You Do Spine Surgery and Don't Monitor Nerves? Why?

Neuro monitoring (a.k.a.: Neurophysiologic Intraoperative Monitoring) may be one of the most exciting and important "old" innovations to come into spine and neuro surgery in decades. Think of it, what surgeon would dare operate without blood gas monitoring? Or blood pressure monitoring? So why operate without nerve monitoring?

We recently talked with Debra Zacharko, who teaches neuro monitoring for NeuroMatrix in Atlanta. She described a case in which one of her clients scheduled a straightforward laminectomy and declined to use neuro monitoring. "So, I told him that I'd perform the monitoring for free," said Zacharko, "and when I showed him the wave form tapes he was amazed to see how much nerve irritation there is even in a simple laminectomy."

Indeed, most spine and neuro surgeons don't realize how much nerve irritation there is in spine surgery. Certainly, scoliosis surgery is close to a "no-brainer" for neuro monitoring. But what about cervical fusions, lumbar fusions, or, as in the case above, a simple laminectomy?

According to recent data, monitoring reduces the incidence of a poor, even catastrophic surgical outcome by 50 - 60%, says Robbie Allen, president of NeuroMatrix, one of the leading suppliers and trainers of intraoperative neuromonitors in the country. When the surgery calls for significant nerve manipulation, particularly cervical or cranial, the data is just unequivocal. Allen's own data from roughly 40,000 cases (collected by his group) points to a clear advantage to those surgeons who use nerve monitoring during surgery.

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While there are many key studies that support the use of intraoperative monitoring (including position papers from the Scoliosis Research Society) the following tells the story.

One thousand, one hundred sixty-eight cases. Reported by Forbes, Allen, Waller, Jones et al. in the U.K. version of JBJS (Journal of Bone and Joint Surgery.1991. 73-B(3):487 - 491). During all of these operations for spinal deformity, these surgeons used an older version of today's electrophysiological monitoring of the spinal cord. They employed epidural measurement of somatosensory evoked potentials (SEPs) in response to stimulation of the posterior tibial nerve.

Again, 1,168 consecutive cases.

When the researchers saw a decrease in the SEP amplitude of more than 50% (which occurred in 119 patients), about a third (32) had clinically detectable postoperative neurological changes.

Now, in another third of those patients (35), the SEP amplitude was rapidly restored and those patients had no postoperative neurological changes.

In 52 patients, persistent, significant, SEP changes were noted but did not result in clinically detectable neurological sequelae.

One surgeon we interviewed for this story who uses intraoperative neuromonitoring described a case in which his pedicle screw placement triggered a sharp spiking in the neuromonitor. He pulled the screw out and waited for the nerve to calm down - to return to a steady state. With that, he was able to replace his pedicle screw without stimulating any nerves.

No drop foot. No postoperative complications

Clearly, operating without nerve monitoring is like working without a safety net.

OK, one more study.

Published in Spine and written by Calancie, Madsen, and Lebwohl in a study funded by NIH (, the study looked at 18 patients in whom a total of 102 pedicle screws were placed. Here are their results (emphasis added):

    Based on results of electrophysiologic and palpatory evaluation, 68% of the screws were placed in a satisfactory manner. Electrophysiologic evidence of a perforation, which could not be confirmed by palpation or visualization, was seen in another 13% of this total. The remaining 19% of screw placements involved sites where a defect was missed originally by palpation alone, but was located based on electrophysiological testing combined with palpation and visualization (11%), and where a perforation was initially palpated (8%). There was no postoperative morbidity associated with malpositioned screws.

    Results indicate that the technique is sensitive and, based on early clinical results, reliable in the detection of perforations in pedicle screw placement.

    Moreover, the method is inexpensive, rapid, and easily implemented into a standard intraoperative monitoring protocol.

What is neuro monitoring?

It's putting sensors on the patient that monitor changes in their electrical signals. When performed by a trained expert it will spot changes in brain, spinal cord, and peripheral nerve function before there is any irreversible damage. Correctly performed, intraoperative monitoring of nerves can guide the surgeon through dissection. The monitoring will alert him or her of a stimulated nerve. It can show nerve stress or damage and even pinpoint the location of the irritation.

The precursor of today's nerve monitoring was Foerster and Alternberger's intraoperative electroencephalography (EEG). In the late 1930s, '40s and '50s EEG was used to localize nerve damage and as a tool in epilepsy surgery. Early researchers also used this low-voltage electrical stimulation technique to map the brain's cortical function.

Since those early days, better amplifiers, integrated circuit boards, smaller equipment, better-trained monitoring professionals, signal processing software, multiple channels, and other advancements have made this tool an indispensable safety net for any surgeon manipulating nerves or dissecting within a hair's breadth of a nerve.

Most surgeons don't realize how much nerve irritation there is in spine surgery. And they can't know unless a monitoring professional is in the OR alongside the anesthesiologist keeping track.

What can a well-trained monitoring professional do for you in the OR? Check it out.

SSEP Monitoring:

  • dorsal columns
  • brachial plexus
  • peripheral nerves
  • local and global ischemic changes
  • patient positioning
  • pedicle screw placement

EMG Monitoring:

  • erve roots
  • recurrent laryngeal nerve
  • Motor Evoked Potential (MEP)
  • lateral and anterior aspect of the spinal cord
  • perfusion
Want more information? See other Spine News Articles at Orthopedics This Week, a weekly publication providing news, analysis, and commentary about the orthopedics industry.

Which brings us to our last point. Finding a well-trained monitoring professional. That's the key.

Not everyone can do it. The accrediting body is ABRET (American Board of Registration of Electroencephalographic and Evoked Potential Technologists). A high-school grad can take the accrediting exam, pass, and go to work in an OR. Only one firm that I'm aware of requires their professionals to take the exam annually. That's the same firm that only hires college graduates and pays higher-than-average salaries.

That's NeuroMatrix out of Atlanta. Catch them at


Other firms perform the same services as well. But before you use them, make sure that the monitoring professionals have the degree and the best credentialing possible. And, most important, will they assume the liability for any mistakes in their monitoring? In other words, will they give you more than just their word?

Intraoperative neuro monitoring is an insurance policy no spine or neurosurgeon can do without. So why go without it?

Written by Robin Young, CFA