Differences in kinematic parameters and plantarflexor reflex responses between manual (Ashworth) and isokinetic mobilisations in spasticity assessment

Torque Onset Angle of the Knee Extensor as a Predictor of Walking Related Balance in Stroke Patients

OBJECTIVE

To investigate the relationship between the torque onset angle (TOA) of the isokinetic test for knee extensors in the paretic side and walking related balance in subacute stroke patients.

METHODS

We retrospectively reviewed patients with first-ever strokes who have had at least two isokinetic tests within 6 months of onset. 102 patients satisfied the inclusion criteria. The characteristics of walking related balance were measured with the Berg Balance Scale sub-score (sBBS), Timed Up and Go test (TUG), 10-m Walk Test (10MWT) and Functional Independence Measure sub-score (sFIM). The second isokinetic test values of the knee extensor such as peak torque, peak torque to weight ratio, hamstring/quadriceps ratio, TOA, torque stop angle, torque at 30 degrees, and peak torque asymmetry ratio between paretic and non-paretic limb were also taken into account. Pearson's correlation, simple regression and multiple regression analysis were used to analyze the correlation between TOA and walking related balance.

RESULTS

TOA of the knee extensor of the paretic limb showed significant correlations with BBS, sBBS, TUG, 10MWT, and sFIM according to Pearson's correlation analysis. TOA also had moderate to good correlations with walking related balance parameters in partial correlation analysis. In multiple regression analysis, TOA of the paretic knee extensor was significantly associated with walking related balance parameters.

CONCLUSION

This study demonstrated that TOA of the paretic knee extensor is a predictable parameter of walking related balance. Moreover, we suggest that the ability to recruit muscle quickly is important in walking related balance.

Technology-assisted assessment of spasticity: a systematic review

BACKGROUND

Spasticity is defined as "a motor disorder characterised by a velocity dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks". It is a highly prevalent condition following stroke and other neurological conditions. Clinical assessment of spasticity relies predominantly on manual, non-instrumented, clinical scales. Technology based solutions have been developed in the last decades to offer more specific, sensitive and accurate alternatives but no consensus exists on these different approaches.

METHOD

A systematic review of literature of technology-based methods aiming at the assessment of spasticity was performed. The approaches taken in the studies were classified based on the method used as well as their outcome measures. The psychometric properties and usability of the methods and outcome measures reported were evaluated.

RESULTS

124 studies were included in the analysis. 78 different outcome measures were identified, among which seven were used in more than 10 different studies each. The different methods rely on a wide range of different equipment (from robotic systems to simple goniometers) affecting their cost and usability. Studies equivalently applied to the lower and upper limbs (48% and 52%, respectively). A majority of studies applied to a stroke population (N = 79). More than half the papers did not report thoroughly the psychometric properties of the measures. Analysis identified that only 54 studies used measures specific to spasticity. Repeatability and discriminant validity were found to be of good quality in respectively 25 and 42 studies but were most often not evaluated (N = 95 and N = 78). Clinical validity was commonly assessed only against clinical scales (N = 33). Sensitivity of the measure was assessed in only three studies.

CONCLUSION

The development of a large diversity of assessment approaches appears to be done at the expense of their careful evaluation. Still, among the well validated approaches, the ones based on manual stretching and measuring a muscle activity reaction and the ones leveraging controlled stretches while isolating the stretch-reflex torque component appear as the two promising practical alternatives to clinical scales. These methods should be further evaluated, including on their sensitivity, to fully inform on their potential.

Quantitative measurement of resistance force and subsequent attenuation during passive isokinetic extension of the wrist in patients with mild to moderate spasticity after stroke

Background

Spasticity is evaluated by measuring the increased resistance to passive movement, primarily by manual methods. Few options are available to measure spasticity in the wrist more objectively. Furthermore, no studies have investigated the force attenuation following increased resistance. The aim of this study was to conduct a safe quantitative evaluation of wrist passive extension stiffness in stroke survivors with mild to moderate spastic paresis using a custom motor-controlled device. Furthermore, we wanted to clarify whether the changes in the measured values could quantitatively reflect the spastic state of the flexor muscles involved in the wrist stiffness of the patients.

