Tonic Stretch Reflex Threshold Research Articles

ENHANCE proof-of-concept three-arm randomized trial: effects of reaching training of the hemiparetic upper limb restricted to the spasticity-free elbow range

Post-stroke motor recovery processes remain unknown. Timescales and patterns of upper-limb (UL) recovery suggest a major impact of biological factors, with modest contributions from rehabilitation. We assessed a novel impairment-based training motivated by motor control theory where reaching occurs within the spasticity-free elbow range. Patients with subacute stroke (≤ 6 month; n = 46) and elbow flexor spasticity were randomly allocated to a 10-day UL training protocol, either personalized by restricting reaching to the spasticity-free elbow range defined by the tonic stretch reflex threshold (TSRT) or non-personalized (non-restricted) and with/without anodal transcranial direct current stimulation. Outcomes assessed before, after, and 1 month post-intervention were elbow flexor TSRT angle and reach-to-grasp arm kinematics (primary) and stretch reflex velocity sensitivity, clinical impairment, and activity (secondary). Results were analyzed for 3 groups as well as those of the effects of impairment-based training. Clinical measures improved in both groups. Spasticity-free range training resulted in faster and smoother reaches, smaller (i.e., better) arm-plane path length, and closer-to-normal shoulder/elbow movement patterns. Non-personalized training improved clinical scores without improving arm kinematics, suggesting that clinical measures do not account for movement quality. Impairment-based training within a spasticity-free elbow range is promising since it may improve clinical scores together with arm movement quality.Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique Identifier: NCT02725853; Initial registration date: 01/04/2016.

The muscle shortening maneuver in individuals with stroke: a consideration-of-concept randomized pilot trial

ABSTRACT Background and Purpose The Muscle Shortening Maneuver (MSM) is derived from Feldman’s λ model of motor control, and seems to induce a more balanced agonist- antagonist-muscular action. The hypothesized mechanism of action is a modulation of the Tonic Stretch Reflex Threshold (TSRT). We designed a pilot, randomized trial aimed to explore the mechanisms of action of the technique. An ancillary objective was to research the implementation of the MSM as a stroke rehabilitation intervention. Methods A sample of 10 participants with chronic stroke was enrolled and randomly assigned to MSM (n, 5) or conventional physical therapy (CPT) (n, 5) treatments. The TSRTs were assessed by the Montreal Spasticity Measure device. A selection of clinical and instrumental outcome measures was taken to investigate function and activity levels. Data were collected at baseline, end-of-treatment, and one month after the end-of-treatment. Results No adverse events were observed. In both between- and within-group post-treatment assessments, in the affected ankle the MSM group showed decreased TSRTs of the plantar flexor, increased strength of the dorsiflexor and active range of motion; also, the time needed to perform the Timed Up and Go test decreased. No changes were evident across assessments in the CPT group. Discussion and Conclusions The MSM seems able to modulate the TSRTs in individuals with stroke. Although with the limitations due to the pilot design, the variation in participants’ responses appear to be promising. Many methodological issues have to be clarified and specified conceiving the progression toward a confirmatory trial.

Virtual reality and serious game therapy for post-stroke individuals: A preliminary study with humanized rehabilitation approach protocol

