Dipole Modeling in Epilepsy Surgery Candidates

Abstract

Summary:Purpose: The validity and clinical significance of dipole modeling in epilepsy surgery candidates is not fully established.Patients and Methods: Interictal and ictal dipole modeling was performed in 43 patients with refractory complex partial seizures (CPS) and intracranial structural abnormalities demonstrated with optimum magnetic resonance imaging (MRI: space-occupying, n = 15; atrophic, n = 26; dysplastic, n = 2). Video-EEG monitoring showed CPS in all patients. In 12 patients, additional intracranial EEG monitoring demonstrated hippocampal seizure onset in 11 patients and medial occipital ictal onset in 1.Results: Spatiotemporal dipole mapping of averaged interictal spikes and epochs of early ictal discharges revealed two distinct dipole patterns. Patients with lesions located in the medial (-+ lateral) temporal lobe (n = 34) and medial occipital lobe (n = 1) uniformly presented a combined interictal dipole that consisted of a radial and a tangential component with a high degree of elevation relative to the axial plane. Eight of 9 patients with extratemporal lesions had a less stable dipole with a predominant radial component. Ictal dipole modeling identified the ictal onset zone correctly as compared with intracranial EEG recordings from bilateral hippocampal depth electrodes. Ictal dipoles showed a striking correspondence with the interictal dipoles in individual patients.Conclusions: Interictal and ictal dipole mapping provided additional, reliable, and relevant localizing information in surgical candidates for refractory CPS. Ictal dipole analysis may limit the number of patients who require intracranial electrodes.

Frequency domain EEG source localization of ictal epileptiform activity in patients with partial complex epilepsy of temporal lobe origin

“…Similar dipole results for interictal epileptiform activity in patients with mesiotemporal epilepsy have been obtained in our previous investigations (Lantz et al, 1996(Lantz et al, , 1997, and the similarity between ictal and interictal dipole results has also been demonstrated by other investigators (Boon et al, 1997).…”

“…Ebersole (1994) found the early ictal rhythms of mesiotemporal seizures to have a strong vertical dipole component, whereas lateral temporal neocortical seizures could be modeled mainly by radial dipoles. Boon et al (1997) found similar differences between ictal dipoles in patients with temporal (mostly medial) lesions compared with patients with extratemporal neocortical lesions. In this investigation, dipole reconstruction of the ictal patterns localized the activity to one temporal lobe, with a specific oblique posterior and elevated dipole orientation (the OPE pattern) that was quite reproducible between patients.…”

Spike voltage topography in temporal lobe epilepsy

“…In conclusion, scalp EEG has the potential to offer more spatial and temporal information [1,[7][8][9]. These techniques are more sophisticated and require more in-depth training and experience for proper application and interpretation.…”

Dipole‐Source Analysis in a Realistic Head Model in Patients with Focal Epilepsy

“…Several noninvasive and interictal diagnostic approaches have been implemented in the presurgical evaluation programs in intractable epilepsy syndromes of uniregional origin, all of them with the intention (a) to add to the complementary information about a regional functional deficit or morphologic lesion corresponding to the hypothesized primary epileptogenic zone, and (b) to reduce the number of invasive EEG recordings (26)(27)(28)(29). For this purpose, the most promising aspect of EEG dipole-source analysis is the theoretic possibility to ameliorate the poor spatial resolution of spikes recorded from the scalp in depth.…”