Isolated Diffusion Restriction Precedes the Development of Enhancing Tumor in a Subset of Patients with Glioblastoma

Low-ADC lesion with progressive tumor supported by MR perfusion and MR spectroscopy. A−C, Fourteen months after treatment for a right temporal lobe tumor, the posterior limb of the right internal capsule shows a new diffusion-restricted lesion visible on DWI (A) and the ADC map (B) that does not enhance on the contrast T1-weighted image (C). D and E, Dynamic susceptibility contrast MR perfusion map (D) shows the lesion (circle) to have a mild hyperperfusion with rCBV = 1.4 (compared with contralateral white matter), and multivoxel spectroscopy (E) reveals increased Cho and decreased NAA with a maximal Cho/NAA ratio of 2:2 (highlighted box). F, Three months later, the diffusion-restricted lesion has increased in size on the ADC map. G, The lesion demonstrates new heterogeneous enhancement on the contrast T1-weighted image (G), which is in the same region of the initially detected focus of diffusion restriction (A).