Materials and methods

Resistance forces were measured in 17 patients during repetitive passive extension of the wrist at velocities of 30, 60, and 90 deg/s. The Modified Ashworth Scale (MAS) in the wrist and finger flexors was also assessed by two skilled therapists and their scores were averaged (i.e., average MAS) for analysis. Of the fluctuation of resistance, we focused on the damping just after the peak forces and used these for our analysis. A repeated measures analysis of variance was conducted to assess velocity-dependence. Correlations between MAS and damping parameters were analyzed using Spearman’s rank correlation.

Results

The damping force and normalized value calculated from damping part showed significant velocity-dependent increases.

There were significant correlations (ρ = 0.53–0.56) between average MAS for wrist and the normalized value of the damping part at 90 deg/s. The correlations became stronger at 60 deg/s and 90 deg/s when the MAS for finger flexors was added to that for wrist flexors (ρ = 0.65–0.68).

Conclusions

This custom-made isokinetic device could quantitatively evaluate spastic changes in the wrist and finger flexors simultaneously by focusing on the damping part, which may reflect the decrease in resistance we perceive when manually assessing wrist spasticity using MAS.

Trial registration UMIN Clinical Trial Registry, as UMIN000030672, on July 4, 2018

Effect of Dry Needling Treatment on Tibial Musculature in Combination with Neurorehabilitation Treatment in Stroke Patients: Randomized Clinical Study

(1) Background: Introducing ultrasound-guided dry needling to neurorehabilitation treatments increases the beneficial effects of therapy. The aim of this study was to compare the effects of including an ultrasound-guided dry needling session in neurorehabilitation treatment on spasticity and gait-balance quality versus neurorehabilitation treatment in subjects who had suffered a stroke. (2) Methods: A single-blind, randomized clinical trial was conducted. Thirty-six patients who had suffered a stroke in the right middle cerebral artery signed the informed consent for participation in the study. Twenty patients finally participated and were randomly assigned to the control group (neurorehabilitation treatment) or experimental group (neurorehabilitation treatment plus ultrasound-guided dry needling). Pre-treatment and post-treatment data were collected on the same day. The experimental group (n = 10) first underwent an ultrasound-guided dry needling intervention on the tibialis anterior and tibialis posterior musculature, followed by neurorehabilitation treatment; the control group (n = 10) underwent their corresponding neurorehabilitation without the invasive technique. Pre-treatment and post-treatment measurements were taken on the same day, assessing the quality of balance-gait using the "Up and Go" test and the degree of spasticity using the Modified Modified Ashworth Scale. (3) Results: The patients who received neurorehabilitation treatment plus ultrasound-guided dry needling showed a greater decrease in spasticity in the tibial musculature after the neurorehabilitation treatment session (p < 0.001), improving balance and gait (p < 0.001). (4) Conclusions: An ultrasound-guided dry needling session combined with neurorehabilitation treatment reduced spasticity and improved balance and gait in stroke patients.

Repetitive peripheral magnetic stimulation for the assessment of wrist spasticity: reliability, validation and correlation with clinical measures

PURPOSE

To determine feasibility and reliability of using repetitive peripheral magnetic stimulation (rPMS) to induce wrist extension movement for the assessment of spasticity in wrist flexors, instead of the passive stretch used in the modified Tardieu scale.

METHODS

Spasticity was assessed with the index of movement restriction (iMR), calculated as the difference between the range of maximum wrist passive movement and the rPMS-induced movement, in 12 healthy subjects (HS), 12 acute stroke patients without spasticity (AS) and 12 chronic stroke patients with spasticity (CS). Test-retest reliability and clinical correlation were assessed in CS patients before Botulinum neurotoxin type A (BoNT-A) treatment.

