Portable measurement system for the objective evaluation of the spasticity of hemiplegic patients based on the tonic stretch reflex threshold

Tonic stretch reflex threshold as a measure of disordered motor control and spasticity - A critical review

The Tonic Stretch Reflex Threshold (TSRT) is the joint angle or muscle length (λ) at which muscle activation begins. In spasticity, the TSRT abnormally lies inside the biomechanical joint range. It is determined by measuring the Dynamic Stretch Reflex Thresholds (DSRTs) by stretching the resting muscle at different velocities. The metric μ, characterizes the velocity-sensitivity of the DSRTs and is expressed as the time required to lengthen the passive muscles from DSRT to TSRT at the respective stretch velocity. The original formulation of the TSRT, DSRT and μ is summarized. Then, a thorough search of literature prior to December 2023 was conducted that returned 25 papers that have used the technique. Eleven of these papers come from the research group of the authors, including 1 reporting on treatment effects. Of the remaining 14 papers, 11 report variations of the methodology with different populations and 3 report on the effects of an intervention. The review discusses how specific modifications to data collection and analysis procedures have either improved the methodology or, in some cases, led to uninterpretable results. The influence of modifications to the data collection and analysis procedures is discussed.

Identification of Neural and Non-Neural Origins of Joint Hyper-Resistance Based on a Novel Neuromechanical Model

Joint hyper-resistance is a common symptom in neurological disorders. It has both neural and non-neural origins, but it has been challenging to distinguish different origins based on clinical tests alone. Combining instrumented tests with parameter identification based on a neuromechanical model may allow us to dissociate the different origins of joint hyper-resistance in individual patients. However, this requires that the model captures the underlying mechanisms. Here, we propose a neuromechanical model that, in contrast to previously proposed models, accounts for muscle short-range stiffness (SRS) and its interaction with muscle tone and reflex activity. We collected knee angle trajectories during the pendulum test in 15 children with cerebral palsy (CP) and 5 typically developing children. We did the test in two conditions - hold and pre-movement - that have been shown to alter knee movement. We modeled the lower leg as an inverted pendulum actuated by two antagonistic Hill-type muscles extended with SRS. Reflex activity was modeled as delayed, linear feedback from muscle force. We estimated neural and non-neural parameters by optimizing the fit between simulated and measured knee angle trajectories during the hold condition. The model could fit a wide range of knee angle trajectories in the hold condition. The model with personalized parameters predicted the effect of pre-movement demonstrating that the model captured the underlying mechanism and subject-specific deficits. Our model may help with the identification of neural and non-neural origins of joint hyper-resistance and thereby opens perspectives for improved diagnosis and treatment selection in children with spastic CP, but such applications require further studies to establish the method's reliability.

Assessment of Passive Upper Limb Stiffness and Its Function in Post-Stroke Individuals Wearing an Inertial Sensor during the Pendulum Test

This article proposes the evaluation of the passive movement of the affected elbow during the pendulum test in people with stroke and its correlation with the main clinical scales (Modified Ashworth Scale, Motor Activity Log, and Fulg Meyer). An inertial sensor was attached to the forearm of seven subjects, who then passively flexed and extended the elbow. Joint angles and variables that indicate viscoelastic properties, stiffness (K), damping (B), E1 amp, F1 amp, and relaxation indices were collected. The results show that the FM scale is significantly correlated with the natural frequency (p = 0.024). The MAL amount-of-use score correlates with the natural frequency (p = 0.024). The variables E1 amp, F1 amp, RI, and ERI are not correlated with the clinical scales, but they correlate with each other; the variable E1 amp correlates with F1 amp (p = 0.024) and RI (p = 0.024), while F1 amp correlates with ERI (p = 0.024). There was also a correlation between the natural frequency and K (r = 0.96, p = 0.003). Non-linear results were found for the properties of the elbow joint during the pendulum test, which may be due to the presence of neural and non-neural factors. These results may serve as a reference for future studies if alternative scales do not provide an accurate reflection.

The Effects of the Biceps Brachii and Brachioradialis on Elbow Flexor Muscle Strength and Spasticity in Stroke Patients

Objective

Muscle weakness and spasticity are common consequences of stroke, leading to a decrease in physical activity. The effective implementation of precision rehabilitation requires detailed rehabilitation evaluation. We aimed to analyze the surface electromyography (sEMG) signal features of elbow flexor muscle (biceps brachii and brachioradialis) spasticity in maximum voluntary isometric contraction (MVIC) and fast passive extension (FPE) in stroke patients and to explore the main muscle groups that affect the active movement and spasticity of the elbow flexor muscles to provide an objective reference for optimizing stroke rehabilitation.

