Augmented Reality in Extratemporal Lobe Epilepsy Surgery

Abstract

Background: Epilepsy surgery for extratemporal lobe epilepsy (ETLE) is challenging, particularly when MRI findings are non-lesional and seizure patterns are complex. Invasive diagnostic techniques are crucial for accurately identifying the epileptogenic zone and its relationship with surrounding functional tissue. Microscope-based augmented reality (AR) support, combined with navigation, may enhance intraoperative orientation, particularly in cases involving subtle or indistinct lesions, thereby improving patient outcomes and safety (e.g., seizure freedom and preservation of neuronal integrity). Therefore, this study was conducted to prove the clinical advantages of microscope-based AR support in ETLE surgery. Methods: We retrospectively analyzed data from ten patients with pharmacoresistant ETLE who underwent invasive diagnostics with depth and/or subdural grid electrodes, followed by resective surgery. AR support was provided via the head-up displays of the operative microscope, with navigation based on automatic intraoperative computed tomography (iCT)-based registration. The surgical plan included the suspected epileptogenic lesion, electrode positions, and relevant surrounding functional structures, all of which were visualized intraoperatively. Results: Six patients reported complete seizure freedom following surgery (ILAE 1), one patient was seizure-free at the 2-year follow-up, and one patient experienced only auras (ILAE 2). Two patients developed transient neurological deficits that resolved shortly after surgery. Conclusions: Microscope-based AR support enhanced intraoperative orientation in all cases, contributing to improved patient outcomes and safety. It was highly valued by experienced surgeons and as a training tool for less experienced practitioners.

Keywords: AR; augmented reality; epilepsy surgery; extratemporal lobe epilepsy; focal cortical dysplasia; multimodality; neuronavigation.

Figure 1

3D Visualization after the second iCT scan showing two SEEG electrodes in relation to their intended location (blue lines), two subdural grid electrodes reconstructed from iCT data, and intraoperatively acquired points corresponding to the intraoperatively accessible electrode contacts (yellow and red dots) using the navigated operating microscope, as well as major left hemispheric white matter tracts.

Figure 2

Preoperative planning after invasive diagnostics, including segmentations of the cerebrum, the motor cortex (light blue), grid electrodes (blue) and SEEG electrode (dark blue), functional areas according to stimulation (green, red, orange), the epileptogenic lesion (yellow), and white matter tracts (corticospinal tract, arcuate fascicle) in close vicinity to the target lesion.

Figure 3

Microscope-based AR visualization of outlined epileptogenic focus (yellow), segmented SEEG contacts (light blue), planned SEEG trajectories (blue and red), reconstructed corticospinal tract (blue) during ECoG before resection (A), in probe’s eye 3D view (B), and in axial, coronal, and sagittal (left to right) navigation views using FLAIR and T2 weighted MRI data sets (C).

Figure 4

Microscope-based navigation update using segmented outlines of the subdural grid electrodes (blue) increased overall navigation accuracy ((A): slight mismatch at contact level, (B): compensation of mismatch by translation of image data). Visualization of various objects and structures in the recent microscope’s focal plane, such as motor cortex (light blue), epileptogenic tissue (yellow and light green), epileptogenic focus according to SEEG (dark blue), subdural grid electrodes (red), and sensory areas according to stimulation (green).

Figure 5

AR-based verification of high navigation accuracy using a 3D visualization of the segmented cortex after microscope-based navigation update while sequentially (A–D) shifting the microscope’s focal plane along the focal axis.

Figure 6

Microscope-based AR visualization of outlined subdural grid electrode contacts, lesion-associated SEEG trajectory and the corticospinal tract before (A) and after grid removal (B) with in-parallel view of the navigation display (C) in probe’s eye view, inline views, and standard axial, coronal, and sagittal views.

Figure 7

Microscope-based AR support throughout the surgery. Three-dimensional visualization of outlined structures (motor cortex: light blue, epileptogenic tissue: yellow and light green, epileptogenic focus according to SEEG: dark blue), SEEG trajectory, and major white matter tracts (corticospinal tract, arcuate fascicle) after durotomy and grid removal within the microscope view (A) and in probe’s eye view (B). Two-dimensional visualization of all structures using microscope-based AR support (C,D) and in-parallel standard navigation views (E,F), at the beginning of corticotomy (C,E) and at the end of resection (D,F).