Intra-Operative Neuro-monitoring (IONM) in Spine and Brain Surgery

Neurosurgery requires a great amount of precision. Whether operating on the spine or the brain, surgeons face the constant challenge of navigating delicate neural structures. This is where intraoperative neuromonitoring (IONM) steps in, it becomes a technological ally that has helped significantly in the landscape of high-risk surgeries.

According to John Hopkins Medicine (n.d.), Intraoperative neuromonitoring (IONM) refers to a group of procedures used during surgery to monitor neural pathways. These procedures assist surgeons in preventing damage and preserving functionality of the nervous system. It primarily detects and prevents injury in real time, allowing surgeons to make informed decisions and adjust their approach instantly.

There are multiple approaches and techniques in applying IONM, as listed by Charalampidis et al. (2020), these include: somatosensory evoked potentials (SSEPs), motor-evoked potentials (MEPS), and spontaneous and triggered electromyography (ECG). 

SSEPs (Somatosensory Evoked Potentials) were first introduced intraoperatively in the 1970s, making them one of the first. These technologies are used to detect potential or actual nerve injury, allowing surgeons to correct / adjust to avoid morbid effects associated with the given brain or spinal surgery. Specifically, it measures the function of the sensory pathways in the spinal cord (Baker & Widrich, 2023b).

Motor-Evoked Potentials (MEPs), on the other hand, measures the function of the motor pathways. Electrodes are placed on the scalp and responses are recorded in peripheral muscle groups, creating transcranial stimulation (Doyal et al., 2023). Changes in the amplitude of these motor evoked potentials can indicate potential injury. 

Lastly, Spontaneous and Triggered Electromyography (EMG). Spontaneous EMG is a passive technique, which continuously monitors a muscle for abnormal electrical activity caused by nerve irritation like stretch or compression, which could also indicate possible injury (Ozyurekoglu & Breidenbach, 2006). In contrast, Triggered EMG involves intentional stimulation of certain nerves to ensure that they are functional and are in the correct position. Together, these techniques are valuable in such surgeries as they allow for immediate action to be taken so as not to compromise the functionality of the nerves. 

In the end, intraoperative neuromonitoring is so much more than a technological advancement, it is continuously being developed to become a useful partner in modern neurosurgery. These could truly improve patient outcomes and help even in the most complex and high-stakes procedures in medicine.

by Sophia Perez at Incisionary

APA References

Johns Hopkins Medicine. (n.d.). Intraoperative Neurophysiological Monitoring. John Hopkins Medicine. https://www.hopkinsmedicine.org/neurology-neurosurgery/specialty-areas/ionm. Retrieved on November 9, 2025.

Charalampidis, A., Jiang, F., Wilson, J. R. F., Badhiwala, J. H., Brodke, D. S., & Fehlings, M. G. (2020). The use of intraoperative neurophysiological monitoring in spine surgery. Global Spine Journal, 10(1_suppl), 104S-114S. https://doi.org/10.1177/2192568219859314. Retrieved on November 9, 2025.

Baker, A., & Widrich, J. (2023b, August 14). Somatosensory evoked potentials. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK544358/. Retrieved on November 9, 2025.

Doyal, A., Schoenherr, J. W., & Flynn, D. N. (2023, April 3). Motor evoked potential. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK580548/. Retrieved on November 9, 2025.

Ozyurekoglu, T. & Breidenback, W.C. (2006). Chapter 2 - Intraoperative nerve recordings in the management of peripheral nerve injuries. Practical Applications in the Upper Extremity, 22(1), 357-368. https://doi.org/10.1016/B978-0-443-06667-2.50030-7. Retrieved on November 10, 2025.