Methods

Fifteen patients with elbow flexor spasticity after stroke were enrolled in this study. sEMG signals of the paretic and nonparetic elbow flexor muscles (biceps and brachioradialis) were detected during MVIC and FPE, and root mean square (RMS) values were calculated. The RMS values (mean and peak) of the biceps and brachioradialis were compared between the paretic and nonparetic sides. Additionally, the correlation between the manual muscle test (MMT) score and the RMS values (mean and peak) of the paretic elbow flexors during MVIC was analyzed, and the correlation between the modified Ashworth scale (MAS) score and the RMS values (mean and peak) of the paretic elbow flexors during FPE was analyzed.

Results

During MVIC exercise, the RMS values (mean and peak) of the biceps and brachioradialis on the paretic side were significantly lower than those on the nonparetic side (p < 0.01), and the RMS values (mean and peak) of the bilateral biceps were significantly higher than those of the brachioradialis (p < 0.01). The MMT score was positively correlated with the mean and peak RMS values of the paretic biceps and brachioradialis (r = 0.89, r = 0.91, r = 0.82, r = 0.85; p < 0.001). During FPE exercise, the RMS values (mean and peak) of the biceps and brachioradialis on the paretic side were significantly higher than those on the nonparetic side (p < 0.01), and the RMS values (mean and peak) of the brachioradialis on the paretic side were significantly higher than those of the biceps (p < 0.01). TheMAS score was positively correlated with the mean RMS of the paretic biceps and brachioradialis (r = 0.62, p = 0.021; r = 0.74, p = 0.004), and the MAS score was positively correlated with the peak RMS of the paretic brachioradialis (r = 0.59, p = 0.029) but had no significant correlation with the peak RMS of the paretic biceps (r = 0.49, p > 0.05).

Conclusions

The results confirm that the biceps is a vital muscle in active elbow flexion and that the brachioradialis plays an important role in elbow flexor spasticity, suggesting that the biceps should be the focus of muscle strength training of the elbow flexors and that the role of the brachioradialis should not be ignored in the treatment of elbow flexor spasticity. This study also confirmed the application value of sEMG in the objective assessment of individual muscle strength and spasticity in stroke patients.

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.

Clinical efficacy of functional electrical stimulation-assisted rehabilitation cycling on the function of lower limbs in patients with stroke

OBJECTIVE

To explore the efficacy of functional electrical stimulation (FES)-assisted rehabilitation cycling on the functional recovery of lower limbs in patients with hemiplegic stroke and the assessment value of surface electromyography (sEMG).

METHODS

A total of 66 patients with stroke accompanied by hemiplegia of the lower limbs were enrolled in the present prospective study and randomly divided into the experimental group and control group, with 33 patients in each group. FES-assisted rehabilitation cycling was applied in the experimental group, while only rehabilitation cycling was performed without setting the stimulation parameters in the control group. sEMG and the Fugl-Meyer assessment (FMA) were carried out, and the modified Barthel index (MBI) of the lower limbs was assessed before treatment and after 4 weeks and 8 weeks of treatment.

RESULTS

There were no significant differences in the evaluation results of sEMG, FMA, and MBI of the lower limbs between the two groups of patients before the treatment (p > 0.05). After 4 weeks of treatment, compared with the control group, there were significant differences in the results of sEMG, FMA, and MBI of the lower limbs in the experimental group (p < 0.05). In the experimental group, the difference in sEMG was statistically significant (p < 0.05). After 8 weeks of treatment, compared with the control group, there were significant differences in the results of sEMG, FMA, and MBI of the lower limbs in the experimental group (p < 0.05). In the experimental group, the differences in the results of sEMG, FMA, and MBI of the lower limbs were statistically significant (p < 0.05). The inter-group comparison of the results of sEMG, FMA and MBI of the lower limbs was statistically significant (p < 0.05) in the control group.

CONCLUSION

FES-assisted rehabilitation cycling might promote the recovery of the motor function of the lower limbs in patients with stroke and improve the sEMG signal of the lower limbs.

