Discriminative sensory dysfunction after unilateral stroke

Limitations in utilization and prioritization of standardized somatosensory assessments after stroke: A cross-sectional survey of neurorehabilitation clinicians

BACKGROUND AND PURPOSE

Somatosensory impairments are common after stroke, but receive limited evaluation and intervention during neurorehabilitation, despite negatively impacting functional movement and recovery.

OBJECTIVES

Our objective was to understand the scope of somatosensory assessments used by clinicians in stroke rehabilitation, and barriers to increasing use in clinical practice.

METHODS

An electronic survey was distributed to clinicians (physical therapists, occupational therapists, physicians, and nurses) who assessed at least one individual with stroke in the past 6 months. The survey included questions on evaluation procedures, type, and use of somatosensory assessments, as well as barriers and facilitators in clinical practice.

RESULTS

Clinicians (N = 431) indicated greater familiarity with non-standardized assessments, and greater utilization compared to standardized assessments (p < 0.0001). Components of tactile sensation were the most commonly assessed modality of somatosensation (25%), while proprioception was rarely assessed (1%). Overall, assessments of motor function were prioritized over assessments of somatosensory function (p < 0.0001).

DISCUSSION

Respondents reported assessing somatosensation less frequently than motor function and demonstrated a reliance on rapid and coarse non-standardized assessments that ineffectively capture multi-modal somatosensory impairments, particularly for proprioceptive deficits common post-stroke. In general, clinicians were not familiar with standardized somatosensory assessments, and this knowledge gap likely contributes to lack of translation of these assessments into practice.

CONCLUSIONS

Clinicians utilize somatosensory assessments that inadequately capture the multi-modal nature of somatosensory impairments in stroke survivors. Addressing barriers to clinical translation has the potential to increase utilization of standardized assessments to improve the characterization of somatosensory deficits that inform clinical decision-making toward enhancing stroke rehabilitation outcomes.

A robot-based interception task to quantify upper limb impairments in proprioceptive and visual feedback after stroke

BACKGROUND

A key motor skill is the ability to rapidly interact with our dynamic environment. Humans can generate goal-directed motor actions in response to sensory stimulus within ~ 60-200ms. This ability can be impaired after stroke, but most clinical tools lack any measures of rapid feedback processing. Reaching tasks have been used as a framework to quantify impairments in generating motor corrections for individuals with stroke. However, reaching may be inadequate as an assessment tool as repeated reaching can be fatiguing for individuals with stroke. Further, reaching requires many trials to be completed including trials with and without disturbances, and thus, exacerbate fatigue. Here, we describe a novel robotic task to quantify rapid feedback processing in healthy controls and compare this performance with individuals with stroke to (more) efficiently identify impairments in rapid feedback processing.

METHODS

We assessed a cohort of healthy controls (n = 135) and individuals with stroke (n = 40; Mean 41 days from stroke) in the Fast Feedback Interception Task (FFIT) using the Kinarm Exoskeleton robot. Participants were instructed to intercept a circular white target moving towards them with their hand represented as a virtual paddle. On some trials, the arm could be physically perturbed, the target or paddle could abruptly change location, or the target could change colour requiring the individual to now avoid the target.

RESULTS

Most participants with stroke were impaired in reaction time (85%) and end-point accuracy (83%) in at least one of the task conditions, most commonly with target or paddle shifts. Of note, this impairment was also evident in most individuals with stroke when performing the task using their unaffected arm (75%). Comparison with upper limb clinical measures identified moderate correlations with the FFIT.

CONCLUSION

The FFIT was able to identify a high proportion of individuals with stroke as impaired in rapid feedback processing using either the affected or unaffected arms. The task allows many different types of feedback responses to be efficiently assessed in a short amount of time.

The locations of stroke lesions next to the posterior internal capsule may predict the recovery of the related proprioceptive deficits

Background

Somatosensory deficits after stroke correlate with functional disabilities and impact everyday-life. In particular, the interaction of proprioception and motor dysfunctions affects the recovery. While corticospinal tract (CST) damage is linked to poor motor outcome, much less is known on proprioceptive recovery. Identifying a predictor for such a recovery could help to gain insights in the complex functional recovery processes thereby reshaping rehabilitation strategies.

Methods

50 patients with subacute stroke were tested before and after neurological rehabilitation. Proprioceptive and motor impairments were quantified with three clinical assessments and four hand movement and proprioception measures using a robotic device. Somatosensory evoked potentials (SSEP) to median nerve stimulation and structural imaging data (MRI) were also collected. Voxel-based lesion-symptom mapping (VLSM) along with a region of interest (ROI) analysis were performed for the corticospinal tract (CST) and for cortical areas.

Results

Before rehabilitation, the VLSM revealed lesion correlates for all clinical and three robotic measures. The identified voxels were located in the white matter within or near the CST. These regions associated with proprioception were located posterior compared to those associated with motor performance. After rehabilitation the patients showed an improvement of all clinical and three robotic assessments. Improvement in the box and block test was associated with an area in anterior CST. Poor recovery of proprioception was correlated with a high lesion load in fibers towards primary sensorymotor cortex (S1 and M1 tract). Patients with loss of SSEP showed higher lesion loads in these tracts and somewhat poorer recovery of proprioception. The VSLM analysis for SSEP loss revealed a region within and dorsal of internal capsule next to the posterior part of CST, the posterior part of insula and the rolandic operculum.

Conclusion

Lesions dorsal to internal capsule next to the posterior CST were associated with proprioceptive deficits and may have predictive value. Higher lesion load was correlated with poorer restoration of proprioceptive function. Furthermore, patients with SSEP loss trended towards poor recovery of proprioception, the corresponding lesions were also located in the same location. These findings suggest that structural imaging of the internal capsule and CST could serve as a recovery predictor of proprioceptive function.

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.

Longitudinal evaluation of the functional connectivity changes in the secondary somatosensory cortex (S2) of the monkey brain during acute stroke

Background

Somatosensory deficits are frequently seen in acute stroke patients and may recover over time and affect functional outcome. However, the underlying mechanism of function recovery remains poorly understood. In the present study, progressive function alteration of the secondary somatosensory cortex (S2) and its relationship with regional perfusion and neurological outcome were examined using a monkey model of stroke.

Methods and materials

Rhesus monkeys (n = 4) were induced with permanent middle cerebral artery occlusion (pMCAo). Resting-state functional MRI, dynamic susceptibility contrast perfusion MRI, diffusion-weighted, T₁ and T₂ weighted images were collected before surgery and at 4-6, 48, and 96 h post stroke on a 3T scanner. Progressive changes of relative functional connectivity (FC), cerebral blood flow (CBF), and CBF/Tmax (Time to Maximum) of affected S2 regions were evaluated. Neurological deficits were assessed using the Spetzler approach.

Results

Ischemic lesion was evidently seen in the MCA territory including S2 in each monkey. Relative FC of injured S2 regions decreased substantially following stroke. Spetzler scores dropped substantially at 24 h post stroke but slightly recovered from Day 2 to Day 4. Relative FC progressively increased from 6 to 48 and 96 h post stroke and correlated significantly with relative CBFand CBF/Tmax changes.

Conclusion

The present study revealed the progressive alteration of function connectivity in S2 during acute stroke. The preliminary results suggested the function recovery might start couple days post occlusion and collateral circulation might play a key role in the recovery of somatosensory function after stroke insult. The relative function connectivity in S2 may provide additional information for prediction of functional outcome in stroke patients.

Characterizing Touch Discrimination Impairment from Pooled Stroke Samples Using the Tactile Discrimination Test: Updated Criteria for Interpretation and Brief Test Version for Use in Clinical Practice Settings

Somatosensory loss post-stroke is common, with touch sensation characteristically impaired. Yet, quantitative, standardized measures of touch discrimination available for clinical use are currently limited. We aimed to characterize touch impairment and re-establish the criterion of abnormality of the Tactile Discrimination Test (TDT) using pooled data and to determine the sensitivity and specificity of briefer test versions. Baseline data from stroke survivors (n = 207) and older neurologically healthy controls (n = 100) assessed on the TDT was extracted. Scores were re-analyzed to determine an updated criterion of impairment and the ability of brief test versions to detect impairment. Updated scoring using an area score was used to calculate the TDT percent maximum area (PMA) score. Touch impairment was common for the contralesional hand (83%) but also present in the ipsilesional hand (42%). The criterion of abnormality was established as 73.1 PMA across older adults and genders. High sensitivity and specificity were found for briefer versions of the TDT (25 vs. 50 trials; 12 or 15 vs. 25 trials), with sensitivity ranging between 91.8 and 96.4% and specificity between 72.5 and 95.0%. Conclusion: Updated criterion of abnormality and the high sensitivity and specificity of brief test versions support the use of the TDT in clinical practice settings.

