Abstracts

Rationale: Anterior temporal lobectomy with hippocampal resection is a highly efficient surgical procedure in patients with refractory mesial temporal lobe epilepsy (TLE). It’s outcome is very favorable in seizure reduction but postsurgical neuropsychological deficits can result as a consequence of the surgery. These deficits are very obvious in cases of left lobectomies (verbal memory,dysphasia) while the right lobectomies have been considered relatively safe. In the Epilepsy Clinic of the General Hospital of Mexico City, we have observed that there is a risk for of behavioral and emotional disorders when right temporal lobectomies are performed. In this study we are registering simultaneous ultrafast oscillations using diagnostic hippocampal electrodes during the test performance. High-frequency oscillations are divided in high frequency oscillations (HFOs) (80-600 Hz) and pathologic (pHFOs) (250- 800 Hz) are consider biomarkers of pathology in epileptic models. This study reports direct hippocampal pHFOs recording during an emotional memory tasks in patients with refractory TLE. This study is approved by the Ethics Commission of the General Hospital of Mexico (DIC/11/403/04/010)Methods: The study included 7 patients with bilateral hippocampal electrodes to determine location of the epileptic focus and 7 healthy controls for the memory test. Once electrodes were implanted the patient had an MRI to verify electrode position, afterwards they were recorded continuously in the Epilepsy ward. Emotion Test: The task is to present a series of faces with different emotional facial expressions from the Ekman battery (1976). Bringing it up 80 black and white photographs. EEG signal analysis: In order to assess the presence of pHFOs during the execution of the cognitive task, the signal was analyzed by filtering and visual sampling (Bragin and Engel, 1999) using Data-Pac and Matlab.Results: Emotional memory performance errors occurred when spikes and ultra-fast oscillations were associated, when visual sign analysis where performed. The experimental group showed more errors and omissions than the control subjects. The left patients had lower reaction times and the right patients had more errors of non-performance in the emotional faces task. The graph B shows the decrease in errors from the session 2 when compared to the session 2b (24 hrs. interval presentation) showing more decrement at session 2b, what tells of an emotional memory preserved. The results plotted in graph A are patients with right focus (orange line) show an altered curve memory as it not only shows an alteration in the memory test. When we compare the session 2 with the 2-b shows an equal alteration in the number of errors and reaction times. The group of patients with right focus epilepsy showed more omission errors than the left, although it took longer to respond the emotional faces task.Conclusions: Results suggest that in epileptic patients, pHFOs is indeed a pathological biomarker since they appear in the epileptic hippocampus exclusively. These pHFOs may be interfering with emotional recognition if they appear associated with spikes in the EEG.