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Stroke often causes long-term motor and somatosensory impairments. Motor planning and tactile perception rely on spatial body representations. However, the link between altered spatial body representations, motor deficit and tactile spatial coding remains unclear. This study investigates the relationship between motor deficits and alterations of anatomical (body) and tactile spatial representations of the hand in 20 post-stroke patients with upper limb hemiparesis. Anatomical and tactile spatial representations were assessed from 10 targets (nails and knuckles) respectively cued verbally by their anatomical name or using tactile stimulations. Two distance metrics (hand width and finger length) and two structural measures (relative organization of targets positions and angular deviation of fingers from their physical posture) were computed and compared to clinical assessments, normative data and lesions sites. Over half of the patients had altered anatomical and/or tactile spatial representations. Metrics of tactile and anatomical representations showed common variations, where a wider hand representation was linked to more severe motor deficits. In contrast, alterations in structural measures were not concomitantly observed in tactile and anatomical representations and did not correlate with clinical assessments. Finally, a preliminary analysis showed that specific alterations in tactile structural measures were associated with dorsolateral prefrontal stroke lesions. This study reveals shared and distinct characteristics of anatomical and tactile hand spatial representations, reflecting different mechanisms that can be affected differently after stroke: metrics and location of tactile and anatomical representations were partially shared while the structural measures of tactile and anatomical representations had distinct characteristics., Competing Interests: Declaration of competing interest None., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Knowing how impaired manual dexterity and finger proprioception affect upper limb activity capacity is important for delineating targeted post-stroke interventions for upper limb recovery., Objectives: To investigate whether impaired manual dexterity and finger proprioception explain variance in post-stroke activity capacity, and whether they explain more variance than conventional clinical assessments of upper limb sensorimotor impairments., Methods: Activity capacity and hand sensorimotor impairments were assessed using clinical measures in N = 42 late subacute/chronic hemiparetic stroke patients. Dexterity was evaluated using the Dextrain Manipulandum to quantify accuracy of visuomotor finger force-tracking (N = 36), timing of rhythmic tapping (N = 36), and finger individuation (N = 24), as well as proprioception (N = 27). Stepwise multivariate and hierarchical linear regression models were used to identify impairments best explaining activity capacity., Results: Dexterity and proprioceptive components significantly increased the variance explained in activity capacity: (i) Box and Block Test was best explained by baseline tonic force during force-tracking and tapping frequency (adjusted R 2  = .51); (ii) Motor Activity Log was best explained by success rate in finger individuation (adjusted R 2  = .46); (iii) Action Research Arm Test was best explained by release of finger force and proprioceptive measures (improved reaction time related to use of proprioception; adjusted R 2  = .52); and (iv) Moberg Pick-Up test was best explained by proprioceptive function (adjusted R 2  = .18). Models excluding dexterity and proprioception variables explained up to 19% less variance., Conclusions: Manual dexterity and finger proprioception explain unique variance in activity capacity not captured by conventional impairment measures and should be assessed when considering the underlying causes of post-stroke activity capacity limitations.URL: https://www.clinicaltrials.gov. Unique identifier: NCT03934073., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: MT, MAM, and PGL have patented the method for multidimensional measurement of manual dexterity (WO2016184935A3). MT and PGL are founding members of start-up company Dextrain (started in 2021) who owns the commercial rights. MT now works for the start-up full-time. PGL, head of the scientific board, reports no financial gain in advising the company. CR is a member of the scientific board of the company but receives no financial benefits. The other authors report no financial interests or potential conflicts of interest.

