Abstract
Study Design
This study is a mixed methods approach.
Objectives
Intraoperative spinal cord injury (ISCI) is a challenging complication in spine surgery. Intra-operative neuromonitoring (IONM) has been developed to detect changes in neural function. We report on the first multidisciplinary, international effort through AO Spine and the Praxis Spinal Cord Institute to develop a comprehensive guideline and care pathway for the prevention, diagnosis, and management of ISCI.
Methods
Three literature reviews were registered on PROSPERO (CRD 42022298841) and performed according to PRISMA guidelines: (1) Definitions, frequency, and risk factors for ISCI, (2) Meta-analysis of the accuracy of IONM for diagnosis of ISCI, (3) Reported management approaches for ISCI and related events. The results were presented in a consensus session to decide the definition of IONM and recommendation of its use in high-risk cases. Based on a literature review of management strategies for ISCI, an intra-operative checklist and overall care pathway was developed by the study team.
Results
An operational definition and high-risk patient categories for ISCI were established. The reported incidence of deficits was documented to be higher in intramedullary tumour spine surgery. Multimodality IONM has a high sensitivity and specificity. A guideline recommendation of IONM to be employed for high-risk spine cases was made. The different sections of the intraoperative checklist include surgery, anaesthetic and neurophysiology. The care pathway includes steps (1) initial clinical assessment, (2) pre-operative planning, (3) surgical/anaesthetic planning, (4) intra-operative management, and (5) post-operative management.
Conclusions
This is the first evidence based comprehensive guideline and care pathway for ISCI using the GRADE methodology. This will facilitate a reduction in the incidence of ISCI and improved outcomes from this complication. We welcome the wide implementation and validation of these guidelines and care pathways in prospective, multicentre studies.
Keywords: spine surgery, care pathway, intraoperative SCI, spinal cord injury
Introduction
Intraoperative spinal cord injury (ISCI) is a serious, time-critical, and challenging complication to manage in spine surgery.1,2 ISCI can have a varied aetiology, including spinal cord trauma, manipulation of the spine 3 or systemic reversible physiological causes like hypotension. There has been heterogenous reporting in the literature of the diagnostic criteria, definition, incidence, and risk factors of ISCI. A series of three literature reviews were designed by this study group and registered on PROSPERO (CRD 42022298841) to summarize the available evidence on the:
(1) Definition, frequency, and risk factors for ISCI.
(2) Use and accuracy of neuromonitoring for the diagnosis of ISCI and,
(3) Reported management approaches for ISCI and related events
Intraoperative neuromonitoring (IONM) provides constant monitoring of spinal cord function. IONM practices have evolved from using only somatosensory evoked potentials (SSEPs) to now utilising multimodal techniques that record sensory and motor evoked potentials (MEPs).4-6 This allows more sensitive and specific detection of neurological injury intra-operatively.
The use of systematic neuromonitoring allows for action to be taken to reverse detected adverse changes and potentially reduce new or worsening neurological deficits.7,8 A pragmatic goal is to improve responses to neuromonitoring changes to reduce permanent neurological deficits. 9 There are several algorithms that have been developed to respond to neuromonitoring changes, but they have not been employed widely.8,10 A surgeon’s performance can suffer under stress and time constraints,11,12 and using a checklist in a critical situation in theatre can have a 6-fold benefit as compared to not adhering to critical management steps. 13
The aim of this study is to create a care pathway and an intra operative checklist with simplified language, standardized and non-redundant steps to decrease the risk of human error in a time-critical and stressful situation.
Methods
This care pathway is informed by three literature reviews and two consensus meetings, which took place on 12.11.22 and 17.12.22. The literature reviews have been registered on PROSPERO (CRD 4202229884):
1: Definition, frequency and risk factors for intra-operative spinal cord injury: A knowledge synthesis ( 14 )
2: Accuracy of intraoperative neuromonitoring in the diagnosis of intraoperative neurological decline in the setting of spinal surgery – a systematic review and meta-analysis ( 15 )
3: The management of intraoperative spinal cord injury – a scoping review ( 16 )
An overview of the methods for each section is provided below. In depth methods are available in the respective referenced manuscripts.
Methods for Definition, Frequency and Risk Factors for Intra-Operative Spinal Cord Injury: A Knowledge Synthesis
The question on definition and frequency of ISCI was answered by conducting a scoping review. The question on risk factors of ISCI was addressed by conducting a systematic review. Methods used for the systematic review of ISCI risk factors are in accordance with the Agency for Health care Research and Quality’s (AHRQ) Methods Guide for Effectiveness and Comparative Effectiveness Review. 17 MEDLINE® and The Cochrane Library were searched from database inception to January 26, 2022. PRISMA guidelines were followed, and pre-planned data points were collected.
