD. Despite many efforts, a disease-modifying treatment is still unavailable for CBD.

Progression of limb apraxia in corticobasal syndrome: neuropychological and functional neuroimaging report of a case series

The current study described the progression of limb apraxia in seven corticobasal syndrome patients through a comprehensive battery, including both gesture production tasks and conceptual tool/action knowledge tasks. The examination of the behavioral and neuroimaging (SPECT) data revealed two patient subgroups. One group consisted of patients with preserved conceptual tool/action knowledge, relatively mild gesture production and neuropsychological deficits with few significantly hypoperfused regions of interest. The other group consisted of those whose conceptual tool/action knowledge and general cognition eventually deteriorated and who were quite severely affected in their gesture production performance. These patients were characterized by bilateral hypoperfusion in parietal regions and in one case bilateral anterior cingulate regions.