Objective: To compare the efficacy of Dextrain Manipulandum™ training of dexterity components such as force control and independent finger movements, to dose-matched conventional therapy (CT) post-stroke., Methods: A prospective, single-blind, pilot randomized clinical trial was conducted. Chronic-phase post-stroke patients with mild-to-moderate dexterity impairment (Box and Block Test (BBT) > 1) received 12 sessions of Dextrain or CT. Blinded measures were obtained before and after training and at 3-months follow-up. Primary outcome was BBT-change (after-before training). Secondary outcomes included changes in motor impairments, activity limitations and dexterity components. Corticospinal excitability and short intracortical inhibition (SICI) were measured using transcranial magnetic stimulation., Results: BBT-change after training did not differ between the Dextrain (N = 21) vs CT group (N = 21) (median [IQR] = 5[2-7] vs 4[2-7], respectively; P = 0.36). Gains in BBT were maintained at the 3-month post-training follow-up, with a non-significant trend for enhanced BBT-change in the Dextrain group (median [IQR] = 3[- 1-7.0], P = 0.06). Several secondary outcomes showed significantly larger changes in the Dextrain group: finger tracking precision (mean ± SD = 0.3 ± 0.3N vs - 0.1 ± 0.33N; P < 0.0018), independent finger movements (34.7 ± 25.1 ms vs 7.7 ± 18.5 ms, P = 0.02) and maximal finger tapping speed (8.4 ± 7.1 vs 4.5 ± 4.9, P = 0.045). At follow-up, Dextrain group showed significantly greater improvement in Motor Activity Log (median/IQR = 0.7/0.2-0.8 vs 0.2/0.1-0.6, P = 0.05). Across both groups SICI increased in patients with greater BBT-change (Rho = 0.80, P = 0.006). Comparing Dextrain subgroups with maximal grip force higher/lower than median (61.2%), BBT-change was significantly larger in patients with low vs high grip force (7.5 ± 5.6 vs 2.9 ± 2.8; respectively, P = 0.015)., Conclusions: Although immediate improvements in gross dexterity post-stroke did not significantly differ between Dextrain training and CT, our findings suggest that Dextrain enhances recovery of several dexterity components and reported hand-use, particularly when motor impairment is moderate (low initial grip force). Findings need to be confirmed in a larger trial. Trial registration ClinicalTrials.gov NCT03934073 (retrospectively registered)., (© 2023. The Author(s).)

Objective: Quantification of lower limb spasticity after stroke and the differentiation of neural from passive muscle resistance remain key clinical challenges. The aim of this study was to validate the novel NeuroFlexor foot module, to assess the intrarater reliability of measurements and to identify normative cut-off values., Methods: Fifteen patients with chronic stroke with clinical history of spasticity and 18 healthy subjects were examined with the NeuroFlexor foot module at controlled velocities. Elastic, viscous and neural components of passive dorsiflexion resistance were quantified (in Newton, N). The neural component, reflecting stretch reflex mediated resistance, was validated against electromyography activity. A test-retest design with a 2-way random effects model permitted study of intra-rater reliability. Finally, data from 73 healthy subjects were used to establish cutoff values according to mean + 3 standard deviations and receiver operating characteristic curve analysis., Results: The neural component was higher in stroke patients, increased with stretch velocity and correlated with electromyography amplitude. Reliability was high for the neural component (intraclass correlation coefficient model 2.1 (ICC2,1) ≥ 0.903) and good for the elastic component (ICC2,1 ≥ 0.898). Cutoff values were identified, and all patients with neural component above the limit presented pathological electromyography amplitude (area under the curve (AUC) = 1.00, sensitivity = 100%, specificity = 100%)., Conclusion: The NeuroFlexor may offer a clinically feasible and non-invasive way to objectively quantify lower limb spasticity.

