title: Motor impairments related to brain injury timing in early hemiparesis. Part II: abnormal upper extremity joint torque synergies.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 1Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Sukal-Moulton
authors.forename: Kristin J
authors.initials: KJ
authors.lastname: Krosschell
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Gaebler-Spira
authors.forename: Julius P A
authors.initials: JP
authors.lastname: Dewald
mesh_terms: D000293:Adolescent; D000328:Adult; D001930:Brain Injuries / Q000150:complications / Q000503:physiopathology*; D002648:Child; D004551:Elbow Joint / Q000503:physiopathology*; D005260:Female; D050823:Hand Joints / Q000503:physiopathology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018908:Muscle Weakness / Q000209:etiology / Q000503:physiopathology; D010291:Paresis / Q000209:etiology / Q000503:physiopathology*; D012785:Shoulder Joint / Q000503:physiopathology*; D019415:Torque; D034941:Upper Extremity / Q000503:physiopathology*
keywords: cerebral palsy; childhood hemiparesis; childhood hemiplegia; independent joint control; selective motor control
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