ObjectiveThe current study proposed the development and preliminary validation of a humanized training approach for upper limb rehabilitation of chronic post-stroke individuals, using serious game (SG) and virtual reality (VR) technologies. Materials and methodsTen individuals with chronic stroke participated in the study. Accompanied by a health professional, 15 sessions of the SG were performed in a laboratory, in a humanized way, lasting between 30 and 45 min each. The assessments were made pre- and post-intervention with the SG, and the following parameters were evaluated (considering the elbow joint): Modified Ashworth Scale (MAS), range of movement (ROM) and tonic stretch reflex threshold (TSRT). Global measures such as quality of life (QOL) were also assessed by the Stroke-Specific Quality of Life Scale (SSQL), Brunnstrom Recovery Scale (BRS) and General Health Questionnaire (GHQ-28). The following tests were applied to verify statistically significant differences: Shapiro-Wilk test, t-test, and Wilcoxon-Mann-Whitney test. ResultsThe parameters ROM, TSRT, BRS, and SSQL showed statistically significant differences between pre- and post-intervention (p < 0.01). The ROM increase was about 8%. The objective evaluation of spasticity (provided by the TRST) showed an increase of 28% over the average pre- and post-intervention values. Three participants showed decreased resistance to passive stretching according to the results of the MAS, and seven participants moved to the next stage of the BRS. For QOL, the scores indicated around 20% of post-intervention improvement. ConclusionThe intervention had no adverse effects, showed a high degree of compliance, provided increased ROM, improved QOL, reduced spasticity and allowed these individuals the opportunity to test a promising technology for upper limb rehabilitation with emphasis in humanized aspects of therapy.

Shared and distinct voxel-based lesion-symptom mappings for spasticity and impaired movement in the hemiparetic upper limb

Hemiparesis and spasticity are common co-occurring manifestations of hemispheric stroke. The relationship between impaired precision and force in voluntary movement (hemiparesis) and the increment in muscle tone that stems from dysregulated activity of the stretch reflex (spasticity) is far from clear. Here we aimed to elucidate whether variation in lesion topography affects hemiparesis and spasticity in a similar or dis-similar manner. Voxel-based lesion-symptom mapping (VLSM) was used to assess the impact of lesion topography on (a) upper limb paresis, as reflected by the Fugl-Meyer Assessment scale for the upper limb and (b) elbow flexor spasticity, as reflected by the Tonic Stretch Reflex Threshold, in 41 patients with first-ever stroke. Hemiparesis and spasticity were affected by damage to peri-Sylvian cortical and subcortical regions and the putamen. Hemiparesis (but not spasticity) was affected by damage to the corticospinal tract at corona-radiata and capsular levels, and by damage to white-matter association tracts and additional regions in the temporal cortex and pallidum. VLSM conjunction analysis showed only a minor overlap of brain voxels where the existence of damage affected both hemiparesis and spasticity, suggesting that control of voluntary movement and regulation of muscle tone at rest involve largely separate parts of the motor network.

Effect of Botulinum Toxin on Spasticity Level Assessed by Tonic Stretch Reflex Threshold: A Feasibility Pilot Study

IntroductionSpasticity is one of the most disabling neurological conditions, generally associated with pain and articular contracture. Its management involves multiple rehabilitation techniques, including botulinum toxin. Studies were developed with the intention of assessing the clinical effects of the Botulinum toxin (BoNT) injection in spastic muscles, however most of them, utilized subjective assessment methods. The aim of this study was to investigate the feasibility of applying Tonic Stretch Reflex Threshold (TSRT) method in clinical practice to assess the spasticity before and after BoNT injection and compare the results with those provided by methods traditionally used for this purpose: Modified Ashworth Scale (MAS) and Range of Motion (ROM). MethodsFive patients were evaluated before and after 21 days of BoNT injection in biceps brachii. Three parameters were considered: MAS, ROM of elbow and TSRT. ResultsAll patients presented improvement in ROM (p = 0.05) and TSRT (p = 0.06), with ROM average improvement bigger than TSRT. Two patients did not present evolution in MAS (p = 0.14). ConclusionsThe feasibility pilot study was the first to utilize the TSRT as an evaluation method after BoNT application. The TSRT method was able to identify improvement in patients that MAS did not able to, and is a good alternative to assess spasticity even when the evolution is small. Hence, TSRT showed to be an effective method for monitoring more precisely spasticity in BoNT treatment.

Predicting post-stroke motor recovery of upper extremity using clinical variables and performance assays: A prospective cohort study protocol.