Sensory retraining for Central Post-Stroke Pain: A subgroup analysis within a randomized controlled trial

BACKGROUND

Explicit Sensory Retraining (SR) has been suggested for pain management in several neuropathic pain syndromes.

OBJECTIVES

To study the effectiveness of SR on Central Post Stroke Pain (CPSP) symptoms.

METHODS

A preplanned subgroup of 23 subjects post-stroke reporting central pain were randomized within a larger study, to receive either explicit sensory discrimination retraining (SR) (in subgroup n = 11) or implicit repeated exposure to stimuli (RE) (in subgroup n = 12), applied to the lower limb. Pain intensity measured by VAS, measures of sensory ability; balance and gait activities; and participation were assessed by a blinded assessor at four points in time.

RESULTS

A group*time interaction effect was demonstrated (p = 0.04) for VAS, as for the SR treatment group VAS decreased from 56/100 to 23/100. Nine out of eleven subjects in the SR group demonstrated positive response to treatment. Pain alleviation was maintained at follow-up. A similar interaction effect was found for tactile threshold (p = 0.03). Significant improvement was noted for all other variables with no group differences.

CONCLUSION

This study provides preliminary evidence to the clinically relevant positive effect of explicit sensory retraining for subjects with CPSP. The positive effect on tactile threshold detection could potentially indicate pain alleviation mechanisms.

Body Schema as Assessed by Upper Limb Left/Right Judgment Tasks Is Altered in Stroke: Implications for Motor Imagery Training

BACKGROUND AND PURPOSE

Individuals with stroke often experience significant impairment of the upper limb. Rehabilitation interventions targeting the upper limb are typically associated with only small to moderate gains. The knowledge that body schema can be altered in other upper limb conditions has contributed to the development of tailored rehabilitation approaches. This study investigated whether individuals with stroke experienced alterations in body schema of the upper limb. If so, this knowledge may have implications for rehabilitation approaches such as motor imagery.

METHODS

An observational study performed online consisting of left/right judgment tasks assessed by response time and accuracy of: (i) left/right direction recognition; (ii) left/right shoulder laterality recognition; (iii) left/right hand laterality recognition; (iv) mental rotation of nonembodied objects. Comparisons were made between individuals with and without stroke. Secondary comparisons were made in the stroke population according to side of stroke and side of pain if experienced.

RESULTS

A total of 895 individuals (445 with stroke) participated. Individuals with stroke took longer for all tasks compared to those without stroke, and were less accurate in correctly identifying the laterality of shoulder (P < 0.001) and hand (P < 0.001) images, and the orientation of nonembodied objects (P < 0.001). Moreover, the differences observed in the hand and shoulder tasks were greater than what was observed for the control tasks of directional recognition and nonembodied mental rotation. No significant differences were found between left/right judgments of individuals with stroke according to stroke-affected side or side of pain.

DISCUSSION AND CONCLUSIONS

Left/right judgments of upper limb are frequently impaired after stroke, providing evidence of alterations in body schema. The knowledge that body schemas are altered in individuals with longstanding stroke may assist in the development of optimal, well-accepted motor imagery programs for the upper limb.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A394).

Wrist Proprioception in Adults with and without Subacute Stroke

Proprioception is critical to motor control and functional status but has received limited study early after stroke. Patients admitted to an inpatient rehabilitation facility for stroke (n = 18, mean(±SD) 12.5 ± 6.6 days from stroke) and older healthy controls (n = 19) completed the Wrist Position Sense Test (WPST), a validated, quantitative measure of wrist proprioception, as well as motor and cognitive testing. Patients were serially tested when available (n = 12, mean 11 days between assessments). In controls, mean(±SD) WPST error was 9.7 ± 3.5° in the dominant wrist and 8.8 ± 3.8° in the nondominant wrist (p = 0.31). In patients with stroke, WPST error was 18.6 ± 9° in the more-affected wrist, with abnormal values present in 88.2%; and 11.5 ± 5.6° in the less-affected wrist, with abnormal values present in 72.2%. Error in the more-affected wrist was higher than in the less-affected wrist (p = 0.003) or in the dominant (p = 0.001) and nondominant (p < 0.001) wrist of controls. Age and BBT performance correlated with dominant hand WPST error in controls. WPST error in either wrist after stroke was not related to age, BBT, MoCA, or Fugl-Meyer scores. WPST error did not significantly change in retested patients. Wrist proprioception deficits are common, bilateral, and persistent in subacute stroke and not explained by cognitive or motor deficits.

Distinguishing transient from persistent tactile agnosia after partial anterior circulation infarcts - Behavioral and neuroimaging evidence for white matter disconnection

From a cohort of 36 patients presenting apperceptive tactile agnosia after first cortical ischemic stroke, 14 showed temporary impairment at admission. A previous multi-voxel analysis of the cortical lesions, using as explanatory variable the course of tactile object recognition performance over the recovery period of 9 months, partitioned the cohort into three subgroups. Of the 14 patients constituting two of the subgroups, 7 recovered from their impairment whereas 7 did not. These two subgroups could not be distinguished at admission. The primary aim of the present study is to present two assessments that can do so. The first assessment comprises a pattern of behavioral measures, determined via principal component analysis, encoded in three tests: picking small objects, macrogeometrical discrimination and tactile object recognition. The receiver operating characteristic curve derived from permutation of the behavioral test scores yielded an 80% probability of correct identification of the patient subgroup and an 8% probability for false identification. As done with the permuted scores, the pattern could predict the persistence of affliction of new stroke patients with tactile agnosia. The second predictive assessment extends our previous evaluation of cortical MRI lesion maps to include subcortical regions. Confirming our previous study, the lesions of the persistently impaired subgroup disrupted significantly the anterior arcuatus fasciculus and associated superior longitudinal fasciculus III in the ipsilesional hemisphere, impeding reciprocal information transfer between supramarginal gyrus and both the ventral premotor cortex and Brodmann area 44. Due to the importance of interhemispheric information transfer in tactile agnosia, we performed a supplementary analysis of tactile object recognition scores. It showed that haptic information transfer from the non-affected to the affected hands in the persistent cases partly restored function during the nine months, possibly following restoration of functional interhemispheric haptic information transfer at the border of posterior corpus callosum and splenium. In conclusion, the combined findings of the cortical lesion at subarea PFt of the inferior parietal lobule and the associated subcortical tract lesions permit almost perfect prediction of persistent impairment of tactile object recognition. The study substantiates the need for combined analysis of both cortical lesions and white matter tract disconnections.

Masticatory function of stroke patients: A systematic review with meta-analysis

PURPOSE

The present systematic review and meta-analysis aimed to summarise the current information on the masticatory function of stroke patients.

METHODS

Four electronic databases (Medline, Embase, CINAHL and Web of Science) were searched for relevant observational studies and clinical trials (up to Jun 2021) on the masticatory function of stroke patients. Two reviewers independently performed study selection and quality assessments (using JBI Critical Appraisal Checklist). Meta-analysis was conducted for the comparison of bite force and masticatory performance using standardised mean difference (SMD). Of the 3837 records identified, nine studies, corresponding to 11 papers and 302 participants, were included in the analysis.

RESULTS

The maximum bite force of stroke patients was significantly lower than that of the healthy individuals (SMD -0.52, 95% CI: -0.95 to -0.08, P = .02). There was no significant difference between the ipsi-lesional and the contra-lesional sides of the same stroke patient (SMD 0.13, 95% CI: -0.14 to 0.39, P = .34). Stroke patients had lower masticatory performance than healthy people (SMD -0.97, 95% CI: 0.57 to 1.37, P < .00001), and the contra-lesional side was worse than the ipsi-lesional side. Electromyographic analysis indicated that muscle activation of stroke patients was poorer than the healthy individuals, and stroke patients seem to exhibit dysfunction in the recruiting and firing of motor units.

CONCLUSIONS

Stroke patients have lower maximum bite force and masticatory performance than healthy people, with masticatory performance being the most affected.

Effectiveness of Somatosensory Stimulation for the Lower Limb and Foot to Improve Balance and Gait after Stroke: A Systematic Review

This systematic review’s purpose was to evaluate the effectiveness of lower-limb and foot somatosensory stimulation to improve balance and gait post-stroke. PRISMA reporting guidelines were followed. Included studies: randomized controlled trials (RCTs), published in English with ethical approval statement. Studies of conditions other than stroke, functional electrical stimulation, and interventions eliciting muscle contraction, were excluded. AgeLine, AMED, CINAHL PLUS, EMBASE, EMCARE MEDLINE, PEDro, PsycARTICLES, PsycINFO, SPORTDiscus, Web of Science and Cochrane central register of controlled trials were searched from 1 January 2002 to 31 March 2022. Two authors independently screened results, extracted data and assessed study quality using Cochrane Risk of Bias 2 tool; 16 RCTs (n = 638) were included. Four studies showed a medium or large standardized between-group effect size (Cohen’s d) in favor of somatosensory stimulation, in relation to: customized insoles (d = 0.527), taping (d = 0.687), and electrical stimulation (two studies: d = 0.690 and d = 1.984). Although limited by study quality and heterogeneity of interventions and outcomes, with only one study’s results statistically significant, several interventions showed potential for benefit, exceeding the minimally important difference for gait speed. Further research with larger trials is required. This unfunded systematic review was registered with PROSPERO (number CRD42022321199).

