Abstracts

Rationale: Temporal resections are the most common and most successful surgery for epilepsy, but outcome is not as good in patients with negative MRI. Some ictal patterns are associated with a good outcome, but the value of interictal discharges in this population is not known. Methods: We reviewed all consecutive patients who had a temporal resection with a normal MRI, and selected those with a clear ictal pattern characterized by well-defined regular rhythmic 5-9 Hz (Type I of Ebersole). We divided them into 3 groups based on interictal discharges: 1) Unilateral (defined as >80% predominance); 2) Bilateral; 3) No interictal discharges. We classified outcome as Engel outcome 1, 2, and 3. Results: A total of 59 patients met our inclusion criteria. Of those, 48 (81.3%) had unilateral interictal discharges (Group 1), 7 (11.9%) had bilateral interictal discharges (group 2), and 4 (6.8%) had no interictal discharges (group 3). Outcome was as follows: Unilateral: 64.6% were Engel 1, 20.8% were Engel 2, and 14.6% were Engel 3. Bilateral: 42.9% were Engel 1, 57.1% were Engel 2, and 0% were Engel 3. No Discharge: 75% were Engel 1, 25% were Engel 2, and 0% were Engel 3. Comparing unilateral interictal discharges vs bilateral or no interictal discharge, and Engel class 1 or 2 vs Engel class 3: Unilateral: 14.6% were Engel class 3. Bilateral/no discharge: 0% was Engel class 3. Fisher Exact test was conducted, and the difference between these two groups was found not statistically significant (P-value = 0.328) Conclusions: This study did not detect any effect of interictal discharges among those with clear ictal EEG patterns on the surgical outcome. We recommend further studies with larger sample size.