Three-dimensional neuronavigation in SEEG-guided epilepsy surgery

SEEG4D: a tool for 4D visualization of stereoelectroencephalography data

Epilepsy is a prevalent and serious neurological condition which impacts millions of people worldwide. Stereoelectroencephalography (sEEG) is used in cases of drug resistant epilepsy to aid in surgical resection planning due to its high spatial resolution and ability to visualize seizure onset zones. For accurate localization of the seizure focus, sEEG studies combine pre-implantation magnetic resonance imaging, post-implant computed tomography to visualize electrodes, and temporally recorded sEEG electrophysiological data. Many tools exist to assist in merging multimodal spatial information; however, few allow for an integrated spatiotemporal view of the electrical activity. In the current work, we present SEEG4D, an automated tool to merge spatial and temporal data into a complete, four-dimensional virtual reality (VR) object with temporal electrophysiology that enables the simultaneous viewing of anatomy and seizure activity for seizure localization and presurgical planning. We developed an automated, containerized pipeline to segment tissues and electrode contacts. Contacts are aligned with electrical activity and then animated based on relative power. SEEG4D generates models which can be loaded into VR platforms for viewing and planning with the surgical team. Automated contact segmentation locations are within 1 mm of trained raters and models generated show signal propagation along electrodes. Critically, spatial-temporal information communicated through our models in a VR space have potential to enhance sEEG pre-surgical planning.

The efficacy of robot-assisted surgery on minor basal ganglia cerebral hemorrhage with neurological dysfunction

OBJECTIVE

This study aims to compare the outcomes of robot-assisted drainage and conservative treatment in minor basal ganglia hemorrhage (10ml< hemorrhage volume ≤ 30 ml) patients with neurological dysfunction, and analyze patients treated with robot-assisted drainage in order to optimize this treatment strategy.

METHODS

In a retrospective study conducted in December 2021 to December 2023, minor basal ganglia cerebral hemorrhage patients with neurological dysfunction were enrolled from the Department of Neurosurgery, Shanghai Ninth People's Hospital. The patients included both the surgical (robot-assisted drainage) and conservative groups. The efficacy of robot-assisted drainage compared with conservative treatment in patients with minor cerebral hemorrhage and neurological dysfunction was evaluated by modified Rankin Scale (mRS) score after 3 months, muscle strength (grade 1 to 5) and cost of hospitalization.

RESULTS

Of the patients included, 23 received robot-assisted drainage and 20 received conservative treatment. There were no significant differences in gender, age, history of hypertension and diabetes, muscle strength and mRS score at admission. Female patients accounted for 32.6%, and male patients accounted for 67.4%. About 90% of the patients enrolled had a pre-existing hypertension history. The mRS score after 3 months indicated that prognosis of the patients was significantly better in the surgical treatment group than the conservative treatment group (favorable prognosis 69.57% VS. 35%, P = 0.034) while the patients underwent surgery paid higher hospital bills than patients treated conservatively.

CONCLUSION

Compared with traditional conservative treatment, robot-assisted drainage surgery is more helpful to improve the prognosis of patients with minor basal ganglia hemorrhage (volume ≤ 30mL) accompanied by neurological dysfunction. Robot assisted surgery can safely and effectively remove the hematoma of minor basal ganglia hemorrhage, and there were 69.6% of surgery group patients had a good prognosis in this study.

Stereo-electroencephalography (SEEG)-Guided Surgery in Epilepsy With Cingulate Gyrus Involvement: Electrode Implantation Strategies and Postoperative Seizure Outcome