Assessing bilateral ankle proprioceptive acuity in stroke survivors: An exploratory study

Background

Bilateral proprioception deficits were reported in stroke survivors. However, whether bilateral proprioception deficits exist in the ankle joint after stroke was unclear. Ankle proprioception is a significant predictor of balance dysfunction after stroke, and previous studies to date are lacking appropriate evaluation methods.

Objectives

We want to determine whether the active movement extent discrimination apparatus (AMEDA) is a reliable tool for assessing ankle proprioceptive acuity in stroke survivors and the presence of deficits in ankle proprioception on the affected and unaffected sides in patients after stroke.

Methods

Bilateral ankle proprioception was assessed in 20 stroke patients and 20 age-matched healthy controls using AMEDA. Test-retest reliability was assessed using the intraclass correlation coefficient (ICC).

Results

The ICC in the affected and unaffected sides was 0.713 and 0.74, respectively. Analysis of variance revealed significant deficits in ankle proprioception in subacute stroke survivors vs. healthy controls (F = 2.719, p = 0.045). However, there were no significant differences in proprioception acuity scores between the affected and unaffected sides in patients after stroke (F = 1.14, p = 0.331).

Conclusions

Stroke survivors had bilateral deficits in ankle proprioceptive acuity during active movements compared with age-matched healthy controls, underscoring the need to evaluate these deficits on both sides of the body and develop effective sensorimotor rehabilitation methods for this patient population. The AMEDA can reliably determine bilateral ankle proprioceptive acuity in stroke survivors.

Effect of novel training to normalize altered finger force direction post-stroke: study protocol for a double-blind randomized controlled trial

BACKGROUND

Functional task performance requires proper control of both movement and force generation in three-dimensional space, especially for the hand. Control of force in three dimensions, however, is not explicitly treated in current physical rehabilitation. To address this gap in treatment, we have developed a tool to provide visual feedback on three-dimensional finger force. Our objective is to examine the effectiveness of training with this tool to restore hand function in stroke survivors.

METHODS

Double-blind randomized controlled trial. All participants undergo 18 1-h training sessions to practice generating volitional finger force of various target directions and magnitudes. The experimental group receives feedback on both force direction and magnitude, while the control group receives feedback on force magnitude only. The primary outcome is hand function as measured by the Action Research Arm Test. Other outcomes include the Box and Block Test, Stroke Impact Scale, ability to direct finger force, muscle activation pattern, and qualitative interviews.

DISCUSSION

The protocol for this clinical trial is described in detail. The results of this study will reveal whether explicit training of finger force direction in stroke survivors leads to improved motor control of the hand. This study will also improve the understanding of neuromuscular mechanisms underlying the recovery of hand function.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03995069 . Registered on June 21, 2019.

What is "usual care" in the rehabilitation of upper limb sensory loss after stroke? Results from a national audit and knowledge translation study

PURPOSE

To characterise the assessments and treatments that comprise "usual care" for stroke patients with somatosensory loss, and whether usual care has changed over time.

MATERIALS AND METHODS

Comparison of cross-sectional, observational data from (1) Stroke Foundation National Audit of Acute (2007-2019) and Rehabilitation (2010-2018) Stroke Services and (2) the SENSe Implement multi-site knowledge translation study with occupational therapists and physiotherapists (n = 115). Descriptive statistics, random effects logistic regression, and content analysis were used.

RESULTS

Acute hospitals (n = 172) contributed 24 996 cases across audits from 2007 to 2019 (median patient age 76 years, 54% male). Rehabilitation services (n = 134) contributed organisational survey data from 2010 to 2014, with 7165 cases (median 76 years, 55% male) across 2016-2018 clinical audits (n = 127 services). Somatoensory assessment protocol use increased from 53% (2007) to 86% (2019) (odds ratio 11.4, 95% CI 5.0-25.6). Reported use of sensory-specific retraining remained stable over time (90-93%). Therapist practice reports for n = 86 patients with somatosensory loss revealed 16% did not receive somatosensory rehabilitation. The most common treatment approaches were sensory rehabilitation using everyday activities (69%), sensory re-education (68%), and compensatory strategies (64%).

CONCLUSION

Sensory assessment protocol use has increased over time while sensory-specific training has remained stable. Sensory rehabilitation in the context of everyday activities is a common treatment approach. Clinical trial registration number: ACTRN12615000933550IMPLICATIONS FOR REHABILITATIONOnly a small proportion of upper limb assessments conducted with stroke patients focus specifically on sensation; increased use of standardised upper limb assessments for sensory loss is needed.Stroke patients assessed as having upper limb sensory loss frequently do not receive treatment for their deficits.Therapists typically use everyday activities to treat upper limb sensory loss and may require upskilling in sensory-specific retraining to benefit patients.

Sensory Stimulation of the Foot and Ankle Early Post-stroke: A Pilot and Feasibility Study

Background: Somatosensory stimulation of the lower extremity could improve motor recovery and walking post-stroke. This pilot study investigated the feasibility of a subsequent randomized controlled trial (RCT) to determine whether task-specific gait training is more effective following either (a) intensive hands-on somatosensory stimulation or (b) wearing textured insoles. Objectives: Determine recruitment and attrition rates, adherence to intervention, acceptability and viability of interventions and outcome measures, and estimate variance of outcome data to inform sample size for a subsequent RCT. Methods: Design: randomized, single-blinded, mixed-methods pilot study. Setting: In-patient rehabilitation ward and community. Participants: n = 34, 18+years, 42-112 days following anterior or posterior circulation stroke, able to follow simple commands, able to walk independently pre-stroke, and providing informed consent. Intervention: Twenty 30-min sessions of task-specific gait training (TSGT) (delivered over 6 weeks) in addition to either: (a) 30-60 min mobilization and tactile stimulation (MTS); or (b) unlimited textured insole (TI) wearing. Outcomes: Ankle range of movement (electrogoniometer), touch-pressure sensory thresholds (Semmes Weinstein Monofilaments), motor impairment (Lower Extremity Motricity Index), walking ability and speed (Functional Ambulation Category, 5-m walk test, pressure insoles) and function (modified Rivermead Mobility Index), measured before randomization, post-intervention, and 1-month thereafter (follow-up). Adherence to allocated intervention and actual dose delivered (fidelity) were documented in case report forms and daily diaries. Focus groups further explored acceptability of interventions and study experience. Analysis: Recruitment, attrition, and dose adherence rates were calculated as percentages of possible totals. Thematic analysis of daily diaries and focus group data was undertaken. Standard deviations of outcome measures were calculated and used to inform a sample size calculation. Results: Recruitment, attrition, and adherence rates were 48.57, 5.88, and 96.88%, respectively. Focus groups, daily-diaries and case report forms indicated acceptability of interventions and outcome measures to participants. The 5-m walk was selected as primary outcome measure for a future trial [mean (SD) at end of intervention: 16.86 (11.24) MTS group and 21.56 (13.57) TI group]; sample size calculation indicated 60 participants are required per group. Conclusion: Recruitment, attrition and adherence rates and acceptability of interventions and outcomes justify a subsequent powered RCT of MTS+TSGT compared with TI+TSGT.

Mesoscale hierarchical organization of primary somatosensory cortex captured by resting-state-fMRI in humans

The primary somatosensory cortex (S1) plays a key role in the processing and integration of afferent somatosensory inputs along an anterior-to-posterior axis, contributing towards necessary human function. It is believed that anatomical connectivity can be used to probe hierarchical organization, however direct characterization of this principle in-vivo within humans remains elusive. Here, we use resting-state functional connectivity as a complement to anatomical connectivity to investigate topographical principles of human S1. We employ a novel approach to examine mesoscopic variations of functional connectivity, and demonstrate a topographic organisation spanning the region's hierarchical axis that strongly correlates with underlying microstructure while tracing along architectonic Brodmann areas. Our findings characterize anatomical hierarchy of S1 as a 'continuous spectrum' with evidence supporting a functional boundary between areas 3b and 1. The identification of this topography bridges the gap between structure and connectivity, and may be used to help further current understanding of sensorimotor deficits.

