Quantitative MRI predicts long-term structural and functional outcome after experimental traumatic brain injury.

In traumatic brain injury (TBI) the initial impact causes both immediate damage and also launches a cascade of slowly progressive secondary damage. The chronic outcome disabilities vary greatly and can occur several years later. The aim of this study was to find predictive factors for the long-term outcome using multiparametric, non-invasive magnetic resonance imaging (MRI) methodology and a clinically relevant rat model of fluid percussion induced TBI. Our results demonstrated that the multiparametric quantitative MRI (T(2), T(1rho), trace of the diffusion tensor D(av), the extent of hyperintense lesion and intracerebral hemorrhage) acquired during acute and sub acute phases 3 h, 3 days, 9 days and 23 days post-injury has potential to predict the functional and histopathological outcome 6 to 12 months later. The acute D(av) changes in the ipsilateral hippocampus correlated with the chronic spatial learning and memory impairment evaluated using the Morris water maze (p<0.05). Similarly, T(1rho), T(2) and D(av) correlated with hippocampal atrophy and with histologically quantified neurodegeneration (p<0.01). The early lesion volume and quantitative MRI changes in the perilesional region prefigured the final lesion extent (p<0.01). Furthermore, the severity of acute intracerebral hemorrhage correlated with the final cortical atrophy (p<0.05), hippocampal atrophy (p<0.01), and also with the water maze performance (p<0.01). We conclude that, assessment of early quantitative MRI changes in the hippocampus and in the perifocal area may help to predict the long-term outcome after experimental TBI.