SummaryObjective
Stereo-electroencephalography (SEEG) is a procedure performed for patients with intractable epilepsy in order to anatomically define the epileptogenic zone (EZ) and the possible related functional cortical areas. By avoiding the need for large craniotomies and due to its intrinsic precision placement features, SEEG may be associated with fewer complications. Nevertheless, intracerebral electrodes have gained a reputation of excessive invasiveness, with a “relatively high morbidity” associated with their placement. A systematic literature review and meta-analysis of SEEG complications has not been previously performed. The goal of this study is to quantitatively review the incidence of various surgical complications associated with SEEG electrode implantation in the literature and to provide a summary estimate. This will allow physicians to accurately counsel their patients about the potential complications related to this method of extraoperative invasive monitoring.

Methods
The systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We conducted MEDLINE, Scopus, and Web of Science database searches with the search algorithm. We analyzed complication rates using a fixed-effects model with inverse variance weighting. Calculations for the meta-analysis and construction of forest plots were completed using an established spreadsheet. The principal summary measures were the effect summary value and 95% confidence intervals (CIs).

Results
The initial 1,901 retrieved citations were reviewed. After removing 787 duplicates, the titles and abstracts of 1,114 publications were screened. At this stage, studies that did not mention the absence or presence of complications following SEEG or that did not fulfill the inclusion criteria in any manner were excluded. After excluding 1,057 citations, the full text was assessed in the resulting 57 articles for eligibility criteria. The most common complications were hemorrhagic (pooled prevalence 1.0%, 95% confidence interval [CI] 0.6–1.4%) or infectious (pooled prevalence 0.8%, 95% CI 0.3–1.2%). Five mortalities were identified (pooled prevalence 0.3%, 95% CI −0.1–0.6%). Overall, our analysis identified 121 surgical complications related to SEEG insertion and monitoring (pooled prevalence 1.3%, 95% CI 0.9–1.7%).

Significance
This review represents a comprehensive estimation of the actual incidence of complications related to SEEG. We report a rate substantially lower than the complication rates reported for other methods of extraoperative invasive monitoring. These data should alleviate the concerns of some regarding the safety of the “stereotactic” method, allowing a better decision process among the different methods of invasive monitoring and ameliorating the fear associated with the placement of depth electrodes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/epi.13298

Is SEEG safe? A systematic review and meta-analysis of stereo-electroencephalography–related complications

Genetic malformations of cortical development (MCDs), such as mild MCDs (mMCD), focal cortical dysplasia (FCD), and hemimegalencephaly (HME), are major causes of severe pediatric refractory epilepsies subjected to neurosurgery. FCD2 are characterized by neuropathological hallmarks that include enlarged dysmorphic neurons (DNs) and balloon cells (BCs). Here, we provide a comprehensive assessment of the contribution of germline and somatic variants in a large cohort of surgical MCD cases. We enrolled in a monocentric study 80 children with drug-resistant epilepsy and a postsurgical neuropathological diagnosis of mMCD, FCD1, FCD2, or HME. We performed targeted gene sequencing ( ≥ 2000X read depth) on matched blood–brain samples to search for low-allele frequency variants in mTOR pathway and FCD genes. We were able to elucidate 29% of mMCD/FCD1 patients and 63% of FCD2/HME patients. Somatic loss-of-function variants in the N-glycosylation pathway-associated SLC35A2 gene were found in mMCD/FCD1 cases. Somatic gain-of-function variants in MTOR and its activators (AKT3, PIK3CA, RHEB), as well as germline, somatic and two-hit loss-of-function variants in its repressors (DEPDC5, TSC1, TSC2) were found exclusively in FCD2/HME cases. We show that panel-negative FCD2 cases display strong pS6-immunostaining, stressing that all FCD2 are mTORopathies. Analysis of microdissected cells demonstrated that DNs and BCs carry the pathogenic variants. We further observed a correlation between the density of pathological cells and the variant-detection likelihood. Single-cell microdissection followed by sequencing of enriched pools of DNs unveiled a somatic second-hit loss-of-heterozygosity in a DEPDC5 germline case. In conclusion, this study indicates that mMCD/FCD1 and FCD2/HME are two distinct genetic entities: while all FCD2/HME are mosaic mTORopathies, mMCD/FCD1 are not caused by mTOR-pathway-hyperactivating variants, and ~ 30% of the cases are related to glycosylation defects. We provide a framework for efficient genetic testing in FCD/HME, linking neuropathology to genetic findings and emphasizing the usefulness of molecular evaluation in the pediatric epileptic neurosurgical population.

/pdf/dissecting-the-genetic-basis-of-focal-cortical-dysplasia-a-56unm2j6mk.pdf

Dissecting the genetic basis of focal cortical dysplasia: a large cohort study

Background:Stereoelectroencephalography (SEEG) was developed by Talairach and Bancaud in Paris in the late 1950s. Subsequently, the Talairach methodology was adopted at a number of additional centers in Europe and Canada. Technical aspects remained essentially unchanged for the following 30 years. O

Implantation of Stereoelectroencephalography Electrodes: A Systematic Review.

