Dissertation/Thesis Abstract

Timing of Pediatric Brain Injury Impacts the Expression of Upper Extremity Weakness, Loss of Independent Joint Control and Loss of Independent Limb Control in Childhood Hemiparesis
by Moulton, Theresa Sukal, Ph.D., Northwestern University, 2012, 220; 3499628
Abstract (Summary)

Throughout the course of typical development, the central nervous system goes through drastic changes. Brain injury occurring before adulthood is often the result of a single incident, but causes long-term consequences due to development that occurs subsequent to the injury. Childhood hemiparesis is an ideal model for studying how timing of injury impacts motor impairments since injuries can be subdivided into distinct timing categories. Here, we identified three groups to compare with typically developing peers: PRE-natal injuries that occurred in the late 2nd/early 3rd trimester of gestation; PERI-natal injuries that occurred around the time of birth; and POST-natal injuries occurring between 6 months and 10 years of age.

To investigate the expression of weakness and loss of independent joint control in the upper extremity, we used multiple-degree-of-freedom load cells to demonstrate that PRE-natal injury group had relatively preserved strength when compared to the PERI- and POST-natal groups, which was especially apparent at the wrist and finger extensors. The same maximal isometric measures were used to identify joint torque coupling patterns, where it was shown that individuals with POST-natal injury demonstrate clear coupling of shoulder abductors with elbow, wrist and finger flexors. In looking at independent limb control, we found that PRE-natal injuries mirror elbow flexion torque during a unilateral task relative to effort exerted, and are unable to suppress this activity when performing a bilateral task.

Taken together, these results indicate that different neural structures are utilized following injury at different points during development. Specifically, the early injury groups (PRE-natal, and to a certain extent PERI-natal) appear to utilize typically transient ipsilateral corticospinal projections from the undamaged hemisphere to control the paretic limb. This results in less weakness, but comes at a cost of decreased resolution of muscle activation across joints and between arms. This study also supports the potential use of remaining bulbospinal pathways for control of the paretic limb in POST-natal injuries. This explains greater weakness at distal joints due to decreased innervation of these muscles, and greater loss of independent joint control due to diffuse projections from the brainstem, but less analogous muscle activation during bilateral tasks.

Indexing (document details)
Advisor: Dewald, Julius P.A.
Commitee: Gaebler-Spira, Deborah J., Heckman, Charles J., Mussa-Ivaldi, Ferdinando
School: Northwestern University
Department: Biomedical Engineering
School Location: United States -- Illinois
Source: DAI-B 73/07(E), Dissertation Abstracts International
Subjects: Neurosciences, Physical therapy, Biomedical engineering
Keywords: Arm weakness, Brain injury, Cerebral palsy, Childhood hemiparesis, Mirror movements
Publication Number: 3499628
ISBN: 9781267242570
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