Maturation of Corticospinal Tracts in Children With Hemiplegic Cerebral Palsy Assessed by Diffusion Tensor Imaging and Transcranial Magnetic Stimulation.

Christos Papadelis,Harper Kaye,Benjamin Shore,Brian Snyder,Patricia Ellen Grant,Alexander Rotenberg

doi:10.3389/fnhum.2019.00254

Abstract

Aim: To assess changes in the developmental trajectory of corticospinal tracts (CST) maturation in children with hemiplegic cerebral palsy (HCP).Methods: Neuroimaging data were obtained from 36 children with HCP for both the more affected (MA) and less affected (LA) hemispheres, and, for purposes of direct comparison, between groups, 15 typically developing (TD) children. With diffusion tensor imaging (DTI), we estimated the mean fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD) of the corticospinal tract, parameters indicative of factors including myelination and axon density. Transcranial magnetic stimulation (TMS) was performed as a neurophysiologic measure of corticospinal tract integrity and organization. Resting motor threshold (rMT) was obtained per hemisphere, per patient.Results: We observed a significant AD and MD developmental trajectory, both of which were inversely related to age (decrease in AD and diffusivity corresponding to increased age) in both hemispheres of TD children (p < 0.001). This maturation process was absent in both MA and LA hemispheres of children with HCP. Additionally, the TMS-derived previously established rMT developmental trajectory was preserved in the LA hemisphere of children with HCP (n = 26; p < 0.0001) but this trajectory was absent in the MA hemisphere.Conclusions: Corticospinal tract maturation arrests in both hemispheres of children with HCP, possibly reflecting perinatal disruption of corticospinal tract myelination and axonal integrity.

Highlights

Hemiplegic cerebral palsy (HCP) is a common subtype of motor dysfunction, affecting one-third of patients with a clinical cerebral palsy diagnosis (Hagberg et al, 2001)
We observed a significant axial diffusivity (AD) and mean diffusivity (MD) developmental trajectory, both of which were inversely related to age
The transcranial magnetic stimulation (TMS)-derived previously established Resting motor threshold (rMT) developmental trajectory was preserved in the less affected (LA) hemisphere of children with HCP (n = 26; p < 0.0001) but this trajectory was absent in the more affected (MA) hemisphere

Summary

Introduction

Hemiplegic cerebral palsy (HCP) is a common subtype of motor dysfunction, affecting one-third of patients with a clinical cerebral palsy diagnosis (Hagberg et al, 2001). The underlying etiology is a non-progressive lesion located most commonly in the periventricular white matter of the developing fetal or infant brain (Rosenbaum et al, 2007). This lesion impairs the structural integrity of the corticospinal tracts (CST), which are the most important tracts for fine motor skills, and among the first tracts to mature. When measured by TMS, CST maturation in healthy children corresponds to a progressive increment of cortical excitability from infancy to adulthood that completes in mid-adolescence (Koh and Eyre, 1988; Nezu et al, 1997; Hameed et al, 2017; Kaye and Rotenberg, 2017). There are no TMS or DTI studies to examine whether and how normal CST maturation is affected by perinatal white matter injury, as occurs in HCP

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