Measurement of movement quality is essential to distinguish motor recovery patterns and optimize rehabilitation strategies post-stroke. Recently, the Stroke Recovery and Rehabilitation Roundtable Taskforce (SRRR) recommended four kinetic and kinematic performance assays to measure upper extremity (UE) movements and distinguish behavioral restitution and compensation mechanisms early post-stroke. The purpose of this study is to develop and validate a prediction model to analyze the added prognostic value of performance assays over clinical variables assessed up to 1-month post stroke for predicting recovery of UE motor impairment, capacity and quality of movement (QoM) measured at 3months post-stroke onset. In this prospective cohort study, 120 stroke survivors will be recruited within seven days post-stroke. Candidate predictors such as baseline characteristics, demographics and performance assays as per SRRR recommendations along with tonic stretch reflex threshold will be measured up to 1-month post-stroke. Upper extremity motor recovery will be evaluated in terms of motor impairment (Fugl-Meyer assessment for UE), UE capacity measured with Action Research Arm Test (ARAT) and QoM (movement smoothness in the form of peak metrics [PM]) assessed with a reach-to-grasp-to-mouth task (mimicking a drinking task) at 3months post-stroke. Three multivariable linear regression models will be developed to predict factors responsible for the outcomes of Fugl-Meyer assessment for upper extremity (FM-UE), ARAT and movement quality. The developed models will be internally validated using a split-sample method. This study will provide a validated prediction model inclusive of clinical and performance assays that may assist in prediction of UE motor recovery. Predicting the amount of recovery and differentiating between behavioral restitution and compensation (as reflected by the FM-UE, QoM and ARAT) would enable us in realistic goal formation and planning rehabilitation. It would also help in encouraging patients to partake in early post-stroke rehabilitation thus improving therecovery potential.

Effect of post-stroke spasticity on voluntary movement of the upper limb

BackgroundHemiparesis following stroke is often accompanied by spasticity. Spasticity is one factor among the multiple components of the upper motor neuron syndrome that contributes to movement impairment. However, the specific contribution of spasticity is difficult to isolate and quantify. We propose a new method of quantification and evaluation of the impact of spasticity on the quality of movement following stroke.MethodsSpasticity was assessed using the Tonic Stretch Reflex Threshold (TSRT). TSRT was analyzed in relation to stochastic models of motion to quantify the deviation of the hemiparetic upper limb motion from the normal motion patterns during a reaching task. Specifically, we assessed the impact of spasticity in the elbow flexors on reaching motion patterns using two distinct measures of the ‘distance’ between pathological and normal movement, (a) the bidirectional Kullback–Liebler divergence (BKLD) and (b) Hellinger’s distance (HD). These measures differ in their sensitivity to different confounding variables. Motor impairment was assessed clinically by the Fugl-Meyer assessment scale for the upper extremity (FMA-UE). Forty-two first-event stroke patients in the subacute phase and 13 healthy controls of similar age participated in the study. Elbow motion was analyzed in the context of repeated reach-to-grasp movements towards four differently located targets. Log-BKLD and HD along with movement time, final elbow extension angle, mean elbow velocity, peak elbow velocity, and the number of velocity peaks of the elbow motion were computed.ResultsUpper limb kinematics in patients with lower FMA-UE scores (greater impairment) showed greater deviation from normality when the distance between impaired and normal elbow motion was analyzed either with the BKLD or HD measures. The severity of spasticity, reflected by the TSRT, was related to the distance between impaired and normal elbow motion analyzed with either distance measure. Mean elbow velocity differed between targets, however HD was not sensitive to target location. This may point at effects of spasticity on motion quality that go beyond effects on velocity.ConclusionsThe two methods for analyzing pathological movement post-stroke provide new options for studying the relationship between spasticity and movement quality under different spatiotemporal constraints.

