Localization of Epileptic Auras Induced on Stimulation by Subdural Electrodes

Abstract

Summary:Purpose: This study evaluates the localization of stimulation-induced auras (SIA) and tries to determine whether the SIA can help to define the boundaries of resection in epilepsy surgery.Methods: Using subdural grid electrodes, 3 1 patients with drug resistant focal epilepsy were examined in a retrospective and prospective study lasting 2 years.Results: On stimulation by subdural electrodes, we elicited habitual auras in 16 patients (52%). The zone of SIA overlapped the epileptogenic lesion in 12 patients (75%), the EEG seizure onset zone in 12 patients (75%), and the irritative zone of interictal spikes in eight patients (50%). Postoperative results showed a significant correlation with the complete removal of the epileptogenic lesion (p c 0.001). Because the number of patients in the study was small, we could not find a significant correlation with the complete removal of the SIA zone, EEG seizure onset zone. and irritative zone.Conclusions: Our study confirms previous analyses which indicate that complete resection of the epileptogenic lesion is essential to achieve a good outcome. Frequent overlap of the SIA zone with the epileptogenic lesion and the EEG seizure onset zone indicates proximity of the SIA with the epileptogenic zone. Nevertheless, this study does not support the concept that the SIA zone and the EEG seizure onset zone have additional value in defining the boundaries of resection in epilepsy surgery. Three case presentations suggest that SIA result from facilitated pathways between the stimulated cortex, the epileptogenic zone around the lesion, and the symptomatogenic zone. Functional reorganization in the vicinity of the cortical lesion cannot be ruled out but was not seen in our patients. Thus, SIA often do not reflect the normal function of the stimulated underlying cortex.

Functional Mapping of the Insular Cortex: Clinical Implication in Temporal Lobe Epilepsy

“…One must be careful when discussing responses evoked after stimulation of epileptic insular cortex, most authors agreeing that stimulation of epileptic cortices do not reflect the normal function of the underlying cortex because of plastic changes that may have occurred in response to repeated seizures (7,8,22). Only one patient in this study had seizures originating in the insular cortex.…”

Reappraisal of the human vestibular cortex by cortical electrical stimulation study

“…14 Obviously, one must be careful when assessing the effect of stimulation of epileptic cortices, because of possible plastic changes that may have occurred in response to repeated seizures. 14,46 This could explain why our stimulation study showed so much interindividual variability for the occurrence and the type of elicited VSs. This theoretical bias was reduced in this study, because we systematically excluded from analysis elicited responses that resembled patient's usual seizures, symptoms associated with an afterdischarge, and stimulations applied inside or at the vicinity of an epileptogenic lesion.…”

Controlling Bursting in Cortical Cultures with Closed-Loop Multi-Electrode Stimulation

“…Alternatively, animal and modeling studies suggest that focal stimulation at the site of the seizure can terminate seizures after they have started (Lesser et al, 1999;Franaszczuk et al, 2003;Slutzky et al, 2003). In humans, focal stimulation in the cortex or hippocampus has indeed been found effective in a number of studies (Cooper et al, 1973(Cooper et al, , 1976(Cooper et al, , 1977Lü ders et al, 1988;Shulz et al, 1997;Velasco et al, 2000Velasco et al, , 2001Motamedi et al, 2002;Vonck et al, 2002). Stimulation through a single electrode offered protection against seizures, but only if the stimulus was strong enough that the entire seizure-prone area was reached (Motamedi et al, 2002;Kellinghaus et al, 2003), which was difficult in practice.…”