Changes in the integrity of thalamocortical connections are associated with sensorimotor deficits in children with congenital hemiplegia

Abstract

Preservation of thalamocortical projections to the sensorimotor cortex is related to improved hand function in children with cerebral palsy (CP). Whether CP is associated with altered microstructure of these sensorimotor projections or other thalamocortical pathways remains unclear. Forty-two children with congenital hemiplegia and fifteen typically developing children (TDC) underwent structural and diffusion-weighted imaging (high-angular-resolution diffusion imaging) using a 3T MRI. Structural T1-images were parcellated into 34 cortical regions and the thalamus per hemisphere. Thalamocortical projections were extracted using probabilistic tractography and the top tan cortical regions with the greatest number of thalamocortical streamlines for the TDC group were selected for further analysis. The thalamus was parcellated based on its cortical connections. Differences between hemispheres for thalamocortical streamline numbers to each cortical region [asymmetry index (AI)], tract volume and tract microstructure [weighted mean fractional anisotropy (FA) and mean diffusivity (MD)] were calculated. Correlations between these measures (AI, FA and MD) and sensorimotor function were performed. Thalamocortical projections showed topographical organisation based on cortical connectivity. Projections to paracentral lobule, pre-central and post-central gyri showed greater AI in CP group, which indicates reduced streamlines on the ipsilesioned hemisphere. Reduced FA, reduced tract volume and increased MD were also found for these thalamocortical projections on the ipsilesioned hemisphere in children with CP. Changes in AI and tract microstructure of these projections were associated with poorer sensorimotor function. The findings suggest CP is associated with reorganisation of thalamocortical projections to the sensorimotor cortex. Integrity in these projections may underpin deficits in sensorimotor function.

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.…”

Motor, sensory and executive function brain networks in children with unilateral cerebral palsy

“…Thalamic changes are not limited to children with primary GM lesions; reduction in the thalamic volume without morphological or organisational change is also seen in children with periventricular white matter lesions 94,95 .…”

“…The superior thalamic radiations (the connection between thalamus and motor cortex) have been shown to exhibit reduced FA, increased MD as well as axial and radial diffusivity in both the non-dominant side of unilateral CP 95,110,171,172 and bilateral CP (contralateral to "more affected" limb) 171 . One study also demonstrated increased MD in the dominant hemisphere in unilateral spastic CP 172 .…”