A case of medial temporal lobe epilepsy associated with occult focal cortical dysplasia in the lateral temporal neocortex

A 29-year-old male with medial temporal lobe epilepsy (MTLE) was revealed to have "occult" focal cortical dysplasia (FCD) in the lateral temporal neocortex. He had no history of febrile convulsion and developed complex partial seizure at the age of 14 year, which became intractable. Although MRI failed to reveal structural abnormality in the temporal lobe, even retrospectively, the findings of non-invasive preoperative examination, such as video-EEG monitoring and interictal ECD-SPECT and FDG-PET, were consistent with those of the left MTLE. Intraoperative electrocorticography (ECoG) demonstrated almost continuous paroxysmal activities on the anterior part of the inferior temporal gyrus (ITG). Anterior temporal lobectomy (ATL) with hippocampectomy was performed. Histological examination revealed FCD in the small area with 0.8 mm in diameter of the resected ITG. In the ATL without preoperative invasive examination such as chronic subdural electrode recording, intraoperative ECoG recording is mandatory.