Background: We developed five tablet-based tasks (applications) to measure multiple components of manual dexterity., Aim: to test reliability and validity of tablet-based dexterity measures in healthy participants., Methods: Tasks included: (1) Finger recognition to assess mental rotation capacity. The subject taps with the finger indicated on a virtual hand in three orientations (reaction time, correct trials). (2) Rhythm tapping to evaluate timing of finger movements performed with, and subsequently without, an auditory cue (inter-stimulus interval). (3) Multi-finger tapping to assess independent finger movements (reaction time, correct trials, unwanted finger movements). (4) Sequence tapping to assess production and memorization of visually cued finger sequences (successful taps). (5) Line-tracking to assess movement speed and accuracy while tracking an unpredictably moving line on the screen with the fingertip (duration, error). To study inter-rater reliability, 34 healthy subjects (mean age 35 years) performed the tablet tasks twice with two raters. Relative reliability (Intra-class correlation, ICC) and absolute reliability (Standard error of measurement, SEM) were established. Task validity was evaluated in 54 healthy subjects (mean age 49 years, range: 20-78 years) by correlating tablet measures with age, clinical dexterity assessments (time taken to pick-up objects in Box and Block Test, BBT and Moberg Pick Up Test, MPUT) and with measures obtained using a finger force-sensor device., Results: Most timing measures showed excellent reliability. Poor to excellent reliability was found for correct trials across tasks, and reliability was poor for unwanted movements. Inter-session learning occurred in some measures. Age correlated with slower and more variable reaction times in finger recognition, less correct trials in multi-finger tapping, and slower line-tracking. Reaction times correlated with those obtained using a finger force-sensor device. No significant correlations between tablet measures and BBT or MPUT were found. Inter-task correlation among tablet-derived measures was weak., Conclusions: Most tablet-based dexterity measures showed good-to-excellent reliability (ICC ≥ 0.60) except for unwanted movements during multi-finger tapping. Age-related decline in performance and association with finger force-sensor measures support validity of tablet measures. Tablet-based components of dexterity complement conventional clinical dexterity assessments. Future work is required to establish measurement properties in patients with neurological and psychiatric disorders., (© 2022. The Author(s).)

Objective: To determine similarities and differences in key predictors of recovery of bimanual hand use and unimanual motor impairment after stroke., Method: In this prospective longitudinal study, 89 patients with first-ever stroke with arm paresis were assessed at 3 weeks and 3 and 6 months after stroke onset. Bimanual activity performance was assessed with the Adult Assisting Hand Assessment Stroke (Ad-AHA), and unimanual motor impairment was assessed with the Fugl-Meyer Assessment (FMA). Candidate predictors included shoulder abduction and finger extension measured by the corresponding FMA items (FMA-SAFE; range 0-4) and sensory and cognitive impairment. MRI was used to measure weighted corticospinal tract lesion load (wCST-LL) and resting-state interhemispheric functional connectivity (FC)., Results: Initial Ad-AHA performance was poor but improved over time in all (mild-severe) impairment subgroups. Ad-AHA correlated with FMA at each time point ( r > 0.88, p < 0.001), and recovery trajectories were similar. In patients with moderate to severe initial FMA, FMA-SAFE score was the strongest predictor of Ad-AHA outcome ( R 2 = 0.81) and degree of recovery ( R 2 = 0.64). Two-point discrimination explained additional variance in Ad-AHA outcome ( R 2 = 0.05). Repeated analyses without FMA-SAFE score identified wCST-LL and cognitive impairment as additional predictors. A wCST-LL >5.5 cm 3 strongly predicted low to minimal FMA/Ad-AHA recovery (≤10 and 20 points respectively, specificity = 0.91). FC explained some additional variance to FMA-SAFE score only in unimanual recovery., Conclusion: Although recovery of bimanual activity depends on the extent of corticospinal tract injury and initial sensory and cognitive impairments, FMA-SAFE score captures most of the variance explained by these mechanisms. FMA-SAFE score, a straightforward clinical measure, strongly predicts bimanual recovery., Clinicaltrialsgov Identifier: NCT02878304., Classification of Evidence: This study provides Class I evidence that the FMA-SAFE score predicts bimanual recovery after stroke., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Background and Purpose- Dexterous object manipulation, requiring generation and control of finger forces, is often impaired after stroke. This study aimed to describe recovery of precision grip force control after stroke and to determine clinical and imaging predictors of 6-month performance. Methods- Eighty first-ever stroke patients with varying degrees of upper limb weakness were evaluated at 3 weeks, 3 months, and 6 months after stroke. Twenty-three healthy individuals of comparable age were also studied. The Strength-Dexterity test was used to quantify index finger and thumb forces during compression of springs of varying length in a precision grip. The coordination between finger forces (CorrForce), along with Dexterity-score and Repeatability-score, was calculated. Anatomical magnetic resonance imaging was used to calculate weighted corticospinal tract lesion load (wCST-LL). Results- CorrForce, Dexterity-score, and Repeatability-score in the affected hand were dramatically lower at each time point compared with the less-affected hand and the control group, even in patients with mild motor impairment according to Fugl-Meyer assessment. Improved performance over time occurred in CorrForce and Dexterity-score but not in Repeatability-score. The Fugl-Meyer assessment hand subscale, sensory function, and wCST-LL best predicted CorrForce and Dexterity-score status at 6 months (R 2 =0.56 and 0.87, respectively). wCST-LL explained substantial variance in CorrForce (R 2 =0.34) and Dexterity-score (R 2 =0.50) at 6 months; two-point discrimination and Fugl-Meyer score accounted for considerable additional variance. Absence of recovery in CorrForce was predicted by wCST-LL >4 cc and in Dexterity-score by wCST-LL >6 cc. Conclusions- Findings highlight persisting deficits in the ability to grasp and control finger forces after stroke. wCST-LL was the strongest predictor of performance at 6 months, but early two-point discrimination and Fugl-Meyer score had substantial additional predictive value. Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT02878304.

