[Surgical resections in functional areas: report of 89 cases]

Awake surgery with mapping-based resection to treat focal epilepsy in eloquent brain areas

OBJECTIVES

Resective surgery is a potential therapeutic option for select patients with intractable focal epilepsy. However, the presence of ictal onset zones within or surrounding highly functional brain areas presents a surgical challenge, leading to poor seizure and functional outcomes. This report describes our experiences with awake mapping-tailored resection of epileptogenic areas involving eloquent cortices and evaluates their feasibility, tolerance, limitations, and significance.

METHODS

The study included patients who underwent surgery for drug-resistant focal epilepsy at our center under awake conditions. The surgical approach aimed to achieve maximum resection of preoperatively defined epileptogenic zones, considering the boundaries defined by surrounding functional areas. We collected data on preoperative evaluations, intraoperative tests and seizures, postoperative status epilepticus, and neurological functional outcomes.

RESULTS

We included 22 patients, 10 of whom had non-lesional epilepsy. Language, motor function, and sensory function were at risk in 19, 9, and 4 patients, respectively. Resection was performed as planned in 14 (63.6%) patients, while modifications were necessary in 8 (36.4%) patients due to functional constraints. The mean follow-up duration was 29.8 months. Sixteen (72.7%) patients achieved Engel class Ia outcomes, indicating seizure freedom, while none of the patients experienced clinically significant permanent postoperative neurological deficits.

SIGNIFICANCE

Resective surgery with intraoperative brain mapping under awake conditions was a valid treatment option for achieving a cure in cases of drug-resistant focal epilepsy, even in situations in which the condition is considered inoperable due to the risk of significant postoperative neurological deficits.

Similarities and differences in neuroplasticity mechanisms between brain gliomas and nonlesional epilepsy

OBJECTIVE

To analyze the conceptual and practical implications of a hodotopic approach in neurosurgery, and to compare the similarities and the differences in neuroplasticity mechanisms between low-grade gliomas and nonlesional epilepsy.

METHODS

We review the recent data about the hodotopic organization of the brain connectome, alongside the organization of epileptic networks, and analyze how these two structures interact, suggesting therapeutic prospects. Then we focus on the mechanisms of neuroplasticity involved in glioma natural course and after glioma surgery. Comparing these mechanisms with those in action in an epileptic brain highlights their differences, but more importantly, gives an original perspective to the consequences of surgery on an epileptic brain and what could be expected after pathologic white matter removal.

RESULTS

The organization of the brain connectome and the neuroplasticity is the same in all humans, but different pathologic mechanisms are involved, and specific therapeutic approaches have been developed in epilepsy and glioma surgery. We demonstrate that the "connectome" point of view can enrich epilepsy care. We also underscore how theoretical and practical tools commonly used in epilepsy investigations, such as invasive electroencephalography, can be of great help in awake surgery in general.

SIGNIFICANCE

Putting together advances in understanding of connectomics and neuroplasticity, leads to significant conceptual improvements in epilepsy surgery.

Surgery for dysembryoplastic neuroepithelial tumors and gangliogliomas in eloquent areas. Functional results and seizure control

INTRODUCTION

Dysembryoplastic neuroepithelial tumors and gangliogliomas are developmental glioneuronal tumors usually revealed by partial epilepsy. High epileptogenicity, childhood epilepsy onset, drug-resistance, temporal location, and seizure freedom after complete resection are common characteristics of both tumors. We report the specificity of surgical management, functional results and seizure outcome in cases of a tumor location in eloquent areas.

METHODS

Among 150 patients (88 males, 3-55 years) operated on for refractory epilepsy due to a glioneuronal tumor (1990-2015), 30 (20%, dysembryoplastic neuroepithelial tumors=21; gangliogliomas=9) had a tumor located in an eloquent cortex (sensory-motor, insular or language areas). Surgery was performed after a preoperative work-up, including stereo-electroencephalography in 48 patients (26%) and functional MRI in 100 (67%). MRI-guided lesionectomy was mainly performed in extra-temporal location, whereas an additional corticectomy was performed in a temporal location. Tumor microsurgical resections were guided using neuronavigation and cortical/subcortical electrical stimulations. Multiple stereotactic thermocoagulations were performed in two insular tumors.

RESULTS

New motor/language deficits related to eloquent areas occurred postoperatively in 6/30 patients (20%) without any major permanent disability. Minor sensorimotor (n=2) and moderate language disturbance (n=1) persisted in three of them. Postoperative seizure-free outcome (mean follow-up>5 years) was obtained in 81% of the entire series, but significantly decreased to 60% in eloquent areas. Incomplete tumor resection was the main cause of surgical failure. However, unfavorable seizure outcome was also observed despite complete tumor resection. Malignant transformation occurred in one ganglioglioma.