RESULTS

In comparison to HS and AS patients, CS patients showed statistically significant reduction of rPMS-induced movement amplitude, velocity, and acceleration. The mean iMR was 2.8 (SD = 2.6) in HS, 13.0 (SD = 11.2) in AS and 59.2 (SD = 23.4) in CS. This score significantly reduced to 41.1 (SD = 19.7) in CS after BoNT-A (p < 0.01). Test-retest reliability was very good, with an intraclass correlation coefficient ranging between 0.85 and 0.99 for the variables analysed.

CONCLUSIONS

We have shown good reliability and feasibility of a new method providing quantifiable data for the assessment of spasticity and its response to BoNT-A treatment.IMPLICATIONS FOR REHABILITATIONThe muscle contraction induced by repetitive peripheral magnetic stimulation (rPMS) in paretic muscles of post-stroke patients was used to assess spasticity.The index of movement restriction (iMR), calculated as the difference between the maximum passive range of movement and the rPMS induced movement, improved after botulinum toxin treatment.Measuring spastic reactions to rPMS provides quantifiable and reliable data for follow-up and assessment of therapeutic benefits.

Applying Stretch to Evoke Hyperreflexia in Spasticity Testing: Velocity vs. Acceleration

In neurological diseases, muscles often become hyper-resistant to stretch due to hyperreflexia, an exaggerated stretch reflex response that is considered to primarily depend on the muscle's stretch velocity. However, there is still limited understanding of how different biomechanical triggers applied during clinical tests evoke these reflex responses. We examined the effect of imposing a rotation with increasing velocity vs. increasing acceleration on triceps surae muscle repsonse in children with spastic paresis (SP) and compared the responses to those measured in typically developing (TD) children. A motor-operated ankle manipulator was used to apply different bell-shaped movement profiles, with three levels of maximum velocity (70, 110, and 150°/s) and three levels of maximum acceleration (500, 750, and 1,000°/s²). For each profile and both groups, we evaluated the amount of evoked triceps surae muscle activation. In SP, we evaluated two additional characteristics: the intensity of the response (peak EMG burst) and the time from movement initiation to onset of the EMG burst. As expected, the amount of evoked muscle activation was larger in SP compared to TD (all muscles: p < 0.001) and only sensitive to biomechanical triggers in SP. Further investigation of the responses in SP showed that peak EMG bursts increased in profiles with higher peak velocity (lateral gastrocnemius: p = 0.04), which was emphasized by fair correlations with increased velocity at EMG burst onset (all muscles: r > 0.33-0.36, p ≤ 0.008), but showed no significant effect for acceleration. However, the EMG burst was evoked faster with higher peak acceleration (all muscles p < 0.001) whereas it was delayed in profiles with higher peak velocity (medial gastrocnemius and soleus: p < 0.006). We conclude that while exaggerated response intensity (peak EMG burst) seems linked to stretch velocity, higher accelerations seem to evoke faster responses (time to EMG burst onset) in triceps surae muscles in SP. Understanding and controlling for the distinct effects of different biological triggers, including velocity, acceleration but also length and force of the applied movement, will contribute to the development of more precise clinical measurement tools. This is especially important when aiming to understand the role of hyperreflexia during functional movements where the biomechanical inputs are multiple and changing.

Assessment of elbow spasticity with surface electromyography and mechanomyography based on support vector machine

The Modified Ashworth Scale (MAS) is the gold standard in clinical for grading spasticity. However, its results greatly depend on the physician evaluations and are subjective. In this study, we investigated the feasibility of using support vector machine (SVM) to objectively assess elbow spasticity based on both surface electromyography (sEMG) and mechanomyography (MMG). sEMG signals and tri-axial accelerometer mechanomyography (ACC-MMG) signals were recorded simultaneously on patients' biceps and triceps when they extended or bended elbow passively. 39 post-stroke patients participated in the study, and were divided into four groups regarding MAS level (MAS=0, 1, 1+ or 2). The three types of features, root mean square (RMS), mean power frequency (MPF), and median frequency (MF), were calculated from sEMG and MMG signal recordings. Spearman correlation analysis was used to investigate the relationship between the features and spasticity grades. The results showed that the correlation between MAS and each of the five features (MMG-RMS of the biceps, MMG-RMS of the triceps, the EMG-RMS of the biceps, EMG-RMS of the triceps, EMG-MPF of the triceps) was significant (p<;0.05). The four spasticity grades were identified with SVM, and the classification accuracy of SVM with sEMG, MMG, sEMG-MMG were 70.9%, 83.3%, 91.7%, respectively. Our results suggest that using the SVM-based method with sEMG and MMG to assess elbow spasticity would be suitable for clinical management of spasticity.

