A preliminary study of white matter disconnections underlying deficits in praxis in left hemisphere stroke patients.

Limb apraxia is a higher-order motor disorder often occurring post-stroke, which affects skilled actions. It is assessed through tasks involving gesture production or pantomime, recognition, meaningless gesture imitation, complex figure drawing, single and multi-object use. A two-system model for the organisation of actions hypothesizes distinct pathways mediating praxis deficits via conceptual, 'indirect', and perceptual 'direct' routes to action. Traditional lesion- symptom mapping techniques have failed to identify these distinct routes. We assessed 29 left hemisphere stroke patients to investigate white matter disconnections on deficits of praxis tasks from the Birmingham Cognitive Screening. White matter disconnection maps derived from patients' structural T1 lesions were created using a diffusion-weighted healthy participant dataset acquired from the human connectome project (HCP). Initial group-level regression analyses revealed significant disconnection between occipital lobes via the splenium of the corpus callosum and involvement of the inferior longitudinal fasciculus in meaningless gesture imitation deficits. There was a trend of left fornix disconnection in gesture production deficits. Further, voxel-wise Bayesian Crawford single-case analyses performed on two patients with the most severe meaningless gesture imitation and meaningful gesture production deficits, respectively, confirmed distinct posterior interhemispheric disconnection, for the former, and disconnections between temporal and frontal areas via the fornix, rostrum of the corpus callosum and anterior cingulum, for the latter. Our results suggest distinct pathways associated with perceptual and conceptual deficits akin to 'direct' and 'indirect' action routes, with some patients displaying both. Larger studies are needed to validate and elaborate on these findings, advancing our understanding of limb apraxia.

Recovery of gestures for persons with severe non-fluent aphasia and limb apraxia: A long-term follow-up study.

Persons with severe non-fluent aphasia would benefit from using gestures to substitute for their absent powers of speech. The use of gestures, however, is challenging for persons with aphasia and concomitant limb apraxia. Research on the long-term recovery of gestures is scant, and it is unclear whether gesture performance can show recovery over time. This study evaluated the recovery of emblems and tool use pantomimes of persons with severe non-fluent aphasia and limb apraxia after a left hemisphere stroke. The Florida Apraxia Screening Test-Revised (FAST-R) was used for measurements. The test includes 30 gestures to be performed (i) after an oral request, (ii) with the aid of a pictorial cue, or (iii) as an imitation. The gestures were rated on their degree of comprehensibility. The comprehensibility of gestures after an oral request improved significantly in five out of seven participants between the first (1-3 months after the stroke) and the last (3 years after) examination. Improvement continued for all five in the period between six months and three years. The imitation model did improve the comprehensibility of gestures for all participants, whereas the pictorial cue did so just slightly. The skill of producing gestures can improve even in the late phase post-stroke. Because of this potential, we suggest that gesture training should be systematically included in the rehabilitation of communication for persons with severe non-fluent aphasia.

Clinical and MRI characterization of apraxic syndrome in corticobasal degeneration: A single-case study.

Objective: To identify the cortical and subcortical distribution of atrophy and the disorganization of white matter bundles underlying the apraxic disorders in a patient with corticobasal degeneration (CBD). Method: Patient underwent appropriate neuropsychological tasks aimed at identifying the nature of the apraxic disorder and morphometric structural MRI with whole-brain voxel-wise analysis. Results: Progressive limbkinetic apraxia (LKA) with onset in the right upper limb with subsequent extension to the limbs, trunk, orofacial district, and eye movements was documented, associated with element of ideomotor apraxia (IMA). The MRI study showed grey matter atrophy extending to much of the frontal cortex bilaterally, including the precentral cortex, and into the inferior parietal regions. Caudate and putamen were involved on the left. Significant clusters of white matter atrophy were found in the bilateral superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF) and corpus callosum (CC). Sensory evoked potentials (SEPs) and motor evoked potentials (MEPs) were normal. Conclusion: Previous observations in CBD indicate lack of inhibitory control from the sensory to the primary motor cortex with dysfunctional frontoparietal and cortico-motoneuron projections. Our neuroimaging data are partially consistent with these observations suggesting that the apraxic disorder in our patient might be produced by the disconnection of the primary motor cortex from the parietal areas that prevents selection and control of muscle movements, in the presence of preserved cortico-motoneuron as demonstrated by normal PEM. Apraxic disorders in CBD are high-level deficits of movement control that spare the motoneuron.

