A previously healthy 67-year-old man presented with a transient isolated episode of partial complex seizures and dysphasia. A previously healthy 67-year-old man presented with a transient isolated episode of partial complex seizures and dysphasia. A, A cortical abnormality that involved the lateral aspect of the left TL (asterisk) and a subtle hyperintensity on coronal T2 were noticed in the ipsilateral hippocampus. B, Restricted diffusion on DWI was visible in the same areas (arrowhead), and a diagnosis of postictal edema was considered. C, After 2 months and a worsening of the clinical manifestations, a necrotic mass in the left TL (arrow) was observed on a T1 postcontrast image. A diagnosis of glioblastoma was confirmed after surgery. High-grade gliomas can manifest early as ill-defined lesions that usually have restricted diffusion and involve the cortex with a lack of a mass effect. Follow-up imaging and advanced imaging techniques are crucial for making the diagnosis. A.J. da Rocha et al. AJNR Am J Neuroradiol 2015;36:2196-2205 ©2015 by American Society of Neuroradiology