Correlation of spasticity with hyperactive stretch reflexes and motor dysfunction in hemiplegia

Relative contributions of positive, negative, and adaptive features to limitations in upper-limb function three months after stroke

PURPOSE

To investigate the contributions of motor impairments to limitations in upper-limb function three months after stroke.

DESIGN

Cross-sectional, exploratory study.

METHODS

Dependent variable was upper-limb function, measured by the Motor Assessment Scale (MAS), which scores range from 0 to 18. Independent variables included measures of strength, dexterity, spasticity, and contracture of the paretic upper limb. Multiple linear regression analysis was employed to identify which of the independent variables could explain the MAS scores (p<0.05). Analysis was performed with the whole sample and with a sub-group of participants, who had high function (MAS≥12).

RESULTS

Sixty-nine individuals participated. Out of them, 63 had high upper-limb function. Regression analysis with the whole sample revealed that strength and dexterity were retained in the models. Together they explained 64% of the variance of the MAS scores (p<0.001), being strength the greater relative contributor. When the regression analysis included only participants with high upper-limb function, dexterity had a greater relative contribution, than strength. Together they explained 52 % of the variance (p< 0.001).

CONCLUSIONS

Strength was the main contributor to upper-limb function in individuals three months after stroke. However, in individuals, who already had higher upper-limb function, dexterity showed to be the major contributor.

Measuring resistance to externally induced movement of the wrist joint in chronic stroke patients using an objective hand-held dynamometer

Objective

We evaluated the resistance to externally induced wrist extension in chronic stroke patients. We aimed to objectively measure and distinguish passive (muscle and soft tissue stiffness) and active (spasticity and spastic dystonia) components of the resistance.

Methods

We used a hand-held dynamometer, which measures torque, joint movement and electromyography (EMG) simultaneously, to assess the resistance to externally induced wrist extension. Slow and fast stretches were applied to the affected and unaffected wrists in 57 chronic stroke patients (57 ± 11 years). We extracted from the data parameters that represent passive and muscle activity components and assessed the validity, test-retest reliability and the clinical utility of the measurement.

Results

The analysis showed (1) a significant difference in the passive and muscle activity components between the affected and unaffected sides; (2) a significant correlation between passive and muscle activity components and the modified Ashworth scale (MAS); (3) a significant difference between the subgroups of patients stratified by the MAS; (4) an excellent intra-rater reliability on each of the passive and muscle activity components with intra-class coefficients between 0.92 and 0.99; (5) and small measurement error.

Conclusions

Using a hand-held dynamometer, we were able to objectively measure the resistance to muscle stretch in the wrist joint in chronic stroke patients and discriminate muscle overactivity components from muscle and soft tissue stiffness. We demonstrated validity, test-retest reliability and the clinical utility of the measurement.

Significance

Quantification of the different components of resistance to externally induced movement enables the objective evaluation of neurorehabilitation effects in chronic stroke patients.

Cut-off score of the modified Ashworth scale corresponding to walking ability and functional mobility in individuals with chronic stroke

PURPOSE

To determine the optimal cut-off score for the Modified Ashworth Scale (MAS) corresponding to unfavorable outcomes for mobility and walking ability.

METHODS

The level of plantar flexor muscle spasticity and the 10-meter walking test (10mWT), timed up and go (TUG), and five time sit-to-stand (FTSTS) outcomes were evaluated in individuals after stroke. The correlation between MAS and the tests was investigated, and the optimal cut-off score, sensitivity, and specificity were evaluated through receiver operating characteristic (ROC) curve.

RESULTS

Twenty-one participants with chronic stroke and plantar flexors spasticity (11 men; 10 women; mean age = 57.6 ± 12.5 years) participated in the study. Significant correlations between MAS and 10mWT (r= -0.45; p < 0.05), MAS and TUG (r = 0.48; p < 0.05) were found. The optimal cut-off scores were MAS > 2 for unfavorable 10mWT (sensitivity = 100%; specificity = 54.5%; ROC = 0.782) and MAS ≤ 2 for favorable TUG outcomes (sensitivity = 55.5%; specificity = 91.6%; ROC = 0.782).

CONCLUSIONS

This study revealed that moderate level of plantar flexors spasticity results in the highest sensitivity to predict poor gait speed performance and the highest specificity to predict good mobility performance in individuals after stroke. These findings will help clinicians in their evidence-based decision making on the role of spasticity for mobility and walking ability.Implications for rehabilitationModerate level of spasticity (MAS <2) is the optimal cut-off score for 10mWT and TUG tests.Reducing the level of spasticity of plantar flexors below this cut-off point might be associated with an increased walking speed in this population.MAS <2 might not limit walking and mobility in individuals after stroke.Calf muscles spasticity might not compromise five time sit-to-stand (FTSTS) performances and might be related to a smaller influence on the sit to stand task.

Treatment of spasticity

Spasticity is characterized by an enhanced size and reduced threshold for activation of stretch reflexes and is associated with "positive signs" such as clonus and spasms, as well as "negative features" such as paresis and a loss of automatic postural responses. Spasticity develops over time after a lesion and can be associated with reduced speed of movement, cocontraction, abnormal synergies, and pain. Spasticity is caused by a combination of damage to descending tracts, reductions in inhibitory activity within spinal cord circuits, and adaptive changes within motoneurons. Increased tone, hypertonia, can also be caused by changes in passive stiffness due to, for example, increase in connective tissue and reduction in muscle fascicle length. Understanding the cause of hypertonia is important for determining the management strategy as nonneural, passive causes of stiffness will be more amenable to physical rather than pharmacological interventions. The management of spasticity is determined by the views and goals of the patient, family, and carers, which should be integral to the multidisciplinary assessment. An assessment, and treatment, of trigger factors such as infection and skin breakdown should be made especially in people with a recent change in tone. The choice of management strategies for an individual will vary depending on the severity of spasticity, the distribution of spasticity (i.e., whether it affects multiple muscle groups or is more prominent in one or two groups), the type of lesion, and the potential for recovery. Management options include physical therapy, oral agents; focal therapies such as botulinum injections; and peripheral nerve blocks. Intrathecal baclofen can lead to a reduction in required oral antispasticity medications. When spasticity is severe intrathecal phenol may be an option. Surgical interventions, largely used in the pediatric population, include muscle transfers and lengthening and selective dorsal root rhizotomy.

Effect and Optimal Timing of Extracorporeal Shock-Wave Intervention to Patients With Spasticity After Stroke: A Systematic Review and Meta-analysis

OBJECTIVE

This study investigated the efficacy of extracorporeal shock wave therapy as well as the optimal intervention timing for extracorporeal shock wave therapy for patients with spasticity after stroke.

