Risk Factors for Seizure Worsening After Epilepsy Surgery in Children and Adults: A Population-Based Register Study

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Abstract
BACKGROUND: Increased seizure frequency and new-onset tonic-clonic seizures (TCS) have been reported after epilepsy surgery. OBJECTIVE: To analyze potential risk factors for these outcomes in a large cohort. METHODS: We studied prospectively collected data in the Swedish National Epilepsy Surgery Register on increased seizure frequency and new-onset TCS after epilepsy surgery 1990-2015. RESULTS: Two-year seizure outcome was available for 1407 procedures, and data on seizure types for 1372. Increased seizure frequency at follow-up compared to baseline occurred in 56 cases (4.0%) and new-onset TCS in 53 (3.9%; 6.6% of the patients without preoperative TCS). Increased frequency was more common in reoperations compared to first surgeries (7.9% vs 3.1%; P = .001) and so too for new-onset TCS (6.7% vs 3.2%; P = .017). For first surgeries, binary logistic regression was used to analyze predictors for each outcome. In univariable analysis, significant predictors for increased seizure frequency were lower age of onset, lower age at surgery, shorter epilepsy duration, preoperative neurological deficit, intellectual disability, high preoperative seizure frequency, and extratemporal procedures. For new-onset TCS, significant predictors were preoperative deficit, intellectual disability, and nonresective procedures. In multivariable analysis, independent predictors for increased seizure frequency were lower age at surgery (odds ratio (OR) 0.70 per increasing 10-yr interval, 95% CI 0.53-0.93), type of surgery (OR 0.42 for temporal lobe resections compared to other procedures, 95% CI 0.19-0.92), and for new-onset TCS preoperative neurological deficit (OR 2.57, 95% CI 1.32-5.01). CONCLUSION: Seizure worsening is rare but should be discussed when counseling patients. The identified risk factors may assist informed decision-making before surgery.

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