Medically intractable epilepsy from insular low-grade gliomas: Improvement after an extended lesionectomy

Objective. With the aim to better evaluate the role of the insula in seizures and the therapeutic implications, we analyzed the rate of insular low-grade gliomas (LGG) presenting with medically refractory epilepsy, detailed their ictal symptoms, and described the epileptological results following their surgical resection. Methods. Eleven patients (8 men, 3 women, mean age: 35 years) harboring an insular LGG generating intractable seizures, underwent tumor removal and perilesional opercular cortex resection (lesionectomy "plus") using intraoperative functional electrical mapping, combined with ultrasonography and/or neuronavigation. Results. Despite the occurrence of five postoperative deficits, the patients recovered in all cases. The epileptological results showed improvement in all cases: 9 Engel's Class I (82%), 1 Class II and 1 Class III. Ten lesionectomies were total [3] or subtotal [7], while one resection was partial (the patient in Engel's 111). Conclusion. The high rate of pharmacologically intractable seizures associated with insular LGG, and the favorable epilepsy outcome following surgical resection of these tumors seemingly indicate that the insular cortex itself may induce chronic seizures when injured. These results suggest, taking account of the technical surgical progress allowing now to minimize the morbidity after surgery in this region, that there is another indication than the sole oncological reason for surgery in patients with diffuse insular glioma - even if total tumor removal is not systematically possible.