Seizure-induced transient hippocampal abnormalities on MR: correlation with positron emission tomography and electroencephalography.

We report transient focal abnormalities on MR in a patient having frequent electrographic seizures that were not obvious clinically. Marked mass effect (confirmed with volumetric studies) and abnormal T2 signal intensity in the right hippocampal region correlated with electroencephalographic ictal activity and with increased positron-emitting radiotracer uptake in the medial temporal lobe. The follow-up MR 2 months later, after electroencephalography findings normalized, revealed no hippocampal abnormalities.