Therapies Targeting Stroke Recovery.

Stroke recovery therapeutics include many classes of intervention and numerous treatment targets. Stroke is a very heterogeneous disease. As such, stroke recovery therapeutics benefit from a personalized medicine approach that considers intersubject differences, such as in infarct location or stroke severity, when assigning treatment. Prediction of treatment responders can be improved by incorporating biological measures, such as neural injury and neural function, as the bedside behavioral phenotype has an incomplete relationship with the biological events underlying stroke recovery. Another ramification of high variability between patients is the need to examine effects of restorative therapies in relation to dose, time poststroke, and stroke severity in clinical trials. For example, enrollment across a wide time interval poststroke or in a population with a very broad range of deficits means high variance across patients in the biological state of the brain. The doses of rehabilitation therapy being studied are often low; it takes substantial practice to acquire a skill in the healthy brain; this is more, not less, pronounced after a stroke. Recognition and treatment of poststroke depression represents a major unmet need. These points are considered in the context of a review of recent advances in stroke recovery therapeutics.

Cognitive Deficits After Stroke.

Cognition is a central feature of human existence and brain function. Cognitive deficits are common after stroke and may strongly impact functional outcome. Recent years have seen substantial advances in our understanding of cognitive functions in the healthy state, and this new body of knowledge promises to open new avenues for understanding and treating poststroke impairments, including cognitive deficits. The 5 reviews in this Focused Update from an international cast of experts provide excellent updates on cognitive syndromes that commonly contribute to poststroke disability: neglect, aphasia, apraxia, loss of executive function, and memory disorders. Cognitive impairment remains a major source of morbidity after stroke; these reviews approach this problem by considering clinical presentations, pathophysiology, measurement tools, and treatment approaches. In doing so, they highlight a number of key questions and critical gaps. A number of issues emerge as common across cognitive domains poststroke and are summarized herein. There is a need for improved methods to measure cognitive impairments, as well as for improved insights into pathophysiology of symptom onset and mechanisms of recovery after stroke, including validated biomarkers. These 5 state of the art summaries are sure to prove useful toward these goals.

Advances in Stroke: Therapies Targeting Stroke Recovery.

Stroke recovery therapies promote favorable neural plasticity, both during spontaneous recovery and the chronic phase. Activity-based therapies based on intense practice, some aided by integration of computers and telehealth, have shown promise. These studies emphasize key therapeutic variables such as dose, intensity, and timing. Preclinical drug studies have shown promise, but human translation has been challenged by identifying the target patient subgroup, requirements for concomitant training, and aligning biomarkers with preclinical evidence.

Simultaneous NODDI and GFA parameter map generation from subsampled q-space imaging using deep learning.

PURPOSE: To develop a robust multidimensional deep-learning based method to simultaneously generate accurate neurite orientation dispersion and density imaging (NODDI) and generalized fractional anisotropy (GFA) parameter maps from undersampled q-space datasets for use in stroke imaging. METHODS: Traditional diffusion spectrum imaging (DSI) capable of producing accurate NODDI and GFA parameter maps requires hundreds of q-space samples which renders the scan time clinically untenable. A convolutional neural network (CNN) was trained to generated NODDI and GFA parameter maps simultaneously from 10× undersampled q-space data. A total of 48 DSI scans from 15 stroke patients and 14 normal subjects were acquired for training, validating, and testing this method. The proposed network was compared to previously proposed voxel-wise machine learning based approaches for q-space imaging. Network-generated images were used to predict stroke functional outcome measures. RESULTS: The proposed network achieves significant performance advantages compared to previously proposed machine learning approaches, showing significant improvements across image quality metrics. Generating these parameter maps using CNNs also comes with the computational benefits of only needing to generate and train a single network instead of multiple networks for each parameter type. Post-stroke outcome prediction metrics do not appreciably change when using images generated from this proposed technique. Over three test participants, the predicted stroke functional outcome scores were within 1-6% of the clinical evaluations. CONCLUSIONS: Estimates of NODDI and GFA parameters estimated simultaneously with a deep learning network from highly undersampled q-space data were improved compared to other state-of-the-art methods providing a 10-fold reduction scan time compared to conventional methods.

Guidelines for Adult Stroke Rehabilitation and Recovery: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association.

