A novel application of neurite orientation dispersion and density imaging to differentiate cognitively recovered versus non-recovered following mild traumatic brain injury

Abstract

Objective: Cognitive deficits in mild traumatic brain injury (mTBI) can persist over three months, and symptomatic patients may not be readily diagnosed. Although diffusion tensor imaging (DTI) can detect microstructural white matter tract (WMT) changes in mTBI, the underlying recovery process is not fully understood. We aimed to investigate WMT changes at 3 months post-mTBI between cognitively recovered (REC) and non-recovered (NREC) mTBI subjects using diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI).

Methods: Fifty-seven mTBI subjects were divided into REC (n=16) and NREC (n=41) groups. Ten healthy controls (HC) were recruited. MRI and Neuropsychological Assessment Battery-Screening Module (S-NAB) performance were assessed at baseline and three months before subjects were classified as REC and NREC. DTI and NODDI parameters of 50 ROIs corresponding to WMTs were compared between REC, NREC and HC.

Results: NODDI detected more significant changes (p<0.05) in multiple ROIs than DTI. Lower Neurite Density Index (NDI) was demonstrated in REC versus NREC at multiple ROIs. Increased Orientation Dispersion Index (ODI) and decreased Isotropic Volume Fraction (ISOVF) were detected at several WMTs in both groups.

Conclusion: Reduced NDI in the overall mTBI cohort suggests axonal degeneration post-trauma. We postulate that at three months’ timeline, there is a combination of axonal degeneration and astrogliosis, which is more extensive in NREC than REC.