Reflex Torque Response to Movement of the Spastic Elbow: Theoretical Analyses and Implications for Quantification of Spasticity (original) (raw)
Related papers
Annals of Biomedical Engineering, 2000
Static and dynamic components of the stretch reflex were studied in elbow flexors of 13 hemiparetic brain-injured individuals. Constant-velocity joint rotations were applied to the elbow, and the resulting stretch reflex torque and electromyographic responses were recorded in the biceps brachii and brachioradialis muscles. Ten elbow extension velocities between 6 and 150 deg s Ϫ1 were applied in random order. The resulting reflex torque response was plotted as a function of elbow angle and fitted with a mathematical model designed to depict elbow flexor activation. We found that four of the six model parameters were essentially independent of test velocity. Conversely, 73% ͑19/26͒ of cases involving the other two model parameters were dependent on velocity of joint extension ͑pϽ0.05͒. We conclude from these results that four of the model parameters reflect the static reflex response while the two remaining velocity-dependent parameters reflect the dynamic reflex response. To describe overall velocity dependence of stretch reflexes in spastic elbow muscles, the two dynamic reflex parameters were fitted to a fractional exponential function of velocity, similar to a model previously used to describe spindle firing rate in the cat hindlimb. We found that the mean velocity exponent of the dynamic reflex parameters was 0.24 ϩ 0.17 ͑s.d.͒ ͑N ϭ 13͒, a value similar to that for muscle spindle velocity sensitivity in reduced animal preparations. We conclude that both static and dynamic reflex sensitivities can be measured by examining different aspects of the torque/angle relation associated with the reflex response to a large-amplitude ramp stretch of the elbow.
Measurement of Elbow Spasticity in Stroke Patients Using a Manual Spasticity Evaluator
2006
Spasticity is often seen in patients with central nervous system lesion, such as stroke. It hinders functional movement and may induce pain. Current measures for assessing spasticity are either quantitative but not convenient to use or convenient to use in clinics but lack of objective quantification. We developed a manual spasticity evaluator (MSE) to evaluate the spasticity quantitatively and potentially suitable for a clinical setting. Joint position and torque from 10 subjects with right hemiplegia and 9 healthy subjects were measured conveniently and used to evaluate spasticity and determine the catch angle. EMG signal was obtained from the biceps brachii and triceps brachii to corroborate the mechanical measurement of the MSE. Results showed that the MSE provided a convenient and quantitative measurement of spasticity, including presence of catch angle, increase in joint stiffness, and decrease in joint range of motion in the stroke patients, as compared with healthy subjects. EMG signals corroborated MSE assessment of the catch angle.
Journal of Electromyography and Kinesiology, 2000
Spasticity after a stroke is usually assessed in a score form by subjectively determining the resistance of a joint to an externally imposed passive movement. This work presents a spasticity measurement system for on-line quantifying the stretch reflex of paretic limbs. Four different constant stretch velocities in a ramp-and-hold mode are used to elicit the stretch reflex of the elbow joint in spastic subjects. The subjects are tested at supine position with the upper limb stretched towards the ground, in contrast with the horizontally stretched movement used in other studies. By subtracting the baseline torque, reflex torque measured at a selected low stretch velocity of 5 deg/sec, the influence of gravity torque and inertial in vertical stretching mode can be minimized. The averaged speed-dependent reflex torque (ASRT), defined as the measured torque deviated from the baseline torque, is used for quantifying the spastic hypertonia. Four subjects having incurred cerebrovascular accident (CVA) are recruited for time-course study in which the measurements are taken at 72 hours, one week, one month, three months, and six months after onset of stroke. During the development of spasticity, the changes of ASRT and velocity sensitivity of ASRT of the involved and the intact elbow joints are discussed.
Correlation of Resting Elbow Angle with Spasticity in Chronic Stroke Survivors
Frontiers in Neurology, 2015
Objective: To evaluate whether resting joint angle is indicative of severity of spasticity of the elbow flexors in chronic stroke survivors. Methods: Seventeen hemiparetic stroke subjects (male: n = 13; female: n = 4; age: 37-89 years; 11 right and 6 left hemiplegia; averaged 54.8 months after stroke, ranging 12-107 months) participated in the study. The number of subjects with modified Ashworth scale score (MAS) = 0, 1, 1+, 2, and 3 was 3, 3, 5, 3, and 3, respectively. In a single experimental session, resting elbow joint angle, MAS, and Tardieu scale score (Tardieu R1) were measured. A customized motorized stretching device was used to stretch elbow flexors at 5, 50, and 100°/s, respectively. Biomechanical responses (peak reflex torque and reflex stiffness) of elbow flexors were quantified. Correlation analyses between clinical and biomechanical assessments were performed. Results: Resting elbow joint angle showed a strong positive correlation with Tardieu R1 (r = 0.77, p < 0.01) and a very strong negative correlation with MAS (r = −0.89, p < 0.01). The resting angle also had strong correlations with biomechanical measures (r = −0.63 to −0.76, p < 0.01). Conclusion: Our study provides experimental evidence for anecdotal observation that the resting elbow joint angle correlates with severity of spasticity in chronic stroke. Resting angle observation for spasticity assessment can and will be an easy, yet a valid way of spasticity estimation in clinical settings, particularly for small muscles or muscles which are not easily measurable by common clinical methods.
