Article

Extensive neuromotor development occurs early in human life, and the
timing of brain injury may affect the resulting motor impairment. In Part I of
this series, it was demonstrated that the distribution of weakness in the upper
extremity depended on the timing of brain injury in individuals with
childhood-onset hemiparesis. The goal of this study was to
characterize how timing of brain injury affects joint torque synergies, or losses
of independent joint control. METHOD: Twenty-four individuals with hemiparesis
were divided into 3 groups based on the timing of their injury: before birth
(PRE-natal, n = 8), around the time of birth (PERI-natal, n = 8), and after 6
months of age (POST-natal, n = 8). Individuals with hemiparesis and 8 typically
developing peers participated in maximal isometric shoulder, elbow, wrist, and
finger torque generation tasks while their efforts were recorded by a multiple
degree-of-freedom load cell. Motor output in 4 joints of the upper extremity was
concurrently measured during 8 primary torque generation tasks to quantify joint
torque synergies. RESULTS: There were a number of significant coupling patterns
identified in individuals with hemiparesis that differed from the typically
developing group. POST-natal differences were most noted in the coupling of
shoulder abductors with elbow, wrist, and finger flexors, while the PRE-natal
group demonstrated significant distal joint coupling with elbow flexion.
CONCLUSION: The torque synergies measured provide indirect evidence for the use
of bulbospinal pathways in the POST-natal group, while those with earlier injury
may use relatively preserved ipsilateral corticospinal motor pathways.

Langue : ANGLAIS