Abnormal cutaneous flexor reflex activity during controlled isometric plantarflexion in human spinal cord injury spasticity syndrome (original) (raw)
Related papers
NeuroRehabilitation, 2018
BACKGROUND: Tibialis Anterior (TA) cutaneous reflex (CR) activity evoked following cutaneous stimulation of the plantar (Pl) surface (Pl-TA CR) has demonstrated hyperreflexia and damage of inhibitory mechanisms in subjects with spinal cord injury (SCI) and spasticity. OBJECTIVES: To modulate Pl-TA CR and Soleus H-reflex activity with transcutaneous electrical nerve stimulation (TENS) and vibratory stimulation of the plantar pad during rest and controlled isometric plantarflexion. METHODS: Non-injured subjects (n = 11) and individuals with incomplete SCI with (n = 14) and without spasticity (n = 14) were recruited. The effect of TENS and vibratory stimuli on Pl-TA CR and soleus H-reflex activity were assessed during rest and controlled ramp-and-hold plantarflexion. RESULTS: Vibration failed to inhibit H-reflex activity during rest or plantarflexoin following SCI compared to healthy subjects. In contrast, vibration-induced inhibition of Pl-TA CR was specifically detected in SCI spastic subjects during both rest and the hold phase of plantarflexion. TENS inhibited Pl-TA CR activity in the SCI spasticity group only during hold plantarflexion. CONCLUSIONS: Plantar vibratory stimuli inhibited the pl-TA CR, but not the H reflex, during rest and controlled movement in SCI spastic subjects. Assessment of Pl-TA CR modulation should contribute to the development of modality-specific sensory stimuli programmes for the neurorehabilitation of SCI spasticity.
Annals of Biomedical Engineering, 2000
Frequency response characteristics of the ankle plantar flexors were studied in adults both with and without spinal cord injury ͑SCI͒ to determine how the muscle contractile properties change after SCI, and to see if there is a relation between the severity of spasticity and how the properties change. Ten controls and ten complete, chronic spinal cord injured subjects were tested, where the tibial nerve was stimulated electrically in a stochastic manner with the ankle fixed isometrically at various joint angles. A nonparametric linear frequency response function was derived, from which a secondorder transfer function was calculated. The contractile dynamics were then characterized by the three classic second-order parameters: gain, damping ratio, and natural frequency. We found that in subjects with low degrees of spasticity ͑as determined by clinical evaluation͒, the contractile dynamics presented the largest changes, in which the speed of contraction increased significantly while there were no statistical differences in the gains between the two groups. This similarity emerged even though there was noticeable atrophy in the SCI patient group. Differences between the controls and subjects with high levels of spasticity were markedly different, in that these SCI subjects had slower contractile speeds than the controls, but significantly lower gains. Moderately spastic subjects fell somewhere in between, where the speed of muscle contraction increased modestly yet the gain was significantly smaller than that of the control subjects. These findings indicate that in subjects with chronic spinal cord injury, the severity of spasticity can significantly influence the degree of change in muscle contractile properties. It appears that high degrees of spasticity tend to preserve contractile dynamics, while in less spastic subjects, muscle contractile properties may display faster response characteristics. © 2002 Biomedical Engineering Society.
Spinal Cord, 2007
Study design: Spinal reflex excitability study in sensory-motor incomplete spinal cord-injured (SCI) and spinal intact subjects. Objectives: To investigate the effects of plantar cutaneous afferent excitation on the soleus H-reflex and flexion reflex in both subject groups while seated. Setting: Rehabilitation Institute of Chicago and City University of New York, USA. Methods: The flexion reflex in SCI subjects was elicited by non-nociceptive stimulation of the sural nerve. In normal subjects, it was also elicited via innocuous medial arch foot stimulation. In both cases, reflex responses were recorded from the ipsilateral tibialis anterior muscle. Soleus H-reflexes were elicited and recorded via conventional methods. Both reflexes were conditioned by plantar cutaneous afferent stimulation at conditioning test intervals ranging from 3 to 90 ms. Results: Excitation of plantar cutaneous afferents resulted in facilitation of the soleus H-reflex and late flexion reflex in SCI subjects. In normal subjects, the soleus H-reflex was depressed while the late flexion reflex was absent. The early flexion reflex was irregularly observed in SCI patients, while in normal subjects a bimodal reflex modulation pattern was observed. Conclusion: The effects of plantar cutaneous afferents change following a lesion to the spinal cord leading to exaggerated activity in both flexors and extensors. This suggests impaired modulation of the spinal inhibitory mechanisms involved in the reflex modulation. Our findings should be considered in programs aimed to restore sensorimotor function and promote recovery in these patients.