Factors influencing allied health professionals' implementation of upper limb sensory rehabilitation for stroke survivors: a qualitative study to inform knowledge translation

OBJECTIVES

Somatosensory loss is common after stroke with one-in-two individuals affected. Although clinical practice guidelines recommend providing somatosensory rehabilitation, this impairment often remains unassessed and untreated. To address the gap between guideline recommendations and clinical practice, this study sought to understand the factors influencing delivery of evidence-based upper limb sensory rehabilitation after stroke.

DESIGN

Qualitative study involving focus groups and interviews. Data analysis used an inductive approach (thematic analysis) and deductive analysis using implementation theory (the Theoretical Domains Framework and Normalisation Process Theory).

SETTING

Eight healthcare organisations in metropolitan and regional areas of Victoria and New South Wales, Australia.

PARTICIPANTS

Eighty-seven rehabilitation therapists (79% occupational therapists and 21% physiotherapists) were purposively sampled and participated in a knowledge translation study with staggered recruitment from 2014 to 2018.

RESULTS

Three types of factors influenced therapists' delivery of upper limb somatosensory rehabilitation: individual ('The uncertain, unskilled therapist'), patient ('Patient understanding and priorities') and organisational ('System pressures and resources'). Deductive analysis using implementation theory identified key determinants of practice change, such as opportunities to consolidate new skills, the anticipated benefits of upskilling as a therapy team and the work anticipated by therapists to incorporate a new somatosensory rehabilitation approach.

CONCLUSIONS

Occupational therapists and physiotherapists hold valuable insights towards practice change in somatosensory rehabilitation from the 'frontline'. Therapists experience barriers to change including a lack of knowledge and skills, lack of resources and organisational pressures. Facilitators for change were identified, including social support and therapists' perceived legitimacy in using new somatosensory rehabilitation approaches. Results will inform the design of a tailored implementation strategy to increase the use of evidence-based somatosensory rehabilitation in Australia.

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry (ACTRN12615000933550).

Does rTMS Targeting Contralesional S1 Enhance Upper Limb Somatosensory Function in Chronic Stroke? A Proof-of-Principle Study

BACKGROUND

Somatosensory deficits are prevalent after stroke, but effective interventions are limited. Brain stimulation of the contralesional primary somatosensory cortex (S1) is a promising adjunct to peripherally administered rehabilitation therapies.

OBJECTIVE

To assess short-term effects of repetitive transcranial magnetic stimulation (rTMS) targeting contralesional (S1) of the upper extremity.

METHODS

Using a single-session randomized crossover design, stroke survivors with upper extremity somatosensory loss participated in 3 rTMS treatments targeting contralesional S1: Sham, 5 Hz, and 1 Hz. rTMS was delivered concurrently with peripheral of sensory electrical stimulation and vibration of the affected hand. Outcomes included 2-point discrimination (2PD), proprioception, vibration perception threshold, monofilament threshold (size), and somatosensory evoked potential (SEP). Measures were collected before, immediately after treatment, and 1 hour after treatment. Mixed models were fit to analyze the effects of the 3 interventions.

RESULTS

Subjects were 59.8 ± 8.1 years old and 45 ± 39 months poststroke. There was improvement in 2PD after 5-Hz rTMS for the stroke-affected (F(2, 76.163) = 3.5, P = .035) and unaffected arm (F(2, 192.786) = 10.6, P < .0001). Peak-to-peak SEP amplitudes were greater after 5-Hz rTMS for N33-P45 (F(2, 133.027) = 3.518, P = .032) and N45-P60 (F(2, 67.353) = 3.212, P = .047). Latencies shortened after 5-Hz rTMS for N20 (F(2, 69.64) = 3.37, P = .04), N60 (F(2, 47.343) = 4.375, P = .018), and P100 (F(2, 37.608) = 3.537, P = .039) peaks. There were no differences between changes immediately after the intervention and an hour later.

CONCLUSIONS

Short-term application of facilitatory high-frequency rTMS (5Hz) to contralesional S1 combined with peripheral somatosensory stimulation may promote somatosensory function. This intervention may serve as a useful adjunct in somatosensory rehabilitation after stroke.

Validity and Reliability of the Semmes-Weinstein Monofilament Test and the Thumb Localizing Test in Patients With Stroke

Background: Somatosensory impairment is common in patients who have had a stroke and can affect their motor function and activities of daily living (ADL). Therefore, detecting and treating somatosensory impairments properly is considered to be very important, and various examinations have been developed. However, the reliability and validity of few of them have been verified due to differences in the procedure of each examiner or poor quantification by the examination itself.

Objective: We hypothesized that, with fixed procedures two convenient clinical examinations, the Semmes-Weinstein Monofilament Test (SWMT) and the Thumb Localizing Test (TLT), could provide reliable assessments of light touch sensation and proprioception. The purpose of this study was to verify the reliability and validity of these two examinations as indices of somatosensory impairment of the upper extremity (UE) in patients with chronic post-stroke hemiparesis.

Methods: Fifty patients with chronic stroke (median time after onset of stroke, 848 [474–1708] days, mean age 57 [standard deviation 14] years) were enrolled at Keio University Hospital from 2017 to 2018. Examiners learned the original method of the SWMT and the TLT rigorously and shared it with each other. The TLT procedure was partially modified by dividing the location of the patient's thumb into four spaces. Two examiners evaluated the SWMT and the TLT for 2 days, and intra-rater and inter-rater reliabilities were calculated using weighted kappa statistics. In addition to this, the evaluator size score of the SWMT was assessed with Bland-Altman analysis to evaluate systematic bias. The Stroke Impairment Assessment Set (SIAS) sensory items were used to assess validity, and Spearman's rank correlation coefficients were calculated.

Results: Intra/inter-rater agreements of the SWMT grade score were 0.89 (thumb, 95%CI: 0.83–0.95)/ 0.75 (0.60–0.91) and 0.80 (index finger, 0.67–0.93)/0.79 (0.66–0.92), and of the TLT they were 0.83 (navel level proximal space, 0.71–0.95)/ 0.83 (0.73–0.92), 0.90 (navel level distal space, 0.85–0.96)/ 0.80 (0.69–0.90), 0.80 (shoulder level proximal space, 0.68–0.92)/ 0.77 (0.65–0.89), and 0.87 (shoulder level distal space, 0.80–0.93)/ 0.80 (0.68–0.92) (P < 0.001, each item). All of them showed substantial agreement, but the MDC of the SWMT evaluator size was 1.28 to 1.79 in the inter-rater test and 1.94–2.06 in the intra-rater test. The SWMT grade score showed a strong correlation with the SIAS light touch sensation item (r = 0.65, p < 0.001), as did the TLT with the SIAS position sense item (r = −0.70–0.62, p < 0.001 each space).

Conclusions: The reliability and validity of the SWMT and the TLT were verified. These tests can be used as reliable sensory examinations of the UE in patients with chronic stroke, and especially for the SWMT, it is more reliable for screening.

Why we should systematically assess, control and report somatosensory impairments in BCI-based motor rehabilitation after stroke studies

The neuronal loss resulting from stroke forces 80% of the patients to undergo motor rehabilitation, for which Brain-Computer Interfaces (BCIs) and NeuroFeedback (NF) can be used. During the rehabilitation, when patients attempt or imagine performing a movement, BCIs/NF provide them with a synchronized sensory (e.g., tactile) feedback based on their sensorimotor-related brain activity that aims at fostering brain plasticity and motor recovery. The co-activation of ascending (i.e., somatosensory) and descending (i.e., motor) networks indeed enables significant functional motor improvement, together with significant sensorimotor-related neurophysiological changes. Somatosensory abilities are essential for patients to perceive the feedback provided by the BCI system. Thus, somatosensory impairments may significantly alter the efficiency of BCI-based motor rehabilitation. In order to precisely understand and assess the impact of somatosensory impairments, we first review the literature on post-stroke BCI-based motor rehabilitation (14 randomized clinical trials). We show that despite the central role that somatosensory abilities play on BCI-based motor rehabilitation post-stroke, the latter are rarely reported and used as inclusion/exclusion criteria in the literature on the matter. We then argue that somatosensory abilities have repeatedly been shown to influence the motor rehabilitation outcome, in general. This stresses the importance of also considering them and reporting them in the literature in BCI-based rehabilitation after stroke, especially since half of post-stroke patients suffer from somatosensory impairments. We argue that somatosensory abilities should systematically be assessed, controlled and reported if we want to precisely assess the influence they have on BCI efficiency. Not doing so could result in the misinterpretation of reported results, while doing so could improve (1) our understanding of the mechanisms underlying motor recovery (2) our ability to adapt the therapy to the patients' impairments and (3) our comprehension of the between-subject and between-study variability of therapeutic outcomes mentioned in the literature.

