High-density 360-degree Circle Grid for Detection of After Discharges During Functional Brain Mapping in Patients with Glioma (S3.006)

Objective: We aimed to identify electrophysiological properties of after-discharges (ADs) elicited during intraoperative direct electrocortical stimulation (DES) for functional brain mapping (FBM) using a customized, high-density (HD) circular grid. Background: Intraoperative FBM has been used to identify eloquent cortex during resection of brain tumors. DES may induce ADs, which may become prolonged and manifest as clinical seizures impairing FBM during awake craniotomy. Design/Methods: Intraoperative DES was performed in conjunction with a customized HD, 22-channel, ring-shaped grid; electrodes 0.3 mm diameter, spaced 5mm apart with an open center. Hand-held DES consisted of alternating current, bipolar electrical stimulation, 50 Hz, 200 ms pulse duration, in escalating amplitudes from 0.5 mA to 10 mA. Electrocorticography was reviewed by two parties independently. Results: 18 patients (mean 49.5 ± 14.7 years; 9 males) underwent resection near eloquent cortex guided by FBM; 16 Caucasian (88.9%) and 2 Hispanic (11.1%). Pathology included 11 glioblastoma (61.1%), 5 anaplastic astrocytoma (27.7%), and 2 oligodendroglioma (11.1%). ADs were elicited in 9 patients (50%, 95% CI 0.26 to 0.74), exceeded 10 seconds in 7 patients (38.8%, 95% CI 0.17 to 0.64), resulted in a clinical seizure in 1 patient (5.5%, 95% CI 0 to 0.27). The mean duration of ADs was 6.3 ± 2.2 s, comprising 25 ADs involving 7 contacts. Multi-directional ADs were present with inter- and intra-individual variation. The mean AD threshold was 3.5 mA (range = 2–5 mA). Eloquence was assessed using DES, and complications occurred in two patients (aphasia, facial weakness) following FBM. Conclusions: Using a customized circular HD-grid, DES identified that the ADs were similar to other reports of ADs in FBM. ADs were present in all directions which are unidentifiable without a 360 degree metric. Early detection of ADs may minimize intraoperative seizures during FBM. Disclosure: Dr. Potluri has nothing to disclose. Dr. McKay has nothing to disclose. Dr. Hanna AL-Shaikh has nothing to disclose. Dr. Feyissa has nothing to disclose. Dr. ReFaey has nothing to disclose. Dr. Quinones-Hinojosa has nothing to disclose. Dr. Tatum has received personal compensation in an editorial capacity for Elsevier. Dr. Tatum has received royalty, license fees, or contractual rights payments from Demos Medical Publishing, LLC.