Improving the test-retest and inter-rater reliability for stretch reflex measurements using an isokinetic device in stroke patients with mild to moderate elbow spasticity

The conventional tools to measure spasticity exhibited insufficient test-retest or inter-rater reliability. Therefore, the spasticity measurement using an isokinetic device has been proposed to improve these reliabilities of the angle of catch (AoC) measurements; however, this proposal has not been investigated in a standardized manner. In this study, the comparison of the AoC measurement was performed using two modes (isokinetic and manual motion) to investigate whether the standardized isokinetic motion could increase the reliabilities. Motion consistency was calculated using a newly developed index. To analyze the effect of the motion standardization, AoC were estimated using EMG data for both modes, and to compare the measurement reliability, AoC for isokinetic mode was estimated using both EMG and torque data. Although the test-retest reliability for manual motion was excellent, the use of isokinetic motion improved it to the level of extremely excellent. Intraclass correlation coefficient (ICC) for the inter-rater reliability of manual motion was 0.788, which was near the lower limit of the excellent. Isokinetic motion improved it to the ICC of 0.890 and 0.931 based on the EMG and torque, respectively. These improvements in reliabilities reduced the measurement errors, sample size, and need for the same rater in clinical trials.

Motorized versus manual instrumented spasticity assessment in children with cerebral palsy

AIM

We compared the outcomes of manual and motorized instrumented ankle spasticity assessments in children with cerebral palsy (CP).

METHOD

Ten children with spastic CP (three males, seven females; mean age 11y [standard deviation 3y], range 6-14y; Gross Motor Function Classification System levels I-III) were included. During motorized assessments, fast (100°/s) rotations were imposed around the ankle joint by a motor-driven footplate; during manual assessments, rotations of comparable speed were applied by a therapist using a foot orthotic. Angular range of motion, maximum velocity, acceleration, work, and muscle activity (electromyography [EMG]) of the triceps surae and tibialis anterior were compared during passive muscle stretch between motorized and manual assessments. Both movement profiles were also compared to CP gait ankle movement profile.

RESULTS

The imposed movement profile differed between methods, with the motorized assessment reaching higher maximum acceleration. Despite equal maximum velocity, the triceps surae were more often activated in motorized assessments, with low agreement of 44% to 72% (κ≤0) for EMG onset occurrence between methods. The manually applied ankle velocity profile matched more closely with the gait profile.

INTERPRETATION

The differences in acceleration possibly account for the different muscle responses, which may suggest acceleration, rather than velocity-dependency of the stretch reflex. Future prototypes of instrumented spasticity assessments should standardize movement profiles, preferably by developing profiles that mimic functional tasks such as walking.

Quantifying Spasticity With Limited Swinging Cycles Using Pendulum Test Based on Phase Amplitude Coupling

Parameters derived from the goniometer measures in the Pendulum test are insufficient in describing the function of abnormal muscle activity in the spasticity. To explore a quantitative evaluation of muscle activation-movement interaction, we propose a novel index based on phase amplitude coupling (PAC) analysis with the consideration of the relations between movement and surface electromyography (SEMG) activity among 22 hemiplegic stroke patients. To take off trend and noise, we use the empirical mode decomposition (EMD) to obtain intrinsic mode functions (IMFs) of the angular velocity due to its superior decomposing ability in nonlinear oscillations. Shannon entropy based on angular velocity (phase)-envelope of EMG (amplitude) distribution was calculated to demonstrate characteristics of the coupling between SEMG activity and joint movement. We also compare our results with those from traditional methods such as the normalized relaxation index derived from the Pendulum test and the mean root mean square (RMS) of the SEMG signals in the study. Our results show effective discrimination ability between spastic and nonaffected limbs using our method . This study indicates the feasibility of using the novel indices based on the PAC in evaluation the spasticity among the hemiplegic stroke patients with less than three swinging cycles.