A fist bump in a political meeting? The influence of social context on affordance selection.

Historically, understanding human cognition such as action processing has been a challenging issue in cognitive neuropsychology and the more we know about cognition, the more we shape it as a complex, multi-determined phenomenon that is embedded in a social context. The present study aimed at understanding how the social context could influence affordance selection. We hypothesized that affordance selection would be modulated by social context and that a given hand configuration would be considered appropriate or not, as a function of the presence or absence of social context. Twenty-six healthy participants were asked to judge the appropriateness of three variants of 10 hand-object interactions based on photographs presented with or without a visual, social context. In our results, hand configurations were intrinsically acceptable or not, but this effect was modulated by the social context. A three-step model of the influence of social context on affordance selection was proposed, according to which selection depends on social norms, in the form of social knowledge and social context analysis.

The Impact of Upper Limb Apraxia on General and Domain-Specific Self-Efficacy in Post-Stroke Patients.

BACKGROUND: Upper limb apraxia (ULA) is a neurological syndrome characterized by the inability to perform purposeful movements. ULA could impact individuals' perceptions, including perceived self-efficacy. The aim of this study is to investigate whether ULA is related to general self-efficacy and self-efficacy for managing symptoms in post-stroke patients. METHODS: A cross-sectional study was conducted involving 82 post-stroke patients. Regression analyses were implemented using a stepwise model including seven dimensions of ULA: imitation (non-symbolic, intransitive, and transitive), pantomime (non-symbolic, intransitive, and transitive), and dimension of apraxic performance in activities of daily living. These dimensions were independent variables, while general self-efficacy and symptom management self-efficacy dimensions were dependent variables. RESULTS: The findings revealed that intransitive imitation accounted for 14% of the variance in general self-efficacy and 10% of self-efficacy for managing emotional symptoms. Transitive imitation explained 10% of the variance in self-efficacy for managing global symptoms and 5% for social-home integration symptoms. The combination of intransitive imitation, non-symbolic pantomime, and alterations in activities of daily living performance associated with ULA explained 24% of the variance in cognitive self-efficacy. CONCLUSIONS: Hence, ULA dimensions seem to be related to the levels of general perceived self-efficacy and self-efficacy for managing symptoms among post-stroke patients.

Shared and distinct routes in speech and gesture imitation: Evidence from stroke.

Dual-route models of high-level (praxis) actions distinguish between an "indirect" semantic route mediating meaningful gesture imitation, and a "direct" sensory-motor route mediates meaningless gesture imitation. Similarly, dual-route language models distinguish between an indirect route mediating production and repetition of words, and a direct route mediating non-word repetition. Although aphasia and limb apraxia frequently co-occur following left-hemisphere cerebrovascular accident (LCVA), it is unclear which aspects of these functional-neuroanatomic dual-route architectures are shared across praxis and language domains. This study focused on gesture imitation to test the hypothesis that semantic information (and portions of the indirect route) are shared across domains, whereas two distinct dorsal routes mediate sensory-motor mapping. Forty chronic LCVA and 17 neurotypical controls completed semantic memory and language tasks and imitated 3 types of gesture stimuli: (1) labeled/"named" meaningful, (2) unnamed meaningful, and (3) meaningless gestures. The comparison of accuracy between meaningless versus unnamed meaningful gestures examined the benefits of semantic information, while the comparison of unnamed meaningful versus named meaningful imitation examined additional benefits of linguistic cueing. Mixed-effects models examined group by task interaction effects on gesture ability. We found that for patients with LCVA, unnamed meaningful gestures were imitated more accurately than meaningless gestures, suggesting that semantic information was beneficial, but there was no benefit of labeling. Reduced benefit of semantic information on gesture accuracy was associated with lesions to inferior frontal and posterior temporal regions as well as semantic memory performance on a pictorial (non-gesture) task. In contrast, there was no relationship between meaningless gesture imitation and nonword repetition, indicating that measures of direct route performance are not associated across language and action. These results provide preliminary evidence that portions of the indirect semantic route are shared across the language and action domains, while two direct sensory-motor mapping routes mediate word repetition and gesture imitation.

Gesture profiles distinguish primary progressive aphasia variants.