OBJECTIVEThe purpose of this study was to compare the accuracy of Neurolocate frameless registration system and frame-based registration for robotic stereoelectroencephalography (SEEG).METHODSThe authors performed a 40-trajectory phantom laboratory study and a 127-trajectory retrospective analysis of a surgical series. The laboratory study was aimed at testing the noninferiority of the Neurolocate system. The analysis of the surgical series compared Neurolocate-based SEEG implantations with a frame-based historical control group.RESULTSThe mean localization errors (LE) ± standard deviations (SD) for Neurolocate-based and frame-based trajectories were 0.67 ± 0.29 mm and 0.76 ± 0.34 mm, respectively, in the phantom study (p = 0.35). The median entry point LE was 0.59 mm (interquartile range [IQR] 0.25–0.88 mm) for Neurolocate-registration–based trajectories and 0.78 mm (IQR 0.49–1.08 mm) for frame-registration–based trajectories (p = 0.00002) in the clinical study. The median target point LE was 1.49 mm (IQ...

/pdf/a-new-tool-for-touch-free-patient-registration-for-robot-22ilv8t6kj.pdf

A new tool for touch-free patient registration for robot-assisted intracranial surgery: application accuracy from a phantom study and a retrospective surgical series.

Stereoelectroencephalography (SEEG) is a method for invasive study of patients with refractory epilepsy. Localization of the epileptogenic zone in SEEG relied on the hypothesis of anatomo-electro-clinical analysis limited by X-ray, analog electroencephalography (EEG), and seizure semiology in the 1950s. Modern neuroimaging studies and digital video-EEG have developed the hypothesis aiming at more precise localization of the epileptic network. Certain clinical scenarios favor SEEG over subdural EEG (SDEEG). SEEG can cover extensive areas of bilateral hemispheres with highly accurate sampling from sulcal areas and deep brain structures. A hybrid technique of SEEG and subdural strip electrode placement has been reported to overcome the SEEG limitations of poor functional mapping. Technological advances including acquisition of three-dimensional angiography and magnetic resonance image (MRI) in frameless conditions, advanced multimodal planning, and robot-assisted implantation have contributed to the accuracy and safety of electrode implantation in a simplified fashion. A recent meta-analysis of the safety of SEEG concluded the low value of the pooled prevalence for all complications. The complications of SEEG were significantly less than those of SDEEG. The removal of electrodes for SEEG was much simpler than for SDEEG and allowed sufficient time for data analysis, discussion, and consensus for both patients and physicians before the proceeding treatment. Furthermore, SEEG is applicable as a therapeutic alternative for deep-seated lesions, e.g., nodular heterotopia, in nonoperative epilepsies using SEEG-guided radiofrequency thermocoagulation. We review the SEEG method with technological advances for planning and implantation of electrodes. We highlight the indication and efficacy, advantages and disadvantages of SEEG compared with SDEEG.

Stereoelectroencephalography: Indication and Efficacy.

Focal cortical dysplasia (FCD) is the most frequent etiology for drug-resistant epilepsy in young children. Complete removal of the lesion is mandatory to cure the epilepsy. Stereo-EEG (SEEG) is an excellent method to delimitate the zone to be resected in older children and adults. We studied its feasibility in younger children. We retrospectively studied 19 children under 5 years of age who underwent SEEG between January 2009 and December 2012 and were subsequently operated on. FCD was diagnosed in all. We reviewed magnetic resonance imaging (MRI), electrophysiological and clinical data, as well as postoperative seizure outcome. We also included fluoro-deoxyglucose positron emission tomography (FDG-PET) studies, which had been systematically performed before invasive recording in 16 of the 19 children. The mean patient’s age at the time of SEEG was 38.6 months, and the mean age at seizure onset was 8 months. Three patients had normal MRI. No SEEG-associated complications occurred. We were able to delineate the epileptogenic zone in all children, and electrode stimulation localized the motor area when necessary (12 patients). Hypometabolic areas on FDG-PET included the epileptogenic zone in 13 of the 16 children, with a lobar concordance in 9 (56 %) and the same anatomical extent in 6 (38 %). Twelve children subsequently underwent focal or sublobar resection, six had multilobar resection, and one had hemispherotomy. The etiology was FCD type 2 in 15 and FCD type 1 or type 3 in three children. Eighty-four percent of our population have remained seizure-free at a mean follow-up of 29 months (12–48 months). Although children with FCD can successfully undergo resective surgery without invasive EEG, poor seizure semiology at this age inclines to perform SEEG when the dysplastic lesion is ill-defined and/or the electroclinical correlation is unclear. In cases with normal imaging as well as with suspected huge malformations, as was the case in 52 % of our patients, we consider it to be indispensable.

F. Archambaud

Papers

Outcome of surgery in children with focal cortical dysplasia younger than 5 years explored by stereo-electroencephalography