L’épilepsie insulaire : l’expérience montréalaise

The Insula in Temporal Plus Epilepsy

Temporal lobe epilepsy (TLE) surgery is the most common type of surgical treatment offered to patients with drug-resistant focal seizures. However, the proportion of patients experiencing long-term freedom from seizures after TLE surgery remains suboptimal. Temporal plus epilepsy, which is characterized by a primary temporal epileptogenic zone extending to neighboring regions, has been demonstrated to be a major predictor of TLE surgery failures. In the context of the temporoperisylvian epilepsies, i.e., the most common type of temporal plus epilepsy, a possible role of the insula has often been hypothesized. As this area is buried deep within the lateral sulcus, the use of invasive recordings is often required. Identifying patients with temporal plus seizures is a relevant issue, as they appear to have a worse postsurgical seizure outcome compared with patients with "pure" temporal lobe seizures. Owing to these prognostic implications, it becomes important to identify, among patients suffering from "atypical" nonlesional TLEs, those who should undergo invasive investigations, in particular to explore the insula. In fact, only a primary involvement of the insula in the epileptogenic network may require to include this area in the resection to achieve seizure freedom. Using modern neurosurgical techniques, insular epilepsy surgery has proved to be safe and beneficial, making the "true" role of the insula in TLE surgery failures more relevant to understand. Further studies are needed to evaluate the efficacy of multilobar resections in patients with temporal plus epilepsy, in particular, when eloquent or difficult to access areas such as insula are suspected to be involved.

Vascular consequences of operculoinsular corticectomy for refractory epilepsy

OBJECT

Surgery in the insular region is considered challenging because of its vascular relationships, the proximity of functional structures, and its deep location in the sylvian fissure. The authors report the incidence and consequences of ischemic lesions after operculoinsular corticectomy for refractory epilepsy.

METHODS

The authors retrospectively reviewed the data of all patients who underwent an insular resection with or without an opercular resection for refractory epilepsy at their center. All patients underwent postoperative MRI, enabling a radiological analysis of the ischemic lesions as a result of the corticectomies. The resections were classified according to the location and extent of the insular corticectomy and the type of operculectomy. Each patient underwent clinical follow-up.

RESULTS

Twenty patients underwent surgery. All patients underwent insular corticectomy with or without an operculectomy. Ischemic lesions were identified in 12 patients (60%). In these patients, 11 ischemic lesions (55%) were related to the insular corticectomy, and 1 was related to the associated periinsular resection. The ischemic lesions associated with the insulectomies were typically located in the corona radiata running from the insula to the periventricular region. Nine patients (45%) developed a postoperative neurological deficit, among whom 6 (67%) had an insular corticectomy–related ischemic lesion. All reported neurological deficits were transient. Five patients (25%) had ischemic lesions without neurological deficit.

CONCLUSIONS

Operculoinsular corticectomies are associated with ischemic lesions in approximately 60% of patients. However, given that no patient had a definitive postoperative deficit, these ischemic lesions have few clinical consequences. Therefore, this surgical procedure can be considered reasonably safe for the treatment of refractory epilepsy.