Abstracts

RATIONALE: In presurgical assessment of epilepsy intra-cranial EEG recordings proved useful in a large number of patients, peculiarly those whose epileptogenic area (EA) is suspected to be located close to, or inside, functional eloquent areas. In our department these recordings are carried out using stereotactically implanted depth electrodes (SEEG). Our purpose was to explore the possibility of using these electrodes to produce TC lesions inside the EA and to evaluate the therapeutic efficiency of this procedure.
METHODS: Five consecutive patients in whom epileptic discharges with focal onset had been identified by Video-SEEG recordings were enrolled in this study. Lesions were produced by inducing a Joule effect between the electrode contacts where discharges onsets had been recorded in each individual. The procedure proved painless and could be performed in an awake patient, able to cooperate, under EEG and clinical monitoring. Two to five TC lesions were performed per patient, immediately before the removal of intra-cranial electrodes. The lesion size and location was assessed by brain MRI 24 hours later.
RESULTS: Three of the five patients presented with a left temporal lobe epilepsy (TLE) without hippocampal sclerosis (HS), seizures originated from the operculo-insular cortex in the fourth patient and in a left peri-ventricular heterotopia facing the language area in the fifth one. Therefore targets locations were different according to patients : entorhinal area in two patients in the group of TLE without (HS) hippocampus and temporo-polar neocortex in the third patient of this group; insula and frontal operculum in the fourth case; heterotopia and left parietal neocortex in the fifth one. No complication occurred during the procedure and no clinically detectable side effect was observed in any patients after TC. Eight months after TC 2 patients with TLE and the patient with heterotopia are in Engel[scquote]s class 2b, the patient with operculo-insular onset seizure is in class 1b and the third TLE patient is seizure-free (1a).
CONCLUSIONS: This study reports on a therapeutic protocol based on the use of intra-cranial SEEG recording electrodes to perform focal TC lesions. It shows that
1) this procedure is feasible, safe and well tolerated; it gives access to regions of which the surgical removal is risky (insular cortex in patient 4) or impossible (language area in patient 5); in case of failure it does not preclude a complementary surgical procedure;
2) TC lesion of the EA has a therapeutic effect. In spite of the limited number of lesions per patients performed in the evaluation phase of the procedure, preliminary results are encouraging. The next step consists in assessing whether larger TC lesions in the EA are able to improve the therapeutic efficiency.
[Supported by: Hospices Civiles de Lyon]