Dipole source localization of ictal epileptiform activity in estimation of epileptogenic zone

Abstract

Localization analysis of epileptogenic zone was performed by dipole tracing method with scalp–skull–brain head model (SSB-DT) in patients with intractable epilepsy. Eight temporal lobe epilepsy (TLE) and one frontal lobe epilepsy were studied. EEG was recorded by digital electroencephalograph with 21 scalp electrodes. Generator source of the peak of ictal epileptiform activity (IEA) was estimated by SSB-DT. All the patients underwent electrocorticography (ECoG) and resection of epileptogenic zone. Surgical outcome was good in every patient. Locations of generator source of the peak of IEA estimated by SSB-DT were consistent with locations of epileptogenic zone determined by ECoG and neuroimagings, such as magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT). In TLE, medial and lateral temporal epileptogenic zone could be discriminated, which could not be determined by visual interpretation of scalp EEG. In medial TLE, as an advance of seizure, generator source of IEA either stayed in the medial temporal lobe, or propagated to the lateral temporal lobe. Locations of epileptogenic zone could be estimated by SSB-DT not invasively. Electrophysiological event in the brain during an advance of seizure attack could also be observed. Application of SSB-DT to IEA was useful in the medical treatment of epilepsy, especially in surgical planning for patients with medically intractable epilepsy.