Temporal Asynchrony but Not Total Energy Nor Duration Improves the Judgment of Numerosity in Electrotactile Stimulation

Stroke patients suffer from impairments of both motor and somatosensory functions. The functional recovery of upper extremities is one of the primary goals of rehabilitation programs. Additional somatosensory deficits limit sensorimotor function and significantly affect its recovery after the neuromotor injury. Sensory substitution systems, providing tactile feedback, might facilitate manipulation capability, and improve patient's dexterity during grasping movements. As a first step toward this aim, we evaluated the ability of healthy subjects in exploiting electrotactile feedback on the shoulder to determine the number of perceived stimuli in numerosity judgment tasks. During the experiment, we compared four different stimulation patterns (two simultaneous: short and long, intermittent and sequential) differing in total duration, total energy, or temporal synchrony. The experiment confirmed that the subject ability to enumerate electrotactile stimuli decreased with increasing the number of active electrodes. Furthermore, we found that, in electrotactile stimulation, the temporal coding schemes, and not total energy or duration modulated the accuracy in numerosity judgment. More precisely, the sequential condition resulted in significantly better numerosity discrimination than intermittent and simultaneous stimulation. These findings, together with the fact that the shoulder appeared to be a feasible stimulation site to communicate tactile information via electrotactile feedback, can serve as a guide to deliver tactile feedback to proximal areas in stroke survivors who lack sensory integrity in distal areas of their affected arm, but retain motor skills.

Errors in proprioceptive matching post-stroke are associated with impaired recruitment of parietal, supplementary motor, and temporal cortices

Deficits in proprioception, the ability to discriminate the relative position and movement of our limbs, affect ~50% of stroke patients and reduce functional outcomes. Our lack of knowledge of the anatomical correlates of proprioceptive processing limits our understanding of the impact that such deficits have on recovery. This research investigated the relationship between functional impairment in brain activity and proprioception post-stroke. We developed a novel device and task for arm position matching during functional MRI (fMRI), and investigated 16 subjects with recent stroke and nine healthy age-matched controls. The stroke-affected arm was moved by an experimenter (passive arm), and subjects were required to match the position of this limb with the opposite arm (active arm). Brain activity during passive and active arm movements was determined, as well as activity in association with performance error. Passive arm movement in healthy controls was associated with activity in contralateral primary somatosensory (SI) and motor cortices (MI), bilateral parietal cortex, supplementary (SMA) and premotor cortices, secondary somatosensory cortices (SII), and putamen. Active arm matching was associated with activity in contralateral SI, MI, bilateral SMA, premotor cortex, putamen, and ipsilateral cerebellum. In subjects with stroke, similar patterns of activity were observed. However, in stroke subjects, greater proprioceptive error was associated with less activity in ipsilesional supramarginal and superior temporal gyri, and lateral thalamus. During active arm movement, greater proprioceptive error was associated with less activity in bilateral SMA and ipsilesional premotor cortex. Our results enhance our understanding of the correlates of proprioception within the temporal parietal cortex and supplementary/premotor cortices. These findings also offer potential targets for therapeutic intervention to improve proprioception in recovering stroke patients and thus improve functional outcome.

Somatosensory Deficits After Ischemic Stroke

Background and Purpose- About 50% to 80% of stroke survivors present with somatosensory deficits. Somatosensory deficits because of an ischemic stroke are determined by the infarct location. However, a detailed understanding of the long-term effect of lesions on somatosensory performance is lacking. Methods- This prospective observational study enrolled 101 ischemic stroke patients. For voxel-based lesion-symptom mapping, magnetic resonance imaging fluid-attenuated inversion recovery imaging infarct lesions were segmented within 5 days after stroke. Standardized tests such as the National Institutes of Health Stroke Scale and the Rivermead Assessment of Somatosensory Performance were performed during acute stage, after 3 and 12 months. This included bilateral testing for multiple tactile and proprioceptive somatosensory modalities (pressure, light touch, sharp-dull discrimination, temperature discrimination, sensory extinction, 2-point discrimination, and joint position and movement sense). We further study the association of acute somatosensory deficit with functional outcome 12 months after stroke assessed by the modified Rankin Scale using univariate and multiple linear regression analysis also including acute motor deficit assessed by the arm research action test. Results- Sixty patients (59.4%) showed impairment in at least one somatosensory modality. Light touch was most frequently affected (38.7%), whereas temperature was least frequently affected (21.8%). After 3 months, significant recovery was observed in all somatosensory modalities, with only minor additional improvements after 12 months. Voxel-based lesion-symptom mapping revealed significant associations of lesions in the primary and secondary somatosensory and insular cortex with somatosensory deficits. Acute somatosensory deficit was associated with functional outcome at 12 months. However, including the acute motor deficit, somatosensory deficit was no longer an independent predictor of functional outcome. Conclusions- Our study confirms that somatosensory deficits are frequent in acute ischemic stroke but largely recover over time. Infarct lesions in the primary and secondary somatosensory cortex and insula show a robust association with somatosensory impairment. Long-term disability is influenced by somatosensory deficits but driven by motor symptoms.

Central Nervous System Correlates of "Objective" Neuropathy in Alcohol Use Disorder

BACKGROUND

Among the neurological consequences of alcoholism is peripheral neuropathy. Relative to human immunodeficiency virus (HIV) or diabetes-related neuropathies, neuropathy associated with alcohol use disorders (AUD) is understudied. In both the diabetes and HIV literature, emerging evidence supports a central nervous system (CNS) component to peripheral neuropathy.

METHODS

In seeking a central substrate for AUD-related neuropathy, the current study was conducted in 154 individuals with AUD (43 women, age 21 to 74 years) and 99 healthy controls (41 women, age 21 to 77 years) and explored subjective symptoms (self-report) and objective signs (perception of vibration, deep tendon ankle reflex, position sense, 2-point discrimination) of neuropathy separately. In addition to regional brain volumes, risk factors for AUD-related neuropathy, including age, sex, total lifetime ethanol consumed, nutritional indices (i.e., thiamine, folate), and measures of liver integrity (i.e., γ-glutamyltransferase), were evaluated.

RESULTS

The AUD group described more subjective symptoms of neuropathy and was more frequently impaired on bilateral perception of vibration. From 5 correlates, the number of AUD-related seizures was most significantly associated with subjective symptoms of neuropathy. There were 15 correlates of impaired perception of vibration among the AUD participants: Of these, age and volume of frontal precentral cortex were the most robust predictors.

CONCLUSIONS

This study supports CNS involvement in objective signs of neuropathy in AUD.

Brainstem and spinal cord MRI identifies altered sensorimotor pathways post-stroke

Damage to the corticospinal tract is widely studied following unilateral subcortical stroke, whereas less is known about changes to other sensorimotor pathways. This may be due to the fact that many studies investigated morphological changes in the brain, where the majority of descending and ascending brain pathways are overlapping, and did not investigate the brainstem where they separate. Moreover, these pathways continue passing through separate regions in the spinal cord. Here, using a high-resolution structural MRI of both the brainstem and the cervical spinal cord, we were able to identify a number of microstructurally altered pathways, in addition to the corticospinal tract, post stroke. Moreover, decreases in ipsi-lesional corticospinal tract integrity and increases in contra-lesional medial reticulospinal tract integrity were correlated with motor impairment severity in individuals with stroke.

There are few studies of structural changes in ascending and descending sensorimotor pathways after stroke, beyond the corticospinal tract, in the brain. Here the authors identify changes in white matter structure in brainstem and spinal cord following stroke, and show its relationship to motor impairment.

Focal neocortical lesions impair distant neuronal information processing

KEY POINTS

Parts of the fields of neuroscience and neurology consider the neocortex to be a functionally parcelled structure. Viewed through such a conceptual filter, there are multiple clinical observations after localized stroke lesions that seem paradoxical. We tested the effect that localized stroke-like lesions have on neuronal information processing in a part of the neocortex that is distant to the lesion using animal experiments. We find that the distant lesion degrades the quality of neuronal information processing of tactile input patterns in primary somatosensory cortex. The findings suggest that even the processing of primary sensory information depends on an intact neocortical network, with the implication that all neocortical processing may rely on widespread interactions across large parts of the cortex.

ABSTRACT

Recent clinical studies report a surprisingly weak relationship between the location of cortical brain lesions and the resulting functional deficits. From a neuroscience point of view, such findings raise questions as to what extent functional localization applies in the neocortex and to what extent the functions of different regions depend on the integrity of others. Here we provide an in-depth analysis of the changes in the function of the neocortical neuronal networks after distant focal stroke-like lesions in the anaesthetized rat. Using a recently introduced high resolution analysis of neuronal information processing, consisting of pre-set spatiotemporal patterns of tactile afferent activation against which the neuronal decoding performance can be quantified, we found that stroke-like lesions in distant parts of the cortex significantly degraded the decoding performance of individual neocortical neurons in the primary somatosensory cortex (decoding performance decreased from 30.9% to 24.2% for n = 22 neurons, Wilcoxon signed rank test, P = 0.028). This degrading effect was not due to changes in the firing frequency of the neuron (Wilcoxon signed rank test, P = 0.499) and was stronger the higher the decoding performance of the neuron, indicating a specific impact on the information processing capacity in the cortex. These findings suggest that even primary sensory processing depends on widely distributed cortical networks and could explain observations of focal stroke lesions affecting a large range of functions.

