Clinical Utility Of Stereo-electro-encephalographies To Locate The Epileptogenic Zones Of The Patients With Intractable Epilepsy

The patients who can not become seizure free with drugs have many problems in psycho-society, with poor quality of life, high mortality and sudden death rates. The surgical methods will be helpful to these patients, if the epileptogenic zone can be found. Because clinical signs and examinations with no invasion are not accurate and with low positive rate, the intracranial electroencepholographies are used to locate epileptogenic zone. As a useful methodology of the intracranial electro—encepholographies, the stereo-electro-encephalography (SEEG) methodology developed by Talairach and Bancaud in France, the objective of placing depth electrode recordings in presurgical evaluation is to study the spatial and temporal organization of a seizure. This defines for each patient the cortical onset zone, the propagation pattern of the seizure, and the possible involvement of eloquent areas of the cortex. This methodology requires a meticulous stereotactic surgical technique to place more than 5 depth electrodes in brains, and the long axis of the depth electrodes are perpendicular to the sagittal plane of the brain. We want to improve and simplify the Talairach methodology.Objective:To locate the the epileptogenic zones of the patients with intractable epilepsy by 1 to 4 chronically indwelling depth electrodes. Methods:After Video-EEG monitoring and EEG spike wave dipole analysis, using image-guided robotic system(16 patients) or Leksell Stereotactic instrument(3 patients) to implant 1 to 4 depth electrodes in brains within 1 to 7 d for stereo-electroencephalographies (SEEG) to locate the epileptogenic zones of the 19 patients with intractable epilepsy. If using the depth electrodes with 10mm intervals, the focal epileptogenic zones had less than 3 electrodes (diameter≤20mm) with onset waveforms, and the epileptogenic lobes had more than 4 electrodes (diameter≥30mm) with onset waveforms. Result:We could locate the epileptogenic zones in 18 (94.7%) of 19 patients and the epileptogenic lobes in 1 (5.3%) of them. After neurosugical treatments 6—27 months,6 (31.6%) patients were classified as Engel's ClassⅠ, 1 (5.3%) patient as Engel's ClassⅡ,2 (10.5%) patients as Engel's ClassⅢ, 5 (26.3%) patients as Engel's ClassⅣa,5 (26.3%) patients as Engel's Class IVb, 2 (10.5%) patients as Engel's ClassⅣc.1 patient (5.3%) of them had mild subarachnoid hemorrhage without neurological function impairment. Conclusion:By carefully planing, the stereo-electroencephalographies could locate the epileptogenic zones in most of the patients whose clinical signs and examinations with no invasion were not coincident.