The primary objective in intraoperative neurophysiologic monitoring is to identify and prevent the development of new neurologic deficits or worsening of a preexisting neurologic injury to a patient who is undergoing surgery. This chapter presents a case study of a 24-year-old right-handed female diagnosed with neurofibromatosis type I at age 3 years, presented with progressive right upper extremity weakness, new onset left upper extremity weakness and difficulty walking. The agents used for anesthesia were fentanyl, sevoflurane, nitrous oxide, and remifentanil. The chapter provides an overview of the anesthetic agents such as inhalational agents, intravenous anesthetic agents and neuromuscular blocking agents and their effects on neurophysiologic monitoring. Almost all of the anesthetic agents can cause depression of the evoked potentials if given at sufficiently high doses and therefore a suitable combination of anesthetic agents should be chosen in discussion with the surgeon, anesthetist, and the monitoring team.