Intraoperative neurophysiological monitoring (IONM), particularly using Transcranial Motor Evoked Potentials (TcMEPs), is routinely employed during complex spinal surgeries to safeguard motor pathway integrity. While intravenous magnesium is frequently used as an opioid-sparing adjunct in these cases, its potential effects on TcMEP monitoring remain unclear, with only limited clinical data available. This study proposes a prospective trial to evaluate how varying plasma magnesium levels influence TcMEP signals, addressing a critical gap in both neuromonitoring and magnesium pharmacokinetics in non-pregnant surgical patients.