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NuVasive® Nerve Monitoring

During spine surgery, it is important to protect the nerves associated with the spinal column. These nerves carry messages to and from the brain, organs, and limbs, aiding them with proper movement and sensation.

The NVM5 Intraoperative Monitoring System provides real-time, precise, and reliable feedback to ensure nerve and spinal cord safety. By using this unique and advanced technology, the surgeon is provided with intraoperative information about the location and function of the nerves, assisting with safe implant placement and surgical technique during minimally disruptive spine procedures.

The NuVasive proprietary monitoring platform has been used to monitor over 160,000 spine surgeries. With the safety afforded by this nerve monitoring system, you can experience a faster recovery and a quicker return to your normal lifestyle.

Electromyography

What is EMG?

EMG stands for electromyography, which is the study of the electrical activity of muscles. It is a test used to determine the health and function of nerves and/or muscles.

Why is EMG Used in Surgery?

Spinal Cord

The spinal cord is the part of the central nervous system which extends from the brain stem to the lower spine through the bony protection of the spinal canal. It acts as a conduit for sensory and motor information to travel to and from the brain, respectively. The spinal cord usually ends at the second lumbar level (L2) and then extends as a bundle of individual nerves known as the cauda equina.

Cauda Equina

“Cauda equina” is Latin for “horse’s tail.” It is the lower extension of the spinal cord, comprised of individual nerve roots, which when bundled, resemble a horse’s tail. These nerve roots exit the spinal canal individually at each spinal level, giving rise to each level’s spinal nerves.

Spinal Nerves

The shape of the vertebrae allow for the passage of the spinal cord from the brain to the lower part of the body through the spinal canal. From the spinal cord, spinal nerves exit the spinal canal between each vertebra on both sides. After exiting the spinal canal, these spinal nerves then further entwine and extend to send signals between your brain and your organs, muscles, and other tissues. The cervical spinal nerves innervate (provide muscle activity and sensation functions to) your upper back, arms, and hands. The lumbar spinal nerves innervate your lower back, abdomen, and legs. If any of these nerves are pinched by a bulging disc or the position of your vertebrae, for example, you might experience back, groin, and/or leg pain or numbness.

Myotomes

Myotomes are muscle groups that are innervated by particular spinal nerve levels. By knowing which spinal nerves innervate specific muscles, we can monitor those muscles for changes in the nerves’ health. For example, we can monitor the following muscle groups for information about the corresponding spinal nerves:

  • Quadriceps (front thigh muscles) L2, L3, L4
  • Anterior Tibialis (shin muscle)L4, L5
  • Hamstrings (back thigh muscles) L5, S1
  • Gastrocnemius (calf muscle) S1, S2

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As mentioned, by knowing each myotome’s specific innervation patterns we can monitor those muscle groups using EMG to determine the health and function of the nerves that innervate them.

For example, EMG can be used to help determine proper pedicle screw placement in fusion surgeries to avoid nerve impingement or nerve proximity during surgical approaches, such as the lateral interbody fusion surgical approach called XLIF®.

Is NuVasive NVM5 EMG Monitoring right for me?

Your physician may determine that intraoperative NVM5 nerve monitoring is a good option for you if you require spine surgery where your cervical or lumbar nerve roots are affected. Example surgeries include:

  • Lumbar Decompression
  • Lumbar Interbody Fusion (from any approach: PLIF, TLIF, ALIF, XLIF)
  • Lumbar Pedicle Screw Instrumentation
  • Lumbar Total Disc Replacement
  • Cauda Equina Surgery
  • Anterior Cervical Decompression and Fusion (ACDF)
  • Cervical Total Disc Replacement

NuVasive NVM5 Potential complications

Intraoperative EMG monitoring can only be performed when muscle relaxants are not in effect. Muscle relaxants are often used for placing the operative breathing tube and for the surgical incision, but can be reversed or allowed to dissipate before EMG monitoring is necessary. If your surgeon determines that a muscle relaxant proves to be necessary throughout the surgery, monitoring cannot effectively be performed.

Electrically stimulated EMG is not recommended in patients who have an electrically-sensitive device implanted, such as a pacemaker or defibrillator.

Intraoperative EMG monitoring is the standard of care for nerve root monitoring, but if your surgery puts the spinal cord at risk, other monitoring techniques are more appropriate. In this case, your surgeon may opt for somatosensory evoked potential (SSEP) or motor evoked potential (MEP) monitoring. The lumbar spine, however, is comprised of nerve roots only, as the spinal cord ends above this region, and therefore EMG monitoring is applicable in all lumbar surgeries.

It is important that you discuss the potential risks, complications, and benefits of spine surgery with your doctor prior to receiving treatment, and that you rely on your physician’s judgment. Only your doctor can determine whether you are a suitable candidate for spine surgery.

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Preoperative Preparation for Intraoperative EMG Monitoring

The best preparation for surgery is being sure that all of your questions are answered. You should also be sure to inform your physician of any health problems you may have or medications that you are taking before surgery. If you have an allergy to adhesives, alert your surgeon, as adhesive surface electrodes are typically used for NVM5™ monitoring. Needle electrodes can alternatively be used in this situation. It will help if you do not apply body lotion prior to surgery and that your legs are shaved.

Once you have been admitted to the hospital, you will be taken to a pre-op room and prepared for surgery. This may include instruction about the surgery, anesthesia, and postoperative period. At this time you will be prepared for intraoperative EMG monitoring, which will entail the placement of adhesive electrodes on the skin overlying your leg or arm myotomes (for lumbar or cervical surgery, respectively). Putting the electrodes on will require cleaning and light abrasion of the skin. If needle electrodes are used, these will be placed in the operating room after anesthesia is given, to minimize any discomfort.

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