Primary progressive aphasia (PPA) is a neurodegenerative syndrome characterized by progressive language deficits. There are three main variants of PPA - semantic (svPPA), logopenic (lvPPA), and nonfluent (nfvPPA) - that can be challenging to distinguish. Limb praxis may also be affected in PPA, but it is unclear whether different variants of PPA are associated with differences in gesture production. Prior research with neurotypical individuals indicates that the left temporal lobe is a critical locus of manipulable object and hand posture representations. Moreover, when imitating gestures, individuals whose strokes include the left temporal lobe show reduced benefit of gesture meaning and disproportionate impairment in hand posture as compared to arm kinematics. We tested the hypothesis that svPPA - who typically exhibit primarily temporal lobe atrophy - would differentially show these expected patterns of gesture imitation performance. Nineteen participants with PPA completed meaningful and meaningless gesture imitation tasks, and performance was scored for hand posture and arm kinematics accuracy. Generalized logistic mixed-effect regression models controlling for dementia severity showed overall benefits from gesture meaning, and greater impairments in hand posture than arm kinematics. We also found that svPPA participants were the most impaired in gesture imitation overall. Critically, there was also a significant three-way interaction of group, meaning, and gesture component: only svPPA participants showed relative impairments of hand posture for meaningful gestures as well as meaningless gestures. Thus, unlike lvPPA and nfvPPA, the hand postures of svPPA failed to benefit from gesture meaning. This research extends prior findings on the role of the temporal lobe in hand posture representations associated with manipulable objects, and is the first to indicate that there may be distinct gesture imitation patterns as a function of PPA variant. Characterizing componential gesture deficits in PPA may help to inform differential diagnosis, compensatory communication strategies, and cognitive praxis models of PPA.

Effects of limb apraxia intervention in patients with stroke: A meta-analysis of randomized controlled trials.

OBJECTIVE: Limb apraxia, a complication of stroke, causes difficulties in performing activities of daily living (ADL). To date, there are no studies on the effectiveness of limb apraxia interventions. We conducted a meta-analysis to assess the effectiveness of limb apraxia interventions in reducing its severity and improving ADL. METHODS: We conducted a search of randomized controlled trials (RCTs) related to limb apraxia till December 2021 using the databases of PubMed, Embase, CINAHL, and the Cochrane Library. We measured the outcome variables in the subgroups of total apraxia (TA), ideational apraxia (IA), ideomotor apraxia (IMA), and ADL. The Physiotherapy Evidence Database (PEDro) scale was used to assess the quality. RESULTS: Five RCTs were selected, and of the 310 participants, 155 were in the experimental and 155 in the control group. A random-effects model was used for the effect size distribution. The limb apraxia intervention methods included gesture and strategy training (three and two studies, respectively). The effect sizes of the outcome variables in the subgroups were small for the TA and IA, with 0.475 (95% confidence interval [CI]: -0.151-1.102; p = 0.137) and 0.289 (95% CI: -0.144-0.722; p = 0.191), respectively. IMA had a medium effect size of 0.731 (95% CI: -0.062-1.525; p = 0.071), not statistically significant, whereas ADL effect size was small and statistically significant, 0.416 (95% CI: 0.159-0.673; p = 0.002). CONCLUSIONS: Gesture and strategy training had statistically significant effects on ADL as limb apraxia interventions. Therefore, the effectiveness of the apraxia interventions needs to be further evaluated through continuous RCTs.

Limb Apraxias: The Influence of Higher Order Perceptual and Semantic Deficits in Motor Recovery After Stroke.

Stroke is a leading cause of disability worldwide. Limb apraxia is a group of higher order motor disorders associated with greater disability and dependence after stroke. Original neuropsychology studies distinguished separate brain pathways involved in perception and action, known as the dual stream hypothesis. This framework has allowed a better understanding of the deficits identified in Limb Apraxia. In this review, we propose a hierarchical organization of this disorder, in which a distinction can be made between several visuomotor pathways that lead to purposeful actions. Based on this, executive apraxias (such as limb kinetic apraxia) cause deficits in executing fine motor hand skills, and intermediate apraxias (such as optic ataxia and tactile apraxia) cause deficits in reaching to grasp and manipulating objects in space. These disorders usually affect the contralesional limb. A further set of disorders collectively known as limb apraxias include deficits in gesture imitation, pantomime, gesture recognition, and object use. These deficits are due to deficits in integrating perceptual and semantic information to generate complex movements. Limb apraxias are usually caused by left-hemisphere lesions in right-handed stroke patients, affecting both limbs. The anterior- to posterior-axis of brain areas are disrupted depending on the increasing involvement of perceptual and semantic processes with each condition. Lower-level executive apraxias are linked to lesions in the frontal lobe and the basal ganglia, while intermediate apraxias are linked to lesions in dorso-dorsal subdivisions of the dorsal fronto-parietal networks. Limb apraxias can be caused by lesions in both dorsal and ventral subdivisions including the ventro-dorsal stream and a third visuomotor pathway, involved in body schema and social cognition. Rehabilitation of these disorders with behavioral therapies has aimed to either restore perceptuo-semantic deficits or compensate to overcome these deficits. Further studies are required to better stratify patients, using modern neurophysiology and neuroimaging techniques, to provide targeted and personalized therapies for these disorders in the future.