Lower Extremity Position Test: A new clinical quantitative assessment tool of proprioception post stroke

OBJECTIVE

To develop a quantitative, inexpensive and easy to use tool, for assessing proprioception of the lower extremity of individuals post-stroke, and examine its test-retest reliability and known-groups validity.

METHODS

The Lower Extremity Position Test was developed. Testing procedure: seated subjects were asked to reproduce 12 cm or 22 cm distances on a plastic surface, by verbally stopping passive movement of the foot produced by the tester. The deviation from the target point was measured as the mismatch score. Fifty one subjects post-stroke (n = 51) participated in prospective test-retest assessment. The tests were performed one week apart by a single assessor, in physical therapy out-patient clinics. The t-test, ICC and Bland-Altman tests were used to determine known-groups validity by determining leg differences and test-retest reliability.

RESULTS

Post-stroke involved foot demonstrated significantly higher mismatch scores then the uninvolved foot did (p < 0.0001). Good test-retest reliability was demonstrated for the involved leg for both 12 cm and 22 cm distances (ICC = 0.79 and 0.85, respectively). The 95% repeatability ranges were leg related.

CONCLUSIONS

The Lower Extremity Position Test (LEPT) is a newly-developed testing tool with good clinical utility, reliable in post-stroke population and has known-group validity (involved versus uninvolved foot).

Sensory retraining of the leg after stroke: systematic review and meta-analysis

OBJECTIVE

This systematic review aimed to investigate the effects of interventions intended for retraining leg somatosensory function on somatosensory impairment, and secondary outcomes of balance and gait, after stroke.

DATA SOURCES

Databases searched from inception to 16 January 2019 included Cochrane Library, PubMed, MEDLINE, CINAHL, EMBASE, PEDro, PsycINFO, and Scopus. Reference lists of relevant publications were also manually searched.

REVIEW METHODS

All types of quantitative studies incorporating interventions that intended to improve somatosensory function in the leg post stroke were retrieved. The Quality Assessment Tool for Quantitative Studies was used for quality appraisal. Standardised mean differences were calculated and meta-analyses were performed using preconstructed Microsoft Excel spreadsheets.

RESULTS

The search yielded 16 studies, comprising 430 participants, using a diverse range of interventions. In total, 10 of the included studies were rated weak in quality, 6 were rated moderate, and none was rated strong. Study quality was predominantly affected by high risk of selection bias, lack of blinding, and the use of somatosensory measures that have not been psychometrically evaluated. A significant heterogeneous positive summary effect size (SES) was found for somatosensory outcomes (SES: 0.52; 95% confidence interval (CI): 0.04 to 1.01; I2 = 74.48%), which included joint position sense, light touch, and two-point discrimination. There was also a significant heterogeneous positive SES for Berg Balance Scale scores (SES: 0.62; 95% CI: 0.10 to 1.14; I2 = 59.05%). Gait SES, mainly of gait velocity, was not significant.

CONCLUSION

This review suggests that interventions used for retraining leg somatosensory impairment after stroke significantly improved somatosensory function and balance but not gait.

Initial severity of somatosensory impairment influences response to upper limb sensory retraining post-stroke

BACKGROUND

Somatosensory loss occurs often following stroke. A proportional recovery model is proposed for spontaneous motor recovery, with implication for treatment planning. It is currently unknown if initial severity of sensory impairment influences stroke survivors' response to treatment to improve sensation.

OBJECTIVE

To examine if initial (pre-treatment) severity of upper limb somatosensory impairment is related to sensation outcomes following treatment.

METHODS

Regression analysis was used to investigate the relationship between initial and post-treatment sensation performance. Data were pooled from two randomized controlled trials of somatosensory discrimination retraining (N = 80). Upper limb somatosensation was measured using standardized tests of sensory discrimination: Fabric Matching Test, Wrist Position Sense Test, and functional Tactile Object Recognition Test.

RESULTS

Post-treatment somatosensory improvement patterns were proportional to the extent of initial pre-treatment somatosensory impairment (Texture discrimination: B = 0.74, 95% CIs [0.52, 0.96]; Proprioception: B = 0.35, 95% CIs [0.24, 0.47]; Object recognition: B = 0.85, 95% CIs [0.75, 0.95]).

CONCLUSIONS

The effect of somatosensory retraining on post-treatment sensation was proportional to the extent of upper limb initial somatosensory impairment. Findings suggest sensory retraining can benefit stroke survivors of varying severity of sensory impairment, including those with more severe somatosensory loss.

Ability of individuals with chronic hemiparetic stroke to locate their forearms during single-arm and between-arms tasks

Background

According to between-arms assessments, more than 50% of individuals with stroke have an impaired position sense. Our previous work, which employed a clinical assessment and slightly differing tasks, indicates that individuals who have a deficit on a between-forearms position-localization task do not necessarily have a deficit on a single-forearm position-localization task.

Objective

Our goal here was to, using robotics tools, determine whether individuals with stroke who have a deficit when matching forearm positions within an arm also have a deficit when mirroring forearm positions between arms, independent of the arm that leads the task.

Methods

Eighteen participants with chronic hemiparetic stroke and nine controls completed a single-arm position-matching experiment and between-arms position-mirroring experiment. For each experiment, the reference forearm (left/right) passively rotated about the elbow joint to a reference target location (flexion/extension), and then the participant actively rotated their same/opposite forearm to match/mirror the reference forearm’s position. Participants with stroke were classified as having a position-matching/-mirroring deficit based on a quantitative threshold that was derived from the controls’ data.

Results

On our single-arm task, one participant with stroke was classified as having a position-matching deficit with a mean magnitude of error greater than 10.7° when referencing their paretic arm. Position-matching ability did not significantly differ for the controls and the remaining seventeen participants with stroke. On our between-arms task, seven participants with stroke were classified as having a position-mirroring deficit with a mean magnitude of error greater than 10.1°. Position-mirroring accuracy was worse for these participants with stroke, when referencing their paretic arm, than the controls.

Concluding remark

Findings underscore the need for assessing within-arm position-matching deficits, in addition to between-arms position-mirroring deficits when referencing each arm, to comprehensively evaluate an individual’s ability to locate their forearm(s).

Functional network connectivity is altered in patients with upper limb somatosensory impairments in the acute phase post stroke: A cross-sectional study

Background

Aberrant functional connectivity in brain networks associated with motor impairment after stroke is well described, but little is known about the association with somatosensory impairments.

Aim

The objective of this cross-sectional observational study was to investigate the relationship between brain functional connectivity and severity of somatosensory impairments in the upper limb in the acute phase post stroke.

Methods

Nineteen first-ever stroke patients underwent resting-state functional magnetic resonance imaging (rs-fMRI) and a standardized clinical somatosensory profile assessment (exteroception and higher cortical somatosensation) in the first week post stroke. Integrity of inter- and intrahemispheric (ipsilesional and contralesional) functional connectivity of the somatosensory network was assessed between patients with severe (Em-NSA< 13/32) and mild to moderate (Em-NSA> 13/32) somatosensory impairments.

Results

Patients with severe somatosensory impairments displayed significantly lower functional connectivity indices in terms of interhemispheric (p = 0.001) and ipsilesional intrahemispheric (p = 0.035) connectivity compared to mildly to moderately impaired patients. Significant associations were found between the perceptual threshold of touch assessment and interhemispheric (r = -0.63) and ipsilesional (r = -0.51) network indices. Additional significant associations were found between the index of interhemispheric connectivity and light touch (r = 0.55) and stereognosis (r = 0.64) evaluation.

Conclusion

Patients with more severe somatosensory impairments have lower inter- and ipsilesional intrahemispheric connectivity of the somatosensory network. Lower connectivity indices are related to more impaired exteroception and higher cortical somatosensation. This study highlights the importance of network integrity in terms of inter- and ipsilesional intrahemispheric connectivity for somatosensory function. Further research is needed investigating the effect of therapy on the re-establishment of these networks.