SpES: A new portable device for objective assessment of hypertonia in clinical practice

Spasticity is a motor disorder that affects millions around the world. It is a particular type of hypertonia characterized by the speed-dependent increase of the muscle stretch reflex, where its correct evaluation is essential for rehabilitation. The preferred method for this assessment is the Modified Ashworth Scale (MAS), a rank derived from clinical observations. Currently, few methods can quantify this disorder objectively. Tonic Stretch Reflex Threshold (TSRT) is a parameter speed-dependent obtained from electromyographic (EMG) measurements and angular signals. Therefore, the objective was to develop portable equipment for quantitative assessments of hypertonia based on TSRT. To this end, we designed an instrument composed of single-channel EMG, flexible optical goniometer, and software for the online computing of TSRT from acquired signals. The new equipment named SpES (Spasticity Evaluation System) was applied to measuring hypertonia of the biceps brachii in twenty-two participants. The experiment was performed during manual passive stretching of the affected limb at predefined speeds. The results provided by SpES presented a satisfactory coefficient of determination (0.70) and a strong correlation with MAS (0.79). In summary, while MAS depends on precise clinical observations, SpES has the TSRT quantitative method embedded for reaching an objective assessment of hypertonia in clinical practice.

Tonic stretch reflex threshold as a measure of spasticity after stroke: Reliability, minimal detectable change and responsiveness

ObjectiveTo determine inter-rater reliability, minimal detectable change and responsiveness of Tonic Stretch Reflex Threshold (TSRT) as a quantitative measure of elbow flexor spasticity. MethodsElbow flexor spasticity was assessed in 55 patients with sub-acute stroke by determining TSRT, the angle of spasticity onset at rest (velocity = 0°/s). Elbow flexor muscles were stretched 20 times at different velocities. Dynamic stretch-reflex thresholds, the elbow angles corresponding to the onset of elbow flexor EMG at each velocity, were used for TSRT calculation. Spasticity was also measured with the Modified Ashworth Scale (MAS). In a sub-group of 44 subjects, TSRT and MAS were measured before and after two weeks of an upper-limb intervention. ResultsThe intraclass correlation coefficient was 0.65 and the 95% minimal detectable change was 32.4°. In the treated sub-group, TSRT, but not MAS significantly changed. TSRT effect size and standardized response mean were 0.40 and 0.35, respectively. Detection of clinically meaningful improvements in upper-limb motor impairment by TSRT change scores ranged from poor to excellent. ConclusionsEvaluation of stroke-related elbow flexor spasticity by TSRT has good inter-rater reliability. Test responsiveness is low, but better than that of the MAS. SignificanceTSRT may be used to complement current scales of spasticity quantification.

The Assessment of Upper-Limb Spasticity Based on a Multi-Layer Process Using a Portable Measurement System.

Spasticity is a common disabling complication caused by the upper motor neurons dysfunction following neurological diseases such as stroke. Currently, the assessment of the spastic hypertonia triggered by stretch reflexes is manually performed by clinicians using perception-based clinical scales, however, their reliability is still questionable due to the inter-rater and intra-rater variability. In order to objectively quantify the complex spasticity phenomenon in post-stroke patients, this study proposed a multi-layer assessment system based on a novel measurement device. The exoskeletal device was developed to synchronously record the kinematic, biomechanical and electrophysiological information in sixteen spastic patients and ten age-matched healthy subjects, while the spastic limb was stretched at low, moderate and high velocities. The mechanical impedance of the elbow joint was identified using a modified genetic algorithm to quantify the alterations in viscoelastic properties underlying pathological resistance. Simultaneously, the time-frequency features were extracted from the surface electromyography (sEMG) signals to reveal the neurophysiological mechanisms of the spastic muscles. By concatenating these single-layer decisions, a support vector regression (SVR)-based fusion model was developed to generate a more comprehensive quantification of spasticity severity. Experimental results demonstrated that the stiffness and damping components of the spastic arm significantly deviated from the nonspastic baseline, and strong correlations were observed between the proposed spasticity assessment and the severity level measured by clinical scales ( R = 0.86, P = 1.67e - 5 ), as well as the tonic stretch reflex threshold (TSRT) value ( R = - 0.89, P = 3.54e - 6 ). These promising results suggest that the proposed assessment system holds great potential to support the clinical diagnosis of motor abnormalities in spastic patients, and ultimately enables optimal adjustment of treatment protocols.

