Topics covered: Overview of science and art of IOM IOM at University of Michigan Hospital and Health Systems What is the purpose of Intraoperative monitoring? Training for physicians Overview of science and art of IOM Over the past 30 years, neurophysiologic intraoperative monitoring (IOM) has grown from an interesting investigational procedure into a widely used method to protect patients from neurologic injury during surgery. IOM techniques include most neurophysiologic modalities commonly used among outpatients. Thesee include electroencephalography (EEG), electromyography (EMG), evoked potentials (EPs), and nerve conduction velocity (NCV) testing of various types. IOM alsoo includes some techniques not used in outpatients, such as transcranial electrical motor EPs (tcemeps). Most techniques are electrical. Some other modalities, though, also have found some use in surgery. The latter include oximetry and transcranial Doppler (TCD). IOM helps in a number of ways. Most obviously, it can warn the surgeon of a serious complication in time to intervene and correct the problem before it becomes permanent. Second, it sometimes identifies a serious systemic problem that needs to be corrected. Third, the surgeon can feel comfortable about the patient s neurologic safety to that point in the case, and therefore go forward to provide a more thorough procedure. Fourth, with IOM the surgeons can feel more confident about a procedure s safety, allowing surgery on a high-risk patient who might otherwise be turned away. Fifth, the patient and his or her family can take comfort that the very real neurologic risks of surgeryy are lessened by IOM. IOM is not a perfect procedure. False positive cases (false alarms) occur in a portion of cases. In scoliosis, that rate is around 1% of procedures. In some other types of procedures, the rate is higher. These may be due to problems with the technique itself, the difficulty of obtaining good quality tracings from some patients, or as a result of anesthetic changes. True positive cases (true predictions of postoperative deficits) also occur. Those are casess where IOM raises an alarm, any available interventions are accomplished, but the patient has neurologic injury anyway. Just because an alarm is raised does not necessarily allow for prompt, complete correction of the problem. False negative cases are those in which the patient suffers from a neurologic injury that was not predicted by IOM changes. False negative cases are rare, but do occur. Some are due to immediate postoperative deterioration. Other cases are a result of injury in pathways not monitored. Occasionally, they are due to errors by the IOM team, who failed to recognizee changes when they occurred.
IOM at University of Michigan Hospital and Health Systems Intraoperative Neurophysiologic Monitoring (IOM) is a complex field with multiple domains which demand a broad range of faculty and staff expertise. Research, teaching, and clinical activity encompass numerous specialty fields including: neurosurgery, orthopedic surgery, endovascular, pediatric surgery, cardiovascular surgery and neuro-urology surgery. As the principle IOM provider to the University of Michigan Health System, covering over 1300 surgical procedures a year, the Neurology IOM program is one of the top programs in the nation. One group of individuals that benefit greatly from this service is the Neurology fellows. The fellows who rotate through the program are provided with a full-breath of IOM science. We have six dedicated faculty members with expertise in all faucets of IOM. In addition, we have a strong core of Certified Neurophysiologist in Intraoperative Monitoring (CNIM) staff that are able trained in the highest level of IOM techniques. Such advanced programs have and will continue to bring in substantial opportunities and experience in the area of IOM. To put things into perspective: in the United States, there are 96 Neurology Programs, 16 fellowship programs and only 5 of those fellowships mandate IOM. The University of Michigan IOM Program is one of those programs. The program has been identified at a national level by becoming one of the first labs to receive accreditation from the American neurophysiology credentialing board. Brian Bush, CNIM Admin Manager Intraoperative Monitoring University of Michigan Health System Department of Neurology office (734) 936-3962 appointments (734) 717-2388 bbush@umich.edu
