Abstracts

Rationale: Neuromodulating the neural tissue for seizure control in patients with mesial temporal lobe seizures instead of performing temporal lobectomy with amygdalo hippocampectomy, is under intensive investigation. Various targets have been proposed: hippocampal foci (Velasco AL . Arch Med Res 2000; 31:316-328), amygdalo-hippocampal (T llez Zenteno JF Neur 2006; 66:1-5, Boon P Epilepsia 2007; 48:1551-1560), thalamic VA (Kerrigan JF Epilepsia 2004; 45:346-354). Nevertheless, patients with hippocampal sclerosis do not have a satisfactory response to neuromodulation (Velasco AL Epilepsia 2007; 48:1985-1903). The purpose of this study is to compare the stimulation of the epileptic hippocampal focus against parahippocampus stimulation in patients with hippocampal sclerosis. Methods: The Ethics and Research Committees of the General Hospital authorized this work; all patients signed complete informed consents. 4 patients with refractory mesial temporal seizures in the dominant hemisphere were studied. Phase I and II (hippocampal electrodes) procedures were performed to localize the epileptic foci. Once localized, the diagnostic electrodes were exchanged for permanent DBS electrodes; in two patients the electrodes were placed directly over the focus and in two patients parallel to the epileptic focus, in the parahippocampus. The same parameters were used: bipolar, 130 Hz, cyclic mode (1 min ON/4 minutes OFF), 350 A, 450 msec pulse width. Follow-up was performed every 3 months during a year. Results: All patients showed seizure reduction. Those with hippocampal foci stimulation took more than 6 months to show a moderate seizure reduction (less than 60%) while those with parahippocampus stimulation took only 3 months to show a progressive seizure reduction from an initial 50% to 90%. Neuropsychologic tests showed no difference with stimulation compared with baseline; no adverse effects were observed. We consider that we are interfering with the propagation of epileptic activity instead of inhibiting epileptic focus per se.Conclusions: The parahippocampus may be an effective and safe to stimulate target to control mesial temporal lobe refractory seizures in patients with hippocampal sclerosis.