(366) External validation of the Epilepsy Surgery Grading Scale in a Japanese cohort of patients with epilepsy

Rationale: The Epilepsy Surgery Grading Scale (ESGS) is a simple method to predict the likelihood of a patient with epilepsy proceeding to surgery and achieving seizure freedom. This numerical scale is based on five diagnostic parameters which adds up to a total score that classifies a patient into three distinct grades based on the total score, with Grade 1 indicating the highest likelihood of a favorable surgical outcome. Usefulness of the ESGS has been confirmed in established epilepsy centers in the United States and Belgium for adult patients with drug-resistant focal epilepsy undergoing presurgical evaluation. However, the applicability of the ESGS has not yet been evaluated in a wider variety of epilepsy patients which resembles the general population of epilepsy patients. The present study validated the ESGS in a Japanese epilepsy center where admission-based comprehensive epilepsy study was indicated beyond presurgical evaluation.

Methods:

This single-center retrospective study included adult patients with epilepsy admitted for the first time to the Epilepsy Monitoring Unit from 2010 to June 2019. Patients were grouped into three cohorts: all patients regardless of epilepsy classification, patients with drug-resistant focal epilepsy, and patients who underwent resective epilepsy surgery. Each patient was classified according to the ESGS score, which was calculated as the sum of the scores obtained from five parameters: Intelligence Quotient (IQ), seizure semiology, MRI, EEG, and concordance between MRI and EEG. From the total score, patients were classified into three categories: Grade 1 (most favorable) with a score of ≥ 7.5, Grade 2 (intermediate) with a score of > 4 to < 7.5, and Grade 3 (least favorable) with a score of ≤ 4. Outcome measures were rate of progression to surgery and rate of seizure freedom defined as ≥ 12 months based on the Engel classification, as assessed during the most recent follow‐up visit.

Results:

Of the 1,158 total admissions, 670 patients met the inclusion criteria, and formed the total cohort. Of these, 435 (64.9%) had drug-resistant focal epilepsy and 78 (11.6%) proceeded to resective surgery. Rates of proceeding to surgery among all patients were 41.3% (31/75), 16.6% (26/157), and 4.8% (21/438) for Grades 1, 2, and 3, respectively, with significant differences between all groups (p < 0.001). Rates of proceeding to surgery among drug-resistant epilepsy patients were 43.1% (31/72), 21.5% (26/121), and 8.7% (21/242) for Grades 1, 2, and 3, respectively, with significant differences between all groups. Overall, rate of one-year seizure freedom was 65.2% (43/66) in the surgical cohort: 85.2% (23/27) in Grade 1 patients, 65.2% (15/23) in Grade 2 patients, and 31.3% (5/16) in Grade 3 patients, with no significant difference between Grades 1 and 2 (p = 0.10), and significant differences between Grades 2 and 3 (p = 0.04) and Grades 1 and 3 (p < 0.001).

Conclusions: Our results indicate that the ESGS is effective for predicting a patient’s likelihood of proceeding to epilepsy surgery and achieving seizure freedom even in the general population of epilepsy patients, regardless of type or status of resistance to antiepileptic drugs.

References:

1. Dugan P, Carlson C, Jetté N, Wiebe S, Bunch M, Kuzniecky R, et al. Derivation and initial validation of a surgical grading scale for the preliminary evaluation of adult patients with drug‐resistant focal epilepsy. Epilepsia 2017;58:792–800.


2. Conte F, Van Paesschen W, Legros B, Depondt C. The Epilepsy Surgery Grading Scale: Validation in an independent population with drug‐resistant focal epilepsy. Epilepsia 2019;60:e78–e82.

Funding: Please list any funding that was received in support of this abstract.: Dr. F Gabriel received a visiting researcher scholarship from the Japan Epilepsy Research Foundation for this study.
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