Abstracts

Rationale: Resective surgical treatment can be curative in a large subset of patients with treatment resistant epilepsy. There is a need for a simple surgical grading scale that can be used by the referring neurologist using information obtained prior to diagnostic hospitalization. Such a tool would provide a simple, systematic method for identifying a patient s likelihood of positive outcome following surgical treatment and would offer a uniform means to improve epidemiology and tracking. Our hypothesis was that a model using interictal EEG, brain MRI, seizure semiology and IQ could stratify patients with treatment resistant epilepsy based upon their likelihood of achieving seizure freedom following assessment for resective epilepsy surgery.Methods: Chart review of patients admitted to the New York University Langone Medical Center epilepsy monitoring unit from 1/1/2007 to 7/31/2008 identified 1,105 unique patients. Of these, 455 met inclusion criteria: age ?18, focal epilepsy diagnosis ?2 years, failed ?1 medication, and ?1 seizure three months prior to admission. Calculation of the Epilepsy Surgery Grading Scale (ESGS) score was based upon MRI, EEG, semiology, IQ (Table 1). Patients with follow-up periods <6 months and those with prior resective surgeries were excluded (32 patients). Outcomes were assessed at the study s conclusion (3/31/2010); patients were classified as either seizure free following resective surgery or not seizure free following surgery/no resection. Three cohorts were used in this study: 1) the full cohort, 2) only patients undergoing surgical multidisciplinary case (MDC) conference evaluation, 3) only patients who underwent resective surgery.Results: Our data demonstrate that of 423 patients initially identified as presurgical admissions to the EMU, only 193 (45.6%) were ultimately considered for surgical management and presented in surgical MDC. Eighty-four (19.9%) then underwent resective surgery. Analysis of the MDC cohort reveals that 53.2% of ESGS Grade 1 patients, 34.1% of Grade 2 patients, and 17.2 % of Grade 3 patients became seizure free from resective surgery. For this cohort, significant differences between Grades 1 and 3 (p=0.0001), and between Grades 2 and 3 (p=0.0463) were seen, and a trend was seen between Grades 1 and 2 (p=0.0743). Analysis of the resection only cohort showed that 89.2% of ESGS Grade 1 patients, 83.3% of Grade 2 patients, and 44.8% of Grade 3 patients became seizure free from resective surgery (Table 2). Significant differences between Grades 1 and 3 (p=0.0009), and between Grades 2 and 3 (p=0.0343) were seen; the difference between Grades 1 and 2 was not statistically significant (p=0.6713).Conclusions: These results indicate that, using basic information obtainable in a doctor s office, patients with treatment resistant epilepsy may be stratified into clinically meaningful groups based upon their likelihood of achieving seizure freedom as a result of resective surgery.