Cerebral palsy (CP) is a motor disorder caused by an injury to the developing fetal or infantbrain. While the corticospinal tract (CST) is related to selective motor control (SMC) function, an underlying deficit in spastic CP, little is known about CST microstructural impairment, its relationship with motor function measures and neuroplasticity in response to a physical therapy intervention focused on intensive practice of lower extremity (LE) SMC exercises. The aim of this dissertation was to study the effect of Camp Leg Power, a novel LE SMC intervention in spastic CP, on measures of white matter (WM) motor tract microstructure and motor function measures.

Children with unilateral or bilateral spastic CP born premature were recruited for CampLeg Power. Diffusion-weighted imaging scans were collected for participants with bilateral CP and periventricular leukomalacia (PVL). Children with typical development (TD) were recruited as brain imaging controls. The Selective Control Assessment of the Lower Extremity (SCALE) and the gross motor function measure were collected for all participants with CP. Motor function measures analyzed included the 10-meter walk/run test, 6-minute walk test, stride length during gait and isokinetic knee joint torque.

Twenty-three children with spastic CP were enrolled (3 unilateral, 20 bilateral; mean age� SD: 10.1 � 2.8 years; age range: 5.6-16.6 years). Diffusion-weighted imaging scans were evaluated for a subset of 12 participants with spastic bilateral CP and PVL and 12 children with TD (mean age � SD: 10.3 � 1.5 years; age range: 7.5-12.8 years). The CP group exhibited lower anisotropy, damaged myelination, decreased axonal integrity and greater overall diffusivity throughout the whole brain including WM motor tracts relative to TD. The CP group improved their motor function following Camp Leg Power coinciding with improved myelination of brain motor regions suggesting neuroplasticity in response to intervention. SCALE is a strong clinical correlate of brain motor impairment, baseline motor function and post-intervention motor outcomes.

This work contributes to the overall understanding of neuroimaging, clinical correlates ofimpaired WM and biomechanics measures, neuroplasticity and motor function changes in response to a novel LE SMC intervention in spastic CP.