Single-case disconnectome lesion-symptom mapping: Identifying two subtypes of limb apraxia.

Influential theories of skilled action posit that distinct cognitive mechanisms and neuroanatomic substrates support meaningless gesture imitation and tool use pantomiming, and poor performance on these tasks are hallmarks of limb apraxia. Yet prior research has primarily investigated brain-behavior relations at the group level; thus, it is unclear whether we can identify individuals with isolated impairments in meaningless gesture imitation or tool use pantomiming whose performance is associated with a distinct neuroanatomic lesion profile. The goal of this study was to test the hypothesis that individuals with disproportionately worse performance in meaningless gesture imitation would exhibit cortical damage and white matter disconnection in left fronto-parietal brain regions, whereas individuals with disproportionately worse performance in tool use pantomiming would exhibit cortical damage and white matter disconnection in left temporo-parietal brain regions. Fifty-eight participants who experienced a left cerebrovascular accident took part in a meaningless gesture imitation task, a tool use pantomiming task, and a T1 structural MRI. Two participants were identified who had relatively small lesions and disproportionate impairments on one task relative to the other, as well as below-control-level performance on one task and not the other. Using these criteria, one participant was disproportionately impaired at meaningless gesture imitation, and the other participant was disproportionately impaired at pantomiming tool use. Graph theoretic analysis of each participant's structural disconnectome demonstrated that disproportionately worse meaningless gesture imitation performance was associated with disconnection among the left inferior parietal lobule, the left superior parietal lobule, and the left middle and superior frontal gyri, whereas disproportionately worse tool use pantomiming performance was associated with disconnection between left temporal and parietal regions. Our results demonstrate that relatively focal lesions to specific portions of the Tool Use Network can be associated with distinct limb apraxia subtypes.

Characterising factors underlying praxis deficits in chronic left hemisphere stroke patients.

Limb apraxia, a disorder of skilled action not consequent on primary motor or sensory deficits, has traditionally been defined according to errors patients make on neuropsychological tasks. Previous models of the disorder have failed to provide a unified account of patients' deficits, due to heterogeneity in the patients and tasks used. In this study we hypothesised that we may be able to map apraxic deficits onto principal components, some of which may be specific, whilst others may align with other cognitive disorders. We implemented principal component analysis (PCA) to elucidate core factors of the disorder in a preliminary cohort of 41 unselected left hemisphere chronic stroke patients who were tested on a comprehensive and validated apraxia screen. Three principal components were identified: posture selection, semantic control and multi-demand sequencing. These were submitted to a lesion symptom mapping (VBCM) analysis in a subset of 24 patients, controlled for lesion volume, age and time post-stroke. The first component revealed no significant structural correlates. The second component was related to regions in inferior frontal gyrus, primary motor area, and adjacent parietal opercular (including inferior parietal and supramarginal gyrus) areas. The third component was associated with lesions within the white matter underlying the left sensorimotor cortex, likely involving the 2nd branch of the left superior longitudinal fasciculus as well as the posterior orbitofrontal cortex (pOFC). These results highlight a significant role of common cognitive functions in apraxia, which include action selection, and sequencing, whilst more specific deficits may relate to semantic control. Moreover, they suggest that previously described 'ideomotor' and 'ideational' deficits may have a common neural basis within semantic control. Further research using this technique would help elucidate the cognitive processes underlying limb apraxia, its neural correlates and their relationship with other cognitive disorders.

The challenge of apraxia: Toward an operational definition?

