Subdural Electrode Grids for Seizure Focus Localization
Subdural Electrode Grids for Seizure Focus Localization
Subdural electrode arrays are placed to localize seizure foci for possible resection. The procedure is usually straightforward when an electrode grid array is placed on the brain convexity but can become complicated if the surface on which the grids are applied is not convex. Arachnoid cysts can be associated with seizures, but their topography presents a challenge to standard techniques for the placement of subdural grids. The authors report on a technique for electrode grid placement that successfully localized seizure foci in the depths of arachnoid cysts in two patients.
Subdural grids were placed to conform to the concave cyst cavity. They were held in place with rolled gelatin foam padding, which filled the arachnoid cyst. The padding was removed before removing the electrode grids and resecting the seizure focus.
Although arachnoid cysts present a technical challenge when seizure foci are located within the cyst cavity, the technique of packing the cyst cavity with gelatin foam provides good electrode contact on the concave cyst wall, allowing adequate seizure focus localization.
Subdural electrodes are widely utilized to gather EEG data from cortical areas to localize seizure foci before resection. Seizure disorders can be associated with the presence of arachnoid cysts, and the question of seizure generation from the cortical surface in the depths of the cyst often arises. The technical issue relates to the tendency of electrode arrays to slide off concave areas of the cortex and thus provide confounding EEG data. We report on a technique for placing a subdural electrode grid into the depths of arachnoid cysts in two patients, which allowed successful localization of seizure foci in both cases.
Abstract and Introduction
Abstract
Subdural electrode arrays are placed to localize seizure foci for possible resection. The procedure is usually straightforward when an electrode grid array is placed on the brain convexity but can become complicated if the surface on which the grids are applied is not convex. Arachnoid cysts can be associated with seizures, but their topography presents a challenge to standard techniques for the placement of subdural grids. The authors report on a technique for electrode grid placement that successfully localized seizure foci in the depths of arachnoid cysts in two patients.
Subdural grids were placed to conform to the concave cyst cavity. They were held in place with rolled gelatin foam padding, which filled the arachnoid cyst. The padding was removed before removing the electrode grids and resecting the seizure focus.
Although arachnoid cysts present a technical challenge when seizure foci are located within the cyst cavity, the technique of packing the cyst cavity with gelatin foam provides good electrode contact on the concave cyst wall, allowing adequate seizure focus localization.
Introduction
Subdural electrodes are widely utilized to gather EEG data from cortical areas to localize seizure foci before resection. Seizure disorders can be associated with the presence of arachnoid cysts, and the question of seizure generation from the cortical surface in the depths of the cyst often arises. The technical issue relates to the tendency of electrode arrays to slide off concave areas of the cortex and thus provide confounding EEG data. We report on a technique for placing a subdural electrode grid into the depths of arachnoid cysts in two patients, which allowed successful localization of seizure foci in both cases.
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