Reliability of the Spinal Cord Assessment Tool for Spastic Reflexes
Archives of Physical Medicine and Rehabilitation, 2017
Reliability of the Spinal Cord Assessment Tool for Spastic Reflexes Objective: To assess the reliability of the Spinal Cord Assessment Tool for Spastic Reflexes (SCATS). Design: Observational reliability study of the SCATS. Setting: Inpatient rehabilitation unit at an education and research hospital. Participants: This study included 47 subjects between the ages of 18 and 88 years with spinal cord injury, American Spinal Injury Association (ASIA) impairment scale grades from A to D with spasticity, and at least 6 months post injury. Interventions: Not applicable. Main outcome measures: Inter-rater and test-retest reliability of the SCATS. Results: The SCATS had substantial to almost perfect inter-rater agreement (κ=0.669-1.000) between the 2 physiatrists. Test-retest agreement of the SCATS was also substantial to almost perfect (κ=0.614-1.000) as well. There was a significant correlation between the SCATS clonus scores and the Modified Ashworth scores of the hip, knee, and ankle. No correlation was found between SCATS extensor spasm scores and Modified Ashworth scores. The SCATS flexor spasm scores were only correlated significantly with the ankle plantar flexor Modified Ashworth scores (p<0.05). Conclusion: The SCATS is a reliable tool for assessing spasm activity and spastic hypertonia in patients with spinal cord injury. Reliability of the Spinal Cord Assessment Tool for Spastic Reflexes (SCATS)
Journal of Neurophysiology, 2010
Knikou M. Plantar cutaneous afferents normalize the reflex modulation patterns during stepping in chronic human spinal cord injury. cutaneous afferent transmission is critical for recovery of locomotion in spinalized animals, whereas a phase-dependent reflex modulation is apparent during fictive or real locomotion. In nine people with a chronic spinal cord injury (SCI) the effects of foot sole stimulation on the soleus H-reflex and tibialis anterior (TA) flexion reflex modulation patterns during assisted stepping were established on different days. The soleus H-reflex was elicited by posterior tibial nerve stimulation followed by a supramaximal stimulus 100 ms after the test H-reflex to control for movement of recording electrodes. The flexion reflex was evoked by sural nerve stimulation with a 30-ms pulse train, recorded from the ipsilateral TA muscle, and elicited at 1.2-to twofold the reflex threshold. During assisted stepping, spinal reflexes were conditioned by percutaneous stimulation of the ipsilateral metatarsals at threefold perceptual threshold with a 20-ms pulse train delivered at 9-to 11-ms conditioning-test intervals. Stimuli were randomly dispersed across the step cycle, which was divided into 16 equal bins. The conditioned soleus H-reflex was significantly facilitated at midstance and depressed during midswing when compared with the unconditioned soleus H-reflex recorded during stepping. Foot sole stimulation induced a significant facilitation of the long-latency TA flexion reflex before, during, and after stance-to-swing transition when compared with the unconditioned long-latency TA flexion reflex during stepping. This study provides evidence that plantar cutaneous afferents remarkably influence the soleus H-reflex and TA flexion reflex modulation patterns during stepping and support that actions of plantar cutaneous afferents onto spinal interneuronal circuits engaged in locomotion are manifested in a phase-dependent manner in chronic SCI subjects.
Intrinsic and reflex stiffness in normal and spastic, spinal cord injured subjects
Experimental Brain Research, 2001
Mechanical changes underlying spastic hypertonia were explored using a parallel cascade system identification technique to evaluate the relative contributions of intrinsic and reflex mechanisms to dynamic ankle stiffness in healthy subjects (controls) and spastic, spinal cord injured (SCI) patients. We examined the modulation of the gain and dynamics of these components with ankle angle for both passive and active conditions. Four main findings emerged. First, intrinsic and reflex stiffness dynamics were qualitatively similar in SCI patients and controls. Intrinsic stiffness dynamics were well modeled by a linear second-order model relating intrinsic torque to joint position, while reflex stiffness dynamics were accurately described by a linear, third-order system relating half-wave rectified velocity to reflex torque. Differences between the two groups were evident in the values of four parameters, the elastic and viscous parameters for intrinsic stiffness and the gain and first-order cut-off frequency for reflex stiffness. Second, reflex stiffness was substantially increased in SCI patients, where it generated as much as 40% of the total torque variance, compared with controls, where reflex contributions never exceeded 7%. Third, differences between SCI patients and controls depended strongly on joint position, becoming larger as the ankle was dorsiflexed. At full plantarflexion, there was no difference between SCI and control subjects; in the mid-range, reflex stiffness was abnormally high in SCI patients; at full dorsiflexion, both reflex and intrinsic stiffness were larger than normal. Fourth, differences between SCI and control subjects were smaller during the active than the passive condition, because intrinsic stiffness increased more in controls than SCI subjects; nevertheless, reflex gain remained abnormally high in SCI patients. These results elucidate the nature and origins of the mechanical abnormalities associated with hypertonia and provide a better understanding of its functional and clinical implications.
Archives of Physical Medicine and Rehabilitation, 2008
Objectives: To isolate and quantify reflex and nonreflex components of the spastic ankle plantarflexors in hemiplegia poststroke and to correlate them with clinical measures of spasticity, which may involve hyperactive stretch reflex and/or increased joint stiffness. Design: To investigate reflex and nonreflex properties associated with spasticity in a case-control manner. Setting: Research laboratory in a rehabilitation hospital. Participants: Hemiplegic patients (nϭ17) and the same number of healthy subjects. Interventions: Not applicable. Main Outcome Measures: Tendon reflexes of spastic muscles were evaluated under an isometric condition, which essentially eliminated passive viscoelastic contributions associated with limb movement. Nonreflex components of spasticity were evaluated by moving the ankle joint slowly, which minimized reflex actions. The reflex and nonreflex measures were investigated and correlated with each other and with clinical measures. Results: Compared with healthy subjects, patients with stroke showed a lower reflex threshold, higher electromyographic gains, and torque reflex gains, indicating hyperactive reflexes. For nonreflex properties, ankles of stroke patients showed higher stiffness, reduced range of motion (ROM), and larger resistant torque at comparable positions, reflecting peripheral soft-tissue changes at the ankle of the chronic stroke patients. Furthermore, the clinical reflex score correlated with all of the quantitative reflex measures but not with the nonreflex measures, whereas the dorsiflexion ROM showed a significant correlation with a nonreflex measure. The Modified Ashworth Scale was correlated with all of the reflex measures and 1 of the nonreflex measures. Conclusions: Comprehensive and convenient evaluation of spasticity should be performed quantitatively with the separate measures of reflex and nonreflex components, especially in chronic conditions. With proper simplifications, the current method of separate quantification can potentially be used for convenient clinical evaluations of spasticity.