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.

Manually controlled instrumented spasticity assessments: a systematic review of psychometric properties

AIM

The first aim of this study was to systematically review and critically assess manually controlled instrumented spasticity assessment methods that combine multidimensional signals. The second aim was to extract a set of quantified parameters that are psychometrically sound to assess spasticity in a clinical setting.

METHOD

Electronic databases were searched to identify studies that assessed spasticity by simultaneously collecting electrophysiological and biomechanical signals during manually controlled passive muscle stretches. Two independent reviewers critically assessed the methodological quality of the psychometric properties of the included studies using the COSMIN guidelines.

RESULTS

Fifteen studies with instrumented spasticity assessments met all inclusion criteria. Parameters that integrated electrophysiological signals with joint movement characteristics were best able to quantify spasticity. There were conflicting results regarding biomechanical-based parameters that quantify the resistance to passive stretch. Few methods have been assessed for all psychometric properties. In particular, further information on absolute reliability and responsiveness for more muscles is needed.

INTERPRETATION

Further research is required to determine the correct parameters for quantifying spasticity based on integration of signals, which especially focuses on distinguishing the neural from non-neural contributions to increased joint torque. These parameters should undergo more rigorous exploration to establish their psychometric properties for use in a clinical environment.

Identification of the neural component of torque during manually-applied spasticity assessments in children with cerebral palsy

Clinical assessment of spasticity is compromised by the difficulty to distinguish neural from non-neural components of increased joint torque. Quantifying the contributions of each of these components is crucial to optimize the selection of anti-spasticity treatments such as botulinum toxin (BTX). The aim of this study was to compare different biomechanical parameters that quantify the neural contribution to ankle joint torque measured during manually-applied passive stretches to the gastrocsoleus in children with spastic cerebral palsy (CP). The gastrocsoleus of 53 children with CP (10.9 ± 3.7 y; females n = 14; bilateral/unilateral involvement n = 28/25; Gross Motor Functional Classification Score I-IV) and 10 age-matched typically developing (TD) children were assessed using a manually-applied, instrumented spasticity assessment. Joint angle characteristics, root mean square electromyography and joint torque were simultaneously recorded during passive stretches at increasing velocities. From the CP cohort, 10 muscles were re-assessed for between-session reliability and 19 muscles were re-assessed 6 weeks post-BTX. A parameter related to mechanical work, containing both neural and non-neural components, was compared to newly developed parameters that were based on the modeling of passive stiffness and viscosity. The difference between modeled and measured response provided a quantification of the neural component. Both types of parameters were reliable (ICC > 0.95) and distinguished TD from spastic muscles (p < 0.001). However, only the newly developed parameters significantly decreased post-BTX (p = 0.012). Identifying the neural and non-neural contributions to increased joint torque allows for the development of individually tailored tone management.

Neuromechanical assessment of lidocaine test block in spastic lower limbs

The objective of this study was to quantify in spastic lower limbs the changes in reflex EMGs and in ankle stiffness after a lidocaine block of the soleus nerve to better understand physiological effects of lidocaine. Twenty patients were prospectively included and assessed before and after lidocaine block of the soleus nerve. We studied clinical and neuromechanical parameters of the triceps surae, including quantification of the maximum Hoffmann’s reflex (Hmax) and tendinous reflex (T) normalized to the maximum direct motor response (Mmax), and passive ankle stiffness assessed by sinusoidal length perturbations. All patients whatever the aetiology of spasticity were improved in clinical parameters of spasticity after the block (62% reduction of the Ashworth score, 85% reduction of stretch reflex scores, increased score on the Physicians’ Rating Scale). All patients presented a reduction of the Hmax–Mmax ratio (mean reduction of 67%) and the T–Mmax ratio (82%). Ankle stiffness was decreased by an average of 23%. Measured stiffness was correlated with the Ashworth score and the T–Mmax ratio. Relatively greater change in the T reflex than in the H reflex suggests that lidocaine block reduces hyperreflexia not only by interfering with generation of afferent volleys in the injected nerve, but also probably by altering generation of the volleys at the level of muscle spindles in the affected spastic muscles, presumably by blocking the transmission along gamma-efferent fibers.

