Sixto Obrador SENEC prize 2019: Utility of diffusion tensor imaging as a prognostic tool in moderate to severe traumatic brain injury. Part I. Analysis of DTI metrics performed during the early subacute stage

Abstract

Background and objectives: Traumatic axonal injury (TAI) contributes significantly to mortality and morbidity after traumatic brain injury (TBI). Its identification is still a diagnostic challenge because of the limitations of conventional imaging techniques to characterized it. Diffusion tensor imaging (DTI) can indirectly identify areas of damaged white matter integrity by detecting water molecule diffusion alterations. Our main objective is to characterize the TAI using DTI at the early subacute stage in our series of moderate to severe TBI patients and to evaluate if there is a relationship between the information provided by the DTI and patient's outcome.

Materials and methods: We have obtained DTI data from 217 patients with moderate to severe TBI acquired at a median of 19 days after TBI, and patient DTI metrics were compared with data obtained from 58 age-matched healthy controls. Region of interest method was applied to obtain mean fractional anisotropy (FA) value in 28 white matter fiber bundles susceptible to TAI.

Results: Our main results were that when we compared patients with controls, patients, regardless of TBI severity, showed significantly reduced mean FA in almost all region of interest measured. We found statistically significant correlation between FA metrics and some clinical characteristics. Additionally, the FA values of the three portions of Corpus callosum, Cingulum and cerebral peduncles measured at the early subacute stage were highly associated with outcome assessed at hospital discharge and at 6 and 12 months after TBI.

Conclusions: We conclude that DTI is a useful tool to characterize TAI and the detection of FA reduction in the subacute stage after TBI is associated with long-term unfavorable outcome.

Keywords: Anisotropía fraccionada; Análisis longitudinal; Axial diffusivity; Diffusion tensor imaging; Difusión axial; Difusión radial; Fractional anisotropy; Longitudinal analysis; Medidas de evolución; Ordinal regression analysis; Outcome measures; Radial diffusivity; Regresión ordinal; Tensor de difusión; Traumatic brain injury; Traumatismo craneoencefálico.