Hemispheric surgery for refractory epilepsy: a systematic review and meta-analysis with emphasis on seizure predictors and outcomes.
OBJECTIVE
Conflicting conclusions have been reported regarding several factors that may predict seizure outcomes after hemispheric surgery for refractory epilepsy. The goal of this study was to identify the possible predictors of seizure outcome by pooling the rates of postoperative seizure freedom found in the published literature.


METHODS
A comprehensive literature search of PubMed, Embase, and the Cochrane Library identified English-language articles published since 1970 that describe seizure outcomes in patients who underwent hemispheric surgery for refractory epilepsy. Two reviewers independently assessed article eligibility and extracted the data. The authors pooled rates of seizure freedom from papers included in the study. Eight potential prognostic variables were identified and dichotomized for analyses. The authors also compared continuous variables within seizure-free and seizure-recurrent groups. Random- or fixed-effects models were used in the analyses depending on the presence or absence of heterogeneity.


RESULTS
The pooled seizure-free rate among the 1528 patients (from 56 studies) who underwent hemispheric surgery was 73%. Patients with an epilepsy etiology of developmental disorders, generalized seizures, nonlateralization on electroencephalography, and contralateral MRI abnormalities had reduced odds of being seizure-free after surgery.


CONCLUSIONS
Hemispheric surgery is an effective therapeutic modality for medically intractable epilepsy. This meta-analysis provides useful evidence-based information for the selection of candidates for hemispheric surgery, presurgical counseling, and explanation of seizure outcomes.
Beijing Neurosurgical Institute and 
Wen-Han
WH
Hu
Departments of 2 Neurosurgery and.
Chao
C
Zhang
Departments of 2 Neurosurgery and.
Kai
K
Zhang
Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.
Xiao-Qiu
XQ
Shao
Beijing Neurosurgical Institute and |Departments of 2 Neurosurgery and.
Jian-Guo
JG
Zhang
D000069279:Drug Resistant Epilepsy / Q000601:surgery*; D038421:Hemispherectomy; D006801:Humans; D019635:Neurosurgical Procedures / Q000379:methods*; D011237:Predictive Value of Tests; D012640:Seizures / Q000601:surgery; D016896:Treatment Outcome
AH = anatomical hemispherectomy; EEG = electroencephalography; FCD = focal cortical dysplasia; FH = functional hemispherectomy; OR = odds ratio; PET = positron emission tomography; WMD = weighted mean difference; epilepsy; hemidecortication; hemispherectomy; hemispheric surgery; hemispherotomy; meta-analysis