SUMMARY

Surgical treatment of cingulate gyrus epilepsy is associated with good results on seizures despite its rarity and challenging aspects. Invasive EEG monitoring is often mandatory to assess the epileptogenic zone in these patients. To date, only small surgical series have been published, and a consensus about management of these complex cases did not emerge. The authors retrospectively analyzed a large surgical series of patients in whom at least part of the cingulate gyrus was confirmed as included in the epileptogenic zone by means of stereo-electroencephalography and was thus resected. One hundred twenty-seven patients were selected. Stereo-electroencephalography-guided implantation of intracerebral electrodes was performed in the right hemisphere in 62 patients (48.8%) and in the left hemisphere in 44 patients (34.7%), whereas 21 patients (16.5%) underwent bilateral implantations. The median number of implanted electrodes per patient was 13 (interquartile range 12-15). The median number of electrodes targeting the cingulate gyrus was 4 (interquartile range 3-5). The cingulate gyrus was explored bilaterally in 19 patients (15%). Complication rate was 0.8%. A favorable outcome (Engel class I) was obtained in 54.3% of patients, with a median follow-up of 60 months. The chance to obtain seizure freedom increased in cases in whom histologic diagnosis was type-IIb focal cortical dysplasia or tumor (mostly ganglioglioma or dysembryoplastic neuroepithelial tumor) and with male gender. Higher seizure frequency predicted better outcome with a trend toward significance. Our findings suggest that stereo-electroencephalography is a safe and effective methodology in achieving seizure freedom in complex cases of epilepsy with cingulate gyrus involvement.

Vertical Hemispherotomy: Contribution of Advanced Three-Dimensional Modeling for Presurgical Planning and Training

Vertical hemispherotomy is an effective treatment for many drug-resistant encephalopathies with unilateral involvement. One of the main factors influencing positive surgical results and long-term seizure freedom is the quality of disconnection. For this reason, perfect anatomical awareness is mandatory during each step of the procedure. Although previous groups attempted to reproduce the surgical anatomy through schematic representations, cadaveric dissections, and intraoperative photographs and videos, a comprehensive understanding of the approach may still be difficult, especially for less experienced neurosurgeons. In this work, we reported the application of advanced technology for three-dimensional (3D) modeling and visualization of the main neurova-scular structures during vertical hemispherotomy procedures. In the first part of the study, we built a detailed 3D model of the main structures and landmarks involved during each disconnection phase. In the second part, we discussed the adjunctive value of augmented reality systems for the management of the most challenging etiologies, such as hemimegalencephaly and post-ischemic encephalopathy. We demonstrated the contribution of advanced 3D modeling and visualization to enhance the quality of anatomical representation and interaction between the operator and model according to a surgical perspective, optimizing the quality of presurgical planning, intraoperative orientation, and educational training.

Target registration errors in navigation-assisted mandibular surgery according to the tracking methods and the type of markers: experiments using human dry mandibular bone

OBJECTIVES

This study was conducted to evaluate the accuracy of navigation process according to the type of tracking methods and registration markers. The target registration errors (TREs) were measured at seven anatomical landmarks of the mandible.

METHODS

Four different experiments were performed to obtain the TREs using two tracking methods, the optical tracker (Polaris) and the electromagnetic (EM) tracker (Aurora), and two types of registration markers, invasive and noninvasive markers. All comparisons of TREs were statistically analyzed using SPSS and Python-based statistical package.

RESULTS

The average TRE values obtained from the four experiments were as follows: (1) 0.85 mm (± 0.07) using invasive marker and Aurora, (2) 1.06 mm (± 0.12) using invasive marker and Polaris, (3) 1.43 mm (± 0.15) using noninvasive marker and Aurora, and (4) 1.57 mm (± 0.23) using noninvasive marker and Polaris. Comparisons between all the experimental results revealed statistically significant differences except for the type of tracking system. Although the comparison between the modality of the tracking system showed no significant differences, the EM-based approach consistently demonstrated better performances than the optical type in all comparisons.

CONCLUSIONS

This study demonstrates that irrespective of the tracking modality, using invasive marker is a better choice in terms of accuracy. When using noninvasive marker, it is important to consider the increased TREs. In this study, the noninvasive marker caused a maximum increment of TREs of 0.81 mm compared with the invasive marker. Furthermore, using an EM-based tracker with invasive marker may result in the best accuracy for navigation.

