A 65-year-old man undergoing posterior cervical decompression and fusion demonstrated absent lower extremity evoked potential (EP) after prone positioning and before incision. Localized EP change pointed to either a technical or positional culprit. After excluding technical causes, we performed a wake-up test to rule out positioning as the culprit. During the test, we observed both symmetrical and asymmetrical hemispheric changes in density spectral array β and γ bands that correlated with awakening, eye-opening, and extremity movements. By providing real-time information on brain state, processed electroencephalogram (EEG) can facilitate a safe wake-up test by showing high-power β and γ activities that precede awakening.
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