The Intraoperative use of the High-Density-ECoG During Awake Craniotomy Karim ReFaey; William Tatum DO; Anteneh M. Feyissa M.D.; Alfredo Quinones-Hinoja MD Department of Neurosurgery, Mayo Clinic, Jacksonville, Florida Department of Neurology, Mayo Clinic, Jacksonville, Florida Introduction Learning Objectives Electrocorticography (ECoG) and electrical cortical stimulation (ECS) are To determine if HD-grid ECoG electrodes can facilitate the extent of often used in tandem during awake craniotomies for mapping the eloquent resection during intraoperative ECS during real-time functional brain cortex, which facilitate tumor resection at the functional margins. mapping of eloquent cortex. To establish if ECoG composed of a 64-channel Intraoperative seizures are of a concern during awake craniotomy, which high-density grid can reveal a higher yield in detecting the epileptiform local lead to limitation of the extent of resection and a significant increase in the field potentials. length of hospitalizations. Due to the manifestation of seizures with brain lesions, epileptiform discharges are of interest. To investigate the frequency References Chatrian GE, Shaw CM, Leffman H. The significance of periodic lateralized epileptiform discharges in of epileptiform discharges we evaluated high-density ECoG (HD-ECoG) EEG: an electrographic, clinical and pathological study. Electroencephalogr. Clin. Neurophysiol. during ECS to assess epileptiform abnormalities and post-surgical 1964;17:177–193. Gurer G, Yemisci M, Saygi S, Ciger A. Structural lesions in periodic lateralized epileptiform outcomes. discharges (PLEDs). Clin. EEG Neurosci. 2004;35:88–93 Snodgrass SM, Tsuburaya K, Ajmone-Marsan C. Clinical significance of periodic lateralized epileptiform discharges: relationship with status epilepticus. J Clin Neurophysiol 1989;6:159–172. Methods Bozkurt MF, Saygi S, Erbas B. SPECT in a patient with postictal PLEDs: is hyperperfusion evidence of A retrospective analysis was done for patients who underwent awake electrical seizure? Clin Electroencephalogr 2002;33:171–173. craniotomy using high-density ECoG (HD-ECoG) (Figure 1A) in combination Reiher J, Rivest J, Grand'Maison F, and Leduc CP. Periodic lateralized epileptiform discharges with with ECS between November 2016 and June 2017. A total of 38 patients with transitional rhythmic discharges: Association with seizures. Electroencephalography Clinical Neurophysiology. 1991;78:12–17. primary brain tumor were identified. All patients underwent awake craniotomy with direct cortical stimulation and neuromonitoring. Preoperative risk, complications, tumor characteristics and functional outcome between patients with no intraoperative seizure (nIOS) and patients with intraoperative seizures Figure 1 were assessed. Results Thirty-eight patients underwent awake craniotomy with HD-ECoG between November 2016 and June 2017 time period. Patients had a mean of the preoperative Karnofsky Performance Score (KPS) of 82.10, while the mean of postoperative KPS was 84.74 (P = 0.2567). Twenty-four patients underwent awake craniotomy with the utilization of the intraoperative HD- (A) Showing high-density ECoG grid during cortical mapping and identification of the ECoG, 67% of these patients showed improvement after surgery (P = eloquent areas and the epileptogenic foci. (B) 1-2 Hz Periodic Focal Epileptiform 0.1022). Only 4 patients (10%) (P < 0.0001) had new or worsened seizures Discharges with a spatial field of distribution that included 3-5 contacts (1.5-2.5 cm) and neurological deficits postoperatively. without concomitant depth involvement. Following ECS-guided surgery in eloquent cortex, FPEDs resolved post-resection. Conclusions We describe PFEDs (Periodic Focal Epileptiform Discharges) on HD-ECoG (Figure 1B). A seizure-free outcome is most likely achieved with HD-EcoG in compared with Strip monitoring and no monitoring. Close surgical resection was achieved without unexpected morbidity and no mortality. More work uses special sensors may assist in further define the utility of ECoG in patients with and without tumor..