A novel mechatronic system for evaluating elbow muscular spasticity relying on Tonic Stretch Reflex Threshold estimation.

Muscular spasticity represents one of the most common motor disorder associated to lesions of the Central Nervous System, such as Stroke, and affects joint mobility up to the complete prevention of skeletal muscle voluntary control. Its clinical evaluation is hence of fundamental relevance for an effective rehabilitation of the affected subjects. Standard assessment protocols are usually manually performed by humans, and hence their reliability strongly depends on the capabilities of the clinical operator performing the procedures. To overcome this limitation, one solution is the usage of mechatronic devices based on the estimation of the Tonic Stretch Reflex Threshold, which allows for a quite reliable and operator-independent evaluation. In this work, we present the design and characterization of a novel mechatronic device that targets the estimation of the Tonic Stretch Reflex Threshold at the elbow level, and, at the same time, it can potentially act as a rehabilitative system. Our device can deliver controllable torque/velocity stimulation and record functional parameters of the musculo-skeletal system (joint position, torque, and multi-channel ElectroMyoGraphyc patterns), with the ultimate goals of: i) providing significant information for the diagnosis and the classification of muscular spasticity, ii) enhancing the recovery evaluation of patients undergoing through therapeutic rehabilitation procedures and iii) enabling a future active usage of this device also as therapeutic tool.Clinical relevance- The contribution presented in this work proposes a technological advancement for a device-based evaluation of motion impairment related to spasticity, with a major potential impact on both the clinical appraisal and the rehabilitation procedures.

A Novel Quantitative Spasticity Evaluation Method Based on Surface Electromyogram Signals and Adaptive Neuro Fuzzy Inference System.

Stroke patients often suffer from spasticity. Before treatment of spasticity, there are often practical demands for objective and quantitative assessment of muscle spasticity. However, the common quantitative spasticity assessment method, the tonic stretch reflex threshold (TSRT), is time-consuming and complicated to implement due to the requirement of multiple passive stretches. To evaluate spasticity conveniently, a novel spasticity evaluation method based on surface electromyogram (sEMG) signals and adaptive neuro fuzzy inference system (i.e., the sEMG-ANFIS method) was presented in this paper. Eleven stroke patients with spasticity and four healthy subjects were recruited to participate in the experiment. During the experiment, the Modified Ashworth scale (MAS) scores of each subject was obtained and sEMG signals from four elbow flexors or extensors were collected from several times (4–5) repetitions of passive stretching. Four time-domain features (root mean square, the zero-cross rate, the wavelength and a 4th-order autoregressive model coefficient) and one frequency-domain feature (the mean power frequency) were extracted from the collected sEMG signals to reflect the spasticity information. Using the ANFIS classifier, excellent regression performance was achieved [mean accuracy = 0.96, mean root-mean-square error (RMSE) = 0.13], outperforming the classical TSRT method (accuracy = 0.88, RMSE = 0.28). The results showed that the sEMG-ANFIS method not only has higher accuracy but also is convenient to implement by requiring fewer repetitions (4–5) of passive stretches. The sEMG-ANFIS method can help stroke patients develop proper rehabilitation training programs and can potentially be used to provide therapeutic feedback for some new spasticity interventions, such as shockwave therapy and repetitive transcranial magnetic stimulation.

