Moderate-severe traumatic brain injury causes delayed loss of white matter integrity: evidence of fornix deterioration in the chronic stage of injury.

Objectives: To examine structural integrity loss in the fornix from 5-30 months after moderate and severe traumatic brain injury (TBI) using diffusion tensor imaging. Methods: MRIs were prospectively undertaken in 29 adults with moderate and severe TBI at two time points. Fractional anisotropy (FA) was calculated for the fornix (column/body, right crux and left crux) at 5 and 30 months post-injury. Results: Paired t-tests revealed significant FA reductions with large effect sizes across time in the column/body, p<0.001, right crux, p<0.001 and left crux, p<0.001. Conclusions: These data contribute to the growing body of evidence that loss of white matter continues in moderate and severe TBI even after the acute neurological effects of TBI have resolved. As the fornix plays a critical role in memory, this may be a contributing factor to the poor clinical outcomes observed in these patients.