Utility of magnetic source imaging in nonlesional focal epilepsy: a prospective study.

OBJECTIVE: For patients with nonlesional refractory focal epilepsy (NLRFE), localization of the epileptogenic zone may be more arduous than for other types of epilepsy and frequently requires information from multiple noninvasive presurgical modalities and intracranial EEG (icEEG). In this prospective, blinded study, the authors assessed the clinical added value of magnetic source imaging (MSI) in the presurgical evaluation of patients with NLRFE. METHODS: This study prospectively included 57 consecutive patients with NLRFE who were considered for epilepsy surgery. All patients underwent noninvasive presurgical evaluation and then MSI. To determine the surgical plan, discussion of the results of the presurgical evaluation was first undertaken while discussion participants were blinded to the MSI results. MSI results were then presented. MSI influence on the initial management plan was assessed. RESULTS: MSI results influenced patient management in 32 patients. MSI results led to the following changes in surgical strategy in 14 patients (25%): allowing direct surgery in 6 patients through facilitating the detection of subtle cortical dysplasia in 4 patients and providing additional concordant diagnostic information to other presurgical workup in another 2 patients; rejection of surgery in 3 patients originally deemed surgical candidates; change of plan from direct surgery to icEEG in 2 patients; and allowing icEEG in 3 patients deemed not surgical candidates. MSI results led to changed electrode locations and contact numbers in another 18 patients. Epilepsy surgery was performed in 26 patients influenced by MSI results and good surgical outcome was achieved in 21 patients. CONCLUSIONS: This prospective, blinded study showed that information provided by MSI allows more informed icEEG planning and surgical outcome in a significant percentage of patients with NLRFE and should be included in the presurgical workup in those patients.

Jean Talairach: a cerebral cartographer.

Although French psychiatrist-turned-neurosurgeon Jean Talairach (1911-2007) is perhaps best known for the stereotaxic atlas he produced with Pierre Tournoux and Gábor Szikla, he has left his mark on most aspects of modern stereotactic and functional neurosurgery. In the field of psychosurgery, he expressed critique of the practice of prefrontal lobotomy and subsequently was the first to describe the more selective approach using stereotactic bilateral anterior capsulotomy. Turning his attention to stereotaxy, Talairach spearheaded the team at Hôpital Sainte-Anne in the construction of novel stereotaxic apparatus. Cadaveric investigation using these tools and methods resulted in the first human stereotaxic atlas where the use of the anterior and posterior commissures as intracranial reference points was established. This work revolutionized the approach to cerebral localization as well as leading to the development of numerous novel stereotactic interventions by the Sainte-Anne team, including tumor biopsy, interstitial irradiation, thermal ablation, and endonasal procedures. Together with epileptologist Jean Bancaud, Talairach invented the field of stereo-electroencephalography and developed a robust scientific methodology for the assessment and treatment of epilepsy. In this article the authors review Talairach's career trajectory in its historical context and in view of its impact on modern stereotactic and functional neurosurgery.

Reliable navigation registration in cranial and spine surgery based on intraoperative computed tomography.

OBJECTIVE: Low registration errors are an important prerequisite for reliable navigation, independent of its use in cranial or spinal surgery. Regardless of whether navigation is used for trajectory alignment in biopsy or implant procedures, or for sophisticated augmented reality applications, all depend on a correct registration of patient space and image space. In contrast to fiducial, landmark, or surface matching-based registration, the application of intraoperative imaging allows user-independent automatic patient registration, which is less error prone. The authors' aim in this paper was to give an overview of their experience using intraoperative CT (iCT) scanning for automatic registration with a focus on registration accuracy and radiation exposure. METHODS: A total of 645 patients underwent iCT scanning with a 32-slice movable CT scanner in combination with navigation for trajectory alignment in biopsy and implantation procedures (n = 222) and for augmented reality (n = 437) in cranial and spine procedures (347 craniotomies and 42 transsphenoidal, 56 frameless stereotactic, 59 frame-based stereotactic, and 141 spinal procedures). The target registration error was measured using skin fiducials that were not part of the registration procedure. The effective dose was calculated by multiplying the dose length product with conversion factors. RESULTS: Among all 1281 iCT scans obtained, 1172 were used for automatic patient registration (645 initial registration scans and 527 repeat iCT scans). The overall mean target registration error was 0.86 ± 0.38 mm (± SD) (craniotomy, 0.88 ± 0.39 mm; transsphenoidal, 0.92 ± 0.39 mm; frameless, 0.74 ± 0.39 mm; frame-based, 0.84 ± 0.34 mm; and spinal, 0.80 ± 0.28 mm). Compared with standard diagnostic scans, a distinct reduction of the effective dose could be achieved using low-dose protocols for the initial registration scan with mean effective doses of 0.06 ± 0.04 mSv for cranial, 0.50 ± 0.09 mSv for cervical, 4.12 ± 2.13 mSv for thoracic, and 3.37 ± 0.93 mSv for lumbar scans without impeding registration accuracy. CONCLUSIONS: Reliable automatic patient registration can be achieved using iCT scanning. Low-dose protocols ensured a low radiation exposure for the patient. Low-dose scanning had no negative effect on navigation accuracy.

Robot-assisted procedures in pediatric neurosurgery.