Somatosensory deficits

The analysis and interpretation of somatosensory information are performed by a complex network of brain areas located mainly in the parietal cortex. Somatosensory deficits are therefore a common impairment following lesions of the parietal lobe. This chapter summarizes the clinical presentation, examination, prognosis, and therapy of sensory deficits, along with current knowledge about the anatomy and function of the somatosensory system. We start by reviewing how somatosensory signals are transmitted to and processed by the parietal lobe, along with the anatomic and functional features of the somatosensory system. In this context, we highlight the importance of the thalamus for processing somatosensory information in the parietal lobe. We discuss typical patterns of somatosensory deficits, their clinical examination, and how they can be differentiated through a careful neurologic examination that allows the investigator to deduce the location and size of the underlying lesion. In the context of adaption and rehabilitation of somatosensory functions, we delineate the importance of somatosensory information for motor performance and the prognostic evaluation of somatosensory deficits. Finally, we review current rehabilitation approaches for directing cortical reorganization in the appropriate direction and highlight some challenging questions that are unexplored in the field.

Mirror Illusion for Sensori-Motor Training in Stroke: A Randomized Controlled Trial

BACKGROUND

Poststroke, sensory deficits are not uncommon. In spite of the close association between the sensory and motor recovery, the deficits are usually underemphasized. Mirror therapy (MT), a neural-based approach for the motor deficit has not been explored for the sensory impairment. The objective of the present study was to develop and determine the effect of a MT program for sensori-motor impairment among poststroke subjects.

METHODS DESIGN

Randomized controlled trial.

SETTING

Functional therapy laboratory of Rehabilitation Institute.

PARTICIPANTS

Thirty-one chronic poststroke subjects (17 experimental and 14 controls), aged between 30 and 60years, with ≤ diminished light touch in the hand.

OUTCOME MEASURE

Semmes Weinstein Monofilament (cutaneous threshold), 2-Point discrimination test (touch discrimination) and Fugl-Meyer Assessment (hand motor recovery).

INTERVENTION

The experimental group received sensory stimulus such as tactile perception and motor tasks on the less-affected hand using mirror box. The control counterparts underwent only dose-matched conventional program. 30 sessions with a frequency of 5/week were imparted to the groups.

RESULTS

Post intervention, there was a significant (P < .004) increase up to 30% positive touch-response for the hand quadrants among the experimental group in comparison to only 13.5% rise for the same among the controls. The cutaneous threshold of the less-affected palm also improved significantly among the experimental subjects in comparison to the controls (P = .04).

CONCLUSION

MT may be considered as a promising regime for enhancing cutaneous sensibility in stroke. The mirror illusion induced by MT may be utilized for sensory and motor deficits as well as for the more-affected and less-affected hands.

Vagus nerve stimulation paired with tactile training improved sensory function in a chronic stroke patient

BACKGROUND

Recent studies indicate that vagus nerve stimulation (VNS) paired with rehabilitation can enhance neural plasticity in the primary sensory and motor cortices, improve forelimb function after stroke in animal models and improve motor function in patients with arm weakness after stroke.

OBJECTIVE

To gain "first-in-man" experience of VNS paired with tactile training in a patient with severe sensory impairment after stroke.

METHODS

During the long-term follow-up phase of a clinical trial of VNS paired with motor rehabilitation, a 71-year-old man who had made good motor recovery had ongoing severe sensory loss in his left hand and arm. He received VNS paired with tactile therapy in an attempt to improve his sensory function. During twenty 2-hour sessions, each passive and active tactile event was paired with a 0.5 second burst of 0.8 mA VNS. Sensory function was measured before, halfway through, and after this therapy.

RESULTS

The patient did not report any side effects during or following VNS+Tactile therapy. Quantitative measures revealed lasting and clinically meaningful improvements in tactile threshold, proprioception, and stereognosis. After VNS+Tactile therapy, the patient was able to detect tactile stimulation to his affected hand that was eight times less intense, identify the joint position of his fingers in the affected hand three times more often, and identify everyday objects using his affected hand seven times more often, compared to baseline.

CONCLUSIONS

Sensory function significantly improved in this man following VNS paired with tactile stimulation. This approach merits further study in controlled clinical trials.

Changing practice in the assessment and treatment of somatosensory loss in stroke survivors: protocol for a knowledge translation study

BACKGROUND

The treatment of somatosensory loss in the upper limb after stroke has been historically overshadowed by therapy focused on motor recovery. A double-blind randomized controlled trial has demonstrated the effectiveness of SENSe (Study of the Effectiveness of Neurorehabilitation on Sensation) therapy to retrain somatosensory discrimination after stroke. Given the acknowledged prevalence of upper limb sensory loss after stroke and the evidence-practice gap that exists in this area, effort is required to translate the published research to clinical practice. The aim of this study is to determine whether evidence-based knowledge translation strategies change the practice of occupational therapists and physiotherapists in the assessment and treatment of sensory loss of the upper limb after stroke to improve patient outcomes.

METHOD/DESIGN

A pragmatic, before-after study design involving eight (n = 8) Australian health organizations, specifically sub-acute and community rehabilitation facilities. Stroke survivors (n = 144) and occupational therapists and physiotherapists (~10 per site, ~n = 80) will be involved in the study. Stroke survivors will be provided with SENSe therapy or usual care. Occupational therapists and physiotherapists will be provided with a multi-component approach to knowledge translation including i) tailoring of the implementation intervention to site-specific barriers and enablers, ii) interactive group training workshops, iii) establishing and fostering champion therapists and iv) provision of written educational materials and online resources. Outcome measures for occupational therapists and physiotherapists will be pre- and post-implementation questionnaires and audits of medical records. The primary outcome for stroke survivors will be change in upper limb somatosensory function, measured using a standardized composite measure.

DISCUSSION

This study will provide evidence and a template for knowledge translation in clinical, organizational and policy contexts in stroke rehabilitation.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ANZCTR) retrospective registration ACTRN12615000933550 .

Multisensory stimulation improves functional recovery and resting-state functional connectivity in the mouse brain after stroke

Stroke causes direct structural damage to local brain networks and indirect functional damage to distant brain regions. Neuroplasticity after stroke involves molecular changes within perilesional tissue that can be influenced by regions functionally connected to the site of injury. Spontaneous functional recovery can be enhanced by rehabilitative strategies, which provides experience-driven cell signaling in the brain that enhances plasticity. Functional neuroimaging in humans and rodents has shown that spontaneous recovery of sensorimotor function after stroke is associated with changes in resting-state functional connectivity (RS-FC) within and across brain networks. At the molecular level, GABAergic inhibitory interneurons can modulate brain plasticity in peri-infarct and remote brain regions. Among this cell-type, a decrease in parvalbumin (PV)-immunoreactivity has been associated with improved behavioral outcome. Subjecting rodents to multisensory stimulation through exposure to an enriched environment (EE) enhances brain plasticity and recovery of function after stroke. Yet, how multisensory stimulation relates to RS-FC has not been determined. In this study, we investigated the effect of EE on recovery of RS-FC and behavior in mice after stroke, and if EE-related changes in RS-FC were associated with levels of PV-expressing neurons. Photothrombotic stroke was induced in the sensorimotor cortex. Beginning 2 days after stroke, mice were housed in either standard environment (STD) or EE for 12 days. Housing in EE significantly improved lost tactile-proprioceptive function compared to mice housed in STD environment. RS-FC in the mouse was measured by optical intrinsic signal imaging 14 days after stroke or sham surgery. Stroke induced a marked reduction in RS-FC within several perilesional and remote brain regions. EE partially restored interhemispheric homotopic RS-FC between spared motor regions, particularly posterior secondary motor. Compared to mice housed in STD cages, EE exposure lead to increased RS-FC between posterior secondary motor regions and contralesional posterior parietal and retrosplenial regions. The increased regional RS-FC observed in EE mice after stroke was significantly correlated with decreased PV-immunoreactivity in the contralesional posterior motor region. In conclusion, experimental stroke and subsequent housing in EE induces dynamic changes in RS-FC in the mouse brain. Multisensory stimulation associated with EE enhances RS-FC among distinct brain regions relevant for recovery of sensorimotor function and controlled movements that may involve PV/GABA interneurons. Our results indicate that targeting neural circuitry involving spared motor regions across hemispheres by neuromodulation and multimodal sensory stimulation could improve rehabilitation after stroke.

Associations Between Sensorimotor Impairments in the Upper Limb at 1 Week and 6 Months After Stroke

BACKGROUND AND PURPOSE

Longitudinal information regarding the prevalence of upper limb somatosensory deficits and the association with motor impairment and activity limitations is scarce. The aim of this prospective cohort study was to map the extent and distribution of somatosensory deficits, and to determine associations over time between somatosensory deficits and motor impairment and activity limitations.