Long-term neuromechanical results of selective tibial neurotomy in patients with spastic equinus foot

BACKGROUND

The neuromechanical consequences of tibial neurotomy have not been extensively studied.

METHODS

Fifteen patients were evaluated before and after selective tibial neurotomy (after 2 months and after 15 months) by means of clinical, neurophysiological [tendon (T) reflexes, Hoffmann (H) reflexes and maximum motor response, Mmax] and mechanical parameters (passive stiffness of plantar flexors at the ankle). The neurotomy concerned the soleus (100 % of cases), gastrocnemius (20 % of cases), posterior tibial (60 % of cases) and flexor digitorum longus (47 % of cases) nerves.

RESULTS

Neurotomy provided more than 90 % improvement of clinical spasticity scores, 20 % improvement of walking scores and the angle of passive dorsiflexion (APDF) of the ankle (mean angle: 7°), temporary reduction of the soleus Mmax (18 % at 2 months with return to the preoperative value at 15 months), and lasting reduction of the soleus Hmax/Mmax (68 % at 2 months, 78 % at 15 months) and T/Mmax (84 % at 2 months, 80 % at 15 months). M and H responses of the gastrocnemius (whether or not they were included in the neurotomy) were not modified, while T/Mmax decreased to the same degree as for soleus. Passive stiffness was lastingly decreased from 64.0 Nm/rad to 49.0 Nm/rad (2 months) and 49.5 Nm/rad (15 months).

CONCLUSION

Selective tibial neurotomy of the soleus nerve induces long-term reduction of reflex hyperexcitability and passive stiffness of plantar flexors in spastic patients, with no lasting impairment of motor efferents. In parallel, it modifies the tendon reflexes of synergistic muscles (gastrocnemius) not concerned by the neurotomy.

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.

Comprehensive quantification of the spastic catch in children with cerebral palsy

In clinical settings, the spastic catch is judged subjectively. This study assessed the psychometric properties of objective parameters that define and quantify the severity of the spastic catch in children with cerebral palsy (CP). A convenience sample of children with spastic CP (N=46; age range: 4-16 years) underwent objective spasticity assessments. High velocity, passive stretches were applied to the gastrocnemius (GAS) and medial hamstrings (MEH). Muscle activity was measured with surface electromyography (sEMG), joint angle characteristics using inertial sensors and reactive torque using a force sensor. To test reliability, a group of 12 children were retested after an average of 13 ± 9 days. The angle of spastic catch (AOC) was estimated by three biomechanical definitions: joint angle at (1) maximum angular deceleration; (2) maximum change in torque; and (3) minimum power. Each definition was checked for reliability and validity. Construct and clinical validity were evaluated by correlating each AOC definition to the averaged root mean square envelope of EMG (RMS-EMG) and the Modified Tardieu Scale (MTS). Severity categories were created based on selected parameters to establish face validity. All definitions showed moderate to high reliability. Significant correlations were found between AOC3 and the MTS of both muscles and the RMS-EMG of the MEH, though coefficients were only weak. AOC3 further distinguished between mild, moderate and severe catches. Objective parameters can define and quantify the severity of the spastic catch in children with CP. However, a comprehensive understanding requires the integration of both biomechanical and RMS-EMG data.