Clinical Neurophysiology, 2018
Objectives: Deficits in regulation of tonic stretch reflex thresholds (TSRTs) after stroke occur in elbow flexors and extensors leading to spasticity in specific joint ranges. Threshold deregulation may also be responsible for other deficits such as abnormal activation of passively shortening muscles. Goals were to characterize activation of shortening elbow extensors during passive elbow flexor stretch in individuals with stroke, and identify its relationship to upper-limb motor impairment. Methods: Thirty-three participants with unilateral stroke participated. TSRTs in elbow flexors were measured by stretching passive elbow flexors at different velocities. EMG responses were recorded from stretched agonist (biceps) and shortened antagonist (triceps) muscles. Results: Triceps activation during passive biceps stretch occurred in all but 4 participants simultaneously with, before or after biceps activation onset. Biceps and triceps activation onsets and durations decreased with stretch velocity. Biceps TSRT and triceps activation magnitude did not correlate with sensorimotor impairment but greater stroke chronicity tended to be related to higher biceps TSRTs (r=0.406, p=0.041). Conclusions: Stroke may result in both limitations in reciprocal inhibition and excessive agonistantagonist co-activation, likely from deficits in TSRT modulation in both muscle groups. Significance: Since both reciprocal inhibition and co-activation are fundamental to normal motor control, their cooperative action should be considered in designing interventions to increase the ranges of regulation of TSRTs in flexors and extensors to enhance upper limb functional recovery. Highlights Triceps activation during biceps stretch occurred in post-stroke patients with spasticity. Triceps activation timing and duration were not tightly coupled to stretched biceps activation. Presence of spasticity and abnormal co-activation at rest may be related to stroke-related deficits in regulation of tonic stretch reflex thresholds in each muscle.
2020
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.
Stretch reflex dynamics in spastic elbow flexor muscles
Annals of Neurology, 1989
Previous studies of stretch reflexes in patients with spastic hypertonia have emphasized the dynamic character of stretch reflex output. In contrast, our own studies of stretch reflex dynamics in spastic elbow flexor muscles of 14 hemiparetic human subjects have shown that stretch-evoked torque displays a relatively weak dependence on stretch velocity, and there is generally no preferential enhancement of dynamic as compared with static reflex output. Moreover, stretch reflex dynamics are broadly similar in voluntarily activated spastic and normal elbow flexor muscles. These findings support our hypothesis that spastic hypertonia results primarily from a decrease in stretch reflex threshold. The strong velocity dependence of stretch-evoked electromyographic activity in initially inactive spastic muscles could be due to a decrease in reflex threshold with increasing stretch velocity, rather than an abnormal velocity-dependent increase in stretch reflex responsiveness. Powers RK, Campbell DL, Rymer WZ. Stretch reflex dynamics in spastic elbow flexor muscles. Ann Neurol 1989;25:32-42 ~~ ~~~~ ~~~~~~ From the Sensory-Motor Performance Program of the Rehabilitation Institute of Chicago, Chicago, IL; and the
Validation of a New Biomechanical Model to Measure Muscle Tone in Spastic Muscles
Neurorehabilitation and Neural Repair, 2011
Background. There is no easy and reliable method to measure spasticity, although it is a common and important symptom after a brain injury. Objective. The aim of this study was to develop and validate a new method to measure spasticity that can be easily used in clinical practice. Methods. A biomechanical model was created to estimate the components of the force resisting passive hand extension, namely ( a) inertia (IC), ( b) elasticity (EC), ( c) viscosity (VC), and ( d) neural components (NC). The model was validated in chronic stroke patients with varying degree of hand spasticity. Electromyography (EMG) was recorded to measure the muscle activity induced by the passive stretch. Results. The model was validated in 3 ways: ( a) NC was reduced after an ischemic nerve block, ( b) NC correlated with the integrated EMG across subjects and in the same subject during the ischemic nerve block, and ( c) NC was velocity dependent. In addition, the total resisting force and NC correlated wi...
Elbow spasticity during passive stretch-reflex: clinical evaluation using a wearable sensor system
Journal of NeuroEngineering and Rehabilitation, 2013
Background: Spasticity is a prevalent chronic condition among persons with upper motor neuron syndrome that significantly impacts function and can be costly to treat. Clinical assessment is most often performed with passive stretch-reflex tests and graded on a scale, such as the Modified Ashworth Scale (MAS). However, these scales are limited in sensitivity and are highly subjective. This paper shows that a simple wearable sensor system (angle sensor and 2-channel EMG) worn during a stretch-reflex assessment can be used to more objectively quantify spasticity in a clinical setting. Methods: A wearable sensor system consisting of a fibre-optic goniometer and 2-channel electromyography (EMG) was used to capture data during administration of the passive stretch-reflex test for elbow flexor and extensor spasticity. A kinematic model of unrestricted passive joint motion was used to extract metrics from the kinematic and EMG data to represent the intensity of the involuntary reflex. Relationships between the biometric results and clinical measures (MAS, isometric muscle strength and passive range of motion) were explored. Results: Preliminary results based on nine patients with varying degrees of flexor and extensor spasticity showed that kinematic and EMG derived metrics were strongly correlated with one another, were correlated positively (and significantly) with clinical MAS, and negatively correlated (though mostly non-significant) with isometric muscle strength. Conclusions: We conclude that a wearable sensor system used in conjunction with a simple kinematic model can capture clinically relevant features of elbow spasticity during stretch-reflex testing in a clinical environment.
Effect of post-stroke spasticity on voluntary movement of the upper limb
Journal of NeuroEngineering and Rehabilitation, 2021
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 sens...