Effects of lesion extent and location on upper limb spasticity following hemispheric stroke

Spasticity of the hemiparetic upper limb (UL) leading to difficulty performing activities of daily living is a major concern in stroke rehabilitation. Spasticity results from impaired control of motoneuronal activation thresholds exerted by descending direct and indirect pathways. This is reflected by pathological alteration of the specific muscle length/joint angle at which the stretch reflex and other proprioceptive reflexes begin to act (tonic stretch reflex threshold, TSRT). The relationship between lesion location and the appearance of spasticity is poorly understood. We investigated the relationship between lesion characteristics and elbow-flexor (biceps) TSRT in the hemiparetic UL, as part of an international multicenter RCT (ENHANCE project; ClinicalTrials.gov, ID: NCT02725853 ). Elbow-flexor TSRT (°) was examined in 8 right-hemisphere damaged (RHD) and 15 left hemisphere damaged (LHD) stroke patients using the Montreal Stretch Reflex Threshold device. Normalized lesion data were used for voxel-based lesion-symptom mapping (VLSM) analyses of lesion impact on biceps spasticity. Application of VLSM using 10 continuous affected voxels as a minimum for consideration, showed in the LHD group, a cluster localized in the superior part of the corona radiata, where damage affected the level of spasticity in the biceps as revealed by its TSRT (smaller clusters were recognized in the external capsule and insula). In the RHD group, VLSM failed to reveal voxel clusters where damage affected the biceps TSRT. The paucity of hemispheric voxels where damage is related to increased spasticity levels may indicate that impaired regulation of motoneuronal activation threshold after stroke is attributed to the sum effect of various brainstem control substrates (which cannot be analyzed using VLSM), rather than to direct corticospinal control.

Objective Assessment of Spasticity With a Method Based on a Human Upper Limb Model.

This paper presents a method based on a human upper limb model that assesses the severity of spasticity in patients with stroke objectively. The kinematic model consists of four moving segments connected by four joints. The joint torques are computed using inverse dynamics with measurements from three inertial measurement units (IMUs) attached to the participant's upper limb. The muscle activations are estimated using the joint torques via a musculoskeletal model which consists of 22 muscles. The severity of spasticity is then quantified by measuring the tonic stretch reflex threshold (TSRT) of the participant. 15 patient participants participated in the experiments where they were assessed by two qualified therapists using modified Ashworth scale (MAS), and their motions and EMG signals were captured at the same time. Using the upper limb model, the TSRT of each patient was measured and ranked. The estimated muscle activation profiles have a high correlation (0.707) to the EMG signal profiles. The null hypothesis that the rankings of the severity using the model and the MAS assessment have no correlation has been tested, and was rejected convincingly ( ). These findings suggest that the model has the potential to complement the existing practices by providing an alternative evaluation method.

Measurement of post-stroke spasticity based on tonic stretch reflex threshold: implications of stretch velocity for clinical practice

Purpose: The most commonly used method for the clinical evaluation of spasticity is the modified Ashworth scale (MAS), which is subjective. In this regard, the spasticity assessment through the tonic stretch reflex threshold, which is an objective method, has emerged as an alternative. It is based on the value of the dynamic stretch reflex threshold, which is measured at different stretch velocities. However, by this definition, it is not possible to define the speed at which passive stretches should be performed during evaluation.Objective: This study aimed to evaluate whether the speed-variation sequence used to acquire the dynamic stretch reflex threshold influences the tonic stretch reflex threshold (TSRT) and, consequently, the estimation of spasticity by this method.Methods: Three forms of stretching-variation speed were adopted, i.e., increasing, decreasing, and randomised. The study was performed using 10 post-stroke patients.Results and Conclusions: The results showed that the stretch protocols were not all the same and that the method of increasing was most suitable for performing manual passive stretches to evaluate TSRT in these patients. Another analysis was the correlation between MAS and tonic stretch reflex threshold; a weak correlation was observed between the increasing and decreasing methods, and moderate correlation was observed between the random methods.Implications for RehabilitationWe demonstrated that the protocol of execution of passive stretches influences in the measurement of the tonic stretch reflex threshold (TSRT). We recommend the method of increasing velocity for performing manual passive stretches.We also build software with a reliable biological data acquisition system, which makes acquisition and processing of data in real time. In this way, the TSRT is a promising quantitative measure to assess post-stroke spasticity, calculated automatically.We also we provided the use of portable instruments to facilitate the assessment of spasticity in clinical practice.

Spasticity may obscure motor learning ability after stroke.

