Diffusion Tensor Imaging data will be analyzed following our previously established protocol. Transcallosal fibers will be traced between homotopic primary language regions in both hemispheres and fractional anisotropy will be measured within those traced fibre bundles as surrogate marker of fibre tract integrity as previously described. FA values will then be correlated with clinical primary outcome measures in each treatment group to test the hypothesis that fibre tract integrity predicts therapeutic response.