Science, Medicine, and the Anesthesiologist

Ideally, neurosurgeons would be able to resect all pathologic brain tissue without disrupting any of the surrounding healthy tissue. However, existing methods to identify the pathologic tissue boundaries are not very accurate. This study examined the potential to use a flexible panel of electrodes to display the intraoperative spatial patterns of the underlying cortical electrical activity in real time. The panel consisted of ultrathin platinum nanorod grids (1,024 channels, each 30-µm diameter), made of brain-conformal parylene C, and coupled to gallium nitride light-emitting diodes (grids of 1,024 or 2,048, each 220- or 100-µm diameter). In an anesthetized pig model, the coverage was 32 × 32mm (1-mm resolution). It was possible to demonstrate anatomic maps of somatosensory-evoked potentials. Phase reversal of these could be used to accurately map the boundary between the primary motor and somatosensory brain regions. The microdisplay could also reliably detect high-frequency (gamma) electroencephalogram (EEG) responses to air-puff sensory stimuli; the response to the standard Ojemann stimuli; and local neurotoxin-induced epileptiform discharges, which corresponded well with subsequent offline EEG automatic seizure-detection analysis. In a rat model, the coverage was 5 × 5mm. The 0.15-mm resolution was able to display high-resolution pathologic activity down to the level of submillimeter-scale cortical columns.

Take home message: The high-resolution and real-time feedback of this EEG-microdisplay system enables the visualization of cortical dynamics, which could be used to make intraoperative brain mapping more precise.