Magnetic-resonance-imaging-based volume studies in patients with bitemporal epileptiform abnormalities

We performed a prospective study of magnetic resonance imaging (MRI) based hippocampal formation (HF) volumetry in 10 patients with intractable partial epilepsy of anterior temporal lobe origin. Extracranial ictal EEG recordings did not allow appropriate localization of the epileptogenic zone, and all patients required depth EEG. Chronic intracranial monitoring revealed the anterior temporal lobe onset of seizures in all patients. MRI showed a lateralized hippocampal alteration, i.e., HF atrophy and/or an increased T2-signal intensity, in 5 of the 10 patients that correctly identified the epileptic temporal lobe. Quantitative HF atrophy coexisted with the site of seizure onset as determined by the intracranial EEG recordings in four patients. Volumetry was indeterminant for atrophy in six patients. An increased mesial temporal T2-signal intensity in one patient correlated with the temporal lobe of seizure origin. MRI-identified hippocampal pathology may be highly specific in patients with bitemporal epileptiform abnormalities to indicate the localization of epileptic brain tissue.