DESIGN

A search of randomized controlled trials was conducted in different electronic databases. We performed a meta-analysis to measure the effect of extracorporeal shock wave therapy versus sham interventions on spasticity and limb functionality. The meta-regression analysis was performed to determine the adequate intervention timing of extracorporeal shock wave therapy. The follow-up period of the outcomes was divided into the short (<2 wks), mid (>2 wks and ≤4 wks), and long (>4 wks and ≤3 mos) terms.

RESULTS

Thirteen studies with 677 participants were evaluated. Spasticity significantly improved throughout the follow-up duration. Limb functionality significantly improved in the short-term follow-up period. The meta-regression analysis showed that patients with stroke duration less than 45 mos may be benefited from extracorporeal shock wave therapy in improving limb function in all follow-up periods.

CONCLUSIONS

Extracorporeal shock wave therapy is an effective method for reducing spasticity in patients with stroke, and the effect could be maintained for up to 3 mos. Its effects on limb functionality could persist for at least 2 wks. Patients who had stroke for less than 45 mos may have significant benefit from extracorporeal shock wave therapy in all follow-up periods.

Combination therapy with repetitive facilitative exercise program and botulinum toxin type A to improve motor function for the upper-limb spastic paresis in chronic stroke: A randomized controlled trial

STUDY DESIGN

An open-label, randomized, controlled, observer-blinded trial.

INTRODUCTION

Repetitive facilitative exercise (RFE) is a movement therapy to recover from hemiparesis after stroke. However, improvement is inhibited by spasticity. Recently, botulinum toxin type A (BoNT-A) injection has been shown to reduce spasticity.

PURPOSE

To examine the combined effect of an RFE program and BoNT-A treatment on upper-limb spastic paresis in chronic stroke.

METHODS

Forty chronic stroke inpatients with upper-limb spastic paresis (Brunnstrom stage ≥III and Modified Ashworth Scale [MAS] score ≥1) were enrolled. Subjects were randomized into 2 groups of 20 each and received 4 weeks of treatment. The intervention group received RFE and BoNT-A injection; the control group underwent RFE only. Assessments were performed at baseline and at study conclusion. The primary outcome was change in Fugl-Meyer Assessment score for the upper extremity (FMA). The Action Research Arm Test (ARAT), active range of motion, Box and Block Test, and MAS were also evaluated.

RESULTS

All participants completed this study. After 4 weeks, the intervention group evidenced a significantly greater increase in FMA score (median 11.0 [range 4-20]) than the control group (median 3.0 [range 0-9]) (P < .01, r = 0.79); as well as improvements in the other measures such as ARAT (median 12.5 [range 4-22] vs 7 [0-13]) (P < .01, r = 0.6), and MAS in the elbow flexors (median -1.5 [range -2 to 0] vs -1 [-2 to 0]) (P < .01, r = 0.45).

DISCUSSION

A high degree of repetitive volitional movement induced by the facilitative technique with concomitant control of spasticity by BoNT-A injection might increase efficiency of motor learning with continuous movement of the affected upper-limb.

CONCLUSIONS

The combination of RFE and BoNT-A for spastic paresis might be more effective than RFE alone to improve upper-limb motor function and to lessen impairment in chronic stroke.

Quantification of grip strength with complexity analysis of surface electromyogram for hemiplegic post-stroke patients

BACKGROUND

Reduction in grip-strength due to spasticity is a common cause of impairment after stroke.

OBJECTIVE

To find an objective measure of post-stroke spasticity affecting grip-strength through quantification of interaction between antagonist and agonist muscles using complexity analysis of surface electromyogrm (sEMG) signals during isometric grip in healthy and post-stroke participants.

METHODS

The interaction between sEMG signals from antagonist and agonist muscles is quantified through Multiscale-Multivariate-Sample-Entropy (MMSE). This is used to quantify dissimilarity between hands of 12 healthy and 8 post-stroke participants during isometric grip. The clinical relevance of MMSE is explored by examining its correlation with spasticity score i.e. Modified-Ashworth-Scale (MAS). Further, potential of sEMG-based approach to quantify muscle-specific dissimilarity in sEMG activation across hands is investigated in terms of Cepstral-coefficients and power content of sEMG during grip tasks.

RESULTS

Mean MMSE scores of sEMG signals were significantly different (p < 0.05) between paretic and non-paretic hands of Post-stroke participants. High negative correlation was observed between spasticity and complexity scores of paretic hand for post-stroke participants.

CONCLUSIONS

A negative correlation between MAS and MMSE shows higher spasticity can lead to reduced complexity in sEMG. Thus, MMSE based complexity analysis can be used as an indicator of spasticity, affecting grip function.

Responsiveness and minimal clinically important difference of Modified Ashworth Scale in patients with stroke

BACKGROUND

Spasticity is a major problem in patients with stroke and influences their activities of daily living, participation, and quality of life. The Modified Ashworth Scale is widely used to assess spasticity. However, the responsiveness and minimal clinically important differences of the Modified Ashworth Scale in patients with stroke have not been explored.

AIM

This study aims to examine the responsiveness and minimal clinically important differences of the Modified Ashworth Scale in patients with stroke.

DESIGN

Longitudinal six-month follow-up study.

SETTING

Rehabilitation wards of a tertiary hospital.

POPULATION

One-hundred and fifteen patients with stroke were recruited.

METHODS

All patients underwent the assessment of Modified Ashworth Scale for the upper extremity (flexors of the elbow, wrist, and fingers) and the lower extremity (hip adductor, knee flexor, and ankle plantar flexor) at baseline and 6-month follow-up. The average Modified Ashworth Scale scores of the upper and lower extremity muscles were obtained for analysis. Responsiveness of the Modified Ashworth Scale was determined using standardized mean response, and the minimal clinically important differences were determined using a distribution-based approach with Effect Sizes of 0.5 and 0.8 standard deviations.

RESULTS

The responsiveness of the Modified Ashworth Scale in the upper and lower extremity muscles was marked (standardized response mean = 0.89-1.09). The minimal clinically important differences of the average Modified Ashworth Scale of Effect Sizes 0.5 and 0.8 standard deviations for the upper extremity muscles were 0.48 and 0.76, respectively, while those for the lower extremity muscles were 0.45 and 0.73, respectively.

CONCLUSIONS

The Modified Ashworth Scale was markedly responsive in detecting the changes in muscle tone in patients with stroke. The minimal clinically important differences of the Modified Ashworth Scale reported in this study can be used by researchers and clinicians in determining whether the observed changes are clinically meaningful post-treatment or at follow-up.

CLINICAL REHABILITATION IMPACT

The minimal clinically important differences of the Modified Ashworth Scale reported in this study will enable clinicians and researchers in determining whether changes in the muscle tone are true and clinically meaningful, and can be used as a reference for clinical decision-making.

Association of spasticity and motor dysfunction in chronic stroke

BACKGROUND

The prevalence of increased muscle tone after stroke is frequently reported as 30% to 40%, and the condition is often concurrent with motor control deficits, manifesting as an inability to isolate paretic-limb joint movements.

