Abstracts

Rationale: Deep brain stimulation (DBS) has been used in an increasing frequency to treat refractory epilepsy over the last years. Patients with bilateral temporal lobe epilepsy, those with temporal lobe epilepsy and normal MRI or in risk for postoperative memory deficits after resective procedures have been considered for hippocampal DBS (Hip-DBS). We describe the technique for Hip-DBS. Methods: Twenty-seven patients were submitted to unilateral (n=9) or bilateral (n=18) Hip-DBS. All patients were operated under general anesthesia. In the first 10 patients an intraoperative EEG and macrostimulation was performed. A frame-based stereotactic CT was obtained and fused with preoperative MRI dataset. The most anterior portion of the hippocampal head was located in coronal slices and visualized in the corresponding sagittal slice. A midpoint within the hippocampal body was selected and together with the previous hippocampal head point used to define a line which was used to determine the occipital bone entry point. The 4-contacts electrode was inserted guided by a rigid cannula under neuronavigational or fluoroscopic control (in the early patients). The generator was connected to the leads in the same procedure. Electrode's position was confirmed by post-operative MRI. Results: All patients had at least two electrodes strictly into the hippocampus proper. No contacts were noted outside the hippocampal-parahippocampal complex. There was no mortality or immediate morbidity. Macrostimulation used low frequency stimuli (6Hz) led to localized recruiting responses exclusively over the stimulated temporal lobe. Conclusions: An occipital approach has proven safe and effective in covering the mesial temporal lobe region in patients submitted to Hip-DBS. Presently, intraoperative neurophysiology is used only for research purposes. Funding: None.