Graduation Date

Spring 5-7-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Medical Sciences Interdepartmental Area

First Advisor

Max Kurz, Ph.D.

Second Advisor

Lois Starr, M.D., Ph.D.

MeSH Headings

cerebral palsy, spinal cord, motor control, sensory, neurophysiology

Abstract

Cerebral palsy (CP) is the most common neurological disorder originating in childhood, but most of the people living with CP are currently adults. While people with CP continue to get older, the amount of research focused on adults has been rather limited. The early childhood insults leading to CP are thought to originate in the brain, but the effects on the entire neuromuscular system across the lifespan have only recently started to be explored. Of note, recent neuroimaging evidence suggests that the cervical spinal cord structure is atypical in adults with CP. However, it is largely unclear how the neurophysiological pathways in the cervical spinal cord may be altered in this patient population. Similarly, the relationship between spinal pathway plasticity and sensorimotor function in people with CP is poorly understood. We sought to address these knowledge gaps by employing a series of studies with adults with CP and neurotypical controls using a combination of non-invasive peripheral nerve stimulation, central tract stimulation and surface electromyography. Overall, we uncovered changes in the size of the upper extremity H-reflex sensory afferent response in adults with CP in comparison to their neurotypical peers, and these changes were related to the level of wrist position sense. We also demonstrated that H-reflex modulation by the post-activation depression pathway was aberrant in adults with CP, confirming findings in the lower extremities. These changes were related to the amount of key grip strength and of manual dexterity in adults with CP. Finally, we found that the corticospinal tract activation of spinal motoneurons was reduced in adults with CP, and the reduction was linked to deficits in manual dexterity, self-reported upper extremity function, and selective voluntary control. Ultimately, these findings provide support for the notion that local spinal circuit activity and their activation by the corticospinal tracts and sensory afferents may be greatly involved in the upper extremity motor control deficits observed in adults with CP.

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