PURPOSE: The aim of this guideline is to provide a synopsis of best clinical practices in the rehabilitative care of adults recovering from stroke. METHODS: Writing group members were nominated by the committee chair on the basis of their previous work in relevant topic areas and were approved by the American Heart Association (AHA) Stroke Council's Scientific Statement Oversight Committee and the AHA's Manuscript Oversight Committee. The panel reviewed relevant articles on adults using computerized searches of the medical literature through 2014. The evidence is organized within the context of the AHA framework and is classified according to the joint AHA/American College of Cardiology and supplementary AHA methods of classifying the level of certainty and the class and level of evidence. The document underwent extensive AHA internal and external peer review, Stroke Council Leadership review, and Scientific Statements Oversight Committee review before consideration and approval by the AHA Science Advisory and Coordinating Committee. RESULTS: Stroke rehabilitation requires a sustained and coordinated effort from a large team, including the patient and his or her goals, family and friends, other caregivers (eg, personal care attendants), physicians, nurses, physical and occupational therapists, speech-language pathologists, recreation therapists, psychologists, nutritionists, social workers, and others. Communication and coordination among these team members are paramount in maximizing the effectiveness and efficiency of rehabilitation and underlie this entire guideline. Without communication and coordination, isolated efforts to rehabilitate the stroke survivor are unlikely to achieve their full potential. CONCLUSIONS: As systems of care evolve in response to healthcare reform efforts, postacute care and rehabilitation are often considered a costly area of care to be trimmed but without recognition of their clinical impact and ability to reduce the risk of downstream medical morbidity resulting from immobility, depression, loss of autonomy, and reduced functional independence. The provision of comprehensive rehabilitation programs with adequate resources, dose, and duration is an essential aspect of stroke care and should be a priority in these redesign efforts. (Stroke.2016;47:e98-e169. DOI: 10.1161/STR.0000000000000098.).

Robot-assisted therapy for long-term upper-limb impairment after stroke.

BACKGROUND: Effective rehabilitative therapies are needed for patients with long-term deficits after stroke. METHODS: In this multicenter, randomized, controlled trial involving 127 patients with moderate-to-severe upper-limb impairment 6 months or more after a stroke, we randomly assigned 49 patients to receive intensive robot-assisted therapy, 50 to receive intensive comparison therapy, and 28 to receive usual care. Therapy consisted of 36 1-hour sessions over a period of 12 weeks. The primary outcome was a change in motor function, as measured on the Fugl-Meyer Assessment of Sensorimotor Recovery after Stroke, at 12 weeks. Secondary outcomes were scores on the Wolf Motor Function Test and the Stroke Impact Scale. Secondary analyses assessed the treatment effect at 36 weeks. RESULTS: At 12 weeks, the mean Fugl-Meyer score for patients receiving robot-assisted therapy was better than that for patients receiving usual care (difference, 2.17 points; 95% confidence interval [CI], -0.23 to 4.58) and worse than that for patients receiving intensive comparison therapy (difference, -0.14 points; 95% CI, -2.94 to 2.65), but the differences were not significant. The results on the Stroke Impact Scale were significantly better for patients receiving robot-assisted therapy than for those receiving usual care (difference, 7.64 points; 95% CI, 2.03 to 13.24). No other treatment comparisons were significant at 12 weeks. Secondary analyses showed that at 36 weeks, robot-assisted therapy significantly improved the Fugl-Meyer score (difference, 2.88 points; 95% CI, 0.57 to 5.18) and the time on the Wolf Motor Function Test (difference, -8.10 seconds; 95% CI, -13.61 to -2.60) as compared with usual care but not with intensive therapy. No serious adverse events were reported. CONCLUSIONS: In patients with long-term upper-limb deficits after stroke, robot-assisted therapy did not significantly improve motor function at 12 weeks, as compared with usual care or intensive therapy. In secondary analyses, robot-assisted therapy improved outcomes over 36 weeks as compared with usual care but not with intensive therapy. (ClinicalTrials.gov number, NCT00372411.)

Rasch analysis staging methodology to classify upper extremity movement impairment after stroke.

