Investigating the white matter structure of the sensorimotor system in children with cerebral palsy

Cerebral palsy (CP) is the leading motor disorder in childhood, primarily caused by a brain insult occurring before birth. CP is typically characterized by spasticity, affecting one side of the body (hemiplegia) or both sides, predominantly the lower limbs (diplegia). The advancements in diffusion-weighted magnetic resonance imaging (dMRI) and tractography, have allowed the identification of altered white matter structure of the brain in CP. However, our understanding of how these alterations differ between hemiplegic and diplegic subtypes, and their relationship with sensorimotor deficits, such as balance, gait and manual dexterity, remains limited. In this thesis, we investigated a cohort of children and adolescents aged 10–18 years diagnosed with hemiplegic (N = 16) or diplegic CP (N = 11) alongside their typically developed peers (N = 31). Using tractography, we investigated the interhemispheric commissural pathways, i.e. corpus callosum, and thalamocortical pathways connecting to the representational areas of the upper and lower limbs. To address the cortical abnormalities seen in CP and enhance the functional relevance of the studied tracts, we introduced a novel seeding approach using proprioceptive simulation (passive movement) of the limbs together with functional neuroimaging. The derived dMRI metrics were compared between the three groups, and their association with behavioral measures was investigated. Our results showed significant alterations in the diffusion properties of the investigated pathways between children with and without CP, indicating changes in the axonal organization. Specifically, participants with hemiplegic CP seemed to have more severe structural changes that were relatively localized when compared to those with diplegic CP. The white matter involvement reflected, to some extent, the topographic presentation of the functional deficit. While we observed some associations between the dMRI-metrics and sensorimotor function, they were weak, and the directionality was non-conclusive, underscoring the complexity of the structure-function relationships. The dMRI holds promising potential as an objective tool for guiding the diagnosis and treatment of CP in the future. By highlighting the differences in location and severity of white matter alterations between hemiplegic and diplegic CP, our findings contribute significantly to the existing literature. Further, our research emphasizes the importance of along-tract analysis and specific outlining of investigated tracts in future studies on both CP and typical development. Research on CP not only enhances our understanding of the disorder itself but also sheds light on the development and plasticity of the human sensorimotor system.