Day: September 7, 2026

J Neurosurg 145:623–633, 2026

Seizure control is a central component of the oncofunctional result after surgery for diffuse grade 2 glioma. This long-term series examines patients with drug-resistant epilepsy before or after awake mapping–guided resection. Just over half became completely seizure-free, whereas persistent or newly intractable epilepsy affected the remainder. Tumor location, preoperative volume and extent of resection were associated with the epileptic outcome, which in turn tracked functional status and return to work. The study argues for integrating seizure goals into surgical planning without compromising functional boundaries.

Objective

To characterize intractable epilepsy before and after awake functional mapping–based surgery for IDH-mutant grade 2 glioma and examine its relationship with tumor, surgical and quality-of-life outcomes.

Methods

The authors retrospectively selected patients operated between June 2002 and March 2024 who had intractable epilepsy before and/or after surgery and more than 1 year of follow-up. All resections were performed awake with functional mapping. Patients were divided into those with preoperative intractable epilepsy who became completely seizure-free (Engel IA), those with intractable epilepsy both before and after surgery, and those who developed it only postoperatively.

Main results

The series comprised 105 patients and 134 awake procedures, with a mean follow-up of 8.3 years. At diagnosis, 101 patients (96.2%) had seizures and 82 (78.1%) had intractable epilepsy. The mean extent of resection was 86.8%; persistent postoperative deterioration occurred in one patient.

Sixty patients (57.1%) achieved Engel IA seizure freedom. Twenty-two (21.0%) had persistent intractable epilepsy and 23 (21.9%) developed it postoperatively. Larger preoperative volume and lower extent of resection correlated with intractable epilepsy. Patients rendered seizure-free had higher postoperative Karnofsky scores and a higher return-to-work rate.

Interpretation

For grade 2 glioma, seizure control is not a secondary outcome: it is closely linked to autonomy and social reintegration. The association with resection extent supports maximizing removal within individually mapped functional limits. The anatomical signal—particularly the poorer pattern in central tumors—also indicates that epileptological success depends on the network involved, not simply on residual volume.

Limitations

This was a retrospective, highly selected single-team series restricted to patients with intractable epilepsy, not the entire grade 2 glioma population. Surgical, molecular and adjuvant-treatment practice evolved over more than two decades. Associations between resection, epilepsy and function do not prove causality, and postoperative antiseizure-medication strategies were not randomized.

Clinical takeaway

Discuss seizure freedom explicitly when planning awake surgery for IDH-mutant grade 2 glioma. Pursue the greatest functionally safe resection, document the epileptogenic network as well as eloquent function, and maintain structured long-term epileptological follow-up even in patients without preoperative pharmacoresistance.