Abstracts

Rationale: Callosotomy has been used over the years to treat seizures in patients with epilepsy and is most effective for atonic seizures ('drop attacks'), tonic-clonic seizures, and tonic seizures. It is believed that the efficacy of this procedure is high in patients with drop attacks (more than 80%) and could be useful for other types of seizures. The objective of this study is to provide evidence-based estimates of the seizure outcome after callosotomy for different type of seizuresMethods: An expert in library resources and electronic databases searched electronic sources such as Medline, Index Medicus, and the Cochrane database. We also searched bibliographies of pertinent reviews and original articles, book chapters and expert consultation. Two reviewers independently applied the following inclusion criteria: studies published since 1980, with more than 10 patients undergoing callosotomy, reporting seizure outcome. We considered outcomes in children and adults. We used seizure freedom as defined by authors. Two investigators independently extracted data, resolving disagreements through discussionResults: Of 795 available articles, 100 potentially eligible were reviewed in full text. Fifty three studies fulfilled eligibility criteria. Overall the median proportion of patients with developmental delay before callosotomy was 94% (95% CI 93-95). The proportion of patients with partial callosotomy was 83% (95% CI 83-84) and complete callosotomy was 10% (95% CI 9-11). Globally the proportion of seizure free patients after callosotomy was 11% (95% CI 9-13). The corresponding proportion of seizure free status for drop attacks was 38% (95% CI 35-41), grand mal seizures was 20% (95% CI 16-24), tonic seizures 17% (95% CI 11-22), absence seizures 24% (95% CI 17-30), myoclonic jerks 15% (95% CI 9-21) and for complex or simple partial seizures was 17% (95% CI 12-22). We explored other outcomes such as year of study and seizure outcome after partial and complete callosotomy. Conclusions: After callosotomy, 11% of patients become seizure of all types of seizures and 38% from drop attacks. This metanalysis reports low rates of seizure free status in general and for the different type of seizures. As was expected, the benefit of callosotomy was higher in patients with drop attacks, although the rate of seizure free is lower compared with the general belief that more than 80% of patients could be seizure after this procedure. Sources of heterogeneity are explored. Sources of heterogeneity and non-seizure outcomes were analysed.