Viswanath Aluru

Effect of auditory constraints on motor performance depends on stage of recovery post-stroke

In order to develop evidence-based rehabilitation protocols post-stroke, one must first reconcile the vast heterogeneity in the post-stroke population and develop protocols to facilitate motor learning in the various subgroups. The main purpose of this study is to show that auditory constraints interact with the stage of recovery post-stroke to influence motor learning. We characterized the stages of upper limb recovery using task-based kinematic measures in 20 subjects with chronic hemiparesis. We used a bimanual wrist extension task, performed with a custom-made wrist trainer, to facilitate learning of wrist extension in the paretic hand under four auditory conditions: (1) without auditory cueing; (2) to non-musical happy sounds; (3) to self-selected music; and (4) to a metronome beat set at a comfortable tempo. Two bimanual trials (15 s each) were followed by one unimanual trial with the paretic hand over six cycles under each condition. Clinical metrics, wrist and arm kinematics, and electromyographic activity were recorded. Hierarchical cluster analysis with the Mahalanobis metric based on baseline speed and extent of wrist movement stratified subjects into three distinct groups, which reflected their stage of recovery: spastic paresis, spastic co-contraction, and minimal paresis. In spastic paresis, the metronome beat increased wrist extension, but also increased muscle co-activation across the wrist. In contrast, in spastic co-contraction, no auditory stimulation increased wrist extension and reduced co-activation. In minimal paresis, wrist extension did not improve under any condition. The results suggest that auditory task constraints interact with stage of recovery during motor learning after stroke, perhaps due to recruitment of distinct neural substrates over the course of recovery. The findings advance our understanding of the mechanisms of progression of motor recovery and lay the foundation for personalized treatment algorithms post-stroke.

Music Upper Limb Therapy—Integrated: An Enriched Collaborative Approach for Stroke Rehabilitation

Stroke is a leading cause of disability worldwide. It leads to a sudden and overwhelming disruption in one’s physical body, and alters the stroke survivors’ sense of self. Long-term recovery requires that bodily perception, social participation and sense of self are restored; this is challenging to achieve, particularly with a single intervention. However, rhythmic synchronization of movement to external stimuli facilitates sensorimotor coupling for movement recovery, enhances emotional engagement and has positive effects on interpersonal relationships. In this proof-of-concept study, we designed a group music-making intervention, Music Upper Limb Therapy-Integrated (MULT-I), to address the physical, psychological and social domains of rehabilitation simultaneously, and investigated its effects on long-term post-stroke upper limb recovery. The study used a mixed-method pre-post design with 1-year follow up. Thirteen subjects completed the 45-min intervention twice a week for 6 weeks. The primary outcome was reduced upper limb motor impairment on the Fugl-Meyer Scale (FMS). Secondary outcomes included sensory impairment (two-point discrimination test), activity limitation (Modified Rankin Scale, MRS), well-being (WHO well-being index), and participation (Stroke Impact Scale, SIS). Repeated measures analysis of variance (ANOVA) was used to test for differences between pre- and post-intervention, and 1-year follow up scores. Significant improvement was found in upper limb motor impairment, sensory impairment, activity limitation and well-being immediately post-intervention that persisted at 1 year. Activities of daily living and social participation improved only from post-intervention to 1-year follow up. The improvement in upper limb motor impairment was more pronounced in a subset of lower functioning individuals as determined by their pre-intervention wrist range of motion. Qualitatively, subjects reported new feelings of ownership of their impaired limb, more spontaneous movement, and enhanced emotional engagement. The results suggest that the MULT-I intervention may help stroke survivors re-create their sense of self by integrating sensorimotor, emotional and interoceptive information and facilitate long-term recovery across multiple domains of disability, even in the chronic stage post-stroke. Randomized controlled trials are warranted to confirm the efficacy of this approach. Clinical Trial Registration: National Institutes of Health, clinicaltrials.gov, NCT01586221.