The diagnosis of limb apraxia relies mainly on exclusion criteria (e.g., elementary motor or sensory deficits, aphasia). Due to the diversity of apraxia definitions and assessment methods, patients may or may not show apraxia depending on the chosen assessment method or theory, making the definition of apraxia somewhat arbitrary. As a result, "apraxia" may be diagnosed in patients with different cognitive impairments. Based on a quantitative and critical review of the literature, it is argued that this situation has its roots in the evolution from a task-based approach (i.e., the use of gold standard tests to detect apraxia) toward a process-based approach, namely, the deconstruction of the conceptual or production systems of action into multiple cognitive processes: language, executive functions, working memory, semantic memory, body schema, body image, visual-spatial skills, social cognition, visual-kinesthetic engrams, manipulation knowledge, technical reasoning, structural inference, and categorical apprehension. The coexistence of both approaches in the current literature is a major challenge that stands in the way of a scientific definition of apraxia. As a step toward a solution, we suggest to focus on symptoms, and on two complementary definition criteria (in addition with traditional exclusion criteria): Specificity (i.e., is apraxia explained by the alteration of cognitive processes specifically dedicated to gesture production?), and consistency (i.e., is the gesture production impairment consistent across tasks?). Two categories of limb apraxia are proposed: symptomatic apraxia (i.e., gesture production deficits that are secondary to more general cognitive impairments) and idiopathic apraxia (i.e., gesture production deficits that can be observed in isolation). It turns out that the only apraxia subtype that fulfills exclusion, specificity, and consistency criteria is limb-kinetic apraxia. A century after Liepmann's demonstration of the autonomy of apraxia toward language, the autonomy of this syndrome toward the rest of cognition remains an open question, while it poses new challenges to apraxia studies.

The autocracy of meaning: Intact visuo-imitative processes may not compensate for meaningful gestures.

The dual-route models of action distinguish between a semantic and a non-semantic visuo-motor route to execute different types of gestures. Despite the large amount of evidence in support to the model, some aspects are debated. One issue concerns the recruitment of the visuo-motor route to correctly execute meaningful gestures when the semantic route is damaged. Debated predictions of the dual-route model were investigated in a sample of 32 patients with left hemisphere stroke lesions compared to 27 healthy controls. Group analysis showed that patients were equally impaired on meaningful and meaningless gestures. Single-case analysis demonstrated that most cases were more impaired on meaningful than on meaningless gestures both when they are given in separate lists and when they are intermingled. Impaired performance on the imitation of meaningful gestures in both the separate and mixed list but spared performance on meaningless gestures in the separate list is against the hypothesis that the intact visuo-motor route compensates for damage to the semantic route. These results suggest that the damaged semantic route interferes with the visuo-motor route and prevents the processing of meaningful gestures along the visuo-motor route. Furthermore, an explorative analysis was conducted to investigate the relationship between gestures imitation and pantomime of object use on verbal command and between gestures imitation and performance on linguistic tasks. Although no significant correlation emerged, patients with moderate/severe impairment on the AAT performed significantly worse on meaningful, but not on meaningless gestures than patients with mild/minimal language impairment, suggesting that praxis and language systems are independent but dynamically interact.

Treating limb apraxia via action semantics: a preliminary study.

Limb apraxia is evident in approximately 50% of patients after left hemisphere cerebral vascular accident (LCVA) and increases disability and caregiver dependence. Individuals with apraxia exhibit abnormalities in spatio-temporal aspects of gesture production and/or in knowledge of tool-related actions (action semantics). This preliminary study of three LCVA participants aimed to (i) explore the efficacy of a novel Action Network Treatment (ANT) that focused on improving the semantic association between tool actions and other types of tool knowledge, an intervention inspired by successful semantic network treatments in aphasia (e.g., Edmonds et al., 2009), and (ii) explore whether there are individuals with apraxia who benefit from ANT relative to a version of a comparatively well-studied existing apraxia treatment (Smania et al., 2006; Smania et al., 2000) that shapes gesture via focus on practicing the spatio-temporal aspects of gesture production (Tool Use Treatment or TUT). One participant demonstrated treatment benefits from both ANT and TUT, while another only benefited from TUT. These findings indicate that our novel semantic network strengthening approach to gesture training may be efficacious in at least some individuals with apraxia, and provide a foundation for future study of the characteristics of people with apraxia who benefit from each approach.

