Directional effect on post-stroke motor overflow characteristics.
Motor overflow (MO) is an involuntary muscle activation associated with strenuous contralateral movement and may become manifested after stroke. The study was undertaken to investigate physiological correlation underlying atypical directional effect of joint movement on post-stroke MO in the affected upper limb. Thirty patients with unilateral post-stroke hemiparesis and fifteen age-matched healthy controls participated in this study. According to motor function assessed with the Fugl-Meyer arm scale, the patients were categorized into two groups of equal number with better (CVA_G; n = 15) or poorer motor functions (CVA_P; n = 15). Surface electromyography (EMG) was used to record irradiated muscle activation from eight muscles of the affected upper limb when the subjects performed maximal isometric contractions in different directions with the unaffected shoulder, elbow and wrist joints. The results showed that only MO amplitude of the CVA_G and the control groups was more sensitive to variations in direction of joint movement in the unaffected arm than the CVA_P group. The CVA_G group exhibited larger amplitudes of MO than the control analog, whereas this tendency was reversed for the CVA_P group. In terms of EMG polar plots, spatial representations of post-stroke MO were insensitive to direction of contralateral movement. The spatial representations of the CVA_G and CVA_P groups were predominated by potent flexion-abduction synergy, contrary to the typical extension adduction synergy seen in the control analog. In conclusion, post-stroke MO amplitude was subject to contralateral movement direction for healthy controls and stroke patients with better motor recovery. However, alterations in MO spatial pattern due to directional effect were not strictly related to the degree of motor deficits of the stroke victims.
Department of Physical Medicine and Rehabilitation, Chi Mei Medical Center, Tainan, Taiwan, Republic of China.
Li-Cheng
LC
Tung
Jeng-Feng
JF
Yang
Chun-Hou
CH
Wang
Ing-Shiou
IS
Hwang
D000328:Adult; D000368:Aged; D001132:Arm / Q000503:physiopathology; D004525:Efferent Pathways / Q000503:physiopathology*; D004551:Elbow Joint / Q000502:physiology; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009069:Movement Disorders / Q000503:physiopathology* / Q000534:rehabilitation; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D012785:Shoulder Joint / Q000502:physiology; D020521:Stroke / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D014955:Wrist Joint / Q000502:physiology