Abstracts

Rationale: The prevalence of epilepsy within a population increases with age. Controversy surrounds the application of surgery as a treatment for epilepsy for older patients. Previous studies regarding epilepsy in older patients have been retrospective, relatively small and contradictory in the rate of seizure freedom following surgery.Methods: A systematic review of the literature from 1997 to 2007 with the keywords “epilepsy,” “seizure” and “surgery” was performed using EMBASE. 3852 articles were identified by the database and 1040 of these were reviewed in full text. Articles were included if they addressed curative surgery in epileptic patients. In addition, an article required at least 5 patients, both younger (< 50 years of age) and older patients (>= 50 years of age) and data regarding the post-operative seizure status for both groups for inclusion. Most articles were discounted due to lack of specific data. Data concerning the number of older and younger patients and their respective post-operative seizure status were extracted. Additional data were collected where possible: gender, duration of epilepsy, age of onset of seizures, type of surgery performed, worst seizure semiology and histology at resection. The goal was individual patient meta-analysis. Statistical significance was set at p=0.05. The primary outcome was the odds ratio of attaining a state of seizure freedom as opposed to a state of persistent seizures when eligible studies were pooled. The secondary outcome was the proportion of patients in each age group who attained either post-operative state. A logistic regression model was created using individual patient data.Results: 85 articles were selected for inclusion and data were extracted concerning 2895 patients. This included 298 older patients, 191 of whom became seizure free and 2597 younger patients, 1773 of whom became seizure free. Data from 81 articles permitted individual meta-analysis of 1637 patients (Figure 1.) A pooled odds ratio regarding the likelihood of attaining seizure freedom in either age group was derived. An odds ratio of 1.384 (p=0.009) favouring younger patients was found. The Q test found no evidence for heterogeneity (p=0.998) and Egger’s test found no evidence of publication bias (p=0.283). (Figure 2) When all patient data was pooled, 68% of younger patients and 64% of older patients attained seizure freedom. Statistically significant predictors of seizure freedom in a logistic model included: age at surgery, the age of onset of epileptic seizures, the presence of generalized tonic-clonic seizures and the presence of hippocampal sclerosis (p<0.02).Conclusions: Based on a meta-analysis of applicable articles, the odds of attaining seizure freedom following curative epilepsy surgery is 1.38 times greater in a younger patient than an older patient above the age of 50. Based on an individual patient logistic regression model, age at surgery was found to be inversely and significantly correlated with seizure freedom. This study suggests that older patients are less likely to attain seizure freedom following epilepsy surgery.