Purpose: The literature regarding seizure outcome and prognostic factors for outcome after temporal lobectomy is often contradictory. This is problematic, as these data are the basis on which surgical decisions and counseling are founded. We sought to clarify inconsistencies in the literature by critically examining the methods and findings of recent research.
Methods: A systematic review of the 126 articles concerning temporal lobectomy outcome published from 1991 was conducted.
Results: Major methodologic issues in the literature were heterogeneous definitions of seizure outcome, a predominance of cross-sectional analyses (83% of studies), and relatively short follow-up in many studies. The range of seizure freedom was wide (33-93%; median, 70%); there was a tendency for better outcome in more recent studies. Of 63 factors analyzed, good outcome appeared to be associated with several factors including preoperative hippocampal sclerosis, anterior temporal localization of interictal epileptiform activity, absence of preoperative generalized seizures, and absence of seizures in the first postoperative week. A number of factors had no association with outcome (e.g., age at onset, preoperative seizure frequency, and extent of lateral resection).
Conclusions: Apparently conflicting results in the literature may be explained by the methodologic issues identified here (e.g., sample size, selection criteria and method of analysis). To obtain a better understanding of patterns of long-term outcome, increased emphasis on longitudinal analytic methods is required. The systematic review of possible risk factors for seizure recurrence provides a basis for planning further research.