Shift in electrocorticography electrode locations after surgical implantation in children

Item Type Thesis; Poster; text

Authors Munter, Bryce

Publisher The University of Arizona.

Rights Copyright © is held by the author. Digital access to this material is made possible by the College of Medicine - Phoenix, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.

Download date 30/09/2021 21:43:15

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Link to Item http://hdl.handle.net/10150/658301 Shift in electrocorticography electrode locations after surgical implantation in children Bryce Taylor Munter, MSE, University of Arizona College of Medicine, Phoenix Stephen T Foldes, PhD, Brian L Appavu, MD, John F Kerrigan, MD, P. David Adelson, MD Department of Research, Barrow Neurological Institute at Phoenix Children’s Hospital

Highlights Results A total of 1140 electrode contacts were assessed across Methods 18 patients with a number of valid electrodes per patients from 24 to 83 (63.3 ± 16.7). Electrodes shift ranged from This was a retrospective analysis of • The shifts after ECoG patients with drug-resistant localized 0.01 to 17.0 mm with an average of 5.64 ± 3.27 mm shift who underwent for implantation surgery which can from the original brain surface immediately after implant placement of intra-cranial monitoring with (Fig. 2). impact the interpretation of surface ECoG in preparation for resective electrode locations. at Phoenix Children's Shift was significantly affected by eTIV (p = 0.038, mixed Hospital (IRB: #17-052). All surgeries were model), lobe (p < 0.001), and grid/strip (p < 0.001), but performed at Phoenix Children's Hospital • Average electrode shift not age (p = 0.926). Age and volume were not by the same surgeon (PDA) from 2014 to significantly related (Fig 2). Fig. 3 shows this relationship 2018, and all included patients had immediately after implant in a between shift and volume (left) and age (right). Age and preoperative T1 MRI and CT taken within pediatric population was 5.64 ± eTIV were not significantly related (linear regression 24 hours postoperatively. Electrode shift analysis, R2 = 0.14, p = 0.132). The number of days was measured by comparing the brain 3.27 mm, and shift was greater between MRI and CT had no effect on shift. surface on an MRI taken prior to electrode with larger estimated intracranial placement with the CT scan taken within 24 hours postoperatively. Shift was volume, in the parietal lobe, and calculated using a validated iElectrodes on grids compared to strips. Table 1: Demographics and Surgery Information. toolbox. A mixed effects model was used to determine effect and significance of age, eTIV, lobe, and type of electrode on • The shift in ECoG immediately electrode shift. eTIV was calculated using FreeSurfer. Electrodes were manually after implantation could lead to a categorized by lobe. misinterpretation of electrode location particularly in patients Figure 2:Distribution of ECoG location shift distances across contacts Conclusion with larger volume and for grid (Left) and relationship of age to eTIV (Right). In this analysis, we successfully contacts over the parietal lobes. characterized post-implant electrode shift due to brain deformation in pediatric Introduction patients. This shift is over half the distance between electrodes and is consistent with Recording electrical activity directly from the brain previous studies but is relatively small surface with subdural electrocorticography (ECoG) considering typical resection sizes. has great value in epilepsy, , and However, surgeries are becoming less developing , and there is a need for Figure 1: Example of brain shift invasive leading to a need for combining information across data types by colocalization from postoperative CT with submillimeter localization and localizing intracranial electrodes on imaging data. electrodes overlayed on preoperative T1 MRI interpretation of epileptic foci. However, localizing post-implant electrode locations Figure 3:ECoG location shift at each contact compared to age (A) and on pre-implant imaging data can be challenging due eTIV (B). Shift was significantly affected by eTIV but not age. One limitation to this study is the time to brain shift, where operative placement of the frame of post-implant CT. We used a single electrodes leads to temporary deformation of the time point <24 hours post surgery, but tissue. This deformation has been somewhat Contacts in grids had further movement of electrodes is characterized in adults, but not yet in pediatric significantly more shift than expected during recovery and again during patients. This discrepancy in ECoG electrode those of the strips (p < 0.001) resection surgery. Another limitation is that location due to brain shift at the cortical surface can (Fig. 4). Parietal contacts were this study cannot speak to the cause of the impact the interpretation of electrophysiological data significantly more shifted than electrode shift. and compromise clinical accuracy of frontal and temporal contacts (p Acknowledgements neuronavigation systems. < 0.001, Tukey) (Fig. 4). There were no contacts over the I’d like to thank my mentor Dr. Stephen In this study, we quantify the post-implant shift in occipital lobe in this cohort. Foldes as well as Austin Jacobson and ECoG contact location for pediatric patients. Our Aaron Raber from the PCH neurosurgery primary aims is to determine if shift is dependent on research group. I’d also like to thank Dr. estimated total intracranial volume (eTIV), age, or McEchron and Kristen Wagner for endless cortical region directly underneath the electrode. Figure 4:Shift distance by lobe and strip/grid categorization. Bars represent the mean and error bars are standard deviation. support through countless SP changes!