OBJECTIVE:A subset of children with febrile status epilepticus (FSE) are at risk for development of temporal lobe epilepsy later in life. We sought a noninvasive predictive marker of those at risk that can be identified soon after FSE, within a clinically realistic timeframe. METHODS:Longitudinal T2 -weighted magnetic resonance imaging (T2 WI MRI) of rat pups at several time points after experimental FSE (eFSE) was performed on a high-field scanner followed by long-term continuous electroencephalography. In parallel, T2 WI MRI scans were performed on a 3.0-T clinical scanner. Finally, chronic T2 WI MRI signal changes were examined in rats that experienced eFSE and were imaged months later in adulthood. RESULTS:Epilepsy-predicting T2 changes, previously observed at 2 hours after eFSE, persisted for at least 6 hours, enabling translation to the clinic. Repeated scans, creating MRI trajectories of T2 relaxation times following eFSE, provided improved prediction of epileptogenesis compared with a single MRI scan. Predictive signal changes centered on limbic structures, such as the basolateral and medial amygdala. T2 WI MRI changes, originally described on high-field scanners, can also be measured on clinical MRI scanners. Chronically elevated T2 relaxation times in hippocampus were observed months after eFSE in rats, as noted for post-FSE changes in children. SIGNIFICANCE:Early T2 WI MRI changes after eFSE provide a strong predictive measure of epileptogenesis following eFSE, on both high-field and clinical MRI scanners. Importantly, the extension of the acute signal changes to at least 6 hours after the FSE enables its inclusion in clinical studies. Chronic elevations of T2 relaxation times within the hippocampal formation and related structures are common to human and rodent FSE, suggesting that similar processes are involved across species.