Previous motor learning studies based on adapting movements of the hemiparetic arm in stroke subjects have not accounted for spasticity occurring in specific joint ranges (spasticity zones), resulting in equivocal conclusions about learning capacity. We compared the ability of participants with stroke to rapidly adapt elbow extension movements to changing external load conditions outside and inside spasticity zones. Participants with stroke ( n = 12, aged 57.8 ± 9.6 yr) and healthy age-matched controls ( n = 8, 63.5 ± 9.1 yr) made rapid 40°-50° horizontal elbow extension movements from an initial (3°) to a final (6°) target. Sixteen blocks (6-10 trials/block) consisting of alternating loaded (30% maximal voluntary contraction) and nonloaded trials were made in one (controls) or two sessions (stroke; 1 wk apart). For the stroke group, the tonic stretch reflex threshold angle at which elbow flexors began to be activated during passive elbow extension was used to identify the beginning of the spasticity zone. The task was repeated in joint ranges that did or did not include the spasticity zone. Error correction strategies were identified by the angular positions before correction and compared between groups and sessions. Changes in load condition from no load to load and vice versa resulted in undershoot and overshoot errors, respectively. Stroke subjects corrected errors in 1-4 trials compared with 1-2 trials in controls. When movements did not include the spasticity zone, there was an immediate decrease in the number of trials needed to restore accuracy, suggesting that the capacity to learn may be preserved after stroke but masked by the presence of spasticity. NEW & NOTEWORTHY When arm movements were made outside, instead of inside, the range affected by spasticity, there was an immediate decrease in the number of trials needed to restore accuracy in response to a change in the external load. This suggests that motor learning processes may be preserved in patients with stroke but masked by the presence of spasticity in specific joint ranges. This has important implications for designing rehabilitation interventions predicated on motor learning principles.

Spasticity Measurement Based on Tonic Stretch Reflex Threshold in Children with Cerebral Palsy Using the PediAnklebot.

Nowadays, objective measures are becoming prominent in spasticity assessment, to overcome limitations of clinical scales. Among others, Tonic Stretch Reflex Threshold (TSRT) showed promising results. Previous studies demonstrated the validity and reliability of TSRT in spasticity assessment at elbow and ankle joints in adults. Purposes of the present study were to assess: (i) the feasibility of measuring TSRT to evaluate spasticity at the ankle joint in children with Cerebral Palsy (CP), and (ii) the correlation between objective measures and clinical scores. A mechatronic device, the pediAnklebot, was used to impose 50 passive stretches to the ankle of 10 children with CP and 3 healthy children, to elicit muscles response at 5 different velocities. Surface electromyography, angles, and angular velocities were recorded to compute dynamic stretch reflex threshold; TSRT was computed with a linear regression through angles and angular velocities. TSRTs for the most affected side of children with CP resulted into the biomechanical range (95.7 ± 12.9° and 86.7 ± 17.4° for Medial and Lateral Gastrocnemius, and 75.9 ± 12.5° for Tibialis Anterior). In three patients, the stretch reflex was not elicited in the less affected side. TSRTs were outside the biomechanical range in healthy children. However, no correlation was found between clinical scores and TSRT values. Here, we demonstrated the capability of TSRT to discriminate between spastic and non-spastic muscles, while no significant outcomes were found for the dorsiflexor muscle.

An improved approach for measuring the tonic stretch reflex response of spastic muscles

