Abstracts

Rationale: Although most patients with low-grade epilepsy-associated neuroepithelial tumors (LEATs) have satisfactory long-term postoperative seizure outcomes, no optimal surgical strategies have been established. We have performed subdural electrode implantation in many patients with LEATs as well as extended resection including the tumor itself and surrounding cortices. We examined whether our strategy led to favorable seizure outcomes during an average 10-year postoperative follow-up.

Methods: This study involved 45 patients (26 men, 19 women) who underwent LEAT removal at NHO Nishiniigata Chuo Hospital from May 1996 to April 2022, with ≥2 years of postoperative follow-up. In 34 (75.6%) patients, the tumor was located in the temporal lobe. Among the remaining 11 patients, the tumor was located mainly in the frontal lobe in 6, occipital lobe in 4, and parietal lobe in 1. In 30 (66.7%) patients, intracranial subdural electrodes were implanted and video-electroencephalography was performed. Seizure outcomes were assessed using the International League Against Epilepsy (ILAE) classification. This study was approved by the institutional review board of NHO Nishiniigata Chuo Hospital (#2404). Univariate and multivariate analyses were performed to investigate the independent prognostic effects of clinical variables, including age at surgery, age at seizure onset, duration of epilepsy, side (left vs right), tumor location, and pathological finding, significantly associated with ILAE class I and Ia outcomes.

Results: Dysembryoplastic neuroepithelial tumor and astrocytoma each affected 15 (33.3%) of 45 patients. Other pathologies included ganglioglioma (n = 13), angiocentric neuroepithelial tumor (n = 1), and ependymoma (n = 1). Among all 45 patients, the median postoperative follow-up was 117.6 (range, 24-319) months. At the final follow-up, 36 (80.0%) of 45 patients were seizure-free (ILAE class I and Ia). Although 62.2% of patients had an ILAE class I and Ia seizure outcome 1 year after surgery (Fig. 1), the 4- and 5-year postoperative seizure-free rates were significantly higher (82.9%, p = 0.033 and 83.8%, p = 0.031, respectively) (Fig. 1). Univariate analysis showed significantly higher seizure-free rates in patients with tumors located in the temporal lobe than in extra-temporal lobes [31 (91.2%) of 34 vs. 5 (45.5%) of 11 patients, respectively; p = 0.003]. Multivariate logistic regression analysis showed that only the tumor location was significantly correlated with seizure outcomes. Kaplan–Meier curves showed a statistically significant difference between patients with tumors located in the temporal lobe versus extra-temporal lobes (log-rank test, p = 0.021) (Fig. 2).

Conclusions: Extended resection of the LEAT and surrounding tissues resulted in a seizure free rate of 80% at an average of 10 years after surgery. Outcomes were more favorable with temporal than extra-temporal lobe tumors. Patients with LEAT likely experience the seizure running-down phenomenon for several years after surgery.


Funding: Funding: None