OBJECTIVE

The objectives of this retrospective analysis were to 1) report the prevalence of increased muscle tone in a convenience sample of 128 chronic stroke survivors with moderate/severe motor deficits and 2) quantify the relation between tone and motor impairment in chronic stroke survivors.

METHODS

Analyses included descriptive statistics and multiple regression modeling, with the modified Ashworth Scale score (MAS; tone) as a predictor of isolated joint movement control (Fugl-Meyer score [FM]; motor impairment).

RESULTS

Increased muscle tone was present in 97% of subjects. Increased muscle tone was associated with impaired motor control (FM; upper extremity, P=0.008; lower extremity, P=0.03) after adjusting for age, time since stroke and sex. We found a significant difference between flexor and extensor strength for finger, elbow, hip and knee joints (P<0.002). Participants were classified in high and low MAS score groups. With high MAS score and for muscles of finger flexion and forearm pronation, we found a trend toward impaired strength of antagonist muscles (finger extensors and forearm supinators, respectively) as compared with low MAS score for these same muscle pairings.

CONCLUSIONS

The prevalence of increased tone was higher in this study than in previous reports. Increased muscle tone in chronic stroke survivors with persistent motor dysfunction could be associated with impaired motor control and differential muscle strength of antagonistic muscles.

Effect of botulinum toxin injection on length and force of the rectus femoris and triceps surae muscles during locomotion in patients with chronic hemiparesis (FOLOTOX)

Background

After stroke, spasticity of the rectus femoris (RF) and triceps surae (TS) muscles frequently alters the gait pattern. Knee flexion and ankle dorsiflexion in swing are often reduced, respectively called Stiff Knee Gait (SKG) and equinus. A preliminary uncontrolled study suggested that botulinum toxin type A (BTX-A) injections could improve muscle length and force generated during gait, improving inter-segmental coordination.

The aim of this randomised controlled study is thus to evaluate changes in the length of the RF and TS muscles during gait 1 month after either BTX-A or placebo injection in patients with chronic stroke, SKG and spastic equinus. The secondary aims are to evaluate peak length and peak force generated during gait, as well inter-segmental coordination assessed using the continuous relative phase method initially described by Barela et al. in patients with stroke.

Methods

This is a prospective, three-centre, randomised, placebo-controlled, triple blind study over 3 months with 4 visits. Forty patients will be included. During visits V1, V3 and V4, length and force generated by RF and TS during gait will be assessed using musculoskeletal models (MSM). Muscle force will also be assessed using an isokinetic dynamometer. Inter segmental coordination will be evaluated using 3D gait analysis and functional tests will be performed. During V2, patients will receive either an injection of BTX-A in the RF and TS muscles or a placebo injection of saline solution.

Discussion

We expect an increase in peak length and a decrease in peak force generated by the RF and TS muscles in the BTX-A group 1 month post injection. Moreover, we expect these parameters to be more improved in the BTX-A than the Control group. This is the first study to assess these parameters in a randomised, controlled trial using instrumented methods (isokinetic evaluation and 3D gait analysis). The results should help to improve understanding of the mechanism(s) underlying improvements in inter-segmental coordination that have been found in many previous uncontrolled studies.

Trial registration

ClinicalTrials.gov: NCT01821573, First received: March 27, 2013 Last updated: September 14, 2016 Last verified: September 2016 Other Study ID Numbers: P110136 AOM11223.

The spasticity in the motor and functional disability in adults with post-stroke hemiparetic

Abstract Introduction: Spasticity acts as a limiting factor in motor and functional recovery after Stroke, impairing the performance of daily living activities. Objective: To analyze the influence of spasticity on main muscle groups and to associate it with motor impairment and functional level of chronic hemiparetic patients after stroke. Methods: Twenty-seven chronic hemiparetic patients of both sexes were selected at the Physical Therapy and Occupational Therapy Service of the Unicamp Clinics Hospital. Assessments were carried out in two sessions, in the first one the motor impairment (Fugl-Meyer Assessment - FM) and functional impairment (Barthel Index - BI) were evaluated, and in the second, the degree of spasticity of the main muscle groups (Modified Ashworth Scale - MAS). Results: A negative correlation was detected between upper limb spasticity and motor and functional impairment. No muscle group evaluated in the lower limbs showed correlation between muscle tone and the level of impairment of the lower extremity on FM and the functional level measured by BI. Conclusion: Spasticity has been shown to be a negative influence factor in the level of motor and functional impairment of the upper limbs of chronic hemiparetic patients after stroke.

Effect of functional electrical stimulation on the proprioception, motor function of the paretic upper limb, and patient quality of life: A case report

Functional electrical stimulation (FES) has shown to improve motor function of the affected side in stroke patients; however, the effects of FES on proprioception, the functional recovery of the paretic upper limb, and the patient quality of life (QoL) are not clear. The aim of the current case report was to determine whether FES can improve joint position sense and the scores on measurements of upper limb function and a QoL survey. The participant was assessed before and after 10 consecutive intervention sessions; in addition, the patient performed the training tasks in the workstation assisted by the FES device. Improvements in angles and time only in the affected wrist and enhancement in the Action Research Arm Test scores for both upper limbs were found after FES intervention. In addition, the patient's health-related QoL measurements improved. FES could ameliorate the proprioceptive deficit and the activity limitations of a stroke survivor.

OXFORD LEVEL OF EVIDENCE

3b; individual case control study.

Positive Effects of Extracorporeal Shock Wave Therapy on Spasticity in Poststroke Patients: A Meta-Analysis

BACKGROUND

Spasticity is a common and serious complication following a stroke, and many clinical research have been conducted to evaluate the effect of extracorporeal shock wave therapy (ESWT) on muscle spasticity in poststroke patients. This meta-analysis aimed to evaluate the therapeutic effect on decreasing spasticity caused by a stroke immediately and 4 weeks after the application of shock wave therapy.

METHODS

We searched PubMed, Embase, Web of Science, and Cochrane Library databases for relevant studies through November 2016 using the following item: (Hypertonia OR Spasticity) and (Shock Wave or ESWT) and (Stroke). The outcomes were evaluated by Modified Ashworth Scale (MAS) grades and pooled by Stata 12.0 (Stata Corp, College Station, TX, USA).

RESULTS

Six studies consisting of 9 groups were included in this meta-analysis. The MAS grades immediately after ESWT were significantly improved compared with the baseline values (standardized mean difference [SMD], -1.57; 95% confidence intervals [CIs], -2.20, -.94). Similarly, the MAS grades judged at 4 weeks after ESWT were also showed to be significantly lower than the baseline values (SMD, -1.93; 95% CIs, -2.71, -1.15).

CONCLUSIONS

ESWT for the spasticity of patients after a stroke is effective, as measured by MAS grades. Moreover, no serious side effects were observed in any patients after shock wave therapy. Nevertheless, our current study with some limitations such as the limited sample size only provided limited quality of evidence; confirmation from a further systematic review or meta-analysis with large-scale, well-designed randomized control trials is required.