OBJECTIVES: To define Fugl-Meyer Assessment of the Upper Extremity (FMA-UE) cutoff scores that demarcate 1 level of upper extremity (UE) impairment from another, and describe motor behaviors for each category in terms of expected FMA-UE item performance. DESIGN: Analysis of existing FMA-UE data. SETTING: University research laboratory. PARTICIPANTS: Persons (N=512) 0 to 145 days poststroke, 42 to 90 years of age. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: An item response Rasch analysis staging method was used to calculate cutoff scores, which were defined as the Rasch-Andrich threshold values of 2 criterion FMA-UE items derived from an analysis of this sample. The analysis enabled conversion of cutoff scores, in logit units, to FMA-UE points assessed on 30 FMA-UE voluntary movement items (60 possible points). RESULTS: The boundary between severe and moderate impairment was defined as -1.59 ± .27 logits or 19 ± 2 points; and between moderate and mild impairment was defined as 2.44 ± .27 logits or 47 ± 2 points. A description of expected performance in each impairment level shows that patients with severe impairment exhibited some distal movements, and patients with mild impairment had difficulties with some proximal movements. CONCLUSIONS: The cutoff scores, which link to a description of specific movements a patient can, can partially, and cannot perform, may enable formation of heterogeneous patient groups, advance efforts to identify specific movement therapy targets, and define treatment response in terms of specific movement that changed or did not change with therapy.

Effect of intense functional task training upon temporal structure of variability of upper extremity post stroke.

STUDY DESIGN: Quasi-experimental design. INTRODUCTION: Although the effectiveness of constraint-induced movement therapy (CIMT) in upper extremity (UE) rehabilitation post stroke is well known, the efficacy of CIMT to enhance the temporal structure of variability in upper extremity movement is not known. PURPOSE: The purpose of this study was to investigate whether CIMT could enhance the temporal structure of variability in upper extremity movement in individuals with chronic stroke. METHODS: Six participants with chronic stroke underwent CIMT for 4 h/day for 2 weeks. Participants performed three trials of functional reach-to-grasp before and after CIMT. Temporal structure of variability was determined by calculating approximate entropy (ApEn) in shoulder, elbow and wrist flexion/extension joint angles. RESULTS: ApEn increased post CIMT, however, statistical significance was not achieved (p > 0.0167). CONCLUSION: Future studies with larger sample size are warranted to investigate the effect of CIMT upon temporal structure of variability in UE movement. LEVEL OF EVIDENCE: 4.

Myoelectric Arm Orthosis Assists Functional Activities: A 3-Month Home Use Outcome Report.

Objective: The objective was to compare task performance in individuals with upper limb impairments with and without a myoelectric arm orthosis. Design: Three-month observational study. Participants met at 4 time points after receiving their myoelectric orthosis (2-Weeks, Month-1, Month-2, Month-3) to complete 4 standardized common daily tasks. Setting: Nationwide sessions completed remotely over videoconference calls at home. There were no specific clinic affiliations. Participants: Adults with upper limb impairment due to stroke who were in the process of being fit with a myoelectric arm orthosis as a first-time user. Interventions: The orthosis was a custom-fabricated myoelectric arm orthosis called the MyoPro®. Main Outcome Measures: Functional tasks were completed at each session with and without the MyoPro. Participants were evaluated on their success and the time required to complete each functional task. Longitudinal mixed and longitudinal mixed logistic regression models were analyzed. Results: Eighteen individuals with chronic arm weakness due to stroke were included in the analysis. Statistically significant and clinically meaningful improvements were observed on the functional tasks in the participants' homes. By 3 months, participants successfully used the MyoPro to accomplish the tasks, reduced the amount of time spent to complete the tasks, and had a higher probability of success as compared with at 2 weeks. With the MyoPro, participants showed significant improvement in overall task completion and completed the tasks in a significantly decreased time as compared with without the MyoPro. Conclusions: The MyoPro provides a stabilizing support to the weak arm of individuals after stroke and enables individuals to use their impaired arm to complete functional tasks independently in the home environment.

Impaired Discrimination of Electrocutaneous Stimulation in the Paretic Hand of Stroke Survivors.

Artificial sensory feedback via electrocutaneous stimulation can be used to assist or rehabilitate stroke survivors with sensory deficits. Conveying the magnitude of tactile stimuli is an important aspect of artificial sensory feedback. Here, we explore how stroke-related sensory deficits impact the ability of electrocutaneous stimulation to convey the magnitude of tactile stimuli. Using classical psychophysical methods, we quantified the threshold of detection and the just-noticeable difference of electrocutaneous stimulation current in five stroke survivors with unilateral sensory deficits. We show significantly greater (40%) stimulation currents are needed for initial perception on the paretic hand compared to the non-paretic hand. We also show significantly greater percent changes in stimulation current (140%) are needed for reliable incremental perception on the paretic hand compared to the non-paretic hand. Lastly, we show little correlation between electrocutaneous discrimination performance and clinical sensory assessments of light-touch and spatial mechanoperception. These findings can help guide the implementation of artificial sensory feedback as an assistive or rehabilitative intervention for individuals experiencing sensory loss after a stroke.Clinical Relevance- Our results can help guide the implementation of electrical stimulation as an assistive or rehabilitative intervention for individuals with sensory loss after stroke.