Verum versus sham tDCS in the treatment of stroke-induced apraxia: study protocol of the randomized controlled trial RAdiCS -"Rehabilitating (stroke-induced) Apraxia with direct Current Stimulation".

INTRODUCTION: Stroke is the leading cause of acquired disability in western societies. (Motor) cognitive deficits like apraxia significantly contribute to disability after stroke, harming activities of daily living and rehabilitation outcome. To date, efficient therapeutic options for apraxia remain sparse. Thus, randomized controlled trials (RCTs) are warranted. METHODS: Based on promising results of a pilot study, the on-going RAdiCS (Rehabilitating stroke-induced Apraxia with direct Current Stimulation) study is a randomized controlled trial, which follows a double-blinded (investigator and patient), two-arm parallel interventional model. It is designed to include 110 apraxic patients (as diagnosed by the Cologne Apraxia Screening, KAS) in the subacute phase after a left hemisphere (LH) stroke. The University of Cologne initiated the trial, which is conducted in two German Neurorehabilitation Centers.The study aims to evaluate the effect of anodal (versus sham) transcranial direct current stimulation (tDCS) applied over the left posterior parietal cortex (PPC) with an intensity of 2 mA for 10 min on five consecutive days on apraxic deficits. In addition to anodal or sham tDCS, all LH stroke patients undergo a motor (cognitive) training that is performed before and after the stimulation (off-line stimulation).The primary outcome measure is the (differential) change in the overall KAS score after five daily sessions of anodal versus sham tDCS when compared to the baseline assessment before tDCS. Secondary study outcomes include further apraxia scores, aphasia severity, and measures of motor performance and disability after stroke. All outcome measures are obtained in the post-stimulation assessment as well as during follow-up (3-4 months after tDCS). PERSPECTIVE: The RCT RAdiCS shall evaluate in a large number of LH stroke patients whether anodal tDCS (compared to sham tDCS) expedites the rehabilitation of apraxia - over and above additional motor (cognitive) training and standard care. A positive study outcome would provide a new strategy for the treatment of apraxia, which hopefully ameliorates the negative impact of apraxia on daily living and long-term outcome. TRIAL REGISTRATION: Clinical Trials Gov: NCT03185234, registered 14 June 2017 ; Deutsches Register für Klinische Studien: DRKS00012292, registered 01 June 2017. TRIAL STATUS: Participant enrollment began on 22 June 2017. The trial is expected to be completed on 30 June 2022.

Structural Disconnection of the Tool Use Network after Left Hemisphere Stroke Predicts Limb Apraxia Severity.

Producing a tool use gesture is a complex process drawing upon the integration of stored knowledge of tools and their associated actions with sensory-motor mechanisms supporting the planning and control of hand and arm actions. Understanding how sensory-motor systems in parietal cortex interface with semantic representations of actions and objects in the temporal lobe remains a critical issue and is hypothesized to be a key determinant of the severity of limb apraxia, a deficit in producing skilled action after left hemisphere stroke. We used voxel-based and connectome-based lesion-symptom mapping with data from 57 left hemisphere stroke participants to assess the lesion sites and structural disconnection patterns associated with poor tool use gesturing. We found that structural disconnection among the left inferior parietal lobule, lateral and ventral temporal cortices, and middle and superior frontal gyri predicted the severity of tool use gesturing performance. Control analyses demonstrated that reductions in right-hand grip strength were associated with motor system disconnection, largely bypassing regions supporting tool use gesturing. Our findings provide evidence that limb apraxia may arise, in part, from a disconnection between conceptual representations in the temporal lobe and mechanisms enabling skilled action production in the inferior parietal lobule.

Limb and face apraxias in frontotemporal dementia: A systematic scoping review.