We propose a new method for detecting the onset of the stretch reflex response for assessment of spasticity based on the Tonic Stretch Reflex Threshold (TSRT). Our strategy relies on a three-stage approach to detect the onset of the reflex EMG activity: (i) Reduction of baseline activity by means of Empirical Mode Decomposition; (ii) Extraction of the complex envelope of the EMG signal by means of Hilbert Transform (HT) and; iii) A double threshold decision rule. Simulated and real EMG data were used to evaluate and compare our method (TSRT-EHD) against three other popular methods described in the literature to assess TSRT (‘Kim’, ‘Ferreira’ and ‘Blanchette’). Four different groups of signals containing simulated evoked stretch reflex EMG activities were generated: groups A and B without spontaneous EMG activity at rest and signal-to-noise ratio (SNR) of 10dB and 20dB respectively; groups C and D with spontaneous EMG activity at rest, as observed frequently in spastic muscles, and SNR of 10dB and 20dB respectively. The results with simulated data showed a significantly higher accuracy of TSRT-EHD for detecting the onset of the reflex EMG activity in groups C and D when compared to the other methods. Analyses using real data from five post stroke spastic subjects demonstrated that the TSRTs generated by each method were dramatically different from one another. Nevertheless, only TSRT-EHD provided valid measures across all subjects.

Effect of myofeedback on the threshold of the stretch reflex response of post-stroke spastic patients

Purpose We propose a visual myofeedback protocol as a coadjuvant therapy to standard rehabilitation of post-stroke spastic patients. We also argue in favor of the tonic stretch reflex threshold (TSRT) as a more sensitive unit for quantifying subtle changes in the spastic response that may be induced by biofeedback training. Method Sixteen volunteers with ischaemic stroke were divided into an experimental group (EG), subjected to myofeedback training in parallel with conventional physical therapy and a control group (CG), receiving only conventional physical therapy. The EG subjects underwent a six-week myofeedback training, with two sessions weekly. Both groups followed the same treatment schedule for physical therapy. The TSRTs of the volunteers’ spastic muscles were assessed before the beginning of the experimental protocol and 3 weeks after it ended. Results Both groups showed some degree of improvement in the level of spasticity when the final TSRT values were compared to the initial values. However, the percentage of improvement (after–before) of the experimental group (38.59%) was significantly higher than that in the control group (18.58%). Conclusion The myofeedback training provided a significant contribution to conventional treatment, allowing for a better improvement of the spastic condition.Implications for rehabilitationBiofeedback is an effective means of improving motor control of post-stroke spastic patients.The Tonic Stretch Reflex Threshold is a more sensitive quantitative measure to assess upper-limb post-stroke spasticity.Spastic patients who participate in myofeedback training along with physical therapy can improve faster then those who participate only in traditional physical therapy rehabilitation protocols.

Tonic Stretch Reflex Threshold as a Measure of Ankle Plantar-Flexor Spasticity After Stroke.

Commonly used spasticity scales assess the resistance felt by the evaluator during passive stretching. These scales, however, have questionable validity and reliability. The tonic stretch reflex threshold (TSRT), or the angle at which motoneuronal recruitment begins in the resting state, is a promising alternative for spasticity measurement. Previous studies showed that spasticity and voluntary motor deficits after stroke may be characterized by a limitation in the ability of the central nervous system to regulate the range of the TSRT. The study objective was to assess interevaluator reliability for TSRT plantar-flexor spasticity measurement. This was an interevaluator reliability study. In 28 people after stroke, plantar-flexor spasticity was evaluated twice on the same day. Plantar-flexor muscles were stretched 20 times at different velocities assigned by a portable device. Plantar-flexor electromyographic signals and ankle angles were used to determine dynamic velocity-dependent thresholds. The TSRT was computed by extrapolating a regression line through dynamic velocity-dependent thresholds to the angular axis. Mean TSRTs in evaluations 1 and 2 were 66.0 degrees (SD=13.1°) and 65.8 degrees (SD=14.1°), respectively, with no significant difference between them. The intraclass correlation coefficient (2,1) was .851 (95% confidence interval=.703, .928). The notion of dynamic stretch reflex threshold does not exclude the possibility that spasticity is dependent on acceleration, as well as on velocity; future work will study both possibilities. Tonic stretch reflex threshold interevaluator reliability for evaluating stroke-related plantar-flexor spasticity was very good. The TSRT is a reliable measure of spasticity. More information may be gained by combining the TSRT measurement with a measure of velocity-dependent resistance.