Theoretical stereoelectroencephalography density on the brain convexity

INTRODUCTION

Invasive electroencephalography (EEG) remains the "gold standard" for diagnosing the epileptogenic zone in patients with drug-resistant epilepsy and discrepancies between seizure semiology, video-EEG and magnetic resonance imaging (MRI) findings. However, the possibilities of stereoelectroencephalography (SEEG) to explore the brain surface remain a matter of debate and subdural EEG (SDEEG) is still preferred in some centers for cases when the supposed epileptogenic zone is on the brain convexity. The aim of our study was to evaluate the theoretical safe SEEG coverage on the brain convexity and to compare the theoretical SEEG cortical density with the usual SDEEG density.

MATERIALS AND METHODS

Our material included 10 hemispheres in 5 patients, who had been already investigated with SEEG for drug-resistant epilepsy. We translated our previously described technique in a theoretical model in an attempt to calculate the maximal number of avascular windows for each cerebral hemisphere. The distance between every entry point and the other entry points for each hemisphere was calculated using a mathematical formula. Subsequently, the theoretical SEEG coverage on the brain convexity was described using the maximal, minimal and average distances between each entry point and the closest 4 neighboring points. This type of measurement allows a direct comparison between SEEG and SDEEG in their ability to explore the brain convexity.

RESULTS

Ten hemispheres had 1328 safe entry points with a safety margin of 2.5 mm and a minimal distance of 2.5 mm between 2 entry points (average number of entry points: 132.8 (SD ± 5). The number of entry points in the explored 10 hemispheres varied from 104 to 156. The average distance between each entry point and its 4 neighbors was 11.47 mm. The maximal distance between two entry points in these 10 hemispheres was ranging from 20.28 to 27.23 mm (average: 24.67 mm). The closest entry points for the explored hemispheres were at an average distance of 4.67 mm (range: 2.82 - 5.96 mm). The average convexity surface was 223.68 cm2 (range: 204.63-238.77 cm2). The safe electrode density without electrode collision on the cortical surface was ranging from 0.46 to 0.69 electrodes per cm2 (average: 0.59 electrodes per cm2) (SD ± 0.023).

CONCLUSION

The theoretical SEEG cortical density is comparable with the usual SDEEG density. These findings, combined with the better safety profile of SEEG and the possibilities to explore deep cortical structures, explain the progressive shift from SDEEG to SEEG during the last years.

Development of an innovative surgical navigation system for sacrospinous fixation in pelvic surgery

STUDY OBJECTIVE

To validate the use of an innovative navigation method for sacrospinous fixation in surgery-like conditions as a new teaching tool and surgical method.

DESIGN

2-month-experiment prospective pilot study between July and August 2021.

SETTING

Biomechanics laboratory academic research.

POPULATION

29 participants: 9 gynecological surgeons and 20 participants with no medical background.

MEASUREMENT AND MAIN RESULTS

The experiment was composed of two training phases dedicated to improve the hand-eye coordination and suture skills on a training mock-up, and of a suturing phase on a pelvic mock-up designed to recreate the surgery-like conditions of a sacrospinous fixation. The surgeons provided qualitative feedback on the bio-accuracy of the mock-ups and evaluated the ease-of-use of the navigation software. Non-surgeons were included to assess the progression of the suture performance between two experiments performed one week apart (Session 1 & 2). The main objective for participants was to reach a virtual target and to stitch sacrospinous ligaments. For Session 1, an overall comfort score of 7.2/10 was attributed to the tool; 14 (42%) surgeon suture attempts and 63 (65%) non-surgeon suture attempts were accurate (i.e. below the 5-mm threshold). 22 (67%) surgeon suture attempts and 28 (34%) non-surgeon suture attempts were fast (i.e. in the first two quantiles of the duration dataset). An improvement of the non-surgeon performance was observed between the two sessions in terms of duration (Session 1: 46±20 sec; Session 2: 37±18 sec; p=0.047) and distance (Session 1: 3.8±1.3 mm; Session 2: 3.2±1.4 mm; p=10^-5) for the last suturing exercise.

CONCLUSION

This new motion-capture-based navigation method for sacrospinous fixation tested under surgery-like conditions seemed to be accurate and effective. The next step will be to design a pelvis model more adapted to the constraints of a sacrospinous fixation and to validate the benefits of this method compared to current techniques.