Objectives: In this longitudinal pilot study, we investigated how manual dexterity recovery was related to corticospinal tract (CST) injury and excitability, in six patients undergoing conventional rehabilitation., Methods: Key components of manual dexterity, namely finger force control, finger tapping rate and independence of finger movements, were quantified. Structural MRI was obtained to calculate CST lesion load. CST excitability was assessed by measuring rest motor threshold (RMT) and the amplitude of motor evoked potentials (MEPs) using transcranial magnetic stimulation (TMS). Measurements were obtained at two weeks, three and six months post-stroke., Results: At six months post-stroke, complete recovery of hand gross motor impairment (i.e., maximal Fugl-Meyer score for hand) had occurred in three patients and four patients had recovered ability to accurately control finger force. However, tapping rate and independence of finger movements remained impaired in all six patients at six months. Recovery in hand gross motor impairment and finger force control occurred in patients with smaller CST lesion load and almost complete recovery of CST excitability, although RMT or MEP size remained slightly altered in the stroke-affected hemisphere compared to the unaffected hemisphere. The two patients with poorest recovery showed persistent absence of MEPs and greatest structural injury to CST., Discussion: The findings support good motor recovery being overall correlated with smaller CST lesion, and with almost complete recovery of CST excitability. However, impairment of manual dexterity persisted despite recovery in gross hand movements and grasping abilities, suggesting involvement of additional brain structures for fine manual tasks., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Background and Objective: The NeuroFlexor is a novel instrument for quantification of neural, viscous and elastic components of passive movement resistance. The aim of this study was to provide normative data and cut-off values from healthy subjects and to use these to explore signs of spasticity at the wrist and fingers in patients recovering from stroke., Methods: 107 healthy subjects (age range 28-68 years; 51 % females) and 39 stroke patients (age range 33-69 years; 33 % females), 2-4 weeks after stroke, were assessed with the NeuroFlexor. Cut-off values based on mean + 3SD of the reference data were calculated. In patients, the modified Ashworth scale (MAS) was also applied., Results: In healthy subjects, neural component was 0.8 ± 0.9 N (mean ± SD), elastic component was 2.7 ± 1.1 N, viscous component was 0.3 ± 0.3 N and resting tension was 5.9 ± 1 N. Age only correlated with elastic component (r = -0.3, p = 0.01). Elasticity and resting tension were higher in males compared to females (p = 0.001) and both correlated positively with height (p = 0.01). Values above healthy population cut-off were observed in 16 patients (41 %) for neural component, in 2 (5 %) for elastic component and in 23 (59 %) for viscous component. Neural component above cut-off did not correspond well to MAS ratings. Ten patients with MAS = 0 had neural component values above cut-off and five patients with MAS ≥ 1 had neural component within normal range., Conclusion: This study provides NeuroFlexor cut-off values that are useful for detection of spasticity in the early phase after stroke.

