Placement of subdural electrode grids for seizure focus localization in patients with a large arachnoid cyst

Abstract

<jats:p>✓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.</jats:p> <jats:p>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.</jats:p> <jats:p>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.</jats:p>

Clinical and Neuroimaging Outcomes of Surgically Treated Intracranial Cysts in 110 Children

“…The indications for treatment are debated far more in cysts with headaches or epilepsy8,15,27,45,47,48). This series included a few cases of patients with headaches (without increased intracranial pressure), and the results of treatment in these patients were not satisfactory.…”

“…Headache remain a controversial indication for cyst surgery47) and there is even skepticism about the effectiveness of cyst treatments48). Epilepsy is frequently associated with intracranial cysts15,25,33), but the seizure etiology remains unknown, and the coexistence of seizures and cysts may be incidental15,27,33,47). Thus, careful preoperative selections are mandatory.…”

Differential EEG

“…Output signals of DEEG and CEEG are expressed in (3) and (4) separately. If the gain of the amplifiers in a CEEG system are exactly the same, the output expression of DEEG and CEEG system should be the same as (3). Minute difference of gain between two amplifiers leads to large artifacts recorded because of high signal level of V CM .…”