Effect of electromyographic biofeedback training on motor function of quadriceps femoris in patients with incomplete spinal cord injury: A randomized controlled trial

BACKGROUND

Electromyographic biofeedback (EMG BF) training is an effective method of promoting motor learning and control in neurorehabilitation, but its effect on quadriceps femoris muscle in individuals with spinal cord injury (SCI) is unknown.

OBJECTIVE

The aim of the study was to investigate the therapeutic effect of EMG BF training on motor function of quadriceps femoris in patients with incomplete SCI.

METHODS

Thirty-three incomplete paraplegic patients with quadriceps femoris strength ranging grade 1 to grade 3 less than 6 months post-injury were enrolled. Control group (n = 16) received conventional physical therapy to enhance quadriceps femoris strength, while intervention group (n = 17) was treated with conventional physical therapy and EMG BF training. All received treatment once a day for 30 days. Surface electromyograph (sEMG), muscle strength and thigh circumference size were assessed to evaluate motor function of quadriceps femoris. Activities of daily living (ADL) was evaluated by Modified Barthel Index (MBI). All the measures evaluated three times in total.

RESULTS

Compared to the control group, intervention group significantly improved on sEMG values and strength of quadriceps femoris (PsEMG < 0.001, Pstrength < 0.05). sEMG values of quadriceps femoris increased earlier than strength of quadriceps femoris in intervention group (Prest = 0.07, Pactive = 0.031). There were no statistical differences in thigh circumference size and ADL scores between groups (Pthigh > 0.05, PADL = 0.423).

CONCLUSIONS

EMG BF training appeared to be a useful tool to enhance motor function of quadriceps femoris in patients with incomplete SCI. sEMG could quantify the changes of single muscle myodynamia precisely before visible or touchable changes occur.

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.

Quantitative Modeling of Spasticity for Clinical Assessment, Treatment and Rehabilitation

Spasticity, a common symptom in patients with upper motor neuron lesions, reduces the ability of a person to freely move their limbs by generating unwanted reflexes. Spasticity can interfere with rehabilitation programs and cause pain, muscle atrophy and musculoskeletal deformities. Despite its prevalence, it is not commonly understood. Widely used clinical scores are neither accurate nor reliable for spasticity assessment and follow up of treatments. Advancement of wearable sensors, signal processing and robotic platforms have enabled new developments and modeling approaches to better quantify spasticity. In this paper, we review quantitative modeling techniques that have been used for evaluating spasticity. These models generate objective measures to assess spasticity and use different approaches, such as purely mechanical modeling, musculoskeletal and neurological modeling, and threshold control-based modeling. We compare their advantages and limitations and discuss the recommendations for future studies. Finally, we discuss the focus on treatment and rehabilitation and the need for further investigation in those directions.

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.

Acupuncture of fascia points to relieve hand spasm after stroke: a study protocol for a multicenter randomized controlled trial

Background

The loss of functional ability of patients after stroke is mostly caused by dysfunction of the upper limbs, especially the hands. Hand functional exercise is the premise of alleviating hand dysfunction, and the relief of hand spasm is the basis of timely and effective hand functional exercise. Previous clinical observation have shown that fascial-point needling can effectively alleviate hand spasm immediately after stroke, but further evidence from large-sample studies is needed. The overall objective of this trial is to further evaluate the clinical efficacy of fascial-point acupuncture on hand spasm after stroke.

Methods/design

This multicenter randomized controlled trial will compare the efficacy of fascial-point acupuncture versus sham acupuncture and routine rehabilitation therapy in stroke patients with hand spasm. Patients will be randomized to undergo either the fascial-point acupuncture, the sham acupuncture or the control (routine rehabilitation therapy). We will recruit 210 stroke inpatients who meet the trial criteria and observe the remission of hand spasm and improvement of limb function after 4 weeks of intervention. The first evaluation indices are the remission of hand spasm and the duration of spasm remission. The second evaluation indices are the hand function of the affected limbs and the activities of daily living. When the accumulative total number of cases included reaches 120, a mid-term analysis will be conducted to determine any evidence that experimental intervention does have an advantage.

Discussion

Our aim is to evaluate the efficacy of fascial-point acupuncture in relieving hand spasm after stroke. The results should provide more evidence for the clinical application of this therapy in the future.

