Abstracts

Rationale: To determine whether the outcome of epilepsy surgery, measured by post-operative Engel score (4-point scale, with lower score meaning better outcome), can be predicted by patient age, duration of epilepsy, gender, presence of a lesion on MRI, cognitive status, or history of prior epilepsy surgery. Methods: Patients who underwent invasive subdural EEG monitoring and/or focal resection for epilepsy were identified in a database that comprehensively included patients who underwent epilepsy surgery at Children's Hospital Boston from 1993 to 2003. Pre-operative data and Engel scores were obtained by retrospective chart review; Engel score was assigned if not reported. We performed univariate and multivariable linear regression analyses of the above pre-operative factors, adjusting for year of surgery to account for changes in practice over time. The outcome of interest was the Engel score at the time of the last clinical encounter, and it was treated as a continuous variable. Based on the results of this regression, we attempted to assess whether MRI lesion type predicted outcome.Results: Of 224 patients in the database, outcome data were available for 196, with mean follow-up time of 25 months. By univariate analyses, presence of an MRI lesion and normal cognition were associated with lower Engel score, or better clinical outcome (p<.05). Linear regression revealed that, when adjusted for year of surgery, the presence of an MRI lesion was associated with Engel score 0.45 lower than no lesion (p<.05); normal cognition with Engel score 0.51 lower than mental retardation (p<.005); and history of prior epilepsy surgery with Engel score 0.56 lower than no prior surgery (p<.05). There was insufficient power to stratify outcome by type of MRI lesion. Age, gender, and duration of epilepsy did not significantly influence outcome in these analyses.Conclusions: In patients considered candidates for epilepsy surgery, the presence of an MRI lesion, normal intelligence, and history of prior epilepsy surgery each predicts favorable post-operative seizure outcome.