Effect of Radial Shock Wave Therapy on Spasticity of the Upper Limb in Patients With Chronic Stroke: A Prospective, Randomized, Single Blind, Controlled Trial

Recently, studies have reported that extracorporeal shock wave therapy (ESWT) is a safe, noninvasive, alternative treatment for spasticity. However, the effect of ESWT on spasticity cannot be determined, because most studies to date have enrolled small patient numbers and have lacked placebo-controlled groups and/or long-term follow-up. In addition, whether varying the number of ESWT sessions would affect the duration of the therapeutic effect has not been investigated in a single study. Hence, we performed a prospective, randomized, single blind, placebo-controlled study to investigate the long-term effect of radial ESWT (rESWT) in patients with poststroke spasticity and surveyed the outcome of functional activity.Sixty patients were randomized into 3 groups. Group A patients received 1 session of rESWT per week for 3 consecutive weeks; group B patients received a single session of rESWT; group C patients received one session of sham rESWT per week for 3 consecutive weeks. The primary outcome was Modified Ashworth Scale of hand and wrist, whereas the secondary outcomes were Fugl-Meyer Assessment of hand function and wrist control. Evaluations were performed before the first rESWT treatment and immediately 1, 4, 8, 12, and 16 weeks after the last session of rESWT.Compared to the control group, the significant reduction in spasticity of hand and wrist lasted at least 16 and 8 weeks in group A and B, respectively. Three sessions of rESWT had a longer-lasting effect than one session. Furthermore, the reduction in spasticity after 3 sessions of rESWT may be beneficial for hand function and wrist control and the effect was maintained for 16 and 12 weeks, respectively.rESWT may be valuable in decreasing spasticity of the hand and wrist with accompanying enhancement of wrist control and hand function in chronic stroke patients.

Combining Afferent Stimulation and Mirror Therapy for Improving Muscular, Sensorimotor, and Daily Functions After Chronic Stroke: A Randomized, Placebo-Controlled Study

OBJECTIVE

Mirror therapy (MT) combined with mesh glove (MG) afferent stimulation (MT + MG) has been suggested as an effective intervention for motor recovery in patients with stroke. This study aimed to further determine the treatment effects of the MT + MG approach on muscular properties, sensorimotor functions, and daily function.

DESIGN

This was a single-blind, randomized, placebo-controlled study. Forty-eight participants with chronic stroke were recruited from medical centers and were randomly assigned to the MT, MT + MG, and MT with sham MG stimulation (MT + sham) groups. The intervention consisted of 1.5 hrs/day, 5 days/wk for 4 wks. Primary outcomes were the Fugl-Meyer Assessment and muscular properties (muscle tone and stiffness). Secondary outcomes included measures of sensorimotor and daily functions.

RESULTS

Compared with the MT and MT + sham groups, the MT + MG group demonstrated improved muscular properties. The MT + MG and MT + sham groups showed greater improvement in manual dexterity and daily function than the MT group did. No beneficial effects on the Fugl-Meyer Assessment and other sensorimotor outcomes were found for the MT + MG group.

CONCLUSIONS

Although no significant group differences were found in the Fugl-Meyer Assessment, MT + MG induced distinctive effects on muscular properties, manual dexterity, and daily function.

Effects of combining robot-assisted therapy with neuromuscular electrical stimulation on motor impairment, motor and daily function, and quality of life in patients with chronic stroke: a double-blinded randomized controlled trial

Background

Robot-assisted therapy (RT) is a widely used intervention approach to enhance motor recovery in patients after stroke, but its effects on functional improvement remained uncertain. Neuromuscular electrical stimulation (NMES) is one potential adjuvant intervention approach to RT that could directly activate the stimulated muscles and improve functional use of the paretic hand.

Methods

This was a randomized, double-blind, sham-controlled study. Thirty-nine individuals with chronic stroke were randomly assigned to the RT combined with NMES (RT + ES) or to RT with sham stimulation (RT + Sham) groups. The participants completed the intervention 90 to 100 minutes/day, 5 days/week for 4 weeks. The outcome measures included the upper extremity Fugl-Meyer Assessment (UE-FMA), modified Ashworth scale (MAS), Wolf Motor Function Test (WMFT), Motor Activity Log (MAL), and Stroke Impact Scale 3.0 (SIS). All outcome measures were assessed before and after intervention, and the UE-FMA, MAL, and SIS were reassessed at 3 months of follow-up.

Results

Compared with the RT + Sham group, the RT + ES group demonstrated greater improvements in wrist flexor MAS score, WMFT quality of movement, and the hand function domain of the SIS. For other outcome measures, both groups improved significantly after the interventions, but no group differences were found.

Conclusion

RT + ES induced significant benefits in reducing wrist flexor spasticity and in hand movement quality in patients with chronic stroke.

Trial registration

ClinicalTrials.gov. NCT01655446

Impaired corrective responses to postural perturbations of the arm in individuals with subacute stroke

Background

Stroke is known to alter muscle stretch responses following a perturbation, but little is known about the behavioural consequences of these altered feedback responses. Characterizing impairments in people with stroke in their interactions with the external environment may lead to better long term outcomes. This information can inform therapists about rehabilitation targets and help subjects with stroke avoid injury when moving in the world.

Methods

In this study, we developed a postural perturbation task to quantity upper limb function of subjects with subacute stroke (n = 38) and non-disabled controls (n = 74) to make rapid corrective responses with the arm. Subjects were instructed to maintain their hand at a target before and after a mechanical load was applied to the limb. Visual feedback of the hand was removed for half of the trials at perturbation onset. A number of parameters quantified subject performance, and impairment in performance was defined as outside the 95th percentile performance of control subjects.

Results

Individual subjects with stroke showed increased postural instability (44%), delayed motor responses (79%), delayed returns towards the spatial target (79%), and greater endpoint errors (74%). Several subjects also showed impairments in the temporal coordination of the elbow and shoulder joints when responding to the perturbation (47%). Interestingly, impairments in task parameters were often found for both arms of individual subjects with stroke (up to 58% for return time). Visual feedback did not improve performance on task parameters except for decreasing endpoint error for all subjects. Significant correlations between task performance and clinical measures were dependent on the arm assessed.

Conclusions

This study used a simple postural perturbation task to highlight that subjects with stroke commonly have difficulties responding to mechanical disturbances that may have important implications for their ability to perform daily activities.

