Introduction: The present study describes a novel device and techniques for intracranial monitoring of cortical electrical activity during awake brain surgery. This novel device is a ring-shaped cortical electrode (the circular grid) that allows for 360 degrees cortical monitoring.

Methods: We prospectively collected the intraoperative electrocorticography (ECoG) data in seven patients who presented with seizures and who underwent an awake craniotomy with intraoperative ECoG recording using the circular grid and validating its efficacy with the conventionally-used high-density grid (HD-Grid).

Results: High-frequency oscillations (HFOs) and periodic-focal-epileptiform-discharges (PFEDs) were observed using the circular grid in two and five patients, respectively. These findings were validated with the HD-Grid with the exception of one patient in which HFOs were initially identified with the circular. Gross total resection was achieved in all of the patients except in one patient due to tumor infiltration to the motor strip. There were no cases with intraoperative seizures. No worsening of neurological deficits was identified. All patients were seizure-free by the time of last follow up (mean 2.6 months).

Conclusions: The circular grid was effective in monitoring cortical electrical activity during awake brain mapping and allowed early detection of cortical electrical signals, e.g., afterdischarges (ADs), HFOs, and PFEDs

Patient Care: During the cortical mapping craniotomies, the existing electrocorticography (ECoG) electrodes is used for continuous monitoring during cortical stimulations and identification of after-discharge (AD) activity, which can occur after direct cortical electrical stimulation and serve as a surrogate for an impending seizure. Intraoperative seizures can limit the use of further stimulation and interfere with perioperative brain mapping and neurological assessment. The existing ECoG devices only allow monitoring in one direction (i.e. superior) unless multiple are placed, and the grid ECoG makes it challenging to operate in the desired area since it covers the entire surgical field. Hence, we devised an ECoG device that allows surgical resection to take place simultaneously while recording the cortical electrical activity. In this study, our proposed describe will allow intracranial monitoring of electrical activity of the brain using a ring-shaped cortical electrode that allows a continuous 360-degree recording during surgical resection. This will allow early detection of intraoperative seizure activities and improve postoperative outcomes.

Learning Objectives: 1. The circular grid’s unique spatial design allows intracranial electrical activity monitoring in a 360o degrees fashion with direct visual and surgical access to the desired brain areas. 2. The circular grid is reliable for monitoring intraoperative ECoG and recording of electrical signals during awake craniotomies, e.g., ADs, HFOs, and PFEDs. 3. The Circular grid permits safe surgical resection while recording of the brain electrical signals which allows early detection seizure detection during awake craniotomies.

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