Seizure Outcomes in Occipital Lobe and Posterior Quadrant Epilepsy Surgery: A Systematic Review and Meta-Analysis

Abstract

Background: Occipital lobe epilepsy (OLE) is an uncommon but debilitating focal epilepsy syndrome with seizures often refractory to medical management. While surgical resection has proven a viable treatment, previous studies examining postoperative seizure freedom rates are limited by small sample size and patient heterogeneity, thus exhibiting significant variability in their results.

Objective: To review the medical literature on OLE so as to investigate rates and predictors of both seizure freedom and visual outcomes following surgery.

Methods: We reviewed manuscripts exploring surgical resection for drug-resistant OLE published between January 1990 and June 2015 on PubMed. Seizure freedom rates were analyzed and potential predictors were evaluated with separate meta-analyses. Postoperative visual outcomes were also examined.

Results: We identified 27 case series comprising 584 patients with greater than 1 yr of follow-up. Postoperative seizure freedom (Engel class I outcome) was observed in 65% of patients, and was significantly predicted by age less than 18 yr (odds ratio [OR] 1.54, 95% confidence interval [CI] 1.13-2.18), focal lesion on pathological analysis (OR 2.08, 95% CI 1.58-2.89), and abnormal preoperative magnetic resonance imaging (OR 3.24, 95% 2.03-6.55). Of these patients, 175 also had visual outcomes reported with 57% demonstrating some degree of visual decline following surgery. We did not find any relationship between postoperative visual and seizure outcomes.

Conclusion: Surgical resection for OLE is associated with favorable outcomes with nearly two-thirds of patients achieving postoperative seizure freedom. However, patients must be counseled regarding the risk of visual decline following surgery.

FIGURE 1.

Flow chart summarizing the manuscript selection process. Overall, 675 manuscripts were examined, 60 met inclusion criteria, and 27 met both inclusion and exclusion criteria. *Inclusion criteria are listed in the Methods.

FIGURE 2.

Postoperative seizure freedom rate across all studies by publication date. Each data point represents a single study, with rate of postoperative seizure freedom (Engel class I outcome) plotted against year of study publication. A line of best fit is provided. No significant trend is observed (r = 0.16, P = .43).

FIGURE 3.

Meta-analyses examining factors associated with seizure freedom after occipital lobe and posterior quadrant epilepsy surgery. Statistically significant predictors of postoperative seizure freedom included A age < 18 (vs ≥18) yr (Cochran Q = 16.5, P < .05, I² = 63.6), B focal (vs nonfocal) lesion on pathological examination (Q = 9.2, P = .16, I² = 34.8), and C abnormal (vs normal) preoperative MRI (Q = 39, P < .01, I² = 79.5). The effect size for each study is represented as OR of factors associated with seizure freedom (larger OR indicates greater likelihood of seizure freedom), with proportional study weight estimated by the size of each point. Error bars represent 95% CI, with arrowheads indicating an upper limit off of the scale. The size of each point estimates proportional study weight, and the vertical dashed line represents OR = 1.