What is the purpose of Intraoperative monitoring? The IOM service provides a number of services to hospital physicians and their patients. IOM helps prevent dysfunction of the brain, cranial nerves, spinal cord and peripheral nerves during certain types of surgeries. IOM can also facilitate mapping of the cortex and spinal cord. IOM is suggested for cases in which surgical complications may cause a loss of neurological function, such as surgery of the spine, brain and nerve plexus. The use of neuromonitoring can assist in preventing or reversing loss of function. Suggested cases that use IOM at University of Michigan Hospital and Health Systems include: surgery of the aortic arch, its branch vessels, including carotid artery surgery, when there is risk of cerebral ischemia resection of epileptogenic brain tissue or tumor Thoracic Aneurysm resection of brain tissue close to the primary motor cortex and requiring brain mapping distinguishing Sensory vs Motor Cortex protection of cranial nerves o tumors that affect optic, trigeminal, facial, auditory nerves o cavernous sinus tumors o microvascular decompression of cranial nerves correction of scoliosis or deformity of spinal cord involving traction on the cord protection of spinal cord where work is performed in close proximity to cord as in the placement or removal of old hardware or where there have been numerous interventions. Myelopathic spinal cords spinal instrumentation requiring pedicle screws or distraction decompressive procedures on the spinal cord or cauda equina carried out for determined myelopathy or claudication where function of spinal cord or spinal nerves are at risk spinal cord tumors neuromas of peripheral nerves of brachial plexus, when there is risk to major sensory or motor nerves surgery or embolization for intracranial AV malformations surgery for arteriovenous malformation of spinal cord cerebral vascular aneurysms surgery for intractable movement disorders arteriography during which there is a test occlusion of the carotid artery circulatory arrest with hypothermia [does not include surgeries performed under circulatory bypass (e.g., CABG, ventricular aneurysms)] distal aortic procedures, where there is risk of ischemia to spinal cord leg lengthening procedures, where there is traction on sciatic nerve or other nerve trunks traumatic injury to the pelvis and sacrum surgery as a result of traumatic injury to spinal cord/brain
Training for physicians Training of young physicians to conduct monitoring needs to include formal basic and clinical learning and experience. This should include training about techniques as applied in the operating room as well as training about how to apply those techniques in a variety of surgical procedures. In general, this forms a part of the training of young physicians in clinical neurophysiology. After training, the fellow should understand basic sciences of anatomy, physiology, and pharmacology of pathways monitored in surgery various neurophysiological techniques used in surgical monitoring and testing how to use IOM to predict and prevent adverse neurologic outcomes how to use IOM to locate and identify neurologic structures during surgery effects of anesthesia, systemic disorders, and comorbidities how to train and supervise technologists to conduct monitoring normal variations and criteria for abnormality and alarms The fellow should have extensive clinical experience in the use of common IOM techniques including: EEG monitoring ECoG somatosensory EP spinal cord monitoring somatosensory EP motor cortex localization motor EP spinal cord monitoring brainstem auditory EP monitoring EMG cranial nerve monitoring EMG monitoring of trunk and limbs pedicle screw stimulation NCV peripheral testing deep brain stimulator placement monitoring from remote sites The fellow should have extensive clinical experience with common clinical uses of IOM including: cerebral aneurysm clipping cerebral tumor resection epilepsy surgery deep brain stimulator implantation cranial base and posterior fossa tumor resection scoliosis correction cervical myelopathy decompression peripheral nerve repair or decompression CEA aortic and cardiac surgery The fellow also should have some additional experience in other occasionally used IOM techniques and clinical situations, and preferably in other types of neurophysiologic monitoring in the critical care unit, epilepsy unit, and during radiological procedures.
Overall, the field of intraoperative neurophysiology has developed from disparate difficult techniques in its earlier days three decades ago. Now, it has become a discipline with a large number of techniques, applied to a variety of surgical and other procedures. The monitoring teams encompass many types of specialists contributing their own expertise. The goals remain the same as before: to enhance patient care, avoid neurological deficits, allow for more complete procedures, allow procedures even on some highrisk patients, and provide feedback to the surgeon about actions that could injure the nervous system. (Reference: Marc R. Nuwer, Department of Clinical Neurophysiology, UCLA School of Medicine, Los Angeles, CA 90095, USA) Good Luck Fawad A. Khan, MD Clinical Neurophysiology Fellow (2011-2012) University of Michigan