Assistant Professor Western University London, Ontario, Canada
This abstract has been invited to present during the Better Patient Outcomes through Diversity Platform poster session
Rationale: The implantation of intracranial EEG (iEEG) is sometimes a part of the pre-surgical evaluation assessment of patients with Therapy-Resistant Epilepsy (TRE). iEEGs, particularly depths, have shown (1) high sensitivity as well as specificity (2), low percentage of complications (3), and robot-assisted devices increase the accuracy of the target point (4). In some cases patients implanted with iEEG have shown a reduction of seizures after implantation or have not had a seizure for a period of time. However, no studies have evaluated the change in frequency of seizures in this group of patients. The goal of this study was to assess the impact on seizure frequency in those implanted with depth electrodes. Methods: We conducted a retrospective analysis of patients with TRE who underwent depth electrode implantation between December 2017 and February 2020, at our institution. We identified the seizure frequency with iEEG three to six months before admission, during the admission, and three to six month after they were discharged. Results: Forty-eight patients were included in the preliminary study, but only 43 were analyzed (five were excluded due to lack of follow up). The mean age of the patient at the time of the implantation of iEEG was 36.8 years (range: 19-64, SD±16.26); 26 (60%) were female. The mean age of epilepsy onset was 16.8 years (range: 1-55, SD±11.31). The mean days of hospitalization was 14.7 (range: 6-38, SD±2.82). Of the total number of patients implanted, 22 (51%) were lesional cases. A total of 493 depth electrodes were implanted. Bilateral implantation was performed in 36 patients (84%). The mean number of depth electrodes implanted per patient was 11.4 (range:8-20, SD±3,53). The mean number of seizures per month before the implantation was 11.8 (range: 1 - 120), after the implantation the mean was 19.1 (range: 0 - 270) and during their admission the mean was 29.21 (range: 0 - 300). Comparing the results after the implantation, 7 (16%) patients had an increase in the frequency of their seizures (ratio of increase = 20.4 times, SD±6.36), 8 (19%) patients experienced a decrease in the frequency of the seizures (ratio of decreasing = 75.6 %, SD±20.5) and 28 (65%) patients had no modification in the frequency of seizures (ratio of modification= 0). The average number of anti-seizure drugs before and after was 2.66 and 2.60 (range: 1-4) respectively. Six patients were discharged with a different medication regimen. In patients implanted with depth electrodes, the risk factors associated with an increase in seizure frequency were: implantation of < 12 electrodes (RR:1.5, OR: 1.7, p= 0.0001), lesional MRI (RR:1.3, OR: 1.3, p= 0.2451) and seizure during cortical stimulation (RR:4.2, OR: 6.0, P=0.175). In contrast, the risk factors associated with a decrease in seizure frequency were: implantation of ≥ 12 electrodes (RR:1.5, OR: 1.6, p= 0.0001), lesional MRI (RR:1.6, OR: 1.8, p= 0.2451) and no seizure during cortical stimulation (RR:1.9, OR: 2.3, P=0.175). Conclusions: The frequency of seizures in patients with therapy resistant epilepsy who underwent implantation of depth electrodes could be impacted by the number of electrodes implanted, suspicion of lesional MRI and presence of seizures during cortical stimulation. Funding: Please list any funding that was received in support of this abstract.: N/A Click here to view image/table
