Age related diffusion and tractography changes in typically developing pediatric cervical and thoracic spinal cord

Abstract

Background and objectiveDiffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) are two techniques that can measure white matter integrity of the spinal cord. Recently, DTI indices have been shown to change with age. The purpose of this study is (a) to evaluate the maturational states of the entire pediatric spinal cord using DTI and DTT indices including fractional anisotropy (FA), mean diffusivity (MD), mean length of white matter fiber tracts and tract density and (b) to analyze the DTI and DTT parameters along the entire spinal cord as a function of spinal cord levels and age.MethodA total of 23 typically developing (TD) pediatric subjects ranging in age from 6 to 16 years old (11.94 ± 3.26 (mean ± standard deviation), 13 females and 10 males) were recruited, and scanned using 3.0 T MR scanner. Reduced FOV diffusion tensor images were acquired axially in the same anatomical location prescribed for the T2-weighted images to cover the entire spinal cord (C1-mid L1 levels). To mitigate motion induced artifacts, diffusion directional images were aligned with the reference image (b0) using a rigid body registration algorithm performed by in-house software developed in Matlab (MathWorks, Natick, Massachusetts). Diffusion tensor maps (FA and MD) and streamline deterministic tractography were then generated from the motion corrected DTI dataset. DTI and DTT parameters were calculated by using ROIs drawn to encapsulate the whole cord along the entire spinal cord by an independent board certified neuroradiologist. These indices then were compared between two age groups (age group A = 6–11 years (n = 11) and age group B = 12–16 years (n = 12)) based on similar standards and age definitions used for reporting spinal cord injury in the pediatric population. Standard least squared linear regression based on a restricted maximum likelihood (REML) method was used to evaluate the relationship between age and DTI and DTT parameters.ResultsAn increase in FA (group A = 0.42 ± 0.097, group B = 0.49 ± 0.116), white matter tract density (group A = 368.01 ± 236.88, group B = 440.13 ± 245.24) and mean length of fiber tracts (group A = 48.16 ± 20.48 mm, group B = 60.28 ± 23.87 mm) and a decrease in MD (group A = 1.06 ± 0.23 × 10−3 mm2/s, group B = 0.82 ± 0.24 × 10−3 mm2/s) were observed with age along the entire spinal cord. Statistically significant increases have been shown in FA (p = 0.004, R2 = 0.57), tract density (p = 0.0004, R2 = 0.58), mean length of fiber tracts (p < 0.001, R2 = 0.5) and a significant decrease has been shown in MD (p = 0.002, R2 = 0.59) between group A and group B. Also, it has been shown DTI and DTT parameters vary along the spinal cord as a function of intervertebral disk and mid-vertebral body level.ConclusionThis study provides an initial understanding of age related changes of DTI values as well as DTT metrics of the spinal cord. The results show significant differences in DTI and DTT parameters which may result from decreasing water content, myelination of fiber tracts, and the thickening...

Atlas-Based Quantification of DTI Measures in a Typically Developing Pediatric Spinal Cord

“…Despite the lack of a significant effect observed between the FA and age, the correlation of age with FA specifically and other DTI-derived indices generally was consistent with that in former studies. 5,21 While examining the effect of age on each individual tract in this study, we observed that there is a relationship of diffusivity metrics and maturation of some tracts (i.e., the spinothalamic tract). This could be because of the myelination process in different tracts.…”

Cerebral White Matter Myelination and Relations to Age, Gender, and Cognition: A Selective Review

“…During the transition from childhood (6–11 years) to adolescence (12–16 years), FA, fiber density and length in the SC increase, whereas MD decreases ( Alizadeh et al, 2018 ). Findings on the association between other DTI metrics and age are controversial.…”

Quantification of DTI in the Pediatric Spinal Cord: Application to Clinical Evaluation in a Healthy Patient Population

“…3,7,8 Before pediatric spinal cord DTI can reach its clinical potential, normal ranges of diffusion indices must be established, including the variation in derived indices across development and cord regions. 9 Previous studies in pediatric patients have shown age-and region-related DTI differences and report positive correlations between age and FA, [10][11][12] negative correlations between age and AD, 11 RD, 11 and MD, [10][11][12] and several regional differences. 11,12 However, these studies used relatively small sample sizes (n ϭ 22-41) [10][11][12] over an incomplete pediatric age range (6 -16 years) 11,12 and/or used suboptimal DTI sequence parameters.…”