A prospective diffusion tensor imaging study in mild traumatic brain injury

TLDR

White matter abnormalities in mild traumatic brain injury (mTBI) are poorly understood, with axonal damage disrupting ionic homeostasis and perpendicular diffusion during the semi‑acute stage. This study aimed to assess white matter integrity with diffusion tensor imaging (DTI) and compare its accuracy to traditional scans and neuropsychological tests for objectively classifying mTBI patients from controls. DTI and an extensive imaging/clinical battery were performed on 22 semi‑acute mTBI patients and 21 matched healthy controls, with a subset followed longitudinally 3–5 months later. mTBI patients showed significantly higher fractional anisotropy from reduced radial diffusivity in the corpus callosum and left‑hemisphere tracts, DTI outperformed conventional measures in classification, and longitudinal data indicated partial normalization, suggesting cytotoxic edema and supporting DTI as a potential biomarker of recovery.

Abstract

Only a handful of studies have investigated the nature, functional significance, and course of white matter abnormalities associated with mild traumatic brain injury (mTBI) during the semi-acute stage of injury. The present study used diffusion tensor imaging (DTI) to investigate white matter integrity and compared the accuracy of traditional anatomic scans, neuropsychological testing, and DTI for objectively classifying mTBI patients from controls.Twenty-two patients with semi-acute mTBI (mean = 12 days postinjury), 21 matched healthy controls, and a larger sample (n = 32) of healthy controls were studied with an extensive imaging and clinical battery. A subset of participants was examined longitudinally 3-5 months after their initial visit.mTBI patients did not differ from controls on clinical imaging scans or neuropsychological performance, although effect sizes were consistent with literature values. In contrast, mTBI patients demonstrated significantly greater fractional anisotropy as a result of reduced radial diffusivity in the corpus callosum and several left hemisphere tracts. DTI measures were more accurate than traditional clinical measures in classifying patients from controls. Longitudinal data provided preliminary evidence of partial normalization of DTI values in several white matter tracts.Current findings of white matter abnormalities suggest that cytotoxic edema may be present during the semi-acute phase of mild traumatic brain injury (mTBI). Initial mechanical damage to axons disrupts ionic homeostasis and the ratio of intracellular and extracellular water, primarily affecting diffusion perpendicular to axons. Diffusion tensor imaging measurement may have utility for objectively classifying mTBI, and may serve as a potential biomarker of recovery.