METHODS

We recruited 32 participants who were assessed 4 to 7 days after stroke, and reassessed at 6 months. Somatosensory measurements included the Erasmus-modified Nottingham sensory assessment (Em-NSA), perceptual threshold of touch, thumb finding test, 2-point discrimination, and stereognosis subscale of the NSA. Evaluation of motor impairment comprised the Fugl-Meyer assessment, Motricity Index, and Action Research Arm Test. In addition, at 6 months, activity limitation was determined using the adult assisting hand assessment stroke, the ABILHAND, and hand subscale of the Stroke Impact Scale.

RESULTS

Somatosensory impairments were common, with 41% to 63% experiencing a deficit in one of the modalities within the first week and 3% to 50% at 6 months. In the acute phase, there were only very low associations between somatosensory and motor impairments (r = 0.03-0.20), whereas at 6 months, low to moderate associations (r = 0.32-0.69) were found for perceptual threshold of touch, thumb finding test, and stereognosis with motor impairment and activity limitations. Low associations (r = 0.01-0.29) were found between somatosensory impairments in the acute phase and motor impairments and activity limitations at 6 months.

DISCUSSION AND CONCLUSIONS

This study showed that somatosensory impairments are common and suggests that the association with upper limb motor and functional performance increases with time after stroke.Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A138).

Assessment of texture discrimination ability at the sole of the foot in subjects with chronic stroke compared with young and elderly subjects with no neurological deficits: a reliability and validity study

PURPOSE

To examine validity and test-retest reliability of a sensory test developed to evaluate ability of elderly subjects with/out a stroke to discriminate between textures with the sole of their foot.

METHODS

Subjects poststroke, old adults and young subjects were tested twice. Twelve materials relevant to foot function (e.g., gravel, sand) were used. Blindfolded subjects were requested to discriminate with the sole of each foot one outstanding texture among three textures presented in each of 12 subtests. ANOVA, ICC and Bland-Altman tests were used to determine group/leg differences and test-retest reliability.

RESULTS

Discrimination ability of the involved lower extremity poststroke is significantly reduced. Ability in individuals with no neurological impairment is age related. Good test-retest (ICC = 0.81) reliability was demonstrated for the impaired foot of subjects poststroke. The 95% repeatability ranges were age related with the highest range demonstrated for the involved foot poststroke. A significant fair negative correlation was demonstrated between texture discrimination ability and tactile detection threshold measured by Semmes-Weinstein monofilaments for the involved foot in poststroke subjects.

CONCLUSION

This newly developed assessment tool demonstrates concurrent and known-groups validity and is reliable for determining texture discriminative ability of the foot in individuals post-stroke and in older adults with no neurological impairment. Implications for rehabilitation The texture discrimination test presented here is a valid and reliable tool, providing quantitative assessment of sensory function at the sole of the foot in older adults with no neurologic deficits and in subjects poststroke. Lower extremity texture discrimination test is easy to administer in the clinic and might suggest directions for individually tailored, lower extremity, sensory retraining protocols.

Oral tactile sensitivity and masticatory performance are impaired in stroke patients

Oro-facial impairment following stroke frequently involves reduced chewing performance, that is oral phase dysphagia. The aim was to investigate the sensitivity of oral tissues following stroke and its potential impact on masticatory function. Therefore, hospitalised post-stroke patients were recruited and compared to healthy controls. Outcome measures comprised masticatory performance employing a colour-mixing ability, that is a bolus-kneading test, maximum lip- and bite force and the one-point and two-point tactile thresholds. Food hoarding and prevalence of dry mouth were evaluated with ordinal scales. Twenty-seven stroke patients (age 64·3 ± 14·1 years) and 27 healthy controls (age 60·8 ± 14·3 years, P = 0·254) participated in this study. The groups had similar numbers of occluding units. Stroke patients reported more frequently dry mouth sensations and food hoarding. The intra-oral tactile sensitivity on the contra-lesional side was significantly lower in stroke patients compared to controls (0·0001 < P < 0·0002), and significant intra-group side differences were found only in the stroke group (0·0001 < P < 0·0010). For the lip, both sides were less sensitive in the stroke group compared with controls. The experiments confirmed lower masticatory performance and lip force in the stroke group, but the bite force was similar compared to healthy controls. Oral sensitivity was correlated with masticatory performance when a global correlation model was applied. A stroke may affect the sensitivity of the intra-oral tissues contra-lesionally, thus potentially affecting chewing function. Rehabilitation should therefore not only focus on motor impairment, but equally stimulate the sensitivity of the oral tissues, employing dry ice application or similar specific treatments.

Effects of Sensory Deficit on Phalanx Force Deviation During Power Grip Post Stroke

The effect of sensory deficits on power grip force from individual phalanges was examined. The authors found that stroke survivors with sensory deficits (determined by the Semmes-Weinstein monofilament test) gripped with phalanx force directed more tangential to the object surface, than those without, although both groups had similar motor deficits (Chedoke-McMaster and Fugl-Meyer), grip strength, and skin friction. Altered grip force direction elevates risk of finger slippage against the object thus grip loss/object dropping, hindering activities of daily living. Altered grip force direction was associated with altered muscle activation patterns. In summary, the motor impairment level alone may not describe hand motor control in detail. Information about sensory deficits helps elucidate patients' hand motor control with functional relevance.

Adaptive and Maladaptive Neural Plasticity Due to Facial Nerve Palsy

Abstract. This paper reviews adaptive and maladaptive mechanisms of cortical plasticity in patients suffering from peripheral facial palsy. As the peripheral facial nerve is a pure motor nerve, a facial nerve lesion is causing an exclusive deefferentation without deafferentation. We focus on the question of how the investigation of pure deefferentation adds to our current understanding of brain plasticity which derives from studies on learning and studies on brain lesions. The importance of efference and afference as drivers for cortical plasticity is discussed in addition to the crossmodal influence of different competitive sensory inputs. We make the attempt to integrate the experimental findings of the effects of pure deefferentation within the theoretical framework of cortical responses and predictive coding. We show that the available experimental data can be explained within this theoretical framework which also clarifies the necessity for maladaptive plasticity. Finally, we propose rehabilitation approaches for directing cortical reorganization in the appropriate direction and highlight some challenging questions that are yet unexplored in the field.

Somatosensory deficits after stroke: a scoping review

In the past years, there have been increasing research activities focusing on somatosensory symptoms following stroke. However, as compared to the large number of clinical and neuroimaging studies on motor symptoms, the number of studies tracing somatosensory symptoms after stroke and their recovery is rather small. It is an ongoing discussion, to which extent somatosensory deficits after stroke influence patient's long-term outcome in motor and sensory performance and functional independence in activities of daily living. Modern brain imaging techniques allow for studying the impact of stroke lesion localization and size on acute and persisting clinical impairment. Here, we review the literature on somatosensory symptoms after stroke. We summarize epidemiological information on frequency and characteristics of somatosensory symptoms affecting all parts of the body in the acute and chronic stage of stroke. We further give an overview of brain imaging studies of stroke affecting the somatosensory system. Finally, we identify open questions which need to be addressed in future research and summarize the implications for clinical practice.

Somatosensory Impairments in the Upper Limb Poststroke: Distribution and Association With Motor Function and Visuospatial Neglect

BACKGROUND

A thorough understanding of the presence of different upper-limb somatosensory deficits poststroke and the relation with motor performance remains unclear. Additionally, knowledge about the relation between somatosensory deficits and visuospatial neglect is limited.

OBJECTIVE

To investigate the distribution of upper-limb somatosensory impairments and the association with unimanual and bimanual motor outcomes and visuospatial neglect.

METHODS

A cross-sectional observational study was conducted, including 122 patients within 6 months after stroke (median = 82 days; interquartile range = 57-133 days). Somatosensory measurement included the Erasmus MC modification of the (revised) Nottingham Sensory Assessment (Em-NSA), Perceptual Threshold of Touch (PTT), thumb finding test, 2-point discrimination, and stereognosis subscale of the NSA. Upper-limb motor assessment comprised the Fugl-Meyer assessment, motricity index, Action Research Arm Test, and Adult-Assisting Hand Assessment Stroke. Screening for visuospatial neglect was performed using the Star Cancellation Test.

RESULTS

Upper-limb somatosensory impairments were common, with prevalence rates ranging from 21% to 54%. Low to moderate Spearman ρ correlations were found between somatosensory and motor deficits (r = 0.22-0.61), with the strongest associations for PTT (r = 0.56-0.61) and stereognosis (r = 0.51-0.60). Visuospatial neglect was present in 27 patients (22%). Between-group analysis revealed somatosensory deficits that occurred significantly more often and more severely in patients with visuospatial neglect (P < .05). Results showed consistently stronger correlations between motor and somatosensory deficits in patients with visuospatial neglect (r = 0.44-0.78) compared with patients without neglect (r = 0.08-0.59).

CONCLUSIONS

Somatosensory impairments are common in subacute patients poststroke and are related to motor outcome. Visuospatial neglect was associated with more severe upper-limb somatosensory impairments.