Year, Volume, Issue, Page(s):16, 16, 2,
Study investigated the direction and magnitude of early longitudinal changes in white matter fractional anisotropy (FA) in patients with traumatic brain injury (TBI) and determined whether acute or subacute FA values correlate more reliably with functional outcomes after TBI. From a prospective TBI outcomes database, 11 patients who underwent acute (≤7 days) and subacute (8 days to rehabilitation discharge) diffusion tensor imaging (DTI) were retrospectively analyzed. Longitudinal changes in FA were measured in 11 white matter regions susceptible to traumatic axonal injury. Correlations were assessed between acute FA, subacute FA and the disability rating scale (DRS) score, which was ascertained at discharge from inpatient rehabilitation. Results indicated that FA declined from the acute-to-subacute period in the genu of the corpus callosum (0.70 vs. 0.55) and inferior longitudinal fasciculus (0.54 vs. 0.49). Acute correlations between FA and DRS score were variable: higher FA in the body (−0.78) and splenium (−0.83) of the corpus callosum was associated with better outcomes (i.e. lower DRS scores), whereas higher FA in the genu of the corpus callosum corresponded with worse outcomes (i.e. higher DRS scores). In contrast, in the subacute period higher FA in the splenium correlated with better outcomes and no inverse correlations were observed. In this study, white matter FA declined during the acute-to-subacute stages of TBI. Variability in acute FA correlations with outcome suggests that the optimal timing of DTI for TBI prognostication may be in the subacute period.