Trial registration

Chinese Clinical Trial Registry (ChiCTR), ID: ChiCTR1900022379. Registered on 9 April 2019

Detection of stretch reflex onset based on empirical mode decomposition and modified sample entropy

Background

Accurate spasticity assessment provides an objective evaluation index for the rehabilitation treatment of patients with spasticity, and the key is detecting stretch reflex onset. The surface electromyogram of patients with spasticity is prone to false peaks, and its data length is unstable. These conditions decrease signal differences before and after stretch reflex onset. Therefore, a method for detecting stretch reflex onset based on empirical mode decomposition denoising and modified sample entropy recognition is proposed in this study.

Results

The empirical mode decomposition algorithm is better than the wavelet threshold algorithm in denoising surface electromyogram signal. Without adding Gaussian white noise to the electromyogram signal, the stretch reflex onset recognition rate of the electromyogram signal before and after empirical mode decomposition denoising was increased by 56%. In particular, the recognition rate of stretch reflex onset under the optimal parameter of the modified sample entropy can reach up to 100% and the average recognition rate is 93%.

Conclusions

The empirical mode decomposition algorithm can eliminate the baseline activity of the surface electromyogram signal before stretch reflex onset and effectively remove noise from the signal. The identification of stretch reflex onset using combined empirical mode decomposition and modified sample entropy is better than that via modified sample entropy alone, and stretch reflex onset can be accurately determined.

Spasticity Measurement Based on the HHT Marginal Spectrum Entropy of sEMG Using a Portable System: A Preliminary Study

To facilitate stretch reflex onset (SRO) detection and improve accuracy and reliability of spasticity assessment in clinical settings, a new method to measure dynamic stretch reflex threshold (DSRT) based on Hilbert-Huang transform marginal spectrum entropy (HMSEN) of surface electromyography (sEMG) signals and a portable system to quantify modified Ashworth scale (MAS) for spasticity assessment were developed. The sEMG signals were divided into frames using a fixed-length sliding window, and the HMSEN of each frame was calculated. An adaptive threshold was set to measure the DSRT. The HMSEN based method can quantify muscle activity through time-frequency and nonlinear dynamics analysis, therefore providing deeper insight about the spastic muscle mechanisms during stretching and a reliable SRO detection method. Experimental results revealed that the HMSEN based method could reliably detect the SRO and measure the DSRT (recognition rate: 95.45%), and could achieve improved performance over the time-domain based method. There was a strong correlation ( to -0.900) between the MAS scores and the DSRT index, and the test-retest reliability was high. Additionally, limitations of the MAS were analyzed. This paper indicates that the presented framework can provide a promising tool to measure DSRT and a clinical quantitative approach for spasticity assessment.

A Regression-Based Framework for Quantitative Assessment of Muscle Spasticity Using Combined EMG and Inertial Data From Wearable Sensors

There have always been practical demands for objective and accurate assessment of muscle spasticity beyond its clinical routine. A novel regression-based framework for quantitative assessment of muscle spasticity is proposed in this paper using wearable surface electromyogram (EMG) and inertial sensors combined with a simple examination procedure. Sixteen subjects with elbow flexor or extensor (i.e., biceps brachii muscle or triceps brachii muscle) spasticity and eight healthy subjects were recruited for the study. The EMG and inertial data were recorded from each subject when a series of passive elbow stretches with different stretch velocities were conducted. In the proposed framework, both lambda model and kinematic model were constructed from the recorded data, and biomarkers were extracted respectively from the two models to describe the neurogenic component and biomechanical component of the muscle spasticity, respectively. Subsequently, three evaluation methods using supervised machine learning algorithms including single-/multi-variable linear regression and support vector regression (SVR) were applied to calibrate biomarkers from each single model or combination of two models into evaluation scores. Each of these evaluation scores can be regarded as a prediction of the modified Ashworth scale (MAS) grade for spasticity assessment with the same meaning and clinical interpretation. In order to validate performance of three proposed methods within the framework, a 24-fold leave-one-out cross validation was conducted for all subjects. Both methods with each individual model achieved satisfactory performance, with low mean square error (MSE, 0.14 and 0.47) between the resultant evaluation score and the MAS. By contrast, the method using SVR to fuse biomarkers from both models outperformed other two methods with the lowest MSE at 0.059. The experimental results demonstrated the usability and feasibility of the proposed framework, and it provides an objective, quantitative and convenient solution to spasticity assessment, suitable for clinical, community, and home-based rehabilitation.

