Intraoperative Neurophysiological Monitoring

Just 40 years ago, surgeons performing surgery had basically just a few methods for determining whether neurological deficits occurred during the procedure: Anesthesiologists could “wake” the patient slightly during surgery and test nerve function, or the surgeons would wait until the procedure was over and determine the patient’s post-surgical level of function. Today, intraoperative neurophysiological monitoring (IONM) — which allows trained technologists to monitor patients’ neurological function in real time during surgery — takes the guesswork about neurological function changes out of the equation.

From head to toe, the body contains about 45 miles of nerves in the skin alone — enough to reach from San Antonio to Canyon Lake. Nerves function as the body’s electrical system, controlling everything from movement to senses to thoughts, so when nerve damage occurs, the results can be catastrophic.

IONM, which was developed during the 1970s, introduces certified in neurophysiological intraoperative monitoring (CNIM) technologists into the operating room to join the surgical team for select surgeries that may place elements of the nervous system at risk for inadvertent damage. IONM provides CNIM technologists with tools they need to monitor as many as 32 channels of information, including brainstem auditory evoked potentials, electroencephalography (brain surface monitoring), and electromyography and brain mapping (to establish precise areas of functioning).

IONM is believed to improve intraoperative decision-making. By guiding the surgeon’s hands, if you will, there is a reduction in neurological risk. This obviously benefits the patient with a better surgical outcome and also greatly reduces a surgeon’s liability.
— Mark Kaitner, MD, board-certified anesthesiologist and Vice President of EPIOM, a San Antonio-based IONM provider

IONM allows for parts of the nervous system to be identified and mapped during the surgical procedure, providing real-time assessment of the neurologic function of the spine, brain and nerves — along with the general health and functionality of a portion of the nervous system — all while the patient is anesthetized,” says George R. “Trey” Lee III, MD, MS, President of the American Society of Neurophysiological Monitoring (ASNM), a leading IONM organization offering educational training to its varied membership. “While most surgeries are performed without complication, this technique reduces the risk for paralysis or loss of sensation during spine or brain surgery.”

Because IONM’s feedback is instantaneous, surgeons are immediately aware of changes to nerve function and have the ability to stop or reverse actions to prevent or reduce damage. This technology has become the surgical standard of care.

Providing Surgeons with Peace of Mind

Karl Swann, MD, neurosurgeon with Neurosurgical Associates of San Antonio, has been using IONM in his practice for nearly two decades. He says that one of IONM’s most interesting aspects is that it doesn’t just provide real-time information about the area on which surgeons are performing a surgical procedure — it provides universal monitoring of the patient’s function.

“For example, if we’re performing an operation on the lower part of the spine, IONM technologists are also monitoring the arms, and the technologist may report a detriment in the arm’s reading during a long operation,” Dr. Swann says. “In fact, this happened recently. Even though our procedure wasn’t affecting the arm, the positioning of the patient’s arm began to affect the arm’s nerve function. I wouldn’t have known that if it were not for IONM.”

Dr. Swann’s team was able to reposition the patient’s arm and provide relaxation for the arm’s nerves so they weren’t compromised.

“IONM provides me with peace of mind,” Dr. Swann says. “In a nutshell, IONM takes out the guesswork and reduces apprehension about how the patient will do after the operation.”

Positive Differences in Outcomes

In 15 years of using IONM in his practice, Frank Garcia, MD, a board-certified orthopedic surgeon with The San Antonio Orthopaedic Group, can cite several cases where the technology made a positive difference in surgical outcomes.

“Particularly in trauma cases — such as major pelvic or shoulder surgeries — IONM has proven immensely beneficial in ensuring we have fixed the bone anatomically while not causing any damage in the process,” Dr. Garcia says.

IONM has also benefited Dr. Garcia in a number of hip, knee and shoulder replacements, and he remarks that IONM was notably beneficial during an orthopedic surgical case in which he was completing a lengthening procedure for a patient with a congenital hip abnormality.

“During the process of lengthening the leg, the patient’s sciatic nerve began to be affected once we got to a certain length,” Dr. Garcia remembers. “The technician warned me immediately, and I corrected it promptly. If we had continued and not known about the effect on the sciatic nerve, the patient would likely have not regained function.”

IONM serves as an effective safeguard in surgeries in which patients’ anatomies are more exposed, when risk of iatrogenic injury is higher than usual.

Increasing Patient Safety

Frank Fichtel, MD, FACS, neurosurgeon with privileges at CHRISTUS Santa Rosa Hospital – Medical Center and CHRISTUS Santa Rosa Hospital – Alamo Heights, has used IONM in his practice for about 20 years. Today, he uses monitoring on all spinal cases, especially in tumor cases when tumor dissection can impact nerve root function.

“I recently had a patient with a tumor that involved the cauda equina nerves at the bottom of the spinal cord,” Dr. Fichtel says. “I was able to use IONM to monitor my dissection and ensure I wasn’t irritating the surrounding nerves. The technology allowed me to test the proximal nerves for function. If the nerve root was nonfunctioning, I could section it and remove the entire tumor with less chance of harm to the patient. In this case, I was able to completely dissect the tumor, and the patient woke up without deficits.”

The Bottom Line

A major concern of surgeons working with delicate structures is that their patients will develop neurological deficits. As a result, they’re always looking for new ways to prevent surgical morbidity and provide additional safety to patients.

“Physicians interested in IONM should start with the literature and see what’s out there — there’s enough literature supporting the use of IONM. I would then encourage them to start using the modality in cases to see its benefits and determine if it alters their surgical techniques. IONM is another tool to maximize patient safety.˝
— Frank Fichtel, MD, FACS, neurosurgeon with privileges at CHRISTUS Santa Rosa Hospital – Medical Center and CHRISTUS Santa Rosa Hospital – Alamo Heights