Effect of blocking tactile information from the fingertips on adaptation and execution of grip forces to friction at the grasping surface

Adaptation of fingertip forces to friction at the grasping surface is necessary to prevent use of inadequate or excessive grip forces. In the current study we investigated the effect of blocking tactile information from the fingertips noninvasively on the adaptation and efficiency of grip forces to surface friction during precision grasp. Ten neurologically intact subjects grasped and lifted an instrumented grip device with 18 different frictional surfaces under three conditions: with bare hands or with a thin layer of plastic (Tegaderm) or an additional layer of foam affixed to the fingertips. The coefficient of friction at the finger-object interface of each surface was obtained for each subject with bare hands and Tegaderm by measuring the slip ratio (grip force/load force) at the moment of slip. We found that the foam layer reduced sensibility for two-point discrimination and pressure sensitivity at the fingertips, but Tegaderm did not. However, Tegaderm reduced static, but not dynamic, tactile discrimination. Adaptation of fingertip grip forces to surface friction measured by the rate of change of peak grip force, and grip force efficiency measured by the grip-load force ratio at lift, showed a proportional relationship with bare hands but were impaired with Tegaderm and foam. Activation of muscles engaged in precision grip also varied with the frictional surface with bare hands but not with Tegaderm and foam. The results suggest that sensitivity for static tactile discrimination is necessary for feedforward and feedback control of grip forces and for adaptive modulation of muscle activity during precision grasp.

The Effect of CAREX on muscle activation during a point-to-point reaching task

Exoskeletons have been used successfully for functional training of human motions. Our designs of the Cable-driven Arm Exoskeleton (CAREX) are targeted to improve arm function in patients with stroke. In this study, we focus on how muscle activation patterns of subjects change during movements with and without CAREX. Our goal was to evaluate whether CAREX distorts the natural pattern of EMG activity in healthy human subjects during arm movements. Eight healthy subjects performed point-to-point reaching tasks under two conditions: (a) with or without CAREX, and (b) with or without a 5 lb weight attached to their wrist. The EMG signals of 10 muscles were recorded and processed. The results showed that (i) EMG pattern of the subjects while wearing CAREX and while not wearing CAREX showed a high correlation, suggesting little alteration to normal EMG patterns while wearing CAREX; (ii) The subjects showed significantly lower muscle activation when they wore CAREX; (iii) The high correlation and the lower activation were observed in both the no weight condition and the 5 lb weight condition. Overall, the results suggest that CAREX can help subjects reduce the magnitude of muscle activation while preserving normal muscle activation patterns.

Quantifying feedforward control: a linear scaling model for fingertip forces and object weight

The ability to predict the optimal fingertip forces according to object properties before the object is lifted is known as feedforward control, and it is thought to occur due to the formation of internal representations of the objects properties. The control of fingertip forces to objects of different weights has been studied extensively by using a custom-made grip device instrumented with force sensors. Feedforward control is measured by the rate of change of the vertical (load) force before the object is lifted. However, the precise relationship between the rate of change of load force and object weight and how it varies across healthy individuals in a population is not clearly understood. Using sets of 10 different weights, we have shown that there is a log-linear relationship between the fingertip load force rates and weight among neurologically intact individuals. We found that after one practice lift, as the weight increased, the peak load force rate (PLFR) increased by a fixed percentage, and this proportionality was common among the healthy subjects. However, at any given weight, the level of PLFR varied across individuals and was related to the efficiency of the muscles involved in lifting the object, in this case the wrist and finger extensor muscles. These results quantify feedforward control during grasp and lift among healthy individuals and provide new benchmarks to interpret data from neurologically impaired populations as well as a means to assess the effect of interventions on restoration of feedforward control and its relationship to muscular control.

Traumatic brain injury results in altered physiologic, but not subjective responses to emotional stimuli

ABSTRACT Background: While the cognitive sequelae of traumatic brain injury (TBI) are well known, emotional impairments after TBI are suboptimally characterized. Lack of awareness of emotional difficulties can make self-report unreliable. However, individuals with TBI demonstrate involuntary changes in heart rate variability which may enable objective quantification of emotional dysfunction. Methods: Sixteen subjects with chronic TBI and 10 age-matched controls were tested on an emotional function battery during which they watched a series of film clips normed to elicit specific positively and negatively valenced emotions: amusement, sexual amusement, sadness, fear and disgust. Subjective responses to the emotional stimuli were also obtained. Additionally, surface electrodes measured cardiac and respiratory signals to compute heart rate variability (HRV), from which measures of parasympathetic activity, the respiratory frequency area (RFA) and sympathetic activity, the low frequency area (LFA), of the HRV frequency spectrum were derived. The Neurobehavioral Rating Scale-Revised (NRS-R) and the King-Devick (KD) test were administered to assess neurobehavioral dysfunction. Results: The two groups showed no differences in subjective ratings of emotional intensity. Subjects with TBI showed significantly decreased sympathetic activity when viewing amusing stimuli and significantly increased sympathetic activity when viewing sad stimuli compared to controls. Most of the subjects did not show agitation, anxiety, depression, blunted affect, emotional withdrawal, decreased motivation or mental fatiguability on the NRS-R. However, 13/16 subjects with TBI demonstrated attention difficulty on the NRS-R which was positively correlated with the increased sympathetic activity during sad stimuli. Both attention difficulty and abnormal autonomic responses to sad stimuli were correlated with the timing on the KD test, which reflected difficulty with visual attention shifting. Conclusions: The HRV spectrum may be useful to identify subclinical emotional dysfunction in individuals with TBI. Attention difficulites, specifically impairment in visual attention shifting, may contribute to abnormal reactivity to sad stimuli that may be detected and potentially treated to improve emotional function.

