Intraoperative monitoring for spinal cord tumor surgery [Neurosurgery Wiki]

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====== Intraoperative monitoring for spinal cord tumor surgery ======

//[[J.Sales-Llopis]]//

//Neurosurgery Department, [[General University Hospital Alicante]], [[Spain]]//
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[[Intraoperative monitoring]] (IOM) is a critical tool in the surgical [[management]] of [[spinal cord tumor]]s. Its primary goal is to enhance [[patient safety]] by minimizing the risk of neurological deficits during surgery. IOM provides real-time [[feedback]] on the functional integrity of the spinal cord, nerve roots, and other neural structures, guiding surgical decision-making and improving outcomes.

===== Key Modalities =====

[[Somatosensory Evoked Potentials]] (SSEPs):

Purpose: Monitors the sensory pathways, including the dorsal columns of the spinal cord.
Method: Electrical stimuli are applied to peripheral nerves (e.g., median or tibial nerves), and responses are recorded over the somatosensory cortex.
Clinical Use: Helps detect ischemia or mechanical injury to sensory pathways during tumor resection.

[[Motor Evoked Potentials]] (MEPs):

Purpose: Monitors the motor pathways, particularly the corticospinal tract.

Method: Transcranial electrical stimulation is applied to the motor cortex, and responses are recorded in peripheral muscles.

Clinical Use: Provides real-time information about motor function and helps prevent postoperative motor deficits.

[[Electromyography]] (EMG):

Purpose: Monitors the function of nerve roots and peripheral nerves.

Method: Spontaneous and triggered EMG activity is recorded from muscles innervated by the monitored nerves.

Clinical Use: Detects nerve root irritation or injury, particularly useful in surgeries near the nerve roots or brachial/lumbosacral plexus.

[[D Wave]] [[Monitoring]]:

Purpose: Assesses the integrity of the corticospinal tract.

Method: A direct response (D-wave) is recorded from the spinal cord using epidural electrodes during transcranial stimulation.

Clinical Use: Provides robust information about motor pathway preservation, even under anesthesia.

[[Brainstem Auditory Evoked Potentials]] (BAEPs):

Purpose: Monitors auditory pathways in surgeries near the cervicomedullary junction.

Clinical Use: Useful for tumors extending into the brainstem or for procedures involving cranial nerves.

Intraoperative Ultrasound and Electrophysiology Integration:

Combines IOM with real-time imaging for precise tumor localization and safe resection.

Advantages of IOM:

Neurological Safety: Reduces the risk of permanent neurological damage by detecting potential issues early.

Surgical Precision: Guides tumor resection while preserving functional neural tissue.

Real-Time Feedback: Allows immediate intraoperative adjustments to surgical techniques.

Improved Outcomes: Contributes to lower rates of neurological deficits and better functional recovery.

Challenges and Considerations:

Technical Expertise: Requires a skilled neurophysiologist and trained surgical team.

Anesthesia Management: Anesthetic agents can influence the reliability of MEPs and SSEPs; total intravenous anesthesia (TIVA) is often preferred.

Cost and Availability: High costs and limited availability in some healthcare settings may restrict its use.
===== Trends =====

[[Intraoperative monitoring]] (IOM) for [[spinal cord tumor surgery]] has become increasingly sophisticated, reflecting [[advancement]]s in [[technology]] and a deeper understanding of [[neural pathway]]s. Current [[trend]]s in IOM aim to enhance surgical [[precision]] while minimizing risks of [[neurological deficit]]s. 

1. [[Multimodal neuromonitoring]]

Trend: Integration of multiple monitoring modalities, including [[somatosensory evoked potentials]] (SSEPs), motor evoked potentials (MEPs), and electromyography (EMG), to provide comprehensive real-time feedback on the spinal cord and peripheral nerve function.

[[Impact]]: Improves the ability to detect and prevent potential damage to motor and sensory pathways during surgery.
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2. Advanced Signal Processing

Trend: Use of AI-driven algorithms and machine learning for more accurate interpretation of IOM signals.

Impact: Enhances the reliability and reduces false positives/negatives in signal interpretation, allowing for more precise surgical decision-making.

