Clinical and imaging characteristics of fever-induced refractory epileptic encephalopathy (FIRES), idiopathic hemiconvulsion-hemiplegia syndrome (IHHS), and related acute encephalopathies are reviewed by researchers at Descartes University, Paris, France; Institute for Pharmacological Research, Milan, Italy: and Institute of Biomedical Imaging, Orsay, France. FIRES begins in school-age children with status epilepticus lasting several weeks, involving perisylvian and mesial temporal structures, and is followed by refractory epilepsy and major cognitive deterioration. IHHS begins in infancy with unilateral clonic status epilepticus and is followed by hemiplegia with refractory epilepsy. The etiology is unknown, but both FIRES and IHHS are acute encephalopathies with inflammation-mediated status epilepticus. The ketogenic diet is recommended to treat both seizures and inflammation.