In 2009, more than 200 physicians from 12 countries attended the annual Mayo Clinic conference on clinical neurophysiology. They came for application updates and training in EMG and EEG, evoked potentials, autonomic testing, and intraoperative monitoring. They knew they would be taught by experienced specialists:
The work of these 5 groundbreaking specialists continues to inform refinements in the science and practice of neurophysiologic testing and monitoring across Mayo's 3 sites, where procedures are performed by experienced specialists in neuromuscular and autonomic diseases.
Large patient volumes and a caseload that, in addition to more common conditions, includes complex neuromuscular diseases, brachial plexus injuries, rare neuropathies, atypical seizure disorders, and postural orthostatic tachycardia syndrome, enhance the breadth and depth of specialist experience (See Box 1 for more information.)
Tests rarely performed at other institutions, such as repetitive stimulation for neuromuscular junction diseases and single-fiber EMG, are done daily by Mayo's electromyographers.
The EMG laboratory at Mayo Clinic in Rochester, Minn., is the largest in the world. There, electromyographers conduct more than 11,000 EMG studies per year. Mayo Clinic's campuses in Arizona and Florida conduct more than 3,700 and 4,500 EMG studies per year, respectively.
The Autonomic Laboratory at Mayo Clinic in Rochester is the largest in the United States. Autonomic testing, also available at Mayo's Florida and Arizona sites, helps determine the presence, severity, distribution, and localization of autonomic dysfunction. Routine autonomic evaluation includes tests of sudomotor, cardiovagal, and adrenergic function (See Box 2 for more information.)
"Awake anesthesia" has made EMG in children feasible. The child is sedated enough to minimize discomfort but awake enough for voluntary movement. The studies take place in a special suite connected to an operating room. The combination of pediatric anesthesiologists titrating the sedation and neurologists experienced in pediatric EMG helps ensure that the tests are completed in the shortest time possible, with minimal discomfort, and in a safe environment.
Mayo Clinic neurologists are among the only physicians in the world who perform single-fiber EMG studies in children. Last year, they conducted approximately 200 pediatric EMG studies in Rochester for diagnostic testing and medication monitoring. Neurologists at Mayo's Florida campus regularly assist in complicated EMG studies in children at Nemours Children's Clinic in Jacksonville.
The volume of Mayo's intraoperative electrophysiologic monitoring has increased. Last year, across 3 sites, Mayo physicians conducted monitoring in 1,300 surgeries (See Box 3 for more information.)
Eric J. Sorenson, M.D., director of the EMG Laboratory at Mayo Clinic in Rochester, notes: "At the vast majority of institutions, evoked potentials waveforms are monitored at off-site centers by technicians who are monitoring numerous cases simultaneously and do not know the patient or the operating conditions. At Mayo, we have people in the operating room who understand the individual case and know if there are changes in anesthesia, the patient's status, or technical concerns during the procedure. It makes a difference."
Devon I. Rubin, M.D., director of the Neurophysiology Laboratory at Mayo Clinic in Florida, is looking forward to a new laboratory, scheduled to open in October 2010, that will centralize testing for movement disorders, EEG, EMG, and autonomic disorders. Located down the hall from the clinical neurology practice, the laboratory will add convenience for patients and physicians.
Mark A. Ross, M.D., director of the Neurophysiology Laboratory at Mayo Clinic in Arizona, agrees with Drs. Rubin and Sorenson that a major advantage of their practice is the standardization of techniques and laboratory procedures across the 3 sites. This standardization enhances collaboration in the practice, in research, and in education.
Uniformity is particularly important in clinical and research EMG studies, for which procedures and interpretations can vary greatly. "Standardized techniques and a broad subject pool for research help us evaluate diagnostic techniques for neuromuscular conditions," notes Dr. Rubin.
Dr. Ross points to an upcoming international study that will use the compound muscle action potential (CMAP) scan as an example. He notes, "With this scan technique, electrical nerve stimulation is divided into very small increments, which allows demonstration of the components of the CMAP. We hope this technique will reveal abnormalities that are not apparent with the routine CMAP measurement and that it may prove to be a very early predictor of certain nerve and muscle disorders."
Education and Training
Most physicians performing EMG at Mayo have been trained at Mayo. In addition to the annual conference, physicians from each of the sites visit the other sites to work with staff residents and fellows and participate in conferences. "It gives all of us a chance to participate in patient care and training at the other sites," notes Dr. Sorenson. Mayo's residents are required to take a 2-month comprehensive neurophysiology course. A monthly teleconference for complex case presentations provides another opportunity for cross-site training and collaboration.
In addition, Dr. Ross points out, "Our technicians are also mostly Mayo trained. They're very dedicated, experienced, and conscientious. Their outstanding work makes our work much easier." Adds Dr. Rubin, "The depth of experience and training of the technicians across Mayo allows for the high quality of the studies we perform."
Referrals for autonomic, EMG, EEG, and outpatient evoked potentials come from many sources beyond neurology practice. Increasing demand has been met with improved efficiency at all 3 sites.
|Box 1. EMG Referral Characteristics|
|Box 2. Symptoms That May Benefit From Autonomic Testing|
|Box 3. Intraoperative Monitoring at Mayo Clinic|
Peripheral nerve surgery