Intimate Relationships and Stroke: Piloting a Dyadic Intervention to Improve Depression.

Stroke affects not only the survivor but also their romantic partner. Post-stroke depression is common in both partners and can have significant negative consequences, yet few effective interventions are available. The purpose of this study was to pilot test a novel 8-week remotely administered dyadic intervention (ReStoreD) designed to help couples better cope with stroke-related changes and reduce depressive symptoms. Thirty-four cohabitating survivor-partner dyads at least 3 months post-stroke and reporting some changes in mood were enrolled. Depressive symptoms were assessed pre- and post-intervention and at 3-month follow-up. Repeated measures analysis of variance was used to assess the effects of ReStoreD over time on depressive symptoms in stroke survivors and their partners. Twenty-six dyads completed the study. Although statistical significance was not reached, there was a large effect size for improvements in depressive symptoms for stroke survivors. There was no significant improvement for partners, and the effect size was minimal. Those with more significant depressive symptoms at baseline were more likely to benefit from the intervention. This pilot study established proof-of-concept by demonstrating that depressive symptoms can be lessened in stroke survivors and partners with more severe depressive symptoms. Future research will establish the efficacy of the intervention in a fully powered study.

An economic analysis of robot-assisted therapy for long-term upper-limb impairment after stroke.

BACKGROUND AND PURPOSE: Stroke is a leading cause of disability. Rehabilitation robotics have been developed to aid in recovery after a stroke. This study determined the additional cost of robot-assisted therapy and tested its cost-effectiveness. METHODS: We estimated the intervention costs and tracked participants' healthcare costs. We collected quality of life using the Stroke Impact Scale and the Health Utilities Index. We analyzed the cost data at 36 weeks postrandomization using multivariate regression models controlling for site, presence of a prior stroke, and Veterans Affairs costs in the year before randomization. RESULTS: A total of 127 participants were randomized to usual care plus robot therapy (n=49), usual care plus intensive comparison therapy (n=50), or usual care alone (n=28). The average cost of delivering robot therapy and intensive comparison therapy was $5152 and $7382, respectively (P<0.001), and both were significantly more expensive than usual care alone (no additional intervention costs). At 36 weeks postrandomization, the total costs were comparable for the 3 groups ($17 831 for robot therapy, $19 746 for intensive comparison therapy, and $19 098 for usual care). Changes in quality of life were modest and not statistically different. CONCLUSIONS: The added cost of delivering robot or intensive comparison therapy was recuperated by lower healthcare use costs compared with those in the usual care group. However, uncertainty remains about the cost-effectiveness of robotic-assisted rehabilitation compared with traditional rehabilitation. Clinical Trial Registration- URL: http://clinicaltrials.gov. Unique identifier: NCT00372411.

Lifestyle Modification Group for Lymphedema and Obesity Results in Significant Health Outcomes.

This study investigated whether a lifestyle modification program that encouraged a ketogenic diet (KD) for participants with lymphedema and obesity would reduce weight and limb volume and improve quality of life. A total of 12 participants with lymphedema and obesity (mean body mass index = 38.38; SD = 7.02) were enrolled in a lifestyle modification group. The timespan from baseline data collection to 30-day follow-up was 18 weeks. Retention rate was 83.3%. Data were analyzed with repeated-measures ANOVA and Pearson correlation. Participants demonstrated statistically significant improvement in most outcome measures. Mean weight loss was 5.18 kg-F(4, 36) = 11.17; P < .001-or 4.8% of mean baseline weight. The average limb volume reduction was 698.9 ml-F(4, 36) = 9.4; P < .001-and was positively correlated with weight loss (r = 0.8; P = .005). There appeared to be a tendency for participants who used a KD (n = 6) to demonstrate superior results in most outcome measures compared with those who did not use the diet (n = 4), although the sample size of the 2 groups was too small to report definitive results. This lifestyle modification program provided insight into the possible value of a KD for obesity and lymphedema management.

