Electroencephalography and clinical Neurophysiology , 87 (1993) 263-276 263 © 1993 Elsevier Scientific Publishers Ireland, Ltd. 0013-4694/93/$06.00 EEG RIO02 Neuromonitoring during surgery. Report of an IFCN committee * Marc R. Nuwer (LosAngeles, CA, USA) (Chairman), Jasper Daube (Rochester, NY,, USA), Catherine Fischer (Lyon, France), Johannes Schramm (Bonn, Germany) and Charles D. Yingling (San Francisco, CA, USA) Introduction Objectives Several techniques from EEG, EMG and evoked potentials can be applied for monitoring the nervous system throughout an operation. Sometimes such test- ing is also done during brief portions of an operation without needing prolonged monitoring. Applied skill- fully, these techniques hold a great potential for im- proving surgical procedures and safeguarding the ner- vous system during surgical procedures. Monitoring's principal goal is identification of new neurologic impairment early enough to allow prompt correction of the cause. Such impairment may be re- lated to easily corrected factors, such as circulatory impairment, excess compression from retraction, bony structures or hematomas, or mechanical stretching. A second goal of monitoring is prompt identification of new systemic impairment, such as that due to sys- temic hypoxia or hypotension. Changes in electrophysi- ologic tests have sometimes been the earliest sign of such systemic complications, changing even prior to vital signs. The presence or absence of EEG, EP or EMG changes can help to distinguish between harmful and harmless systemic changes. Inadequate anesthetic depth can be recognized on EEG and EMG, too, prior to the patient moving. Third, intraoperative neurophysiologic testing can help a surgeon to identify uncertain or unrecognized tissue, especially helping to identify which structures are nerves around and in a tumor. Correspondence to: Dr. Marc R. Nuwer, Department of Clinical Neurophysiology, Reed Neurological Center, University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA 94024 (USA). Fax: 310-206.8461. * This report is partially based on the work of Dr. Pamela Prior, J.W. Osselton and R.A.F. Pronk in the previous IFCN committee. Fourth, testing can help identify the location of a lesion by demonstrating which nerves or tracts are still functional and which are not. A fifth use of neurophysiologic monitoring is to provide reassurance to the surgeon during the course of an operation. The monitoring can indicate to the surgeon that complications are unlikely to have oc- curred up to that point in the procedure. This allows the surgeons to feel comfortable in proceeding further in the procedure, providing the patient with a greater degree of surgical intervention than would have been provided in the absence of monitoring. The sixth use is for high risk patients. Some patients may only be considered surgical candidates if monitor- ing is available and performed. Such patients might otherwise have been ineligible for an operation be- cause of the relative risks of an adverse outcome. A seventh role for intraoperative electrophysiologic moni- toring of the nervous system is more psychological than medical: it can provide a degree of reassurance to patients and their families. General principles Monitoring requires a team approach. Operating room EEG, evoked potential recording and EMG is usually directly carried out by an extra, specifically designated, individual during a particular operation. It is difficult for the primary anesthesiologist to carry out intensive neurologic monitoring alone while simultane- ously carrying out all the other responsibilities related to the general anesthesia. A physician-neurophysiolo- gist, or a medically qualified (non-physician) neuro- physiologist or well-trained, experienced neurophysiol- ogy technologist is designated to perform the electro- physiologic monitoring techniques. The presence of this designated monitoring specialist allows for careful attention to signal interpretation throughout the proce- dures, as well as providing a person to deal promptly with whatever technical problems arise. The designated monitoring specialist can also carry monitoring into the