Prognostic value of diffusion tensor imaging parameters in severe traumatic brain injury

Diffusion tensor imaging (DTI) has recently emerged as a useful tool for assessing traumatic brain injury (TBI). In this study, the prognostic value of the relationship between DTI measures and the clinical status of severe TBI patients, both at the time of magnetic resonance imaging (MRI), and their discharge to acute TBI rehabilitation, was assessed. Patients (n=59) admitted to the trauma center with severe closed head injuries were retrospectively evaluated after approval from the institution's institutional review board, to determine the prognostic value of DTI measures. The relationship of DTI measures, including apparent diffusion coefficient (ADC), fractional anisotropy (FA), axial (λ_∥) and radial diffusivity (λ_⊥) from the whole brain white matter, internal capsule, genu, splenium, and body of the corpus callosum, were compared with neurological status at MRI and at discharge to acute TBI rehabilitation. Whole brain white matter averages of ADC, λ_∥, and λ_⊥, and their coefficient of variation (CV) were significantly correlated with the Glasgow Coma Scale (GCS) score on the day of MRI. The average λ_∥ was significantly correlated with GCS scores on the day of MRI in all measured brain regions. Outcomes were associated with whole brain white matter averages of ADC and λ_∥, and the CVs of FA, ADC, λ_∥, and λ_⊥; and the averages and CVs of FA and λ_∥ in all corpus callosum regions. The inclusion of regional and global DTI measures improved the accuracy of prognostic models, when adjusted for admission GCS score and age (p<0.05). Whole brain white matter and regional DTI measures are sensitive markers of TBI, and correlate with neurological status both at MRI and discharge to rehabilitation. The addition of DTI measures adjusted for age, gender, and admission GCS score significantly improved prognostic models.