Abstracts

Rationale: Commonly used outcome scales for epilepsy surgery may not be the most suitable for individuals with neuromodulation therapies such as deep brain stimulation (DBS). The ILAE surgical outcome scale [1] prioritizes seizure freedom, a less likely outcome with neuromodulation, which is typically recommended for palliative purposes [2]. Using the same scale for both curative surgery and neuromodulatory procedures may undervalue the efficacy of neuromodulation. Research indicates that DBS can lead to reduced seizure frequency, decreased seizure severity, and improved quality of life over time [2], but these benefits are challenging to measure with the ILAE scale. Neuromodulation-specific outcomes, such as changes in seizure frequency and severity, are crucial for guiding treatment.

Methods: The Penn Epilepsy Center created a standardized DBS visit note using the SmartPhrase Manager in Epic. The DBS Surgical Interval History portion of the note is to be completed at 3 months and 6 months post-op and then annually. Changes in seizure frequency and severity were assessed for each DBS patient, and ILAE surgical outcome scale scores were collected for comparison.

Results: Of the 15 DBS patients included in this project, 11 (73.3%) reported better or much better seizure severity after at least 6 months of therapy. 5/15 (33.3%) patients had a 0-24% decrease in seizure frequency, 2/15 (13.3%) a 25-49% decrease, 2/15 (13.3%) a 50-74% decrease, 3/15 (20%) a 75-89% decrease, and 3/15 (20%) were seizure free. This was stratified by target and year of implantation (see Images 1-2). 7/15 (46.7%) patients had an ILAE surgical outcome score of 5, 4 (26.7%) a score of 4, 1 (6.7%) a score of 3, and 3 (20%) a score of 1. Of the 12 patients with better or much better seizure severity and/or greater than 24% decrease in seizure frequency, 4 had an ILAE score of 5, 4 had an ILAE score of 4, and 1 had a score of 3. The 3 seizure free patients had ILAE scores of 1.

Conclusions: ILAE surgical outcome scores do not fully capture the outcomes in DBS neuromodulation patients. At the Penn Epilepsy Center, 12/15 DBS patients experienced improvements in seizure frequency ( > 24% decrease) and/or severity (better or much better), but their ILAE scores did not necessarily reflect these changes. Notably, 4/12 (33.3%) patients with documented improvements had an ILAE score of 5 (indicating no change). Tailored neuromodulation outcome assessments are essential for guiding individual DBS programming and for larger reviews of surgical outcomes in DBS patients across epilepsy centers.

References

1. Commission on Neurosurgery of the International League Against Epilepsy (ILAE) 1997-2001:, Wieser HG, Blume WT, Fish D, Goldensohn E, Hufnagel A, King D, Sperling MR, Lüders H, Pedley TA. Proposal for a new classification of outcome with respect to epileptic seizures following epilepsy surgery. Epilepsia. 2008 Jul 7;42(2):282–6.

2. Li MCH, Cook MJ. Deep brain stimulation for drug-resistant epilepsy. Epilepsia. 2018;59(2):273-290.


Funding: N/A