Short-latency stretch reflexes do not contribute to premature calf muscle activity during the stance phase of gait in spastic patients

OBJECTIVE

To identify whether a relationship exists between stretch and activity of the calf muscles during the stance phase of gait in patients with upper motor neuron syndrome (UMNS), while taking into account the physiologic phase shift between these entities.

DESIGN

Survey.

SETTING

Ambulatory care and general community.

PARTICIPANTS

Patients with UMNS (n=15; 9 patients with stroke, 6 patients with hereditary spastic paraparesis) with premature calf muscle activity during the stance phase of gait and healthy controls (n=13).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Timing of optimal association (phase shift) between the lengthening velocity of the gastrocnemius muscle and its electromyographic activity as revealed by cross-correlation analyses.

RESULTS

Although premature calf muscle activity was evident in the patient groups, the phase shift between calf muscle stretch and its activity did not correspond with the monosynaptic stretch reflex latency (40- to 80-ms time window). However, there was a main effect of group on the phase shifts (F(3,33)=3.23, P=.035). Post hoc analysis revealed that in the paretic leg of stroke patients, the electromyographic activity preceded the lengthening velocity by 9 ± 54ms, whereas in the control group, the electromyographic activity followed the pattern of the muscle-lengthening velocity with a delay of 61 ± 54ms (P=.029).

CONCLUSIONS

Short-latency stretch reflexes do not significantly contribute to premature calf muscle activity in the stance phase of (spastic) gait. This notion questions the validity of the clinical assessment of hyperreflexia and clonus of the calf as a predictor of calf muscle spasticity during gait.

The relation between neuromechanical parameters and Ashworth score in stroke patients

Background

Quantifying increased joint resistance into its contributing factors i.e. stiffness and viscosity ("hypertonia") and stretch reflexes ("hyperreflexia") is important in stroke rehabilitation. Existing clinical tests, such as the Ashworth Score, do not permit discrimination between underlying tissue and reflexive (neural) properties. We propose an instrumented identification paradigm for early and tailor made interventions.

Methods

Ramp-and-Hold ankle dorsiflexion rotations of various durations were imposed using a manipulator. A one second rotation over the Range of Motion similar to the Ashworth condition was included. Tissue stiffness and viscosity and reflexive torque were estimated using a nonlinear model and compared to the Ashworth Score of nineteen stroke patients and seven controls.

Results

Ankle viscosity moderately increased, stiffness was indifferent and reflexive torque decreased with movement duration. Compared to controls, patients with an Ashworth Score of 1 and 2+ were significantly stiffer and had higher viscosity and patients with an Ashworth Score of 2+ showed higher reflexive torque. For the one second movement, stiffness correlated to Ashworth Score (r² = 0.51, F = 32.7, p < 0.001) with minor uncorrelated reflexive torque. Reflexive torque correlated to Ashworth Score at shorter movement durations (r² = 0.25, F = 11, p = 0.002).

Conclusion

Stroke patients were distinguished from controls by tissue stiffness and viscosity and to a lesser extent by reflexive torque from the soleus muscle. These parameters were also sensitive to discriminate patients, clinically graded by the Ashworth Score. Movement duration affected viscosity and reflexive torque which are clinically relevant parameters. Full evaluation of pathological joint resistance therefore requires instrumented tests at various movement conditions.

Roles of reflex activity and co-contraction during assessments of spasticity of the knee flexor and knee extensor muscles in children with cerebral palsy and different functional levels

BACKGROUND AND PURPOSE

Spasticity is a common impairment in children with cerebral palsy (CP). The purpose of this study was to examine differences in passive resistive torque, reflex activity, coactivation, and reciprocal facilitation during assessments of the spasticity of knee flexor and knee extensor muscles in children with CP and different levels of functional ability.

SUBJECTS

Study participants were 20 children with CP and 10 children with typical development (TD). The 20 children with CP were equally divided into 2 groups: 10 children classified in Gross Motor Function Classification Scale (GMFCS) level I and 10 children classified in GMFCS level III.