Coupled Bimanual Training Using a Non-Powered Device for Individuals withSevere Hemiparesis: A Pilot Study

Background Few options exist for training arm movements in participants with severe post-stroke hemiparesis who have little active range of motion. The purpose of this study was to test the safety and feasibility of training with a non-powered device, the Bimanual Arm Trainer (BAT), to facilitate motor recovery in individuals with severe hemiparesis. The BAT enabled coupled bimanual training of shoulder external rotation, which is reduced in individuals with severe post-stroke hemiplegia. The rationale for bimanual training was to harness contralesional cortical activity to drive voluntary movement in the affected arm in patients who could barely perform unimanual movements. Methods Nine participants with post-stroke hemiparesis, preserved passive range of motion and Modified Ashworth score of <3 in the shoulder and elbow joints, trained with the device for 45 minutes, twice a week for six weeks, and were assessed pre- and post-training. Results All participants tolerated the training and no adverse events were reported. Participants showed significant improvement in the upper extremity Fugl-Meyer score post-training with an effect size of 0.89. Changes in the flexor synergy pattern accounted for 64.7% of the improvement. Improvement in active range of motion in the paretic limb occurred for both trained and untrained movements. Some participants showed improvement in the time taken to perform selected tasks on the Wolf Motor Function Test post-training. Conclusion The results demonstrate the safety and feasibility of using the Bimanual Arm Trainer to facilitate motor recovery in individuals with severe hemiparesis.

Poster 21 Leptomeningeal Carcinomatosis Presenting as Tetraparesis: A Very Rare Case of Small Cell Prostate Carcinoma

replacement of the tube. BBS is commonly diagnosed only after a patient complains of abdominal pain, however as in our patient with no intact sensation in the lower abdomen, it should be part of the differential in SCI patients with difficulty flushing the PEG. Conclusions: It is important to consider BBS in patients with ongoing PEG obstruction as failure to do so could result in further complications such as peritonitis and death. Preventing traction on the PEG will reduce the chances of developing BBS. Allowing for 1.5-2cm between the external bumper and the skin, gently rotating and manipulating the PEG in and out daily, and measuring the length of the external tube can help to recognize migration of the tube. Level of Evidence: Level V

Poster 78 Physiologic Mechanisms of Emotional Impairment in Traumatic Brain Injury

Interventions: PubMed, CINAHL, PsycINFO and EMBASE were queried with the subject heading terms “pressure sore,” “pressure ulcer,” “position or turn in bed, wheelchair,” “ pressure relief,” and “ pressure release.” Results or Clinical Course: We identified 2820 publications, of which 49 met inclusion criteria. Of these the subject population was 2834 (923 persons with SCI, 717 non-SCI patients, 1194 healthy controls). Procedures for measuring skin pressure and metabolism were highly variable by anatomic location, measurement technique, outcome measure, study site, participant characteristics, description of positioning/turning for bed and seated interventions. Several studies suggest that skin response to pressure differs between SCI and non-SCI subjects. No clear optimal bed positioning or turning frequency could be determined beyond the 90 degree lateral position resulting in high pressure over the trochanters. Conflicting results and insufficient evidence for optimal bed and seated positioning, and turning and pressure reliefs to prevent pressure ulcers in both SCI and non-SCI populations were limiting factors. Conclusion: Based on the existing evidence, current “guidelines” cannot be considered evidence-based and consideration should be given to reevaluating existing guideline-based turning intervals and related policy implications for this high-risk population. We conclude that PU risk is highly individualized, with the SCI population at a higher risk, which demands flexible PU prevention strategies for bed/seated positioning and pressure reliefs.