![]() ![]() For some participants, joint torque and muscle activation generated during maximal voluntary contractions were lower than during maximal synergy-induced contractions (i.e., contractions about a different joint), particularly for wrist and fingers. ![]() Isometric joint torques and surface EMG were recorded from shoulder, elbow, wrist, and finger joints and muscles. Twelve participants with moderate-to-severe hemiparetic stroke and six without stroke performed maximal isometric torque generation in eight directions: shoulder abduction/adduction and elbow, wrist, and finger flexion/extension. If upregulation of brainstem motor pathways occurs following stroke-induced corticofugal tract damage, then we would expect a pattern of muscle dependency in the observed behaviors consistent with such neural reorganization. Here we formally investigated these observations and interpreted them within the context of the neural mechanisms thought to underlie stereotypical movement patterns. distal muscles and associated reactions in the paretic limb occurred during maximal efforts with the non-paretic limb, the strength of which seemed to vary depending on which muscles in the non-paretic limb were contracting. It seemed that: paretic wrist/finger muscles were activated maximally during contractions of muscles at a different joint differences in the magnitude of synergy expression occurred when elicited via contraction of proximal vs. During our recent work on differences in synergy expression among proximal and distal joints, we serendipitously observed some notable characteristics of synergy-driven muscle activation. Accumulating evidence indicates that these synergies emerge because of upregulation of diffusely projecting brainstem motor pathways following stroke-induced damage to corticofugal pathways. 10.Individuals with moderate-to-severe post-stroke hemiparesis cannot control proximal and distal joints of the arm independently because they are constrained to stereotypical movement patterns called flexion and extension synergies. Motor skill training may restore impaired corticospinal tract fibers in children with cerebral palsy. Task-dependent weakness at the elbow in patients with hemiparesis. Impact of gravity loading on post-stroke reaching and its relationship to weakness. Early intervention after perinatal stroke: opportunities and challenges. ABILHAND-Kids–a measure of manual ability in children with cerebral palsy. We interpret this conservation of independent control of the paretic shoulder and elbow as the use of more direct corticospinal projections instead of indirect cortico-reticulospinal pathways used in individuals with adult-onset hemiplegia.Ĭerebral palsy flexion synergy independent joint control pediatric hemiparesis perinatal stroke reaching.Īrnould C., Penta M., Renders A., Thonnard J. Relative maintenance in reaching seen in individuals with early brain injuries highlights minimal expression of the flexion synergy. Individuals with early-onset PH achieved lower peak velocities when reaching with the paretic arm compared to controls however, no differences in reaching distance were found between groups. Descending drive, and the possible expression of the upper extremity flexion synergy, was modulated by increasing shoulder abduction loading. Fifteen individuals with brain injuries before birth ( n = 8) and around full-term ( n = 7) and nine age-matched controls with no known neurological impairment completed a set of reaches in an admittance controlled robotic device. This study uses kinematics of a ballistic reaching task to evaluate the expression of the flexion synergy in individuals with pediatric hemiplegia (PH) ages six to seventeen years. An early unilateral brain injury occurring prior to six months post full-term may preserve corticospinal projections which can be used for independent joint control and thus minimizing the expression of the flexion synergy. The expression of the flexion synergy in individuals with brain injuries onset earlier in the lifespan is currently unknown. It is well established that the flexion synergy induces reaching constraints in individuals with adult-onset hemiplegia. Hemiparetic stroke in adulthood often results in the grouped movement pattern of the upper extremity flexion synergy thought to arise from an increased reliance on cortico-reticulospinal pathways due to a loss of lateral corticospinal projections. ![]()
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