Biomechanical and electromyographic assessment of spastic hypertonus in motor complete traumatic spinal cord-injured individuals

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.

Protocol for rapid onset of mobilisation in patients with traumatic spinal cord injury (PROMPT-SCI) study: a single-arm proof-of-concept trial of early in-bed leg cycling following acute traumatic spinal cord injury

INTRODUCTION

Activity-based therapy (ABT) is an important aspect of rehabilitation following traumatic spinal cord injury (SCI). Unfortunately, it has never been adapted to acute care despite compelling preclinical evidence showing that it is safe and effective for promoting neurological recovery when started within days after SCI. This article provides the protocol for a study that will determine the feasibility and explore potential benefits of early ABT in the form of in-bed leg cycling initiated within 48 hours after the end of spinal surgery for SCI.

METHODS AND ANALYSIS

PROMPT-SCI (protocol for rapid onset of mobilisation in patients with traumatic SCI) is a single-site single-arm proof-of-concept trial. Forty-five patients aged 18 years or older with a severe traumatic SCI (American Spinal Injury Association Impairment Scale grade A, B or C) from C0 to L2 undergoing spinal surgery within 48 hours of the injury will be included. Participants will receive daily 30 min continuous sessions of in-bed leg cycling for 14 consecutive days, initiated within 48 hours of the end of spinal surgery. The feasibility outcomes are: (1) absence of serious adverse events associated with cycling, (2) completion of 1 full session within 48 hours of spinal surgery for 90% of participants and (3) completion of 11 sessions for 80% of participants. Patient outcomes 6 weeks and 6 months after the injury will be measured using neurofunctional assessments, quality of life questionnaires and inpatient length of stay. Feasibility and patient outcomes will be analysed with descriptive statistics. Patient outcomes will also be compared with a matched historical cohort that has not undergone in-bed cycling using McNemar and Student's t-tests for binary and continuous outcomes, respectively.

ETHICS AND DISSEMINATION

PROMPT-SCI is approved by the Research Ethics Board of the CIUSSS NIM. Recruitment began in April 2021. Dissemination strategies include publications in scientific journals and presentations at conferences.

TRIAL REGISTRATION NUMBER

NCT04699474.

Properties of the surface electromyogram following traumatic spinal cord injury: a scoping review

Traumatic spinal cord injury (SCI) disrupts spinal and supraspinal pathways, and this process is reflected in changes in surface electromyography (sEMG). sEMG is an informative complement to current clinical testing and can capture the residual motor command in great detail-including in muscles below the level of injury with seemingly absent motor activities. In this comprehensive review, we sought to describe how the sEMG properties are changed after SCI. We conducted a systematic literature search followed by a narrative review focusing on sEMG analysis techniques and signal properties post-SCI. We found that early reports were mostly focused on the qualitative analysis of sEMG patterns and evolved to semi-quantitative scores and a more detailed amplitude-based quantification. Nonetheless, recent studies are still constrained to an amplitude-based analysis of the sEMG, and there are opportunities to more broadly characterize the time- and frequency-domain properties of the signal as well as to take fuller advantage of high-density EMG techniques. We recommend the incorporation of a broader range of signal properties into the neurophysiological assessment post-SCI and the development of a greater understanding of the relation between these sEMG properties and underlying physiology. Enhanced sEMG analysis could contribute to a more complete description of the effects of SCI on upper and lower motor neuron function and their interactions, and also assist in understanding the mechanisms of change following neuromodulation or exercise therapy.

Bilateral and asymmetrical contributions of passive and active ankle plantar flexors stiffness to spasticity in humans with spinal cord injury

