Electromyographic Analyses of Global Synkinesis in the Paretic Upper Limb After Stroke

Abstract

Background and Purpose. Global synkinesis (GS), or motor irradiation, is an involuntary movement associated with the coactivation of numerous muscles in one limb when the opposite limb is active. The electromyographic (EMG) patterns of people with stroke and people who were healthy were analyzed to characterize GS development in relation to joint involvement and to attempt to relate these findings to clinical observations. Subjects and Methods. Twenty patients with stroke, divided into 2 groups with either greater levels of irradiation (SG, n=10) or lesser levels of irradiation (SL, n=10), and 20 subjects in a control group were studied. A dynamometer was used to provide resistance for voluntary isometric muscle contractions of the flexor muscle groups of the shoulder, elbow, and wrist. The summated and standardized net EMG amplitudes of 8 principal muscles of the unexercised (paretic) upper extremity were used to characterize intensity and spatial representation of GS. Clinical measurements included the Fugl-Meyer Assessment Scale (FMA), Barthel Index of Activities of Daily Living (BI), and the stage on the Brunnström Stages of Motor Recovery Scale (BR). Results. In the SG and control groups, a more substantial GS intensity was associated with muscle contractions of the flexor muscles of the opposite proximal joint than was the case for contractions of the flexor muscles of the distal joint, whereas such a gradient change was absent in the SL group. The corresponding spatial patterns of GS exhibited a predominant cross-excitation over the unexercised pectoralis major and extensor carpi radialis muscles in the control group, contrary to the enhanced activation of the brachioradialis and biceps brachii muscles noted in patients with stroke. The SG group had a better FMA score and a more satisfactory BR stage than did the SL group, and the 2 neurological scores were related to GS intensity for patients with stroke, depending on joint involvement. Discussion and Conclusion. Intensity of GS provided an affiliation with motor deficits and a promising window for poststroke recovery mechanisms.

Directional Effect on Post-Stroke Motor Overflow Characteristics

“…Moreover, those stroke survivors with better motor recovery and control analogs demonstrated a more marked directional effect on overflow amplitude than the stroke survivors with poorer recovery. A previous study reported that the amount of motor overflow decreased progressively with involvement of more distal joints (18), but this patterned organization of MO was not seen in the stroke survivors with poor recovery. Together with gradient-change in MO with joint involvement (18), insufficient directional effect on MO found in this study seems to be another physiological watershed in the stroke recovery process.…”

“…A previous study reported that the amount of motor overflow decreased progressively with involvement of more distal joints (18), but this patterned organization of MO was not seen in the stroke survivors with poor recovery. Together with gradient-change in MO with joint involvement (18), insufficient directional effect on MO found in this study seems to be another physiological watershed in the stroke recovery process. Although physiological mechanisms underlying the directional effect is not completely clear, it probably pertains to usagedependent decline in transcallosal inhibition commonly found in professional musicians with intensive practices for years (29,30).…”

“…Although MO has been considered as reflexively stereotyped and functionally non-purposive (4,25), yet this viewpoint is being challenged, considering the fact that MO is modifiable to attentional focus (1), task characteristics (11,16,27) and exertion level (17,24). Also, post-stroke MO seemingly evolves with the stroke-recovery process and/or restorative cortical reorganization (18,21,26). As MO is a sensorimotor consequence of inter-hemispheretic disinhibition (14), it has been used for designing rehabilitation strategies to facilitate feeble muscles in the paralyzed body portions (4,33,35).…”

Zerebral bedingte Paresen und Spastik

“…Auchdas Auftretenv on Synkinesien ist entgegender in derBobath-Therapie vertre-tenenL ehrmeinung für denW iedererwerb motorischer Fertigkeitenn icht ungünstig, sondern geht mitverbessertenfunktionellen Fertigkeiteneinher (24).…”

Abnormal coactivation of knee and ankle extensors is related to changes in heteronymous spinal pathways after stroke

“…In patients with central nervous system lesions, abnormal synergistic coactivations have been mostly measured during isolated contractions in static conditions [ 10 - 12 ]. In such tasks, where constraints due to movement are reduced and where the central nervous system has fewer parameters to control, the relationship between the coupling of the torques generated across the joints and the pattern of muscular recruitment is more easily interpreted than in dynamic tasks [ 11 ].…”