Background: A high degree of manual dexterity is a central feature of the human upper limb. A rich interplay of sensory and motor components in the hand and fingers allows for independent control of fingers in terms of timing, kinematics and force. Stroke often leads to impaired hand function and decreased manual dexterity, limiting activities of daily living and impacting quality of life. Clinically, there is a lack of quantitative multi-dimensional measures of manual dexterity. We therefore developed the Finger Force Manipulandum (FFM), which allows quantification of key components of manual dexterity. The purpose of this study was (i) to test the feasibility of using the FFM to measure key components of manual dexterity in hemiparetic stroke patients, (ii) to compare differences in dexterity components between stroke patients and controls, and (iii) to describe individual profiles of dexterity components in stroke patients., Methods: 10 stroke patients with mild-to-moderate hemiparesis and 10 healthy subjects were recruited. Clinical measures of hand function included the Action Research Arm Test and the Moberg Pick-Up Test. Four FFM tasks were used: (1) Finger Force Tracking to measure force control, (2) Sequential Finger Tapping to measure the ability to perform motor sequences, (3) Single Finger Tapping to measure timing effects, and (4) Multi-Finger Tapping to measure the ability to selectively move fingers in specified combinations (independence of finger movements)., Results: Most stroke patients could perform the tracking task, as well as the single and multi-finger tapping tasks. However, only four patients performed the sequence task. Patients showed less accurate force control, reduced tapping rate, and reduced independence of finger movements compared to controls. Unwanted (erroneous) finger taps and overflow to non-tapping fingers were increased in patients. Dexterity components were not systematically related among each other, resulting in individually different profiles of deficient dexterity. Some of the FFM measures correlated with clinical scores., Conclusions: Quantifying some of the key components of manual dexterity with the FFM is feasible in moderately affected hemiparetic patients. The FFM can detect group differences and individual profiles of deficient dexterity. The FFM is a promising tool for the measurement of key components of manual dexterity after stroke and could allow improved targeting of motor rehabilitation.

Adequate grip force modulation is critical to manual dexterity and often impaired in hemiparetic stroke patients. Previous studies in hemiparetic patients suggest that aspects of grip force control may be differently affected by the lesion. We developed a visuomotor power grip force-tracking task allowing quantification of tracking error, force variability and release duration. We investigated force control in 24 chronic stroke patients with varying severity of hemiparesis and in healthy control subjects. Force tracking was performed at 10, 20, and 30% maximal voluntary contraction (MVC). Control subjects were also tested at absolute force levels similar to those of the patients. Patients tracking with their paretic hand at similar relative (%MVC) grip force levels showed increased error, force variability and release duration, but surprisingly, there was no difference in tracking error or variability between patients and control subjects performing at similar absolute force levels. Furthermore, patients improved their tracking performance across repeated blocks similar to control subjects. Release duration, however, was increased (also in the non-paretic hand), was force-independent and did not correlate with MVC strength. Of the three performance measures, only release duration explained some of the variance in arm and hand function (Frenchay Arm Test score), independent of MVC strength. The findings show (i) that hemiparetic stroke patients preserve the ability to modulate (generate and maintain) power grip force within their limited force range and (ii) that MVC grip strength and duration of grip release are differently affected and are two complementary predictors of arm function after stroke., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background and Purpose: wallerian degeneration (WD) in descending motor tracts after stroke is described at the level of the internal capsule and the brainstem. We investigated whether diffusion tensor imaging (DTI) can detect degeneration in the lateral cervical spinal cord after stroke., Methods: DTI at 1.5 T of the cervical spinal cord was performed in 4 chronic hemiparetic patients after ischemic stroke. Stroke lesions included the corticospinal tract. DTI was also performed in 12 healthy controls. Diffusion parameters were obtained for left and right (i) half and (ii) lateral spinal cord extending from C2 to C7., Results: relative fractional anisotropy (FA) in the lateral tracts on the affected side compared with the unaffected side (left/right) was reduced in stroke patients as compared with controls (P= .007). FA was lowest in patients with severe upper limb hemiparesis. Relative apparent diffusion coefficient in the lateral tracts was increased in the patients (P= .03)., Conclusions: this study provides preliminary evidence that DTI at 1.5 T can be used for identification and quantification of WD in the lateral cervical spinal cord in stroke patients. This may prove useful for prognosis of motor outcome after stroke.

