scholarly journals Modification of Spastic Stretch Reflexes at the Elbow by Flexion Synergy Expression in Individuals With Chronic Hemiparetic Stroke

2018 ◽  
Vol 99 (3) ◽  
pp. 491-500 ◽  
Author(s):  
Jacob G. McPherson ◽  
Arno H. Stienen ◽  
Justin M. Drogos ◽  
Julius P. Dewald
Keyword(s):  
Stretch Reflexes ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Flexion Synergy

scholarly journals Evidence for Increased Activation of Persistent Inward Currents in Individuals With Chronic Hemiparetic Stroke

2008 ◽  
Vol 100 (6) ◽  
pp. 3236-3243 ◽  
Author(s):  
Jacob G. McPherson ◽  
Michael D. Ellis ◽  
C. J. Heckman ◽  
Julius P. A. Dewald
Keyword(s):  
Repeated Measures ◽  
Afferent Feedback ◽  
Joint Torque ◽  
Emg Activity ◽  
Tonic Vibration Reflex ◽  
Stretch Reflexes ◽  
Persistent Inward Currents ◽  
Inward Currents ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke

Despite the prevalence of hyperactive stretch reflexes in the paretic limbs of individuals with chronic hemiparetic stroke, the fundamental pathophysiological mechanisms responsible for their expression remain poorly understood. This study tests whether the manifestation of hyperactive stretch reflexes following stroke is related to the development of persistent inward currents (PICs) leading to hyperexcitability of motoneurons innervating the paretic limbs. Because repetitive volleys of 1a afferent feedback can elicit PICs, this investigation assessed motoneuronal excitability by evoking the tonic vibration reflex (TVR) of the biceps muscle in 10 awake individuals with chronic hemiparetic stroke and measuring the joint torque and electromyographic (EMG) responses of the upper limbs. Elbow joint torque and the EMG activity of biceps, brachioradialis, and the long and lateral heads of triceps brachii were recorded during 8 s of 112-Hz biceps vibration (evoking the TVR) and for 5 s after cessation of stimulation. Repeated-measures ANOVA tests revealed significantly ( P ≤ 0.05) greater increases in elbow flexion torque and EMG activity in the paretic as compared with the nonparetic limbs, both during and up to 5 s following biceps vibration. The finding of these augmentations exclusively in the paretic limb suggests that contralesional motoneurons may become hyperexcitable and readily invoke PICs following stroke. An enhanced tendency to evoke PICs may be due to an increased subthreshold depolarization of motoneurons, an increased monoaminergic input from the brain stem, or both.

scholarly journals The Impact of Shoulder Abduction Loading on Volitional Hand Opening and Grasping in Chronic Hemiparetic Stroke

2017 ◽  
Vol 31 (6) ◽  
pp. 521-529 ◽  
Author(s):  
Yiyun Lan ◽  
Jun Yao ◽  
Julius P. A. Dewald
Keyword(s):  
Shoulder Abduction ◽  
Grasping Forces ◽  
Finger Flexion ◽  
Enhanced Expression ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
And Control ◽  
The Impact ◽  
Hand Opening ◽  
Flexion Synergy

Background. Up to 60% of individuals with moderate to severe chronic hemiparetic stroke experience excessive involuntary wrist/finger flexion that constrains functional hand movements including hand opening. It’s not known how stroke-induced brain injury impacts volitional hand opening and grasping forces as a result of the expression of abnormal coupling between shoulder abduction and wrist/finger flexion or the flexion synergy. Objective. The goal of this study is to understand how shoulder abduction loading affects volitional hand opening and grasping forces in individuals with moderate to severe chronic hemiparetic stroke. Methods. Thirty-six individuals (stroke, 26; control, 10) were recruited for this study. Each participant was instructed to perform maximal hand opening and grasping forces while the arm was either fully supported or lifted with a weight equal to 25% or 50% of the participant’s maximal shoulder abduction torque. Hand pentagon area, defined as the area formed by the tips of thumb and fingers, was calculated during hand opening. Forces were recorded during grasping. Results. In individuals with moderate stroke, increasing shoulder abduction loading reduced the ability to maximally open the hand. In individuals with severe stroke, who were not able to open the hand, grasping forces were generated and increased with shoulder abduction loading. Stroke individuals also showed a reduced ability to control volitional grasping forces due to the enhanced expression of flexion synergy. Conclusions. Shoulder abduction loading reduced the ability to volitionally open the hand and control grasping forces after stroke. Neural mechanisms and clinical implications of these findings are discussed.

The NIH Stroke Scale Lacks Validity in Chronic Hemiparetic Stroke

2015 ◽  
Vol 96 (10) ◽  
pp. e35
Author(s):  
Heather Tanksley Peters ◽  
Susan White ◽  
Stephen Page
Keyword(s):  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke

scholarly journals Biomechanical parameters of the elbow stretch reflex in chronic hemiparetic stroke

2018 ◽  
Vol 237 (1) ◽  
pp. 121-135 ◽  
Author(s):  
Jacob G. McPherson ◽  
Arno H. A. Stienen ◽  
Brian D. Schmit ◽  
Julius P. A. Dewald
Keyword(s):  
Stretch Reflex ◽  
Biomechanical Parameters ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke

scholarly journals Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns

2017 ◽  
Vol 31 (9) ◽  
pp. 814-826 ◽  
Author(s):  
Natalia Sánchez ◽  
Ana Maria Acosta ◽  
Roberto Lopez-Rosado ◽  
Arno H. A. Stienen ◽  
Julius P. A. Dewald
Keyword(s):  
Lower Extremity ◽  
Degrees Of Freedom ◽  
Joint Torque ◽  
Motor Impairments ◽  
Lower Extremity Weakness ◽  
Joint Torques ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Hip Extension ◽  
Flexion And Extension

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were measured. Relative weakness (paretic extremity compared with the nonparetic extremity) was measured in poststroke participants. Differences in EMGs and joint torques associated with maximum voluntary torques were tested using linear mixed effects models. Results indicate significant poststroke torque weakness in all degrees of freedom except hip extension and adduction, adductor coactivation during extensor tasks, in addition to synergistic muscle coactivation patterns. This was more pronounced in the paretic extremity compared with the nonparetic extremity and with controls. Results also indicated significant interjoint torque couples during maximum and submaximal hip extension in both extremities of poststroke participants and in controls only during maximal hip extension. Additionally, significant interjoint torque couples were identified only in the paretic extremity during ankle plantarflexion. A better understanding of these motor impairments is expected to lead to more effective interventions for poststroke gait and posture.

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