METHODS

One set of 10 passive movements between 25 and 90 degrees of knee flexion and one set of 10 passive movements between 90 and 25 degrees of knee flexion were completed with an isokinetic dynamometer at 15 degrees /s, 90 degrees /s, and 180 degrees /s and concurrent surface electromyography of the vastus lateralis and medial hamstring muscles.

RESULTS

Children in the GMFCS level III group demonstrated significantly more peak knee flexor torque with passive movements at 180 degrees /s than children with TD. Children in the GMFCS level I and level III groups demonstrated significantly more repetitions with medial hamstring muscle activity, vastus lateralis muscle activity, and co-contraction than children with TD during the assessment of knee flexor spasticity at a velocity of 180 degrees /s.

DISCUSSION AND CONCLUSION

Children with CP and more impaired functional mobility may demonstrate more knee flexor spasticity and reflex activity, as measured by isokinetic dynamometry, than children with TD. However, the finding of increased reflex activity with no increase in torque in the GMFCS I group in a comparison with the TD group suggests that reflex activity may play a less prominent role in spasticity.

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.

Examination of spasticity of the knee flexors and knee extensors using isokinetic dynamometry with electromyography and clinical scales in children with spinal cord injury

BACKGROUND/OBJECTIVE

To examine the role of reflex activity in spasticity and the relationship between peak passive torque, Ashworth Scale (AS), and Spasm Frequency Scale (SFS) of the knee flexors and extensors during the measurement of spasticity using an isokinetic dynamometer in children with spinal cord injury (SCI).

METHODS

Eighteen children with chronic SCI and 10 children of typical development (TD) participated. One set of 10 passive movements was completed using an isokinetic dynamometer at 15, 90, and 180 degrees per second (deg/s) while surface electromyographic data were collected from the vastus lateralis (VL) and medial hamstrings (MH). Spasticity was clinically assessed using the AS and SFS.

RESULTS

There were no significant differences in peak passive torque of the knee flexors and extensors at any velocity for children with SCI compared to children with TD. Children with TD demonstrated significantly more reflex activity of the MH during the assessment of knee flexor spasticity at all movement velocities than did children with SCI. Children with TD demonstrated significantly more reflex activity of the VL during the assessment of knee-extensor spasticity with movements at 180 deg/s. The relationship between peak passive torque, AS, and SFS was significant during movements at a velocity of 90 deg/s only.

CONCLUSIONS

The role of increased reflexes in spasticity needs further examination. Isokinetic dynamometry may be measuring a different aspect of spasticity than the AS and SFS do in children with SCI.

Quantitative assessment of the velocity-dependent increase in resistance to passive stretch in spastic plantarflexors

BACKGROUND

Although numerous studies revealed that isokinetic dynamometers were valuable tools for assessing spastic hypertonia, no standard methodology using such devices is currently widespread in clinical setting. The aim of this study was to standardize a protocol to assess spastic hypertonia in the triceps surae.

METHODS

The passive resistance during dorsiflexions imposed from 10 to 300 degrees /s with an isokinetic dynamometer was measured at the neutral position in 15 patients with spastic hypertonia and 12 healthy subjects. The normalized passive resistance was obtained by expressing raw passive resistance as a percent of the values measured at the lowest velocity (10 degrees /s). EMG signals from plantar and dorsiflexors were also recorded.

FINDINGS

While no significant difference between spastic patients and control subjects was observed in raw passive resistance values, the difference was significant for each tested velocity when considering the normalized values. Furthermore, the Ashworth score was significantly correlated with the normalized passive resistance for each velocity whereas no correlation was observed with the raw passive resistance. For the patients, except at the highest velocity, the normalized passive resistance was not affected by the fact that reflex responses in the triceps surae were elicited or not.

INTERPRETATION

The normalized passive resistance, expressed with respect to the initial one, i.e., measured at very low velocity, seems a very effective parameter to quantify the velocity-dependent increase in resistance to passive stretch in spastic plantarflexors. However, while the simplicity of the isokinetic tests and the reduced time of data treatment seems to support the clinical use of this methodology, further investigations are required to definitely standardize the protocol.