MRI Structural Connectivity, Disruption of Primary Sensorimotor Pathways, and Hand Function in Cerebral Palsy

Abstract

Brain injury and subsequent plasticity of sensory and corticospinal pathways play an integral role in determining paretic hand function in congenital hemiplegia. There is limited knowledge regarding the relationship between the disruption of sensorimotor thalamic pathways projecting into the primary motor cortex and motor control. This study sought to investigate the relationship between the structural connectivity of motor networks that anatomically link the brain stem with the precentral and postcentral gyri with paretic motor sensory function by using an automated analysis strategy. Magnetic resonance imaging structural connectivity was measured by using high-angular-resolution diffusion imaging, probabilistic tractography, and the anatomic parcellation of high-resolution structural images in 16 children with congenital unilateral periventricular white-matter damage. Connectivity of the corticospinal and corticothalamic pathways was determined by using an asymmetry index based on the number of streamlines contained within these projections and compared with measures of paretic hand function and bimanual coordination. For cortical development, the volume of the ipsilesional precentral gyrus was significantly reduced. For connectivity measures, the numbers of streamlines in corticospinal tracts and corticothalamic pathways within the ipsilesional hemisphere were decreased compared with the contralesional side. The sensorimotor thalamic projections were more significantly correlated with paretic hand functions than were the corticospinal tracts. These data support the concept that preservation of sensorimotor thalamic pathways that directly project into the primary motor cortex has more influence on motor function control of the paretic hand than does preservation of corticospinal tracts.

Advanced Fiber Tracking in Early Acquired Brain Injury Causing Cerebral Palsy

“…Probabilistic fiber tracking with CSD of the CST and the TRS1 from their assumed starting points and including distant Waypoints appears to provide reliable and anatomically accurate tracking results. This finding is supported by Rose et al 6 and Tsao et al, 7 who also used probabilistic CSD fiber tractography to successfully track motor and sensory pathways. An alternative could have been to define the cortical ROIs from functional data such as fMRI.…”

“…Findings in recent studies in CP support this assumption. [5][6][7] In CP, studies have shown alterations in major fiber tracts, including the corticospinal tract (CST), the corticobulbar tract, superior and posterior thalamic radiations, the superior longitudinal fasciculus, and transcallosal fibers (for a review, see Scheck et al 8 ). Parametric changes include decreased fractional anisotropy (FA) and increased mean diffusivity (MD), indicating altered tract microstructure.…”

“…[14][15][16] In addition, correlations have been shown between diffusion measures in motor and sensory tracts and specific measures of sensory and/or motor functions. [5][6][7][17][18][19][20] Some studies suggest that sensory and motor functions correlate more strongly with changes in the sensory pathways (superior and posterior thalamic radiation) than changes in the motor pathways (CST). 6,19 These findings indicate that preservation of sensory pathways is important for motor function.…”

“…[5][6][7][17][18][19][20] Some studies suggest that sensory and motor functions correlate more strongly with changes in the sensory pathways (superior and posterior thalamic radiation) than changes in the motor pathways (CST). 6,19 These findings indicate that preservation of sensory pathways is important for motor function. However, most tractography studies in CP have used deterministic diffusion tensor tractography, which is a limitation because the algorithm cannot progress in areas where the tensor model shows a high uncertainty in the estimated fiber directions due to complex fiber architecture or pathologic changes.…”

Early reach to grasp development of infants with asymmetric brain injury on the Grasp and Reach Assessment of Brisbane (GRAB)

“…Evidence from advanced diffusion imaging has suggested that the developing connectivity and symmetry of the thalamocortical pathways connecting M1 with the motor thalamus is at least as important as the symmetry of the CS tracts for upper limb unimanual capacity and bimanual coordination in children with congenital hemiplegia. 214 Our group studied 16 children with congenital hemiplegia, of whom 9 were classified as having periventricular leukomalacia and 7 were classified as having predominantly deep gray matter lesions, according to the Krägeloh-Mann qualitative scheme. 215 Advanced diffusion imaging utilising the HARDI model (high angular diffusion imaging) was performed to elucidate the symmetry in the CS (motor) and the thalamocortical (sensorimotor) tracts (Figure 9.1.2., Table 9.1.2.).…”