Abstracts

Rationale: Responsive neurostimulator (RNS) placement planning in clinical trials as well as in published reports thus far has employed subdural grids and strips for seizure foci deleniation. The emerging use of stereo-EEG (SEEG) as an intracranial technique for seizure localization has been used extensively at our center for planning RNS.  Herein, we report our case series of our experience with this minimally invasive surgical strategy that streamlines diagnosis and treatment in the most difficult to treat epilepsy patients .  Methods: SEEG was placed in refractory epilepsy patients to localize seizure onset based upon hypothetical sites for the epileptic zone derived by the epilepsy team from seizure semiology, brain MRI, and neuropsychological testing, as well as Wada results and brain PET when appropriate.  In cases where the seizure foci were deemed to dangerous to resect or ablate, SEEG results guided the responsive neurostimulator placement. Results: Nineteen patients underwent intracranial evaluation using SEEG with subsequent RNS placement without an intervening grids and strips implant. The cohort  age was 11-54 years (median 6 patients 24-19); 8 were female.  All except two SEEG investigations were bilateral and 15  out of 19 included bilateral hippocampal, amygdalar and orbital frontal electrodes.  Subsequent RNS placement was as follows: Seven patients had bilateral hippocampal depth electrodes placed. 2 patients had a unilateral combination of a stip/depht electrode. 4 patients had a combination of thalamic depths with either cortical strips or depths, 5 lobe specific depth constructs, and 1 a rolandic sulcus strip contruct. Exact placement of RNS electrodes and those which were initially activated are present in the table.  Seizure capture by intial RNS was 17 out of 18, with one pt pending detection. Conclusions: SEEG is a minimally invasive, safe and accurate localization technique for planning RNS placement.  This represents a paradigm shift from maximally invasive open craniotomy with subdural grids followed by resection, which is an irreversible ablative treatment.  An updated approach may be offering patients minimally invasive diagnostic method followed by a reversible modifiable,  modulatory option. Further, this approach in some patients provides increased confidence in resective treatment planning by capturing chronic, real-world seizure occurrence.  This approach expands the benefit of epilepsy surgery to a population where fear was barrier to surgery or who were not clear-cut candidates for respective surgery.  In our experience, we found SEEG to RNS suited for evaluation of temporal lobe epilepsy. Funding: none