June 28, 2016
Intraoperative monitoring (IOM) to measure neural function and integrity is an established strategy to reduce the risk of injury occurring during surgery. For maximum effectiveness, IOM requires close cooperation between neurophysiologists and neurosurgeons. At Mayo Clinic, IOM is used extensively in spinal, cranial and brainstem surgeries, with neurologists and neurosurgeons consulting on pre-surgery planning as well as working together during procedures.
"Our Neurosurgery and Neurology departments are integrated, so surgical procedures are a collaboration between the two services," says Bernard R. Bendok, M.D., chair of Neurosurgery at Mayo Clinic in Phoenix/Scottsdale, Arizona.
"Intraoperative monitoring is the ultimate team-based practice," adds Joseph I. Sirven, M.D., chair of Neurology at Mayo Clinic's campus in Arizona. "IOM is characterized by real-time instant communication between neurologist and neurosurgeon, all with the goal of a positive outcome for the patient."
At Mayo Clinic, IOM is performed by highly trained technicians and monitored by a neurophysiologist on-site, not at a remote location. Standard protocols help ensure uniform procedures to maintain quality control. "It's the Swiss cheese model of safety — everyone plays a certain role, and there are checks and balances throughout the process," says Eric J. Sorenson, M.D., a consultant in Neurology at Mayo Clinic in Rochester, Minnesota.
Awake and playing music
At Mayo Clinic's campus in Arizona, awake brain surgery is an option for surgical treatment of tumors, focal epilepsy, cavernous malformations and select arteriovenous malformations. "Awake surgery is the ultimate neurological monitoring," Dr. Bendok says.
Electrical stimulation of the brain is used before surgery to assess the functioning of brain tissue. During cranial incision and closing, the patient is under mild intravenous sedation and can respond to requests to perform tasks. Patients with musical ability might be asked to play a musical instrument during surgery.
Awake brain surgery allows surgeons to maximize resection of tumors while minimizing damage to eloquent brain tissue. "Assessment of the functioning of tissue before resection, augmented with awake surgery, provides a strong safety umbrella," Dr. Bendok says, adding that patients who undergo awake brain surgery for neurovascular disease generally have shorter hospital stays and less discomfort.
The number of awake brain surgeries at Mayo Clinic's campus in Arizona grew from 20 in 2014 to almost 120 in 2015. A neurologist is present in the operating room during awake brain surgery cases.
"That participation is absolutely critical," Dr. Bendok says. "The neurologist has met the patient beforehand and can follow the neurological exam during surgery based on his or her knowledge of electrophysiology and of the patient's case. So the entire operation can be tailored to the particular patient."
Innovation from collaboration
Normal motor response in evoked potentials monitoring
A. Illustration shows normal motor response in evoked potentials monitoring. B. Minor fluctuations in the motor responses can arise during surgery due to changes in anesthesia. C. Abrupt loss of motor response raises concerns of neurological injury during surgery.
Mayo Clinic has a distinguished history in neurophysiology, particularly in the development of electromyography (EMG). EMG, electroencephalography and evoked potentials are used frequently in surgeries of the cervical, thoracic and lumbar spine as well as in brainstem and cranial procedures. Monitoring plans are developed and baseline recordings are taken before surgery, with additional recordings taken during critical parts of the procedure, such as tumor removal or insertion of spinal hardware.
Collaboration between neurosurgeons and neurologists can lead to innovation that increases patient safety. James C. Watson, M.D., a consultant in Neurology at Mayo Clinic's campus in Minnesota, recalls a Mayo Clinic neurosurgeon expressing interest in IOM of nerves controlling facial muscles near the eyes. Although such a test existed, it didn't yield consistent recordings. Working with neurosurgeons, Dr. Watson and colleagues developed a more effective technique.
"If we don't work together, we can't plan the most efficient way to get the information we need to keep the patient safe," Dr. Watson says. "As a neurophysiologist, I don't know what the surgeons see during a procedure or what they need to put in the surgical field. They don't know what I have the capabilities to monitor. Together, we can meet our shared goals of patient safety and identification of risk in real time."
Jamie J. Van Gompel, M.D., a consultant in Neurosurgery at Mayo Clinic's campus in Minnesota, agrees that cooperation between neurologists and neurosurgeons in IOM is increasingly important. "We're figuring out ways to talk the same language preoperatively, to increase patient safety," he says.
At Mayo Clinic, on-site neurophysiologists communicate with surgeons and IOM technicians and can enter the operating room if necessary. IOM technicians receive six to 12 months of additional training at Mayo Clinic before they lead monitoring during a procedure.
"Intraoperative monitoring is a niche practice. It takes a lot of skill and commitment to do it well," Dr. Sorenson says. "At Mayo Clinic, there's a great deal of trust between the surgeons, anesthesiologists, neurophysiologists and technicians. We all know one another."
The benefits of IOM are difficult to quantify, as rigorous comparisons of surgical cases pose challenges. However, "every week we see cases where the nerve responses decline during surgery, the team intervenes — maybe pushing blood pressure, or the surgeon taking a step back and reversing something — and then the responses come back up," Dr. Watson says. "If the responses look good at the end of surgery, then hopefully we've preserved some neurological function that was at risk in surgery."