Authors :
Presenting Author: Po Ching Chen, PhD – AdventHealth Orlando
James Baumgartner, MD – Director, Neurosurgery, AdventHealth Orlando; Ki Hyeong Lee, MD – Director, Epilepsy Center, AdventhHealth Orlando; Amy Cummiskey, PA – Neurosurgery – amy.cummiskey@adventhealth.com; Seo Joo Hee, MD – Epilepsy Center – AdventHealth; Elakkat Dharmaraj Gireesh, MD – Epilepsy Center – AdventHealth Orlando; Holly Skinner, MD – Epilepsy Center – AdventHealth Orlando; Ammar Hussain, MD – Epilepsy Center – AdventHealth Orlando; Angel Claudio, MD – AdventHealth Orlando; Eduardo Castillo, PhD – MEG Lab – AdventHealth Orlando
Rationale:
The conventional stereo-electroencephalography (sEEG) electrode implantation strategy follows the classic Talairach methodology using orthogonal trajectories perpendicular to the sagittal plane which was created under historical technical limitations. The advancement of robotic assisted stereotactic surgery and 3D imaging enable convenient targeting from a wide range of locations at various angles. This have opened new possibilities to further optimize the sEEG electrode placement strategy using different approaches. We have been utilizing long trajectories to sample deep structures along the oblique parasagittal planes (Figure 1). By using long electrodes in the anterior-posterior direction, we can longitudinally sample cingulate gyrus, amygdala, and hippocampus without interruption, while employing oblique trajectories to better cover insular gyrus and orbital frontal lobe by using fewer electrodes. These alternative approaches often require longer trajectories ( >60 mm) compared to conventional orthogonal trajectories (< 50 mm). However, the increased travel distance may pose challenges to accuracy. Therefore, this study aims to analyze the impact of long trajectories and evaluate how the placement, distribution, and location of fiducial markers affect accuracy at the same time.
Methods:
A retrospective review was conducted on 48 consecutive sEEG implantation procedures using the proposed long trajectories. Five skull bone screws were used as fiducials in each case for registration. Post operative CT scans were acquired to localize each electrode contact. Instead of solely measuring the errors only at entry and target points. We measured the radial errors of each electrode contact to the planned trajectories at different depths. A total of 560 electrodes and 8298 contacts were analyzed, with 51% of contacts reaching depths greater than 60 mm.
Results:
The length of trajectory is significantly associated with the accuracy (p< 0.01). For contacts at a depth < 60 mm, the average error is 1.48 mm. Contacts at a depth >60 mm exhibit an average error of 2.22 mm. Furthermore, the analysis revealed a decrease in error when the entry point is closer to a fiducial marker. Moreover, a greater coverage area encompassed by fiducials is correlated with smaller errors. No complications were observed as a result of sEEG electrode implantation in the cohort of patients.
Conclusions:
At shorter trajectory distances, our errors are well curbed within the range reported in the literature, which primarily focusing on orthogonal electrodes. Although longer lengths have a negative impact on accuracy, the increased deviation could be well tolerated when targeting larger structures such as insular and cingulate cortexes. By carefully selecting specific desired targets, the advantages of using longer trajectories could outweigh the slight decrease in accuracy. Additionally, the placement of fiducial markers could be another potential factor that affects accuracy.
Funding: N/A