Electromyographic analysis of upper limb muscles during standardized isotonic and isokinetic robotic exercise of spastic elbow in patients with stroke

Although it has been reported that strengthening exercise in stroke patients is beneficial for their motor recovery, there is little evidence about which exercise method is the better option. The purpose of this study was to compare isotonic and isokinetic exercise by surface electromyography (EMG) analysis using standardized methods. Nine stroke patients performed three sets of isotonic elbow extensions at 30% of their maximal voluntary isometric torque followed by three sets of maximal isokinetic elbow extensions with standardization of mean angular velocity and the total amount of work for each matched set in two strengthening modes. All exercises were done by using 1-DoF planner robot to regulate exact resistive torque and speed. Surface electromyographic activity of eight muscles in the hemiplegic shoulder and elbow was recorded. Normalized root mean square (RMS) values and co-contraction index (CCI) were used for the analysis. The isokinetic mode was shown to activate the agonists of elbow extension more efficiently than the isotonic mode (normalized RMS for pooled triceps: 96.0±17.0 (2nd), 87.8±14.4 (3rd) in isokinetic, 80.9±11.0 (2nd), 81.6±12.4 (3rd) in isotonic contraction, F[1,8]=11.168; P=0.010) without increasing the co-contraction of muscle pairs, implicating spasticity or synergy.

Assessments in Australian stroke rehabilitation units: a systematic review of the post-stroke validity of the most frequently used

PURPOSE

In Australia, stroke is the leading cause of adult disability. For most stroke survivors, the recovery process is challenging, and in the first few weeks their recovery is supported with stroke rehabilitation services. Stroke clinicians are expected to apply an evidence-based approach to stroke rehabilitation and, in turn, use standardised and validated assessments to monitor stroke recovery. In 2008, the National Stroke Foundation conducted the first national audit of Australia's post acute stroke rehabilitation services and findings identified a vast array of assessments being used by clinicians. This study undertook a sub-analysis of the audit's assessment tools data with the aim of making clinically relevant recommendations concerning the validity of the most frequently selected assessments.

METHOD

Data reduction ranked the most frequently selected assessments across a series of sub-categories. A serial systematic review of relevant literature using Medline and the Cumulative Index to Nursing and Allied Health Literature identified post-stroke validity ranking.

RESULTS

The study found that standardised and non-standardised assessments are currently in use in stroke rehabilitation. It recommends further research in the sub-categories of strength, visual acuity, dysphagia, continence and nutrition and found strengths in the sub-categories of balance and mobility, upper limb function and mood.

CONCLUSIONS

This is the first study to map national usage of post-stroke assessments and review that usage against the evidence. It generates new knowledge concerning what assessments we currently use post stroke, what we should be using and makes some practical post stroke clinical recommendations.

The effect of modified constraint-induced movement therapy on spasticity and motor function of the affected arm in patients with chronic stroke

PURPOSE

The purpose of this study was to explore the effect of modified constraint-induced movement therapy (CIMT) in a real-world clinical setting on spasticity and functional use of the affected arm and hand in patients with spastic chronic hemiplegia.

METHOD

A prospective consecutive quasi-experimental study design was used. Twenty patients with spastic hemiplegia (aged 22-67 years) were tested before and after 2-week modified CIMT in an outpatient rehabilitation clinic and at 6 months. The Modified Ashworth Scale (MAS), active range of motion (AROM), grip strength, Motor Activity Log (MAL), Sollerman hand function test, and Box and Block Test (BBT) were used as outcome measures.

RESULTS

Reductions (p<0.05-0.001) in spasticity (MAS) were seen both after the 2-week training period and at 6-month follow-up. Improvements were also seen in AROM (median change of elbow extension 5°, dorsiflexion of hand 10°), grip strength (20 Newton), and functional use after the 2-week training period (MAL: 1 point; Sollerman test: 8 points; BBT: 4 blocks). The improvements persisted at 6-month follow-up, except for scores on the Sollerman hand function test, which improved further.

CONCLUSION

Our study suggests that modified CIMT in an outpatient clinic may reduce spasticity and increase functional use of the affected arm in spastic chronic hemiplegia, with improvements persisting at 6 months.

Botulinum Toxin to Treat Upper-Limb Spasticity in Hemiparetic Patients: Analysis of Function and Kinematics of Reaching Movements

Background. Poor control of reaching in spastic hemiparetic patients could be because of a combination of poor individuation of joints, weakness, spasticity, and/or sensory loss. Objective. To assess the effect of botulinum toxin injections (BTIs) on spasticity, upper-limb function, and kinematics of reaching movements in patients with spastic hemiparesis caused by brain injury. Methods. Fifteen patients with spastic hemiparesis and 9 healthy controls were included in this single-site, open-labeled study. The trajectories of reaching movements were recorded, and kinematic variables were computed. A clinical evaluation included the Motor Activity Log, the Action Research Arm Test (ARAT), and the Box and Block Test (BBT). Patients were assessed before (M0), 1 month after a first (M1), and 1 month after a second BTI (M4, at 4 months) in proximal and distal muscles. Results. Significant differences were found between hemiparetic patients and healthy participants for all kinematic parameters. All parameters tended to improve after BTI. This effect was significant for velocity and smoothness. Functional scores also tended to improve. Improvements were greater at M4 than at M1, although the differences were not significant. Conclusions. Kinematic parameters improved following BTI, without significant changes in clinical outcomes such as ARAT and BBT. The decrease in spasticity alone does not seem to explain the results, which may be a result of adaptation to the decrease in hypertonicity leading to increased use of the arm and possibly an increase in antagonist muscle strength.

REPAS, a summary rating scale for resistance to passive movement: Item selection, reliability and validity

PURPOSE

To establish: (i) item characteristics and item selection for the REPAS; (ii) internal consistency, inter-rater and test-retest reliability of the final REPAS version and its subtests; (iii) the association between the REPAS and selected other clinical scales of impairment and activity limitation.

METHOD

Thirty-three neurological patients with central paresis. Two REPAS assessments with a one-week interval by two independent raters. Concurrent assessment of the Motricity Index, Box-and-Block test, Functional Ambulation Category, Timed walking, Barthel Index, Disability Rating Scale, Carer Burden Scale, and Hygiene Score.

RESULTS

Twenty-six of 52 REPAS items fulfilled the item selection criteria. The final test version showed a high internal consistency, inter-rater and test-retest reliability (correlation coefficients: 0.87-0.97, no significant difference between raters or with test repetition). Reliability of the arm and leg subtests was substantial (correlation coefficients: arm subtest 0.63-0.98, leg subtest 0.56-0.96). REPAS scores were moderately associated with basic ADL competence and a carer's burden with arm or leg adductor spasticity. The REPAS, arm subtest scores, degree of arm paresis and gross manual dexterity showed a moderately high association.

CONCLUSIONS

The Ashworth scale-based guidelines assured comparability of test administration and scoring. The REPAS is a reliable and valid summary rating scale for resistance to passive movement.

