Intraoperative Raw EEG Monitoring for Anesthetic Depth Assessment in Scoliosis Correction Surgery: A Case Report

Abstract

Background:
General anesthesia aims to provide adequate hypnosis, analgesia, amnesia, and muscle relaxation. Conventional intraoperative monitoring mainly relies on hemodynamic parameters, which do not directly reflect brain function—the primary target organ of anesthesia. This limitation may lead to excessively light or deep anesthesia, increasing the risk of intraoperative awareness, hemodynamic instability, and postoperative neurocognitive disorders. In prolonged and highly stimulating procedures such as scoliosis correction surgery, accurate assessment of anesthetic depth is crucial. Electroencephalography (EEG) offers real-time insight into cortical activity and may improve anesthetic depth monitoring.

Case:
We report a 17-year-old female with adolescent idiopathic scoliosis (Lenke 3AN, Risser stage 5) who underwent spinal deformity correction under intraoperative monitoring. General anesthesia was maintained with propofol and remifentanil. Raw EEG monitoring using dual channels (CP3–Fpz and CP4–Fpz) was applied throughout the procedure. During induction, incision, spinal rotation/translation, and closure, EEG consistently demonstrated symmetric, dominant frontal alpha activity, corresponding with stable anesthetic depth. Anesthetic titration was guided by EEG patterns without reliance on processed EEG indices. The surgery was completed uneventfully, and the patient recovered without neurological complications.

Discussion:
EEG waveforms change in a dose-dependent manner with anesthetic agents. Dominant frontal alpha activity (alpha anteriorization) is associated with adequate hypnotic depth under propofol anesthesia, whereas excessive slowing or burst suppression may indicate overly deep anesthesia. Raw EEG monitoring provides direct neurophysiological information and may be more sensitive than processed indices such as the Bispectral Index, particularly in surgeries requiring intraoperative neurophysiological monitoring.

Conclusion:
Intraoperative raw EEG monitoring is a valuable adjunct for assessing anesthetic depth in long-duration scoliosis correction surgery. Maintaining dominant alpha activity may help prevent anesthetic overdose while preserving neurological stability.