Motor impairments related to brain injury timing in early hemiparesis. Part II: abnormal upper extremity joint torque synergies

Neurorehabil Neural Repair. 2014 Jan;28(1):24-35. doi: 10.1177/1545968313497829. Epub 2013 Aug 1.


Background: 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.

Objective: 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.

Keywords: cerebral palsy; childhood hemiparesis; childhood hemiplegia; independent joint control; selective motor control.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Brain Injuries / complications
  • Brain Injuries / physiopathology*
  • Child
  • Elbow Joint / physiopathology*
  • Female
  • Hand Joints / physiopathology*
  • Humans
  • Isometric Contraction / physiology
  • Male
  • Muscle Weakness / etiology
  • Muscle Weakness / physiopathology
  • Paresis / etiology
  • Paresis / physiopathology*
  • Shoulder Joint / physiopathology*
  • Torque
  • Upper Extremity / physiopathology*