Modulation of stretch reflexes of the finger flexors by sensory feedback from the proximal upper limb poststroke

Neural coupling of proximal and distal upper limb segments may have functional implications in the recovery of hemiparesis after stroke. The goal of the present study was to investigate whether the stretch reflex response magnitude of spastic finger flexor muscles poststroke is influenced by sensory input from the shoulder and the elbow and whether reflex coupling of muscles throughout the upper limb is altered in spastic stroke survivors. Through imposed extension of the metacarpophalangeal (MCP) joints, stretch of the relaxed finger flexors of the four fingers was imposed in 10 relaxed stroke subjects under different conditions of proximal sensory input, namely static arm posture (3 different shoulder/elbow postures) and electrical stimulation (surface stimulation of biceps brachii or triceps brachii, or none). Fast (300 degrees/s) imposed stretch elicited stretch reflex flexion torque at the MCP joints and reflex electromyographic (EMG) activity in flexor digitorum superficialis. Both measures were greatest in an arm posture of 90 degrees of elbow flexion and neutral shoulder position. Biceps stimulation resulted in greater MCP stretch reflex flexion torque. Fast imposed stretch also elicited reflex EMG activity in nonstretched heteronymous upper limb muscles, both proximal and distal. These results suggest that in the spastic hemiparetic upper limb poststroke, sensorimotor coupling of proximal and distal upper limb segments is involved in both the increased stretch reflex response of the finger flexors and an increased reflex coupling of heteronymous muscles. Both phenomena may be mediated through changes poststroke in the spinal reflex circuits and/or in the descending influence of supraspinal pathways.

The relationship between upper limb activity and impairment in post-stroke hemiplegia

PURPOSE

To investigate the relationship between upper limb impairments and activity limitation.

METHOD

A cross sectional, single assessment observational study in which people with hemiplegia as a result of a stroke underwent a testing procedure in an instrumented wrist rig in which the following measures of impairment were recorded: Spasticity; motor control (ability to track a moving target); muscle activation patterns during tracking; stiffness; range of active movement and isometric muscle strength. Participants also performed clinical tests of upper limb activity (Action Research Arm Test) and hyper-tonicity (Modified Ashworth Scale).

RESULTS

Seventeen people with hemiplegia whose mean age was 57 (SD 13.4) took part. Their mean upper limb activity, measured by the Action Research Arm Test, was 19.3 (SD 11.2). Statistically significant positive relationships between level of activity and the negative features of the upper motor neuron syndrome such as motor control r = 0.710 (p = 0.003), active range of movement r = 0.540 (p = 0.025) and strength into flexion r = 0.515 (p = 0.034) and extension r = 0.575 (p = 0.016) were identified, but not with the positive features, such as spasticity or the secondary features such as stiffness.

CONCLUSIONS

The negative features of the upper motor neuron syndrome appear more likely to affect upper limb activity than the positive or secondary features, but findings need confirming in different study populations, preferably with larger samples.

Electromyographic Response to Manual Passive Stretch of the Hemiplegic Wrist: Accuracy, Reliability, and Correlation With Clinical Spasticity Assessment and Function

Background. The management of spasticity is important in neurorehabilitation and needs to be assessed accurately. The commonly used clinical tools have been criticized for lack of validity and sensitivity. Objective. To investigate the reliability of electromyographic (EMG) response to manual stretches of the hemiplegic wrist and its correlation with clinical assessments of spasticity and physical function. Methods. EMG activity was measured in 10 stroke patients and control participants (53.7 ± 10 and 32 ± 9.1 years respectively, mean ± SEM) during 3 cycles of 10 seconds passive manual movements of the wrist at 60 to 360° • s-1. Isometric maximal voluntary contractions (MVC) strength, range of movement (ROM) of the wrist flexors and extensors, spasticity (Modified Ashworth Scale [MAS]) and hand function (Block and Box Test [BBT]) were also assessed. Results. EMG activity of the stroke patients increased with velocity from 4% to 40% MVC ( P < .001) but there was none in the controls. It was unaffected by repetition and good to moderate reliability occurred at all speeds (ICC, 0.71-0.81). EMG correlated negatively with MVC strength ( r = -.9), active wrist flexion ROM ( r = -.8), and hand function scores ( r = —.7), but not with clinical measures of spasticity except at the lowest velocity ( r = .72). Conclusions. Consistent and accurate stretch velocities and EMG responses can be achieved with manual wrist stretches for the assessment of the neural component of spasticity. These objective tests did not correlate well with the standard clinical assessment of spasticity. They showed significant negative relationships with function, indicating that increased reflex excitability contributes to hand disability after stroke.

Spasticity measurement based on tonic stretch reflex threshold in stroke using a portable device

OBJECTIVES

We investigated intra- and inter-evaluator reliability to quantify spasticity based on the tonic stretch reflex threshold (TSRT) and the correlation between TSRT and resistance to stretch.

METHODS

Spasticity was evaluated in 20 subjects with chronic stroke-related spasticity using a portable device and the Modified Ashworth Scale (MAS). Evaluations were done on 2 days, by three evaluators. Biceps brachii EMG signals and elbow displacement were recorded during 20 elbow stretches applied at different velocities for each evaluation. Velocity-dependent dynamic stretch reflex thresholds (angle where EMG signal increased in the biceps for a given velocity of stretch) were recorded. These values were used to compute TSRT (excitability of motoneurons at 0 degrees /s). Spasticity was also measured with MAS.

RESULTS

Reliability was moderately good for subjects with moderate to high spasticity (intra-evaluator: 0.46-0.68, and inter-evaluator: 0.53-0.68). The TSRT measure of spasticity did not correlate with resistance to stretch (MAS).

CONCLUSIONS

TSRT may be a more representative measure for subjects with moderate to high spasticity. Further improvements are suggested for the portable device in order to quantify all the levels of spasticity.

SIGNIFICANCE

TSRT may be an alternative clinical measure to current clinical scales.

The relation between Ashworth scores and neuromechanical measurements of spasticity following stroke

Background

Spasticity is a common impairment that follows stroke, and it results typically in functional loss. For this reason, accurate quantification of spasticity has both diagnostic and therapeutic significance. The most widely used clinical assessment of spasticity is the modified Ashworth scale (MAS), an ordinal scale, but its validity, reliability and sensitivity have often been challenged. The present study addresses this deficit by examining whether quantitative measures of neural and muscular components of spasticity are valid, and whether they are strongly correlated with the MAS.

Methods

We applied abrupt small amplitude joint stretches and Pseudorandom Binary Sequence (PRBS) perturbations to both paretic and non-paretic elbow and ankle joints of stroke survivors. Using advanced system identification techniques, we quantified the dynamic stiffness of these joints, and separated its muscular (intrinsic) and reflex components. The correlations between these quantitative measures and the MAS were investigated.

Results

We showed that our system identification technique is valid in characterizing the intrinsic and reflex stiffness and predicting the overall net torque. Conversely, our results reveal that there is no significant correlation between muscular and reflex torque/stiffness and the MAS magnitude. We also demonstrate that the slope and intercept of reflex and intrinsic stiffnesses plotted against the joint angle are not correlated with the MAS.

Conclusion

Lack of significant correlation between our quantitative measures of stroke effects on spastic joints and the clinical assessment of muscle tone, as reflected in the MAS suggests that the MAS does not provide reliable information about the origins of the torque change associated with spasticity, or about its contributing components.