Effects of trunk restraint combined with intensive task practice on poststroke upper extremity reach and function: a pilot study.

BACKGROUND: Poststroke reaching is characterized by excessive trunk motion and abnormal shoulder-elbow coordination. Little attention is typically given to arm-trunk kinematics during task practice. Preventing compensatory trunk motion during short-term practice immediately improves kinematics, but effects of longer-term practice are unknown. OBJECTIVE: This study compared the effects of intensive task practice with and without trunk restraint on poststroke reaching kinematics and function. METHODS: A total of 11 individuals with chronic stroke, baseline Fugl-Meyer Upper Extremity Assessment scores 26 to 54, were randomized to 2 constraint-therapy intervention groups. All participants wore a mitt on the unaffected hand for 90% of waking hours over 14 days and participated in 10 days/6 hours/day of supervised progressive task practice. During supervised sessions, one group trained with a trunk restraint (preventing anterior trunk motion) and one group did not. Tasks for the trunk-restraint group were located to afford repeated use of a shoulder flexion-elbow extension reaching pattern. Outcome measures included kinematics of unrestrained targeted reaching and tests of functional arm ability. RESULTS: Posttraining, the trunk-restraint group demonstrated straighter reach trajectories (P=.000) and less trunk displacement (P=.001). The trunk-restraint group gained shoulder flexion (P=.006) and elbow extension (P=.022) voluntary ranges of motion, the nonrestraint group did not. Posttraining angle-angle plots illustrated that individuals from the trunk-restraint group transitioned from elbow flexion to elbow extension during mid-reach; individuals in the nonrestraint group retained pretraining movement strategies. Both groups gained functional arm ability (P<.05 all tests). CONCLUSION: Intensive task practice structured to prevent compensatory trunk movements and promote shoulder flexion-elbow extension coordination may reinforce development of "normal" reaching kinematics.

Multicenter randomized trial of robot-assisted rehabilitation for chronic stroke: methods and entry characteristics for VA ROBOTICS.

BACKGROUND: Chronic upper extremity impairment due to stroke has significant medical, psychosocial, and financial consequences, but few studies have examined the effectiveness of rehabilitation therapy during the chronic stroke period. OBJECTIVE: . To test the safety and efficacy of the MIT-Manus robotic device for chronic upper extremity impairment following stroke. METHODS: . The VA Cooperative Studies Program initiated a multicenter, randomized, controlled trial in November 2006 (VA ROBOTICS). Participants with upper extremity impairment >/=6 months poststroke were randomized to robot-assisted therapy (RT), intensive comparison therapy (ICT), or usual care (UC). RT and ICT consisted of three 1-hour treatment sessions per week for 12 weeks. The primary outcome was change in the Fugl-Meyer Assessment upper extremity motor function score at 12 weeks relative to baseline. Secondary outcomes included the Wolf Motor Function Test and the Stroke Impact Scale. RESULTS: . A total of 127 participants were randomized: 49 to RT, 50 to ICT, and 28 to UC. The majority of participants were male (96%), with a mean age of 65 years. The primary stroke type was ischemic (85%), and 58% of strokes occurred in the anterior circulation. Twenty percent of the participants reported a stroke in addition to their index stroke. The average time from the index stroke to enrollment was 56 months (range, 6 months to 24 years). The mean Fugl-Meyer score at entry was 18.9. CONCLUSIONS: . VA ROBOTICS demonstrates the feasibility of conducting multicenter clinical trials to rigorously test new rehabilitative devices before their introduction to clinical practice. The results are expected in early 2010.

Predicting Motor Outcomes in Stroke Patients Using Diffusion Spectrum MRI Microstructural Measures.