The Effect of Functional Stretching Exercises on Neural and Mechanical Properties of the Spastic Medial Gastrocnemius Muscle in Patients with Chronic Stroke: A Randomized Controlled Trial

BACKGROUND

Following spasticity, neural and mechanical changes of the paretic muscle often occur, which affect the muscle function. The aim of this study was to investigate the effect of functional stretching exercises on neural and mechanical properties of the spastic muscle in patients with stroke.

MATERIALS AND METHODS

This study was a single-blinded, randomized control trial. Forty five patients with stroke (experimental group: n = 30; control group: n = 15) participated in this study. Subjects in the experimental group participated in a functional stretching program 3 times a week for 4 weeks. Subjects in both groups were evaluated before the training, at the end of training, and then during a 2-month follow-up. Neural properties, including H-reflex latency and Hmax/Mmax ratio, were acquired. Mechanical properties, including fascicle length, pennation angle, and muscle thickness in the spastic medial gastrocnemius muscle, were evaluated. Repeated measure analysis of variance was used in the analysis.

RESULTS

Time by group interaction in the pennation angle (P = .006), and in muscle thickness (P = .030) was significant. The results indicated that the H-reflex latency (P = .006), pennation angle (P < .001), and muscle thickness (P = .001) were altered after stretching training program and these changes were at significant level after 2-month follow-up.

CONCLUSION

The results indicated that the use of functional stretching exercises can cause significant differences in neural and mechanical properties of spastic medial gastrocnemius muscle in patients with chronic stroke.

Spasticity assessment based on the Hilbert-Huang transform marginal spectrum entropy and the root mean square of surface electromyography signals: a preliminary study

BACKGROUND

Most of the objective and quantitative methods proposed for spasticity measurement are not suitable for clinical application, and methods for surface electromyography (sEMG) signal processing are mainly limited to the time-domain. This study aims to quantify muscle activity in the time-frequency domain, and develop a practical clinical method for the objective and reliable evaluation of the spasticity based on the Hilbert-Huang transform marginal spectrum entropy (HMSEN) and the root mean square (RMS) of sEMG signals.

METHODS

Twenty-six stroke patients with elbow flexor spasticity participated in the study. The subjects were tested at sitting position with the upper limb stretched towards the ground. The HMSEN of the sEMG signals obtained from the biceps brachii was employed to facilitate the stretch reflex onset (SRO) detection. Then, the difference between the RMS of a fixed-length sEMG signal obtained after the SRO and the RMS of a baseline sEMG signal, denoted as the RMS difference (RMSD), was employed to evaluate the spasticity level. The relations between Modified Ashworth Scale (MAS) scores and RMSD were investigated by Ordinal Logistic Regression (OLR). Goodness-of-fit of the OLR was obtained with Hosmer-Lemeshow test.

RESULTS

The HMSEN based method can precisely detect the SRO, and the RMSD scores and the MAS scores were fairly well related (test: χ2 = 8.8060, p = 0.2669; retest: χ2 = 1.9094, p = 0.9647). The prediction accuracies were 85% (test) and 77% (retest) when using RMSD for predicting MAS scores. In addition, the test-retest reliability was high, with an interclass correlation coefficient of 0.914 and a standard error of measurement of 1.137. Bland-Altman plots also indicated a small bias.

CONCLUSIONS

The proposed method is manually operated and easy to use, and the HMSEN based method is robust in detecting SRO in clinical settings. Hence, the method is applicable to clinical practice. The RMSD can assess spasticity in a quantitative way and provide greater resolution of spasticity levels compared to the MAS in clinical settings. These results demonstrate that the proposed method could be clinically more useful for the accurate and reliable assessment of spasticity and may be an alternative clinical measure to the MAS.

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 Rehabilitation We 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.

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 Radial Extracorporeal Shock Wave Therapy on Hemiplegic Shoulder Pain Syndrome

Objective

To investigate the effect of radial extracorporeal shock wave therapy (rESWT) on hemiplegic shoulder pain (HSP) syndrome.

Methods

In this monocentric, randomized, patient-assessor blinded, placebo-controlled trial, patients with HSP were randomly divided into the rESWT (n=17) and control (n=17) groups. Treatment was administered four times a week for 2 weeks. The visual analogue scale (VAS) score and Constant-Murley score (CS) were assessed before and after treatment, and at 2 and 4 weeks. The Modified Ashworth Scale and Fugl-Meyer Assessment scores and range of motion of the shoulder were also assessed.

