• William O Tatum, Anteneh M Feyissa, Karim ReFaey, Sanjeet S Grewal, Mohammed A Alvi, Ramiro Castro-Apolo, Grayson Roth, Ivan Segura-Duran, Deependra Mahato, Henry Ruiz-Garcia, Eva Pamias-Portalatin, Kirsten Yelvington, Kaisorn Chaichana, Perry Bechtle, and Alfredo Quinones-Hinojosa.
• Department of Neurology, Mayo Clinic, Jacksonville, FL, USA. Electronic address: tatum.william@mayo.edu.
• Clin Neurophysiol. 2019 Aug 1; 130 (8): 1320-1328.

ObjectiveTo report intraoperative periodic focal epileptiform discharges (PFEDs) during awake craniotomy using high-density electrocorticography (HD-ECoG).MethodsWe retrospectively analyzed 81 patients undergoing awake craniotomy between 9/29/2016 and 7/5/2018. Intraoperative HD-ECoG was performed with direct electrocortical stimulation (DECS) for functional brain mapping. Real-time interpretation was performed and compared to scalp EEG when performed. Perioperative seizures, surgical complications, and characteristics of PFEDs were assessed.Results69/81 patients (mean age 48.5 years) underwent awake surgery; 55 operated for brain tumor, 11 for epilepsy and 3 for cavernomas. A focal abnormality on brain MRI was present in 63/69 (91.3%) patients. 43/69 (62.3%) patients had seizures preoperatively, 4/69 (5.7%) had seizures during DECS. PFEDs were identified in 11 patients (15.9%); 2 on depth recording and 9 during intraoperative HD-ECoG. 32 patients (46.3%) had preoperative EEG. HD-ECoG detected more epileptiform discharges (EDs) than standard EEG (32/43; 74.4% vs 9/32; 28.1%) (p = <0.001). Of 9/43 patients with PFEDs on HD-ECoG, 7 patients also had scalp EEG but only one case had EDs (p = 0.02), and 0/32 had periodic EDs.ConclusionsIntraoperative PFEDs are novel, highly focal EDs approximating a single gyrus. In patients with brain tumors, PFEDs did not demonstrate a relationship to pre-operative seizures though has similarities to other common waveforms in patients with epilepsy.SignificancePFEDs expand our understanding of the interictal-ictal continuum and highlight improved temporo-spatial information obtained from increasing sensor density during intracranial EEG recording.Copyright © 2019 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

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