PURPOSE: To investigate the literature for frequencies, profiles and neural correlates of limb and face apraxias in frontotemporal dementia (FTD). METHOD: The search conducted in Ovid Medline, PsycINFO and Scopus yielded 487 non-duplicate records, and 43 were included in the final analysis. RESULTS: Apraxias are evident in diverse forms in all clinical variants of FTD within the first four years of the disease. Face apraxia and productive limb apraxia co-occur in the behavioural and nonfluent variants. The logopenic variant resembles Alzheimer's disease in terms of pronounced parietal limb apraxia and absence of face apraxia. The semantic variant exhibits conceptual praxis deficits together with relatively preserved imitation skills. Concerning the genetic variants of FTD, productive limb apraxia is common among carriers of the progranulin gene mutation, and subtle gestural alterations have been documented among carriers of the chromosome 9 open reading frame 72 gene mutation before the expected disease onset. The data on neural correlations suggest that the breakdown of praxis results from bilateral cortical and subcortical damage in FTD and that Alzheimer-type pathology of the cerebrospinal fluid increases the severity of limb apraxia in all of the variants. Face apraxia correlates with degeneration of the medial and superior frontal cortices. CONCLUSIONS: Each of the clinical variants of FTD exhibits a characteristic profile of apraxias that may support early differentiation between the variants and from Alzheimer's disease. However, the screening procedures developed for stroke populations seem insufficient, and a multifaceted assessment tool is needed. Although valid and practical tests already exist for dementia populations, a concise selection of test items that covers all of the critical domains is called for.

A combined therapy for limb apraxia and related anosognosia.

Left hemisphere stroke frequently leads to limb apraxia, a disorder that has been reported to impact independence in daily life and rehabilitation success. Nonetheless, there is a shortcoming in research and availability of applicable trainings. Further, to date, anosognosia for limb apraxia has largely been neglected. Therefore, we developed a Naturalistic Action Therapy that trains object selection and application with an errorless learning approach and which includes supported self-evaluation. The current study presents the results of two stroke patients participating in the training. The procedure entailed two baseline and one post-training sessions including standardized limb apraxia and anosognosia assessments as well as 18 naturalistic action tasks. The training consisted of 15 sessions during which 4-6 of the 18 naturalistic action tasks (e.g., pour water into a glass, make a phone call) were trained. Both patients showed improvement in trained and untrained tasks as well as in standardized apraxia and anosognosia assessments. Training effects appeared strongest for the trained items. The procedure is documented in detail and easy to administer and thus may have the potential to be applied by relatives. The results of this pilot-study are promising and suggest that the approach is suitable for further evaluation.

[Formula: see text] Limb apraxia profiles in different clinical samples.

Objective: Limb apraxia is a motor cognitive disorder that has been mainly studied in patients with dementia or left hemisphere stroke (LHS). However, limb apraxia has also been reported in patients with right hemisphere stroke (RHS), multiple sclerosis (MS) or traumatic brain injury (TBI). This study's aim was to report detailed praxis performance profiles in samples suffering from these different neurological disorders by use of the Diagnostic Instrument for Limb Apraxia (DILA-S).Method: 44 LHS patients, 36 RHS patients, 27 patients with dementia, 26 MS and 44 TBI patients participated. The diagnostics included the imitation of meaningless and meaningful hand gestures, pantomime of tool-use, single real tool-use as well as a multistep naturalistic action task (preparing breakfast).Results: Apraxia occurred in all tested samples but to a varying degree and with dissimilar profiles. LHS patients demonstrated most severe deficits in pantomime, but they were also vulnerable to deficits in real tool-use. Dementia patients showed high incidence rates of apraxia in almost all subscales of the DILA-S. RHS patients demonstrated difficulties in imitation and pantomime of tool-use, but they did not show severe difficulties with real tool-use. TBI patients appeared challenged by multistep naturalistic actions. The tested MS sample did not show clinically relevant symptoms in the DILA-S.Conclusion: Different types of patients display varying limb apraxic symptoms detectable by the DILA-S. In these limb apraxia susceptible populations, testing should be warranted as standard. Prospectively, individual error profiles may be helpful for shaping motor cognitive training.

Limb Apraxia: a Disorder of Learned Skilled Movement.

PURPOSE OF REVIEW: This chapter focuses on limb apraxia, a cognitive-motor disorder of learned skilled movement, and the nature of the spatiotemporal errors that disrupt movement sequences. RECENT FINDINGS: A cognitive model that attempts to reconcile conceptual and preparatory aspects of the motor program with perceptual and kinematic features will be discussed. An update on the localization of the praxis network will be provided. In addition, a long-held view that limb apraxia does not have ecological relevance will be disputed in the context of studies that have shown that limb apraxia (i) is one of the most important predictors of increased caregiver burden and (ii) is associated with impaired activities of daily living in post-stroke patients. This review summarizes current screening tools and the few randomized clinical controlled treatment studies to date. Limb apraxia is underdiagnosed and very few therapeutic options are available. Cognitive process models should be used to inform future controlled multi-modal treatment strategies.