Spasticity is one of the most common symptoms present in humans with spinal cord injury (SCI); however, its clinical assessment remains underdeveloped. The purpose of the study was to examine the contribution of passive muscle stiffness and active spinal reflex mechanisms to clinical outcomes of spasticity after SCI. It is important that passive and active contributions to increased muscle stiffness are distinguished to make appropriate decisions about antispastic treatments and to monitor its effectiveness. To address this question, we combined biomechanical and electrophysiological assessments of ankle plantarflexor muscles bilaterally in individuals with and without chronic SCI. Spasticity was assessed using the Modified Ashworth Scale (MAS) and a self-reported questionnaire. We performed slow and fast dorsiflexion stretches of the ankle joint to measure passive muscle stiffness and reflex-induced torque using a dynamometer and the soleus H reflex using electrical stimulation over the posterior tibial nerve. All SCI participants reported the presence of spasticity. While 96% of them reported higher spasticity on one side compared with the other, the MAS detected differences across sides in only 25% of the them. Passive muscle stiffness and the reflex-induced torque were larger in SCI compared with controls more on one side compared with the other. The soleus stretch reflex, but not the H reflex, was larger in SCI compared with controls and showed differences across sides, with a larger reflex in the side showing a higher reflex-induced torque. MAS scores were not correlated with biomechanical and electrophysiological outcomes. These findings provide evidence for bilateral and asymmetric contributions of passive and active ankle plantar flexors stiffness to spasticity in humans with chronic SCI and highlight a poor agreement between a self-reported questionnaire and the MAS for detecting asymmetries in spasticity across sides.NEW & NOTEWORTHY Spasticity affects a number of people with spinal cord injury (SCI). Using biomechanical, electrophysiological, and clinical assessments, we found that passive muscle properties and active spinal reflex mechanisms contribute bilaterally and asymmetrically to spasticity in ankle plantarflexor muscles in humans with chronic SCI. A self-reported questionnaire had poor agreement with the Modified Ashworth Scale in detecting asymmetries in spasticity. The nature of these changes might contribute to the poor sensitivity of clinical exams.

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.

Development of a clinical spasticity scale for evaluation of dogs with chronic thoracolumbar spinal cord injury

OBJECTIVE To develop a spasticity scale for dogs with chronic deficits following severe spinal cord injury (SCI) for use in clinical assessment and outcome measurement in clinical trials. ANIMALS 20 chronically paralyzed dogs with a persistent lack of hind limb pain perception caused by an acute SCI at least 3 months previously. PROCEDURES Spasticity was assessed in both hind limbs via tests of muscle tone, clonus, and flexor and extensor spasms adapted from human scales. Measurement of patellar clonus duration and flexor spasm duration and degree was feasible. These components were used to create a canine spasticity scale (CSS; overall score range, 0 to 18). Temporal variation for individual dogs and interrater reliability were evaluated. Gait was quantified with published gait scales, and CSS scores were compared with gait scores and clinical variables. Owners were questioned regarding spasticity observed at home. RESULTS 20 dogs were enrolled: 18 with no apparent hind limb pain perception and 2 with blunted responses; 5 were ambulatory. Testing was well tolerated, and scores were repeatable between raters. Median overall CSS score was 7 (range, 3 to 11), and flexor spasms were the most prominent finding. Overall CSS score was not associated with age, SCI duration, lesion location, or owner-reported spasticity. Overall CSS score and flexor spasm duration were associated with gait scores. CONCLUSIONS AND CLINICAL RELEVANCE The CSS could be used to quantify hind limb spasticity in dogs with chronic thoracolumbar SCI and might be a useful outcome measure. Flexor spasms may represent an integral part of stepping in dogs with severe SCI.

Mechanical and neural changes in plantar-flexor muscles after spinal cord injury in humans

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

To determine the effect of injury duration on plantar-flexor elastic properties in individuals with chronic spinal cord injury (SCI) and spasticity.

SETTING

National Rehabilitation Center for Persons with Disabilities, Japan.

METHODS

A total of 16 chronic SCI patients (age, 33±9.3 years; injury localization, C6-T12; injury duration, 11-371 months) participated. Spasticity of the ankle plantar-flexors was assessed using the Modified Ashworth Scale (MAS). The calf circumference and muscle thickness of the medial gastrocnemius (MG), lateral gastrocnemius and soleus were assessed using tape measure and ultrasonography. In addition, the ankle was rotated from 10° plantar-flexion to 20° dorsiflexion at 5 deg s(-1) with a dynamometer, and the ankle angle and torque were recorded. After normalizing the data (the initial points of angle and torque were set to zero), we calculated the peak torque and energy. Furthermore, angle-torque data (before and after normalization) were fitted with a second- and fourth-order polynomial, and exponential (Sten-Knudsen) models, and stiffness indices (SISOP, SIFOP, SISK) and AngleSLACK (the angle at which plantar-flexor passive torque equals zero) were calculated. The stretch reflex gain and offset were determined from 0-10° dorsiflexion at 50, 90, 120 and 150 deg s(-1). After logarithmic transformation, Pearson's correlation coefficients were calculated.

RESULTS

MAS, calf circumference, MG thickness, peak torque and SIFOP significantly decreased with injury duration (r log-log=-0.63, -0.69, -0.63, -0.53 and -0.55, respectively, P<0.05). The peak torque and SIFOP maintained significant relationships even after excluding impacts from muscle morphology.

CONCLUSION

Plantar-flexor elasticity in chronic SCI patients decreased with increased injury duration.