Comparative Value of Spontaneous and Chemically and Electrically Induced Seizures in Establishing the Lateralization of Temporal Lobe Seizures

Abstract

Summary: A retrospective clinical study is presented which is based on 133 patients with uncontrolled temporal lobe seizures who underwent bilateral stereoelectroencephalographic exploration. The aim of the study was to evaluate quantitatively the degree of agreement among spontaneous and chemically and electrically induced seizures, as well as between each of these seizures and the spontaneous interictal activity (“spiking”). To simplify the problem, only the side of origin and not the exact site of onset of the ictal discharge within the temporal lobe was dealt with. Special attention was paid to whether or not a seizure propagated to the homotopic regions of the opposite hemisphere, thus dealing with the still controversial question of the independent secondary epileptogenic lesion or “mirror” focus in man. The clinical outcome of surgery in 64 cases of temporal lobe epilepsy in which the operation was based on the conclusions of the SEEG exploration with or without recording of spontaneous seizures confirmed the outstanding importance of the spontaneous seizures in identifying the side of the primary epileptogenic zone. The degree of positive correlation between the spontaneous and the induced seizures varied from 77% for the electrically and 60% for the chemically induced seizures. On the other hand, the spontaneous interictal activity agreed only in approximately two‐thirds of cases: best with the electrically induced and less with the spontaneous seizure. Chemically induced seizures agreed the least. The authors conclude: (1) Because of relatively frequent discrepancies between the side of onset of the seizures and the lateralization of interictal epileptic activity, the recording of seizures is of primary importance for assessing the results of the SEEG examination. (2) The recording of spontaneous seizures is preferable to that of electrically or chemically induced seizures. (3) The reliability of the lateralization suggested by electrically induced seizures is somewhat higher than that of chemically provoked seizures. (4) Special caution should be exercised in determining the lateralization of seizures with contralateral propagation. RÉSUMÉ Une étude clinique rétrospective est faite sur 133 malades présentant une épilepsie du lobe temporal résistant à la thérapeutique et ayant subi une exploration stéréo‐EEG bilatérale. Le but de ce travail est Ďévaluer quantitativement les rapports entre les différents types de crises (spontanées, induites par des moyens chimiques et par la stimulation électrique). Une corrélation a également été faite entre les différents types de crises et Ľactivité intercritique spontanea (pointes). Pour simplifier le probleme, seul le côté de la décharge critique onginelle dans le lobe temporal a été envisage. Un interet particulier a porte sur le probleme de la propagation dventuelle aux regimes homologues de l'hemisphere oppose dans le but de discuter la question controversy des lesions epileptogènes secondares indépendantes ou des “foyers en miroir” chez l'homme. Les interventi...

Temporal Epileptogenesis: Localizing Value of Scalp and Subdural Interictal and Ictal EEG Data

“…Our data indicate that subdural interictal spike location should not be ignored in assessing epileptogenesis: if initial subdurally recorded temporal seizures arise contralateral to subdural or scalp spikes, additional seizures should be sought before explantation of electrodes. Weaker spike-seizure correlations have been found with depth electrode studies (11,(18)(19)(20)(21)(22), perhaps because of smaller cortical volume sampled with depth electrodes. Using automated means to detect, describe, and localize spikes recorded by depth and/or subdural electrodes, Hufnagel et al (23) obtained good correlations with regions of seizure origin.…”

Spatiotemporal dynamics of optogenetically induced and spontaneous seizure transitions in primary generalized epilepsy

“…Bottom, wave propagating in the opposite direction, recorded during the self-sustained SWDs following stimulation but sometimes seen during the stimulation period, as well (see also Supplemental Movie 2). Wykes et al 2012) and to induce seizure-like afterdischarges in the hippocampus of nonepileptic rats (e.g., Osawa et al 2013). It has never been applied, however, to the study of seizure initiation in awake, freely behaving epileptic animals with primary generalized seizures.…”

“…We first used the Monte Carlo method of photon transport in a scattering medium (Wang et al 1995) to obtain the distribution of absorbed volume power density and then numerically solved the heat equation. Specifically, we launched 10 7 photon packets from a 50-m-diameter aperture (NA ϭ 0.22) on a three-dimensional Cartesian grid of step size dx ϭ dy ϭ dz ϭ 10 m. We used a brain refractive index of 1.36, absorption and scattering coefficients of 42.3 and 10,600 m Ϫ1 , respectively, and an anisotropy factor of 0.887, values that were previously obtained from optical measurements of human gray matter at 532 nm (Yaroslavsky et al 2002). These simulations yielded the absorbed volume power density, P V .…”

Induction of Partial Epileptic Seizures by Flumazenil

“…As with other activation methods, however, the question of whether the induced seizures correctly localized the seizure-onset zone remains (56,57,58). In all eight patients who developed seizures after FMZ injection in this study, the seizure semiology was typical and, at times, had high localizing value (eg, simple partial seizures with clonic twitching of the arm).…”