CONCLUSION

Epilepsy surgery for benign glioneuronal tumors in eloquent areas provides acceptable results regarding the functional risks. Complete tumor resection is crucial for long-term favorable outcome.

Seizures Outcome After Stereoelectroencephalography-Guided Thermocoagulations in Malformations of Cortical Development Poorly Accessible to Surgical Resection

BACKGROUND:

Radiofrequency thermocoagulation (RFTC) guided by stereoelectroencephalography (SEEG) has proved to be a safe palliative method to reduce seizure frequency in patients with drug-resistant partial epilepsy. In malformation of cortical development (MCD), increasing the number of implanted electrodes over that needed for mapping of the epileptogenic zone could help to maximize RFTC efficiency.

OBJECTIVE:

To evaluate the benefit of SEEG-guided RFTC in 14 patients suffering from drug-resistant epilepsy related to MCD located in functional cortical areas or in regions poorly accessible to surgery.

METHODS:

Ten men and 4 women were treated by RFTC. Thermolesions were produced by applying a 50-V, 120-mA current for 10 to 30 seconds within the epileptogenic zone as identified by the SEEG investigation.

RESULTS:

An average of 25.8 ± 17.5 thermolesions were made per procedure. The median follow-up after the procedure was 41.7 months. Sixty-four percent of the patients experienced a long-term decrease in seizure frequency of >50%, of whom 6 (43%) presented long-lasting freedom from seizure. When a focal low-voltage fast activity was present at seizure onset on SEEG recordings, 87.5% of patients were responders or seizure free. All of the patients in whom electric stimulation reproduced spontaneous seizures were responders.

CONCLUSION:

Our results show the good benefit-risk ratio of the SEEG-guided procedure for patients suffering from MCD in whom surgery is risky. This study identifies 2 factors, focal low-voltage, high-frequency activity at seizure onset and lowered epileptogenic threshold in the coagulated area, that could be predictive of a favorable seizure outcome after RFTC.

Epilepsies associated with focal cortical dysplasias (FCDs)

Focal cortical dysplasias (FCDs) are increasingly recognized as one of the most common causes of pharmaco-resistant epilepsies. FCDs were recently divided into various clinico-pathological subtypes due to distinct imaging, electrophysiological, and outcome characteristics. In this review, we will overview the international consensus classification of FCDs in light of more recently reported clinical, electrical, imaging and functional observations, and will also address areas of ongoing debate. In addition, we will summarize our current knowledge on pathobiology and epileptogenicity of FCDs as well as its underlying molecular and cellular mechanisms. The clinical (electroencephalographic, imaging, and functional) characteristics of major FCD subtypes and their implications on the presurgical evaluation and surgical management will be discussed in light of studies describing these characteristics and postoperative seizure outcomes in patients with medically intractable focal epilepsy due to histopathologically confirmed FCDs.

Resection frequency map after awake resective surgery for non-lesional neocortical epilepsy involving eloquent areas

Background

The resection of eloquent areas is challenging due to postoperative neurological deficits. The purpose of this study was to assess the efficacy and risk of awake brain surgery for non-lesional epilepsy involving the eloquent areas or their adjacent areas and to advocate the generation of a resection frequency map.

Methods

We enrolled 55 patients who underwent awake surgery between 1994 and 2007 for non-lesional epilepsy involving the primary sensori-motor or language areas. All patients underwent two-staged operations including subdural electrode monitoring and awake resective surgery. For each case, the preoperative and postoperative images were spatially normalized and compared on a standard atlas, and the resection map was then computed by summing up each resected area on the atlas.

Results

The postoperative seizure outcome was Engel class I in 27 patients (49.1%), II in nine (16.4%), III in 14 (25.5%) and IV in five (9.1%). Ten patients (18.2%) experienced postoperative neurological deficits including seven transient (12.7%) and three permanent, but mild ones (5.5%). The neurological complication rate of purely eloquent area resection was 36.8% (7/19). The resection frequency map computed in this study showed that the resection of eloquent areas was tolerable, with the exception of the Broca’s area.

Conclusions

Awake resective surgery with intraoperative brain mapping is an effective and safe treatment option for non-lesional epilepsy involving eloquent areas. The resection frequency map can show the resected area of a group as well as individuals and provide an objective measure of neurological risk.

Electronic supplementary material

The online version of this article (doi:10.1007/s00701-011-1074-6) contains supplementary material, which is available to authorized users.