Results

VAS scores improved post-intervention and at the 2-week and 4-week follow-up in the intervention group (p<0.05). Respective differences in VAS scores between baseline and post-intervention in the intervention and control groups were –1.69±1.90 and –0.45±0.79, respectively (p<0.05), between baseline and 2-week follow-up in the intervention and control groups were –1.60±1.74 and –0.34±0.70, respectively (p<0.05), and between baseline and 4-week follow-up in the intervention and control groups were –1.61±1.73 and –0.33±0.71, respectively (p<0.05). Baseline CS improved from 19.12±11.02 to 20.88±10.37 post-intervention and to 20.41±10.82 at the 2-week follow-up only in the intervention group (p<0.05).

Conclusion

rESWT consisting of eight sessions could be one of the effective and safe modalities for pain management in people with HSP. Further studies are needed to generalize and support these results in patients with HSP and a variety conditions, and to understand the mechanism of rESWT for treating HSP.

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

BACKGROUND

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.

OBJECTIVE

The study objective was to assess interevaluator reliability for TSRT plantar-flexor spasticity measurement.

DESIGN

This was an interevaluator reliability study.

METHODS

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.

RESULTS

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).

LIMITATIONS

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.

CONCLUSIONS

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.

The Intra- and Inter-Rater Reliability of an Instrumented Spasticity Assessment in Children with Cerebral Palsy

AIM

Despite the impact of spasticity, there is a lack of objective, clinically reliable and valid tools for its assessment. This study aims to evaluate the reliability of various performance- and spasticity-related parameters collected with a manually controlled instrumented spasticity assessment in four lower limb muscles in children with cerebral palsy (CP).

METHOD

The lateral gastrocnemius, medial hamstrings, rectus femoris and hip adductors of 12 children with spastic CP (12.8 years, ±4.13 years, bilateral/unilateral involvement n=7/5) were passively stretched in the sagittal plane at incremental velocities. Muscle activity, joint motion, and torque were synchronously recorded using electromyography, inertial sensors, and a force/torque load-cell. Reliability was assessed on three levels: (1) intra- and (2) inter-rater within session, and (3) intra-rater between session.

RESULTS

Parameters were found to be reliable in all three analyses, with 90% containing intra-class correlation coefficients >0.6, and 70% of standard error of measurement values <20% of the mean values. The most reliable analysis was intra-rater within session, followed by intra-rater between session, and then inter-rater within session. The Adds evaluation had a slightly lower level of reliability than that of the other muscles.

CONCLUSIONS

Limited intrinsic/extrinsic errors were introduced by repeated stretch repetitions. The parameters were more reliable when the same rater, rather than different raters performed the evaluation. Standardisation and training should be further improved to reduce extrinsic error when different raters perform the measurement. Errors were also muscle specific, or related to the measurement set-up. They need to be accounted for, in particular when assessing pre-post interventions or longitudinal follow-up. The parameters of the instrumented spasticity assessment demonstrate a wide range of applications for both research and clinical environments in the quantification of spasticity.

A clinical measurement to quantify spasticity in children with cerebral palsy by integration of multidimensional signals

Most clinical tools for measuring spasticity, such as the Modified Ashworth Scale (MAS) and the Modified Tardieu Scale (MTS), are not sufficiently accurate or reliable. This study investigated the clinimetric properties of an instrumented spasticity assessment. Twenty-eight children with spastic cerebral palsy (CP) and 10 typically developing (TD) children were included. Six of the children with CP were retested to evaluate reliability. To quantify spasticity in the gastrocnemius (GAS) and medial hamstrings (MEH), three synchronized signals were collected and integrated: surface electromyography (sEMG); joint-angle characteristics; and torque. Muscles were manually stretched at low velocity (LV) and high velocity (HV). Spasticity parameters were extracted from the change in sEMG and in torque between LV and HV. Reliability was determined with intraclass-correlation coefficients and the standard error of measurement; validity by assessing group differences and correlating spasticity parameters with the MAS and MTS. Reliability was moderately high for both muscles. Spasticity parameters in both muscles were higher in children with CP than in TD children, showed moderate correlation with the MAS for both muscles and good correlation to the MTS for the MEH. Spasticity assessment based on multidimensional signals therefore provides reliable and clinically relevant measures of spasticity. Moreover, the moderate correlations of the MAS and MTS with the objective parameters further stress the added value of the instrumented measurements to detect and investigate spasticity, especially for the GAS.