Comparison of the Results Obtained from Ictal Recordings and Cortical Stimulation in Patients with Refractory Epilepsy Investigated with Subdural Electrodes.
Abstract number :
2.163
Submission category :
Year :
2000
Submission ID :
2616
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Viviane B Ferreira, Jose A Buratini, Meire Argentoni, Elcio Machado, Arthur Cukiert, Cassio Forster, Leila Frayman, Alcione Sousa, Joaquim Vieira, Hosp Brigadeiro, Sao Paulo Sp, Brazil; Hosp Brigadeiro, Sao Paulo Sp, Brazil.
RATIONALE: Patients with refractory extra-temporal epilepsy (ExTE) and normal MRI often need invasive investigation for focus localization prior to cortical resection. Subdural electrodes have been used to obtain ictal recordings and for cortical stimulation. This paper compares the accuracy for focus localization of data obtained from ictal recordings or direct cortical stimulation. METHODS: Eight consecutive patients with refractory ExTE who were submitted to subdural electrodes'implantation were studied. Three patients were implanted bilaterally and simmetrically. In all patients, several typical seizures were recorded and cortical stimulation was carried out with square pulses at 100 Hz, 0,1 msec of duration and current ranging from 4 to 8 mA. RESULTS: It was possible to obtained the typical partial seizures in 7 patients afer cortical stimulation. In one patient submitted to bilateral subdural implantation the typical seizure was obtained from a site contralateral to the actual focus and not ipsolaterally. All seizures obtained with cortical stimulation originated from a restricted area comprising 1 or 2 electrodes only. The epileptogenic area as defined by ictal recordings comprised always at least 4 contacts. In all patients, the resected area included the ictally-defined cortex. Six patients has been seizure-free since surgery and 2 are in Engel's class II. Five out of the 6 patients in whom there was a congruence of the epileptogenic area as defined by ictal recording or cortical stimulation have been rendered seizure-free by surgery. CONCLUSIONS: Obtaining the patients' typical seizures after stimulation of restricted cortical areas represent an important item in focus localization in refractory epileptic patients submitted to subdural electrodes implantation. On the other hand, in some patients stimulation may be unable to trigger seizures or may generated them from sites outside the actual focus in patients with more diffuse epileptogenesis. The congruence of the data generated by cortical stimulation and ictal recording might yield a better prognosis.