Abstract
In this study, we quantified the coverage of gray and white matter during intracranial electroencephalography in a cohort of epilepsy patients with surface and depth electrodes. We included 65 patients with strip electrodes (n = 12), strip and grid electrodes (n = 24), strip, grid, and depth electrodes (n = 7), or depth electrodes only (n = 22). Patient-specific imaging was used to generate probabilistic gray and white matter maps and atlas segmentations. Gray and white matter coverage was quantified using spherical volumes centered on electrode centroids, with radii ranging from 1 to 15 mm, along with detailed finite element models of local electric fields. Gray matter coverage was highly dependent on the chosen radius of influence (RoI). Using a 2.5 mm RoI, depth electrodes covered more gray matter than surface electrodes; however, surface electrodes covered more gray matter at RoI larger than 4 mm. White matter coverage and amygdala and hippocampal coverage was greatest for depth electrodes at all RoIs. This study provides the first probabilistic analysis to quantify coverage for different intracranial recording configurations. Depth electrodes offer increased coverage of gray matter over other recording strategies if the desired signals are local, while subdural grids and strips sample more gray matter if the desired signals are diffuse.
Highlights
In this study, we quantified the coverage of gray and white matter during intracranial electroencephalography in a cohort of epilepsy patients with surface and depth electrodes
A total of 65 patients were included in our study, falling into the following categories: (1) patients using only subdural strip electrodes (S), (2) patients using a combination of subdural strip electrodes and subdural grid electrodes (S + G), (3) patients using a combination of subdural strip, subdural grid, and depth electrodes (S + G + D), (4) and patients using only depth electrodes (D) (i.e., SEEG)
Despite decades of clinical use, it is unclear whether subdural grid and strip arrays record from more cortical gray matter than penetrating depth leads in normal clinical settings
Summary
We quantified the coverage of gray and white matter during intracranial electroencephalography in a cohort of epilepsy patients with surface and depth electrodes. Depth electrodes offer increased coverage of gray matter over other recording strategies if the desired signals are local, while subdural grids and strips sample more gray matter if the desired signals are diffuse. While many factors may guide the choice to use a certain intracranial monitoring technique, if one modality demonstrates superior gray matter coverage, it may increase the likelihood that the epileptic zone would be appropriately sampled. To elucidate these differences, we aimed to quantify the coverage of gray and white matter. Total Female Male Age Epilepsy onset age Bilateral Unilateral Total electrodes Strip electrodes Grid electrodes Depth electrodes
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