OBJECTIVE During the last 3 decades, robotic technology has rapidly spread across several surgical fields due to the continuous evolution of its versatility, stability, dexterity, and haptic properties. Neurosurgery pioneered the development of robotics, with the aim of improving the quality of several procedures requiring a high degree of accuracy and safety. Moreover, robot-guided approaches are of special interest in pediatric patients, who often have altered anatomy and challenging relationships between the diseased and eloquent structures. Nevertheless, the use of robots has been rarely reported in children. In this work, the authors describe their experience using the ROSA device (Robotized Stereotactic Assistant) in the neurosurgical management of a pediatric population. METHODS Between 2011 and 2016, 116 children underwent ROSA-assisted procedures for a variety of diseases (epilepsy, brain tumors, intra- or extraventricular and tumor cysts, obstructive hydrocephalus, and movement and behavioral disorders). Each patient received accurate preoperative planning of optimal trajectories, intraoperative frameless registration, surgical treatment using specific instruments held by the robotic arm, and postoperative CT or MR imaging. RESULTS The authors performed 128 consecutive surgeries, including implantation of 386 electrodes for stereo-electroencephalography (36 procedures), neuroendoscopy (42 procedures), stereotactic biopsy (26 procedures), pallidotomy (12 procedures), shunt placement (6 procedures), deep brain stimulation procedures (3 procedures), and stereotactic cyst aspiration (3 procedures). For each procedure, the authors analyzed and discussed accuracy, timing, and complications. CONCLUSIONS To the best their knowledge, the authors present the largest reported series of pediatric neurosurgical cases assisted by robotic support. The ROSA system provided improved safety and feasibility of minimally invasive approaches, thus optimizing the surgical result, while minimizing postoperative morbidity.

A novel robot-guided minimally invasive technique for brain tumor biopsies.

OBJECTIVEAs decisions regarding tumor diagnosis and subsequent treatment are increasingly based on molecular pathology, the frequency of brain biopsies is increasing. Robotic devices overcome limitations of frame-based and frameless techniques in terms of accuracy and usability. The aim of the present study was to present a novel, minimally invasive, robot-guided biopsy technique and compare the results with those of standard burr hole biopsy.METHODSA tubular minimally invasive instrument set was custom-designed for the iSYS-1 robot-guided biopsies. Feasibility, accuracy, duration, and outcome were compared in a consecutive series of 66 cases of robot-guided stereotactic biopsies between the minimally invasive (32 patients) and standard (34 patients) procedures.RESULTSApplication of the minimally invasive instrument set was feasible in all patients. Compared with the standard burr hole technique, accuracy was significantly higher both at entry (median 1.5 mm [range 0.2-3.2 mm] vs 1.7 mm [range 0.8-5.1 mm], p = 0.008) and at target (median 1.5 mm [range 0.4-3.4 mm] vs 2.0 mm [range 0.8-3.9 mm], p = 0.019). The incision-to-suture time was significantly shorter (median 30 minutes [range 15-50 minutes] vs 37.5 minutes [range 25-105 minutes], p < 0.001). The skin incision was significantly shorter (median 16.3 mm [range 12.7-23.4 mm] vs 28.4 mm [range 20-42.2 mm], p = 0.002). A diagnostic tissue sample was obtained in all cases.CONCLUSIONSApplication of the novel instrument set was feasible in all patients. According to the authors' data, the minimally invasive robot-guidance procedure can significantly improve accuracy, reduce operating time, and improve the cosmetic result of stereotactic biopsies.

Utility of depth electrode placement in the neurosurgical management of bottom-of-sulcus lesions: technical note.

OBJECTIVE: Small lesions at the depth of the sulcus, such as with bottom-of-sulcus focal cortical dysplasia, are not visible from the surface of the brain and can therefore be technically challenging to resect. In this technical note, the authors describe their method of using depth electrodes as landmarks for the subsequent resection of these exacting lesions. METHODS: A retrospective review was performed on pediatric patients who had undergone invasive electroencephalography with depth electrodes that were subsequently used as guides for resection in the period between July 2015 and June 2017. RESULTS: Ten patients (3-15 years old) met the criteria for this study. At the same time as invasive subdural grid and/or strip insertion, between 2 and 4 depth electrodes were placed using a hand-held frameless neuronavigation technique. Of the total 28 depth electrodes inserted, all were found within the targeted locations on postoperative imaging. There was 1 patient in whom an asymptomatic subarachnoid hemorrhage was demonstrated on postprocedural imaging. Depth electrodes aided in target identification in all 10 cases. CONCLUSIONS: Depth electrodes placed at the time of invasive intracranial electrode implantation can be used to help localize, target, and resect primary zones of epileptogenesis caused by bottom-of-sulcus lesions.

Minimally invasive techniques for epilepsy surgery: stereotactic radiosurgery and other technologies.

Minimally invasive surgical techniques for the treatment of medically intractable epilepsy, which have been developed by neurosurgeons and epileptologists almost simultaneously with standard open epilepsy surgery, provide benefits in the traditional realms of safety and efficacy and the more recently appreciated realms of patient acceptance and costs. In this review, the authors discuss the shortcomings of the gold standard of open epilepsy surgery and summarize the techniques developed to provide minimally invasive alternatives. These minimally invasive techniques include stereotactic radiosurgery using the Gamma Knife, stereotactic radiofrequency thermocoagulation, laser-induced thermal therapy, and MRI-guided focused ultrasound ablation.