Several Factors Influence Seizure Freedom After Epilepsy Surgery

Elysa Widjaja, MD, MPH

Findings from a systematic review and meta-analyses confirmed the superior seizure freedom benefits of epilepsy surgery over medical therapy in pediatric patients with intractable seizures.

Researchers compiled 258 studies across Medline, Embase, and Cochrane libraries conducted between 1990 and 2017 to evaluate the long-term outcomes of pediatric patients who underwent epilepsy surgery. Of the 258 studies reviewed, 244 were retrospective and 11 were controlled studies. Investigators noted the seizure-free percentages at 1, 2, 5, and 10 years after surgery.

Studies that included palliative surgery, including vagal nerve or deep brain stimulator insertion or corpus callosotomy, were excluded from the study. Other exclusions included studies that did not report separate pediatric epilepsy surgery outcomes if both adult and pediatric epilepsy surgery candidates were included in the study, nonhuman studies, gray literature, conference abstracts, and editorials.

The primary outcome observed was seizure freedom at 12 months or longer follow-up. Investigators estimated effect sizes for controlled studies, uncontrolled studies on surgery locations (temporal lobe [TL], extratemporal lobe [ETL], or hemispheric surgery), pathologies, nonlesional epilepsy, and incomplete resection using random effects models.

As part of the meta-analysis, investigators combined vascular, infarcts, encephalomalacia, and atrophy as encephalomalacia. Cortical dysplasia, focal cortical dysplasia, and cortical malformations were combined under malformations of cortical development.

In the meta-analysis of controlled studies, investigators noted higher odds of seizure-free outcome in patients who opted for surgery compared to those who were treated with medical therapy (odds ratio [OR] 6.49; 95% CI, 2.87-14.70; P <.001). Follow-up in those studies ranged from 1 to 13.5 years among 456 patients in the surgical group and 415 patients in the medical group. Studies including mixed pathologies and surgery locations demonstrated a pooled seizure-free percentage of 64.8% (95% CI, 61.3%-68.1%) among 68 studies.

Seizure freedom in the subgroup analysis declined from 64% (95% CI, 51.2%-76.4%) at 1 year, to 62.9% (95% CI, 56.2%-69.2%) at 2 years, 60.3% (95% CI, 52.9%-67.4%) at 5 years, and 39.7% (95% CI, 28.4%-52.2%) at 10 year follow-up.

In terms of surgical locations, 44 were hemispheric surgery, 57 were temporal lobe epilepsy surgery, and 45 were extratemporal lobe epilepsy surgery. Hemispheric surgery was associated with the greatest rate of seizure freedom (74.7%; 95% CI, 71.2%-77.8%). Temporal lobe epilepsy surgery and extratemporal lobe epilepsy surgery followed, with seizure freedom rates of 73.3% (95% CI, 70.0%-76.4%) and 60.2% (95% CI, 55.9%-64.3%), respectively.

Among different pathologies, tumor was associated with the highest seizure-free percentages (79.8%; 95% CI, 74.8%-84.0%), followed by mesial temporal sclerosis (77.9%; 95% CI, 68.5%-85.1%) and hypothalamic hamartoma (45.9%; 95% CI, 30.7%-61.9%).

Of the 19 studies on nonlesional epilepsy, investigators noted seizure freedom rates of 51.5% (95% CI, 44.1%-58.8%). Seizure freedom numbers were lower in nonlesional epilepsy in studies that contained both nonlesional and lesional epilepsy (OR 0.54; 95% CI, 0.34-0.88; P=.013).

When comparing incomplete versus complete resection, the odds of achieving seizure freedom were lower in nonlesional epilepsy (OR 0.54; 95% CI, 0.34—0.88; P=.013).

Notably, the study authors found that age at surgery and age at seizure onset were associated with seizure freedom for mixed pathologies, surgery locations, and temporal lobe surgery, but not hemispheric surgery, tumor, and cortical development malformations.

“The findings suggest that epilepsy surgery should be the treatment of choice among children with focal [drug-resistant epilepsy] who are eligible for surgery, particularly those with lesional epilepsy, such as tumor and mesial temporal sclerosis, where seizure freedom could be achieved in greater than 70% of patients,” the study authors concluded. “The results provided evidence to inform presurgical counseling and could improve prognostication of pediatric epilepsy surgery.”

REFERENCE:

Widjaja E, Jain P, Demoe L, Guttmann A, Tomlinson G, Sander B. Seizure outcome of pediatric epilepsy surgery. Neurology. 2020;94:1-11. doi:10.1212/WNL.0000000000008966.