Sex as a Prognostic Factor for Surgical Outcome in Mesial Temporal Lobe Epilepsy

Burneo and colleages¹ recently reported that ethnicity and socioeconomic status are not isolate predictors for seizure control in surgical mesial temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS). These interesting results perhaps suggest that studies analyzing surgical outcome in MTLE-HS conducted in populations with diverse socioeconomic status or ethnic backgrounds might have broader external validity. However, they also found that men had better outcomes than women. If this finding is accurate, it could have important neurobiological or clinical consequences. However, we feel this last result needs some further consideration.

Although some sex differences have been reported in MTLE-HS,^{2 - 3} sex influence in postsurgical outcome is hardly one of them.^{4 - 6} There seems to exist poor biological plausibility to support such result. The authors pointed out methodological problems in a previous article reporting a lack of such association.¹ In this line, perhaps some methodological issues should be also considered in their study. For example, the authors did not specifically state whether their study was hypothesis-driven regarding sex with a specific research hypothesis about possible influences of sex in surgical MTLE-HS outcomes. Results obtained without a specific research hypothesis established a priori might lack robustness to support strong conclusions.

Moreover, P values were not presented in the article. Although results might have been statistically significant, there was still an uncertain chance of a type I error. In this case, perhaps the authors should have considered and recognized that they might have rejected a null hypothesis regarding sex influence in MTLE-HS surgical outcomes that was indeed true. In other words, the authors might have had a false-positive result. Also, another possibility is that the authors obtained a spurious result due to some lurking variable. Although these possibilities had small chance to occur, they cannot be completely discharged and they need to be acknowledged in the study, especially because all other reports failed to find such an association.^{4 - 6}

To contribute to this issue, we analyzed our MTLE-HS surgical cohort (more than 500 patients) for possible differences but were unable to find any clinically important sex impact in surgical outcome (unpublished data, M.M.B., T.R.V., A.P.P.M., A.C.S., October 1994 to May 2006). Thus, at this point we believe it might be too early to assume that sex has any clinically significant importance in MTLE-HS surgical outcome. Additional studies specifically designed to access whether male sex is a protective factor against a bad surgical outcome in MTLE-HS are necessary before any definitive conclusion is made.

Correspondence: Dr Bianchin, Center for Epilepsy Surgery at Ribeirão Preto, Hospital das Clínicas de Ribeirão Preto, Ribeirão Preto, São Paulo, 14048-900, Brazil (mmbianchin@rnp.fmrp.usp.br).

Financial Disclosure: None reported.