TIRDA Originating From Lateral Temporal Cortex in a Patient With mTLE Is Not Related to Hippocampal Activity

Electrophysiological studies have suggested that temporal intermittent rhythmic delta activity (TIRDA) has a localizing value similar to interictal spikes in patients with temporal lobe epilepsy and is associated with a favorable outcome after temporal lobectomy. However, it remains controversial whether TIRDA is an EEG marker for mesial or lateral temporal epileptogenesis. We simultaneously recorded scalp EEG and stereoencephalography in a patient with mesial temporal lobe epilepsy during epilepsy presurgical evaluation. Seizure onset was localized to the hippocampus. However, TIRDA originated from the lateral temporal cortex, and rhythmic delta activity was not observed concomitantly in the hippocampus. In addition, TIRDA was not associated with repetitive interictal spikes or subclinical seizures in the hippocampus as previously speculated. This case suggests that TIRDA can be an EEG marker that is independent of hippocampal activity and can represent temporal neocortical epileptogenesis.