Intractable epilepsy before and/or after awake functional mapping–based surgery for IDH-mutant grade 2 glioma: a consecutive series of 105 patients

OBJECTIVE: Awake resection in grade 2 glioma (G2G) improves quality of life (QOL) and overall survival (OS). Nonetheless, epilepsy occurs frequently in this context and can impair QOL, especially when the disorder is pharmacoresistant. Herein, the goal was to study patients with intractable epilepsy (IE) before and/or after surgery for a G2G. METHODS: Patients who underwent awake functional mapping-based resection of an IDH-mutant G2G in the period from June 2002 to March 2024 and had IE before and/or after surgery (follow-up > 1 year) were selected for this retrospective study. Onco-functional outcomes were compared among patients with preoperative IE who were completely seizure free (Engel class IA) postoperatively (group 1), patients with preoperative and postoperative IE (group 2), and patients who experienced IE only postoperatively (group 3). RESULTS: In a consecutive series of 105 patients (61 males [58.1%]) with a mean age of 35.6 ± 12.2 years, 134 awake surgeries were performed. At diagnosis, 101 patients (96.2%) presented with seizures, and 82 patients (78.1%) presented with IE. The mean preoperative Karnofsky Performance Status (KPS) was 88.7 ± 7.4, and 74 patients (70.5%) were able to work preoperatively. Sixty-three gliomas (60%) were left-sided and 42 were right-sided, which consisted of 66 insula-centered/paralimbic (62.8%), 13 central (12.4%), 14 frontal (13.3%), 6 temporal (5.7%), and 6 parietal (5.7%) tumors. The mean preoperative tumor volume was 82.8 ± 47.9 cm3. Only 1 patient (0.9%) had persistent postoperative deterioration, and the mean postoperative KPS was 89.2 ± 6.4. Sixty-one patients returned to work (82.4%). The mean extent of resection (EOR) was 86.8% ± 8.3% (mean residual volume 13 ± 18.4 cm3). Histopathologically, there were 65 astrocytomas (61.9%) and 40 oligodendrogliomas (38.1%). Twenty-two patients (21.0%) had immediate adjuvant therapy, and 29 patients (27.6%) underwent reoperation(s). The mean follow-up was 8.3 ± 4.7 years with an OS rate of 70.5%. Sixty patients (57.1%) were completely seizure free after surgery (group 1), and 45 patients (42.8%) had postoperative IE (22 patients [21.0%] in group 2 and 23 patients [21.9%] in group 3). The proportion of insula-centered/paralimbic G2Gs was higher in group 1 (p = 0.002), whereas the percentage of central G2Gs was greater in groups 2 and 3 (p = 0.01). Higher preoperative tumor volume (p < 0.00001) and lower EOR (p = 0.05) were correlated to IE. The postoperative KPS (p < 0.00002) and return to work (RTW) rate (p = 0.0004) were higher in group 1. CONCLUSIONS: These original findings show that G2G location, tumor volume, and EOR are associated with perioperative IE, itself correlated to QOL, especially KPS and RTW. Such data may help neurosurgeons better evaluate the epilepto-onco-functional balance of surgery in G2G.