Oral baclofen increases maximal voluntary neuromuscular activation of ankle plantar flexors in children with spasticity due to cerebral palsy

Although spasticity is a common symptom in children with cerebral palsy, weakness may be a much greater contributor to disability. We explore whether a treatment that reduces spasticity may also have potential benefit for improving strength. Ten children with cerebral palsy and spasticity in the ankle plantar flexor muscles were treated with oral baclofen for 4 weeks. We tested voluntary ability to activate ankle plantar flexor muscles using the ratio of the surface electromyographic signal during isometric maximal voluntary contraction to the M-wave during supramaximal electrical stimulation of the tibial nerve and tested muscle strength using maximal isometric plantar flexion torque. Mean maximal voluntary neuromuscular activation increased from 1.13 +/- 1.02 to 1.60 +/- 1.30 ( P < .05) after treatment, corresponding to an increase in 9 of 10 subjects. Mean maximal plantar flexion torque did not change. We conjecture that antispasticity agents could facilitate strength training by increasing the ability to voluntarily activate muscle.

Inter- and intrarater reliability of the Modified Modified Ashworth Scale in patients with knee extensor poststroke spasticity

Muscle spasticity is a common motor disorder following upper motor neuron syndrome. A reliable and valid clinical tool is essential to document the effect of therapeutic interventions aimed to improve function by reducing spasticity. The Modified Ashworth Scale (MAS) is the most widely used and accepted clinical scale of spasticity. The MAS has been recently modified. The aim of this investigation was to determine the interrater and intrarater reliability of clinical test of knee extensor post-stroke spasticity graded on a Modified Modified Ashworth Scale (MMAS). Two raters scored the muscle spasticity of 15 patients with ischaemic stroke. For the inter- and intrarater reliability, two raters agreed on 80.1% and 86.6%, respectively. The Kappa values were good (kappa=0.72, SE=0.14, p<0.001) between raters and very good (kappa=0.82, SE=0.12, p<0.001) within one rater. The values of Kendall tau-b correlation were acceptable for clinical use with 0.87 (SE=0.06, p<0.001) between raters and 0.92 (SE=0.05, p<0.001) within one rater. The MMAS demonstrated reliable measurements for a single rater and between raters for measuring knee extensor post-stroke spasticity. The results encourage further study on the reliability and the validity of the scale.

Upper limb impairments associated with spasticity in neurological disorders

Background

While upper-extremity movement in individuals with neurological disorders such as stroke and spinal cord injury (SCI) has been studied for many years, the effects of spasticity on arm movement have been poorly quantified. The present study is designed to characterize the nature of impaired arm movements associated with spasticity in these two clinical populations. By comparing impaired voluntary movements between these two groups, we will gain a greater understanding of the effects of the type of spasticity on these movements and, potentially a better understanding of the underlying impairment mechanisms.

Methods

We characterized the kinematics and kinetics of rapid arm movement in SCI and neurologically intact subjects and in both the paretic and non-paretic limbs in stroke subjects. The kinematics of rapid elbow extension over the entire range of motion were quantified by measuring movement trajectory and its derivatives; i.e. movement velocity and acceleration. The kinetics were quantified by measuring maximum isometric voluntary contractions of elbow flexors and extensors. The movement smoothness was estimated using two different computational techniques.

Results

Most kinematic and kinetic and movement smoothness parameters changed significantly in paretic as compared to normal arms in stroke subjects (p < 0.003). Surprisingly, there were no significant differences in these parameters between SCI and stroke subjects, except for the movement smoothness (p ≤ 0.02). Extension was significantly less smooth in the paretic compared to the non-paretic arm in the stroke group (p < 0.003), whereas it was within the normal range in the SCI group. There was also no significant difference in these parameters between the non-paretic arm in stroke subjects and the normal arm in healthy subjects.

Conclusion

The findings suggest that although the cause and location of injury are different in spastic stroke and SCI subjects, the impairments in arm voluntary movement were similar in the two spastic groups. Our results also suggest that the non-paretic arm in stroke subjects was not distinguishable from the normal, and might therefore be used as an appropriate control for studying movement of the paretic arm.

Clinometric properties of a clinical spasticity measurement tool

PURPOSE

To investigate clinometric properties of an Anglo-Dutch spasticity measurement tool (ADSMT), an objective tool providing information about both neurophysiological and biomechanical aspects of spasticity about the wrist joint in the clinical setting.

METHOD

ADSMT measurements were performed with 12 healthy and 11 participants with post-stroke spasticity, and consisted of assessing the maximum range of passive wrist movement (pROM) and passive wrist extension at different cycle rates. Outcome measures were wrist angle, flexor and extensor activation, and resistance to movement. Intra-class Correlation Coefficients (ICCs) were calculated for inter-rater and test-retest reliability. Validity was investigated by calculating Spearman's rho between ADSMT outcome measures and the Modified Ashworth Scale (n=12), the Action Research Arm Test (n=6), and a validated wrist rig (n=6).

RESULTS

Impaired participants had higher flexor activity and higher resistance to movement during passive wrist extension compared to unimpaired participants. For all outcome measures inter-rater and test-retest reliability were satisfactory to good and concurrent validity was sufficient.

CONCLUSIONS

Outcome measures related to wrist flexor activity and resistance to movement during extension are promising for spasticity assessment using the ADSMT. Further knowledge on reference values and practicality is necessary for this tool to become incorporated in the clinical setting.

Characterization of the mechanical and neural components of spastic hypertonia with modified H reflex

As the H reflex remains unable to assess mechanical changes intrinsic to a muscle, the aim of this study was to modify the H reflex techniques and to characterize the neural and mechanical components of muscle spasticity, relating the two components to clinical observations. Thirty-four patients featuring either a spinal-cord lesion (n=15) or stroke (n=19) and 23 neurologically normal subjects were recruited. Soleus H reflex and maximal M response (M(max)) were measured with electromyography and mechanomyography (MMG). The motoneuronal excitability was represented with the adjusted ratio of the H reflex to the M(max) (H/M(max)) and the ratio of the paired H reflexes (H(2)/H(1)). Muscle mechanical properties were characterized by the amplitude and median frequency of maximal M response recorded with MMG (MMG(Mmax)). The results showed that spastic patients exhibited a larger H/M(max), H(2)/H(1) and amplitude of MMG(Mmax) than the control group. H/M(max) and amplitude of MMG(Mmax) accounted for 55.7% of the variance in the Modified Ashworth Scale, the clinical hypertonia assessment. The amplitude of MMG(Mmax) correlated with functional impairments, as assessed with the Barthel index and Fugl-Meyer motor-assessment scale. It was concluded that spastic hypertonia involved an atypical increase in motoneuronal excitability and muscle mechanical properties, while impairment of functional performance and daily activity was attributable primarily to altered mechanical properties of a spastic muscle.