Improved understanding of neuroimaging signal changes and their relation to patient outcomes after ischemic stroke is needed to improve ability to predict motor improvement and make therapy recommendations. The posterior limb of the internal capsule (PLIC) is a hub of afferent and efferent motor signaling and this work proposes new, image-based methods for prognosis based on interhemispheric differences in the PLIC. In this work, nine acute supratentorial ischemic stroke patients with motor impairment received a baseline, 203-direction diffusion brain MRI and a clinical assessment 3-12 days post-stroke and were compared to nine age-matched healthy controls. Asymmetries based on the mean and Kullback-Leibler divergence in the ipsilesional and contralesional PLIC were calculated for diffusion tensor imaging (DTI) and diffusion spectrum imaging (DSI) measures from the baseline MRI. Predictions of upper extremity Fugl-Meyer (FM) scores at 5-weeks follow-up from baseline measures of PLIC asymmetry in diffusion tensor imaging (DTI) and diffusion spectrum imaging (DSI) models were evaluated. For the stroke participants, the baseline asymmetry measures in the PLIC for the orientation dispersion index of the neurite orientation dispersion and density imaging (NODDI) model were highly correlated with upper extremity FM outcomes (r 2 = 0.83). Use of DSI and the NODDI orientation dispersion index parameter shows promise of being more predictive of stroke recovery and to help better understand white matter changes in stroke, beyond DTI measures. The new finding that baseline interhemispheric differences in the PLIC calculated from the orientation dispersion index of the NODDI model are highly correlated with upper extremity functional outcomes may lead to improved image-based motor-outcome prediction after middle cerebral artery ischemic stroke.

Movement-dependent stroke recovery: a systematic review and meta-analysis of TMS and fMRI evidence.

Evidence indicates that experience-dependent cortical plasticity underlies post-stroke motor recovery of the impaired upper extremity. Motor skill learning in neurologically intact individuals is thought to involve the primary motor cortex, and the majority of studies in the animal literature have studied changes in the primary sensorimotor cortex with motor rehabilitation. Whether changes in engagement in the sensorimotor cortex occur in humans after stroke currently is an area of much interest. The present study conducted a meta-analysis on stroke studies examining changes in neural representations following therapy specifically targeting the upper extremity to determine if rehabilitation-related motor recovery is associated with neural plasticity in the sensorimotor cortex of the lesioned hemisphere. Twenty-eight studies investigating upper extremity neural representations (e.g., TMS, fMRI, PET, or SPECT) were identified, and 13 met inclusion criteria as upper extremity intervention training studies. Common outcome variables representing changes in the primary motor and sensorimotor cortices were used in calculating standardized effect sizes for each study. The primary fixed effects model meta-analysis revealed a large overall effect size (ES=0.84, S.D.=0.15, 95% CI=0.76-0.93). Moreover, a fail-safe analysis indicated that 42 null effect studies would be necessary to lower the overall effect size to an insignificant level. These results indicate that neural changes in the sensorimotor cortex of the lesioned hemisphere accompany functional paretic upper extremity motor gains achieved with targeted rehabilitation interventions.

Bilateral arm training with rhythmic auditory cueing in chronic stroke: not always efficacious.

OBJECTIVE: Bilateral arm training with rhythmic auditory cueing (BATRAC) has been reported to be efficacious in promoting upper-extremity (UE) recovery in chronic stroke. We tested a modified form of BATRAC (modBATRAC) in a new group of participants with a condensed treatment regime to determine whether we could replicate these reported results. METHODS: Fourteen subjects with chronic stroke completed 2 weeks of 2.25 hours per session, 4 sessions per week of modBATRAC. RESULTS: No significant changes were observed in UE Fugl-Meyer or Wolf Motor Function Test scores. Subjects did report increased paretic UE use on the Motor Activity Log (mean change, 0.50; SD = 0.70). CONCLUSIONS: The results of this study offer only partial support for the efficacy of modBATRAC. As in previous trials, modBATRAC facilitated increased use of the paretic arm, but unlike previous trials, it did not increase motor performance. These differences may reflect a more temporally condensed training schedule and less impaired patients.

Longitudinal stability of the Fugl-Meyer Assessment of the upper extremity.

OBJECTIVE: To investigate the longitudinal stability of the Fugl-Meyer Assessment (FMA) of the upper-extremity item difficulties by using Rasch analysis. DESIGN: Secondary analysis of existing data from a cohort longitudinal study of stroke recovery. SETTING: University research center. PARTICIPANTS: A total of 377 people, ages 69.2+/-11.2 years, to whom the assessment was administered at 2 weeks and 6 months poststroke. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Differential item function analysis performed by using the Winsteps software program examined whether the item difficulty hierarchical order of a modified 30-item FMA for the upper extremity (reflex items removed) was invariant across 2 testing occasions. RESULTS: Only 2 items (shoulder flexion to 180 degrees, movement with normal speed) showed large differences in test-retest item difficulty calibration. Item instability had no practical consequences on the longitudinal measurement of person ability. CONCLUSIONS: The 30-item assessment shows a longitudinally stable item difficulty order and is valid for measuring volitional arm motor ability over time.