Yield of Non-Invasive Phase 1 Presurgical Evaluation in Drug-Resistant Epilepsy Patients

Background: Resective epilepsy surgery is an accepted treatment option for patients with drug-resistant epilepsy (DRE). Presurgical evaluation consists of a phase 1 non-invasive evaluation and a phase 2 invasive evaluation, when necessary. Objectives: To assess the results of phase 1 evaluation in patients with focal DRE. Methods: This observational retrospective study was performed in all consecutive DRE patients admitted to our clinic from January 2001 to July 2010, and who underwent a presurgical evaluation which included at least magnetic resonance imaging (MRI) scan and long-term video EEG monitoring (LTVEM). Results: A total of 253 consecutive patients with a diagnosis of DRE (according to the ILAE recommendations) who underwent presurgical evaluation were extracted from our clinic and department registry. In 45 of these patients either imaging or ictal video EEG data were missing; the final analysis therefore involved 208 patients. The combined result of the LTVEM and the MRI scan were as follows: 102 patients (49% of the cohort) had a lesion on the MRI scan, in 77 patients (37% of the cohort) the LTVEM results were localizing and congruent with the MRI findings, and in 25 patients (12% of the cohort) the LTVEM results were either non-localizing or incongruent with the MRI findings. In 106 patients (51% of the cohort) the MRI scan was normal or had a non-specific lesion. The LTVEM was localizing in 66 of these patients (31.7% of the cohort) and non-localizing in 40 (19.2% of the cohort). Conclusions: Although some of the patients with focal DRE can be safely treated with resective surgery based solely on the findings of phase 1 evaluation, a substantial percent of patients do need to undergo a phase 2 evaluation before a final surgical decision is made.