An EMG-to-force processing approach for determining ankle muscle forces during normal human gait

Muscle forces move our limbs. These forces must be estimated with indirect techniques, as direct measurements are neither generally possible nor practical. An electromyography (EMG)-to-force processing technique was developed. Ankle joint moments and, by extension, ankle muscle forces were calculated. The ankle moment obtained by inverse dynamics was calculated for ten normal adults during free speed gait. There was close correlation between inverse dynamics ankle moments and moments determined by the EMG-to-force processing approach. Muscle forces were determined. The gait peak Achilles tendon force occurred in late single limb support. Peak force observed (2.9 kN) closely matched values obtained where force transducers were used to obtain in vivo muscle forces (2.6 kN). The EMG-to-force processing model presented here appears to be a practical means to determine in vivo muscle forces.

Reliability of elbow stretch reflex assessment in chronic post-stroke hemiparesis

OBJECTIVE

To establish reliability of quantitative measures of elbow joint spastic hypertonia in post-stroke hemiparesis.

METHODS

Nine subjects with post-stroke hemiparesis (mn duration: 42 months) were tested on three separate days. Biceps brachii and brachioradialis EMG were recorded during passive ramp-and-hold extensions applied at seven speeds between 30 and 210 degrees /s. EMG burst duration, onset position threshold, and burst intensity were used to evaluate reflex activity. Torque at 40 degrees of elbow flexion was used as a mechanical indicator of spastic hypertonia.

RESULTS

Across speeds ICCs were consistent, means ranged between 0.63 and 0.85. Thus, relative reliability was fair to excellent for all parameters. Absolute reliability, determined using standard error of measurement expressed as a percentage of the mean score (%SEM), improved at higher speeds (> or = 120 degrees/s).

CONCLUSIONS

These results establish reliability of reflex and mechanical measures of elbow spastic hypertonia post-stroke. The data demonstrate greater reflex detection at high speeds, indicating greater potential to document meaningful changes in these distinct aspects of spastic hypertonia following intervention.

SIGNIFICANCE

Based on findings of this study, reliability was demonstrated using four parameters of reflex EMG and torque indicating measurement consistency across sessions. These observations motivate determination of requisite effect sizes for clinical trials that evaluate treatment outcome.

Reflex contribution of spindle group Ia and II afferent input to leg muscle spasticity as revealed by tendon vibration in hemiparesis

OBJECTIVE

Foot dorsiflexion evokes a short- (SLR) and a medium-latency EMG response (MLR) in the soleus of standing subjects. SLR is mediated by spindle group Ia, while group II fibres contribute to MLR through an oligosynaptic circuit. We studied the effects of Achilles' tendon vibration on both responses in spastic patients to disclose any abnormal excitability of these pathways.

METHODS

SLR and MLR were evoked in 11 hemiparetics and 11 normals. The vibration-induced changes in both responses were correlated to the Ashworth score of the affected leg.

RESULTS

There were no differences between normals and patients in the size of control SLR or MLR. Vibration decreased SLR to 70% in normal subjects, but increased it to 110% in patients, in both affected and unaffected leg. Vibration did not affect MLR in normals, but increased it to 165% on the affected and 120% on the unaffected side of patients. Ashworth score was solely correlated with the degree of vibration-induced increase of MLR.

CONCLUSIONS

While the lack of inhibitory effect of vibration on SLR confirms a reduced inhibitibility of the monosynaptic reflex, the increased MLR indicates a disinhibition of group II pathway in patients, connected to the loss of descending control on group II interneurones. Spastic hypertonia depends on release of group II rather than group Ia reflex pathways.

SIGNIFICANCE

These findings give a neurophysiological support for the pharmacological treatment of spastic hypertonia and suggest a method for the assessment of its effects.

Pathophysiology of pediatric movement disorders

Pediatric movement disorders constitute a relatively small cluster of symptoms that can be associated with many different underlying diseases. To provide effective treatment, it is essential to understand the relationship between etiology and clinical expression. This article reviews the recent literature on several common pediatric movement disorders, including spasticity, dystonia, chorea, myoclonus, bradykinesia, and tics, and it discusses current models of physiology that may help link the cellular pathology of specific diseases to the expression of clinical symptoms.

Classification and definition of disorders causing hypertonia in childhood

OBJECTIVE

This report describes the consensus outcome of an interdisciplinary workshop that was held at the National Institutes of Health in April 2001. The purpose of the workshop and this article are to define the terms "spasticity," "dystonia," and "rigidity" as they are used to describe clinical features of hypertonia in children. The definitions presented here are designed to allow differentiation of clinical features even when more than 1 is present simultaneously.

METHODS

A consensus agreement was obtained on the best current definitions and their application in clinical situations.

RESULTS

"Spasticity" is defined as hypertonia in which 1 or both of the following signs are present: 1) resistance to externally imposed movement increases with increasing speed of stretch and varies with the direction of joint movement, and/or 2) resistance to externally imposed movement rises rapidly above a threshold speed or joint angle. "Dystonia" is defined as a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both. "Rigidity" is defined as hypertonia in which all of the following are true: 1) the resistance to externally imposed joint movement is present at very low speeds of movement, does not depend on imposed speed, and does not exhibit a speed or angle threshold; 2) simultaneous co-contraction of agonists and antagonists may occur, and this is reflected in an immediate resistance to a reversal of the direction of movement about a joint; 3) the limb does not tend to return toward a particular fixed posture or extreme joint angle; and 4) voluntary activity in distant muscle groups does not lead to involuntary movements about the rigid joints, although rigidity may worsen.

CONCLUSION

We have provided a set of definitions for the purpose of identifying different components of childhood hypertonia. We encourage the development of clinical rating scales that are based on these definitions, and we encourage research to relate the degree of hypertonia to the degree of functional ability, change over time, and societal participation in children with motor disorders.

Botulinum treatment of spasticity: why is it so difficult to show a functional benefit?

Clinical experience seems to indicate that botulinum toxin injections can, in selected patients with upper motor neurone syndrome, reduce spasticity and improve voluntary movement and active function. However, double-blind placebo-controlled trials have had difficulty showing active functional improvement, despite the clear ability of botulinum toxin to reduce spasticity. This prompts a re-analysis of the basic assumption that spasticity impairs voluntary movement and a review of the methodology of the clinical trials. Motor dysfunction is usually caused by weakness and the other "negative" features of upper motor neurone syndrome, rather than muscle overactivity. Recent research has explored the pathophysiological basis of the voluntary movement disorder, in particular the role of the various forms of motor overactivity, which might be amenable to botulinum toxin treatment. The failure of double-blind placebo-controlled clinical trials to show improvement in active function is, to a large extent, a result of their methodology, especially patient selection, injection protocols, and the choice of outcome measures. Clinical trials need to be re-designed and based upon expert experience and a better understanding of the pathophysiology of the motor disorder.