Background: The role of spinal networks in spasticity is well investigated, but little is known about possible cortical contributions to hypertonicity across a joint., Objective: The authors hypothesized that there are cortical activation correlates to spasticity in stroke patients with increased muscle tone of the wrist flexors., Methods: Stroke patients and controls were scanned using event-related functional magnetic resonance imaging (fMRI) during slow and fast passive movements of the hand with simultaneous recording of passive movement resistance (PMR)., Results: Control participants had velocity-dependent activity (greater for slow than fast movements) of 2 types, in areas that were also more active in passive movement than rest (eg, relative increase in activation in contralateral S1 and M1 was greater for slow than fast) and in areas that were also more active in rest than passive movement (eg, relative decrease in activation in occipital areas and ipsilateral precentral gyrus was greater for fast than slow). In the patient group, with large interindividual variation of spasticity, we found an association between PMR and the velocity-dependent activity in ipsilateral S1 (area 3b) extending into M1 (area 4a), contralateral cingulate cortex, supplementary motor area (SMA), Brodmann Area 45 (BA 45), and cerebellum. Post hoc testing also revealed a similar correlation in S1 and M1 bilaterally in controls and showed that patients activated ipsilateral S1 and M1 more than controls in the velocity-dependent condition., Conclusions: The findings suggest the possibility of ipsilateral sensory and motor cortical involvement in spasticity after stroke, which warrant further investigation.

Objective: This study tested the hypothesis that degeneration of the corticofugal tracts (CFTs) is related to poor functional outcome in the upper limb after stroke., Methods: . The authors used diffusion tensor imaging to determine the degree of white matter integrity of the CFT (FA(AH/UH)) in chronic stroke patients and controls. The functional integrity of the corticospinal pathway was examined using transcranial magnetic stimulation. Recruitment curves and silent period duration were measured. The relationship between FA(AH/UH) and functional outcome of the upper limb was also assessed using a battery of upper limb function tests., Results: In patients, FA( AH/UH) correlated positively with the slope of recruitment curves (RC(AH/UH)) and grip strength. FA(AH/UH) also correlated negatively with the silent period duration (SP(AH/UH)). According to the FA(AH/UH), patients were also classified into groups with minimal or extensive Wallerian degeneration (WD). Patients with more extensive WD had poorer grip strength, dexterity, and range of movement., Conclusions: The authors' results suggest that structural and functional integrity of the CFT is essential to maintain function of the upper limb after stroke.

Objective: To examine whether cerebral activity during passive movements decreases with time after stroke, and if reduced activity in the representation for the upper extremity can be reversed with training., Methods: Brain activity was measured by functional magnetic resonance imaging (fMRI) during passive wrist flexion-extension in 7 patients at varying time points after stroke, in a cross-sectional design. Upper limb function was also measured in all patients. Five of the patients took part in a training program and were measured again, behaviorally and with fMRI posttraining. Healthy control individuals of comparable age were also studied., Results: In patients, reduced activity over time after stroke was found for the group in the supplementary motor area (SMA), contralateral primary motor cortex, and prefrontal and parietal association areas along with ipsilateral cerebellum. Activity in most of these areas was also reduced in the patient group as compared to the control group. After a half-hour of daily training for 4 weeks with repetitive passive and active arm movements, cerebral activation increased in the pre-SMA and SMA, ipsilateral primary sensory cortex and intraparietal sulcus, and contralateral cerebellum in parallel with functional improvements of the upper limb. Areas common to both analyses included the SMA, pre-SMA, primary sensory cortex, intraparietal sulcus, and cerebellum., Conclusions: Our findings suggest that a down-regulation of sensorimotor activity occurs progressively over time as a result of inactivity and that training may reverse the reduced brain activity.