Diffusion tensor MRI of axonal plasticity in the rat hippocampus

The aim of this study was to explore non-invasive imaging methods to detect post-injury structural axonal plasticity. Brain injury was launched by status epilepticus induced by intraperitoneal injection of either kainic acid or pilocarpine. Several months later, ex vivo diffusion tensor magnetic resonance imaging (DTI) showed increased FA in the dentate gyrus of both kainic acid (p < 0.01) and pilocarpine animals (p < 0.01). Importantly, FA changes correlated (p < 0.01) with histologically verified axonal plasticity of myelinated and non-myelinated neuronal fibers. The changes observed in DTI parameters ex vivo in the septal dentate gyrus were also seen by in vivo DTI. As DTI is completely a non-invasive imaging method, these results may pave the way for non-invasive in vivo imaging of axonal plasticity after brain insults.