The peroneal nerve is susceptible to injury due to compression at the fibular head for patients placed in the lithotomy, hemilithotomy or lateral decubitus positions during surgery. Upper extremity somatosensory and transcranial electric motor evoked potential monitoring has proven efficacious for identifying impending positional brachial plexopathy or upper extremity peripheral neuropathy in adult and pediatric patients undergoing spine surgery. We report on two cases to illustrate the usefulness of monitoring transcranial electric motor evoked potentials recorded from tibialis anterior muscle to identify emerging peroneal nerve compression secondary to lateral decubitus positioning.