Role of Subdural Interhemispheric Electrodes in Presurgical Evaluation of Epilepsy Patients.

OBJECTIVE: Surgery is a well-established and safe treatment option for focal drug resistant epilepsy. However, difficulties are often encountered in diagnosing mesial cortical lesions. The aim of this study was to evaluate the usefulness and overall complication rate of subdural interhemispheric electrodes (IHEs) as part of an invasive presurgical evaluation of epilepsy patients. METHODS: A total of 100 patients who underwent implantation of subdural IHE were included in the study. Data on surgical complications, subdural electrodes and contacts, benefits of invasive electroencephalography recording, and final seizure outcome were collected and analyzed. RESULTS: A total of 343 subdural strip electrodes with a total of 1470 contacts were implanted. There were 6 perioperative/postoperative complications, none of them leading to a permanent neurologic deficit. An increased number of IHE (P = 0.005) and IHE-contacts (P = 0.03) also increased the rate of focus detection, while not significantly changing complication rate (P = 0.26). Two benefits of IHE (focus detection of interhemispheric lesions and mapping) in extratemporal resections were significantly associated with excellent seizure outcome (ILEA1) (P = 0.03, respectively P < 0.001). Other features associated with excellent seizure outcome are pure resections (w/o multiple subpial transection, P = 0.006), specific histology (P < 0.001), and a visible magnetic resonance imaging lesion (P = 0.002). CONCLUSION: Implantation of IHE for the preoperative evaluation of epilepsy patients is an established surgical procedure with an acceptable complication profile. The benefits delivered from IHE can positively influence final seizure outcome in the challenging group of extratemporal resections due to interhemispheric lesions. Thus IHEs demonstrate a useful diagnostic utility for the presurgical evaluation of selected epilepsy patients.

Epilepsy surgery of the rolandic and immediate perirolandic cortex: surgical outcome and prognostic factors.

OBJECTIVE: Herein we present a single-center retrospective study of patients who underwent epilepsy surgery for seizures arising from the sensorimotor (rolandic) cortex. The goal was to find prognostic factors associated with better seizure outcome and to evaluate both surgical and neurologic outcomes. PATIENTS, METHODS, AND MATERIALS: A total of 66 patients fulfilled eligibility criteria and were included in the study. Patients were divided into two groups for analysis: patients with resections within rolandic cortex (RO group; n = 46), and patients with resections in immediate perirolandic cortex and simultaneous sensorimotor multiple subpial transections (IPR group; n = 20). RESULTS: Favorable postoperative seizure outcome (International League Against Epilepsy [ILAE]; ILAE1-ILAE3) was achieved in 42 patients (64%), 39 (59%) of whom were completely seizure-free (ILAE1). The favorable seizure outcome in the RO group (72%) was better than in the IPR group (45%) (p = 0.04, relative risk [RR] 0.51 [0.28-0.94, 95% CI]). Eighteen patients (34%) had a postoperative permanent neurologic deficit. Independent predictors for excellent seizure outcome (ILAE1) after multivariate regression analysis were complete resection of the lesion (p < 0.001), pathology (p = 0.009), age at surgery (p = 0.03), and the absence of preoperative simple partial seizures (p = 0.01). SIGNIFICANCE: With a 64% favorable seizure outcome, surgery for intractable epilepsy arising from sensorimotor cortex is possible and can be worthwhile. The increased risk for postoperative neurologic deficits is higher than in other locations, and this must be discussed with patients in detail prior to surgery. Best postoperative results can be achieved in cases in which a complete resection is possible without damaging eloquent cortical areas.