Abstracts

Rationale: Despite the introduction of new anti-epileptic drugs, approximately 30% of the epilepsy patients remain medically refractory. For this patient population, epilepsy surgery should be considered a viable option¹. Seizure reduction and improved quality of life are frequently reported after surgery 2. However, increasing body of literature demonstrates delayed identification of surgical candidates and delayed referral to comprehensive epilepsy centers.Epilepsy surgery has been offered at the Comprehensive Epilepsy Center at the University of Michigan for many years. With progressive advancement of diagnostic modalities, the number of surgeries being performed every year has continued to increase. The aim of this study was to determine the short-term outcomes of epilepsy surgery (Resective, Responsive Neurostimulation (RNS), Vagus Nerve stimulation (VNS)) at our institution over a 5-year period. A secondary aim was to evaluate the duration between the first clinic evaluation identifying the need for surgery until completion of pre-surgical workup and actual surgery. Methods: Our study was a retrospective analysis of prospectively collected data. Our cohort included pediatric and adult patients who underwent invasive intracranial monitoring followed by epilepsy surgery at the University of Michigan Epilepsy Program from August 2013 to May 2018 (n= 45). Cohort Outcomes were ascertained from review of electronic medical records. Surgical outcomes were assessed using the Engel Epilepsy Surgery Outcome Scale. We also collected demographic (sex, race, age of onset), time to surgery, complications, implantation type, surgery type and diagnostic testing prior to surgery. Results: 45 patients underwent epilepsy surgery. 33 adult and 12 pediatric patients. 25 males and 20 females.  76% had Engel Class I outcome defined as free of disabling seizures, 24% had Engel Class II/III outcome defined as rare disabling seizures, and worthwhile improvement respectively, 2.9% had Engel Class IV outcome defined as no worthwhile improvement. There was one case of SUDEP. 8% of the surgeries were palliative. The most common pathology was cortical dysplasia 47%, followed by gliosis in 38% and the rest were glial cell and stem cell tumors 15%.  The average time between the first clinic visit to completion of the pre-surgical work up and presentation at refractory epilepsy conference (REC) was 3 years. However, 44% of the patients were presented at REC in less than a year from clinic visit and 22 % were presented within 6 months.  The number of surgeries has increased from 4 offered in 2013 up to 16 in 2017. A steady trend toward more complex sEEG implantation schemes was noticed over time in addition to a trend towards neurostimulation via using the responsive neurostimulation device. Conclusions: Our study demonstrates that surgery is effective in providing long-term seizure freedom in patients with refractory epilepsy and our findings are in line with the literature 3. 76% of the medically refractory patients achieved Engel Class I outcome across different types of surgical resections, majority of whom with temporal lobe epilepsy (n=19/45). Three years was the average time from first clinic visit to completion of presurgical work-up. The number of surgical procedures have increased steadily over the 5-year follow-up period with a trend towards stereo-EEG techniques and neurostimulation. Funding: No funding was received.