3. Neuroanatomical Mapping

Trend: Techniques like direct cortical stimulation and D-wave monitoring are increasingly used for mapping motor tracts in real time, especially in challenging cases like intramedullary tumors.

Impact: Enables surgeons to navigate complex anatomical regions with minimal disruption to critical neural pathways.

4. [[Minimally Invasive]] and [[Endoscopic]] Approaches

Trend: Adaptation of IOM for minimally invasive or endoscopic spinal tumor surgeries.

Impact: Ensures neural integrity while accommodating the constrained visualization and access of minimally invasive techniques.

5. [[Integration]] with Advanced Imaging

Trend: Combined use of IOM with intraoperative imaging, such as ultrasound, CT, or MRI.

Impact: Provides an additional layer of anatomical and functional verification, enhancing the precision of tumor resection.

6. Real-Time Feedback to Surgical Robots

Trend: Incorporation of IOM data into robotic surgical systems.

Impact: Assists in guiding robotic arms to avoid neural structures, improving safety in spinal surgeries.

7. Personalized Monitoring Protocols

Trend: Tailoring IOM protocols based on patient-specific anatomy, tumor location, and pre-existing neurological conditions.

Impact: Optimizes monitoring and intervention strategies for individual cases.

8. Remote and Telemetric IOM

Trend: Implementation of remote IOM, allowing experts to monitor surgeries in real time from distant locations.

Impact: Expands access to specialized neurophysiological expertise, especially in underserved regions.

9. Outcome-Driven Protocol Development

Trend: Emphasis on correlating intraoperative findings with postoperative outcomes to refine monitoring techniques.

Impact: Drives the evolution of evidence-based practices, improving the overall efficacy of IOM.

10. Training and Standardization

Trend: Development of standardized protocols and enhanced training programs for IOM personnel.

Impact: Ensures consistency and reliability across different surgical centers.

Challenges and Future Directions:

Standardization: Variability in IOM practices between institutions.

Accessibility: High costs and technical expertise required for IOM limit its availability in some settings.

Innovation: Exploration of non-invasive neuromonitoring techniques and integration with wearable devices.

These trends highlight the dynamic progress in intraoperative monitoring, making it a cornerstone of safe and effective spinal cord tumor surgery.

===== Usefullness =====

==== Retrospective cohort studies ====


Due to the absence of studies supporting the role of [[intraoperative neurophysiological monitoring]] (IONM) in [[intradural spinal tumor]]s, this study evaluates the [[clinical outcome]] after these surgeries through the use of advanced intraoperative neurophysiological techniques.
In this [[observational]], [[descriptive]], and [[retrospective]] study of two [[cohort]] groups about the presence or absence of IONM during the intervention and the subsequent evaluation of the clinical and functional results in the short and medium terms. Ninety-six patients with extra- or intramedullary intradural spinal tumors operated on by the neurosurgery [[team]] completed the current study. 
They observed improvements in the monitored patients' scores on the Prolo, Brice, McKissock, and McCormick scales. These results examine the usefulness of IONM in preserving neurological functions and, therefore, its impact on quality of life. The rate of neurological deficits in the unmonitored patients was 14.5%, whereas 8.3% of the patients whose treatment included IONM.
It is important to emphasize the importance of implementing IONM for early [[recognition]] of possible neurological damage, the improvement of postoperative functional outcomes, and for decreasing the rate of neurological complications. Significance: This study provides reliable results on the importance of IONM in intradural spinal tumor surgeries
((Cabañes-Martínez L, Fedirchyk-Tymchuk O, López Viñas L, Abreu-Calderón F, Carrasco Moro R, Del Álamo M, Regidor I. Usefulness of Intraoperative Neurophysiological Monitoring in Intradural Spinal Tumor Surgeries. J Clin Med. 2024 Dec 13;13(24):7588. doi: 10.3390/jcm13247588. PMID: 39768514.)).

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This study provides valuable [[preliminary]] [[evidence]] supporting the use of IONM in surgeries for intradural spinal tumors. Despite its limitations, it highlights IONM’s potential to enhance neurological outcomes and reduce postoperative complications. However, more rigorous research is needed to validate these findings and establish IONM as a standard of care.

==== Narrative reviews ====


Many studies have recommended the routine use of electrophysiological monitoring, mostly [[somatosensory evoked potential]] (SSEP), although in some cases [[motor evoked potential]] (MEP) are also used; however, only a few studies have evaluated their effective impact 
((Costa P, Bruno A, Bonzanino M, Massaro F, Caruso L, Vincenzo I, Ciaramitaro P, Montalenti E. Somatosensory- and motor-evoked potential monitoring during spine and spinal cord surgery. Spinal Cord. 2007;45(1):86–91. doi: 10.1038/sj.sc.3101934.))
((Kothbauer KF, Deletis V, Epstein FJ. Motor-evoked potential monitoring for intramedullary spinal cord tumor surgery: correlation of clinical and neurophysiological data in a series of 100 consecutive procedures. Neurosurg Focus. 1998;4(5):E1. doi: 10.3171/foc.1998.4.5.4.))
((Morota N, Deletis V, Constantini S, Kofler M, Cohen H, Epstein FJ. The role of motor evoked potentials during surgery for intramedullary spinal cord tumors. Neurosurgery. 1997;41(6):1327–1336. doi: 10.1097/00006123-199712000-00017.))
((Sala F, Bricolo A, Faccioli F, Lanteri P, Gerosa M. Surgery for intramedullary spinal cord tumors: the role of intraoperative (neurophysiological) monitoring. Eur Spine J. 2007;16(Suppl 2):130–139. doi: 10.1007/s00586-007-0423-x.)).


Intraoperative monitoring of somatosensory evoked potentials and transcranial electrical motor evoked potentials has been used previously to limit complications. Electromyography offers an opportunity for the surgeon to map the eloquent tissue associated with the tumor using intraoperative motor fiber stimulation. Similar to the use of cortical simulation in the resection of supratentorial gliomas, this technique can potentially advance the safety of intramedullary spinal cord tumor resection. 

This technique led to protection of these tracts during resection of the tumor
((Gandhi R, Curtis CM, Cohen-Gadol AA. High-resolution direct microstimulation
mapping of spinal cord motor pathways during resection of an intramedullary
tumor. J Neurosurg Spine. 2015 Feb;22(2):205-10. doi: 10.3171/2014.10.SPINE1474. 
Epub 2014 Nov 28. PubMed PMID: 25431960.
)).

==== Prospective observational studies ====


Identification of neurophysiologically viable dorsal columns (DC) and of neurophysiologically inert tissue, e.g. median raphe (MR), as a safe incision site is crucial for avoiding post-operative neurologic deficits. 

The right and left DC were stimulated using a bipolar electric stimulator and the triggered somatosensory evoked potentials (SSEPs) recorded from the scalp. Phase reversal and amplitude changes of SSEPs were used to neurophysiologically identify the laterality of DC, the inert MR, as well as other safe incision sites.

The MR location was neurophysiologically confirmed in all patients in whom this structure was first visually identified as well as in those in whom it was not, with one exception. DC were identified in all patients, regardless of whether they could be visually identified. In three cases, negative mapping using this method enabled the surgeon to reliably identify additional inert tissue for incision. None of the patients had postoperative worsening of the DC function.

The technique is safe, reliable, and can be easily incorporated into routine intramedullary spinal cord tumor resection. It provides crucial information to the neurosurgeon in order to prevent post-operative neurological deficits
((Nair D, Kumaraswamy VM, Braver D, Kilbride RD, Borges LF, Simon MV. Dorsal Column Mapping via Phase Reversal Method: The Refined Technique and Clinical Applications. Neurosurgery. 2014 Jan 19. [Epub ahead of print] PubMed PMID: 24448182.)).

Intraoperative vascular flow assessment using ICG-VA was easy, repeatable, and practical without any significant procedure-related risks. ICG-VA can be used for careful analysis of spinal microvascular flow or anatomical orientation, which is necessary to ensure safe and precise resection of spinal intramedullary tumors
((Takami T, Yamagata T, Naito K, Arima H, Ohata K. Intraoperative assessment of 
spinal vascular flow in the surgery of spinal intramedullary tumors using
indocyanine green videoangiography. Surg Neurol Int. 2013 Oct 4;4:135. doi:
10.4103/2152-7806.119352. eCollection 2013. PubMed PMID: 24232309; PubMed Central
PMCID: PMC3815013.
)).