Pre-defined criteria were used to assess the risk of bias of included nonrandomized studies using the Quality in Prognosis Studies (QUIPS) tool for studies evaluating risk factors. 6 Data was qualitatively synthesised and reported. The overall quality/strength of evidence was assessed based on the application of Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) described in the AHRQ Methods Guide. 3 GRADE guidance related to syntheses of risk factors was used.18,19
Methods for Meta-Analysis of the Role of Neuromonitoring for Detecting Intraoperative Spinal Cord Injury During Spinal Surgery
This section was performed using the Preferred Reporting Items for a Systematic Review and Meta-analysis of Diagnostic Test Accuracy Studies (PRISMA-DTA). A comprehensive search was performed using MEDLINE, EMBASE and SCOPUS for all studies assessing the diagnostic accuracy of neuromonitoring, including somatosensory evoked potential (SSEP), motor evoked potential (MEP) and electromyography (EMG), either by their own or in combination (multimodal). Pooled sensitivity and specificity were calculated to evaluate the overall efficacy of each modality type using a bivariate model adapted by Reitsma et al., 20 for all spine surgery and for individual disease groups and regions of the spine. The risk of bias (ROB) of included studies was assessed using the quality assessment tool for diagnostic accuracy studies (QUADAS-2).
Methods for the Management of Intraoperative Spinal Cord Injury – A Scoping Review
The aim was to summarize information on checklists and algorithms for responding to IONM alerts as this is a knowledge gap. MEDLINE was searched from inception through January 26, 2022 and gray literature sources were searched based on the original protocol and limited targeted searches for guidelines were done. Citations suggested by the clinical authors and guideline development group were considered. We attempted to obtain guidelines and/or consensus statements from spine surgery organizations as well. A summary of the literature pertaining to treatment protocols and care pathways for ISCIs were then documented and reported.
Methods for the Consensus Meetings
Clinicians from a variety of surgical and nonsurgical specialties comprised the multidisciplinary guideline development group (GDG). Conflict of interest was vetted, and a consensus-based grading recommendations, assessments, development, and evaluation (GRADE) process was followed. Methodology for the guidelines was developed using the Conference on Guideline Standardization checklist.12,13
The GRADE Working Group’s methods were used to gauge the overall quality (strength) of the evidence supporting important outcomes.17,18 The GRADE Guideline Development Tool was used to record the procedure, evaluate the advantages and disadvantages of different choices, and assess the strength of the recommendation.19,21-23
A consensus meeting was held on 17.12.22 with the GDG to determine if a final recommendation that intraoperative neurophysiologic monitoring be employed for “high risk” patients could be achieved through GRADE process. This went through an Evidence-to-Decision framework and straw man polling that took place over a Zoom platform. Consensus was defined at a threshold of 80%.
Results
Results for Definition, Frequency and Risk Factors for Intra-operative Spinal Cord Injury: A Knowledge Synthesis
After the first scoping literature review on definitions, frequency, and risk factors for SCI, a panel of experts was convened to discuss the evidence and the group arrived at an operational definition of ISCI as:
“A new or worsening neurological deficit attributable to spinal cord dysfunction during spine surgery that is diagnosed intraoperatively via neurophysiologic monitoring and/or wake up test or immediately post-operatively based on clinical assessment.”
From the first literature review, the reported frequency of new deficits ranged from 0 to 61%. When stratified by pathology/level of surgery, tumor surgery had a greater range of incidence of intra-operative deficits (0%–61%) 24 as compared to deformity surgery (0%–17.8%), while studies with mixed pathologies had an intermediate range of 0%–9.4%. The greatest prevalence of deficit was found in lumbar-level surgeries (0%–28.5%). Deformity-related ISCI was more likely to resolve with up to 8% of deficits remaining persistent, while tumor patients had up to 26.9% of persistent deficits.
Risk factors that have been identified to contribute to intra-operative neurological deficits are deformity correction, cardiac and respiratory comorbidities, and significant mean arterial pressure changes.3,25 The most prevalent risk factors identified include pre-operative spinal cord dysfunction, age, sex, and BMI. One of the most cited risk factors was found to be the pre-operative neurological status and evidence of pre-operative spinal cord dysfunction. 26 In summary, putting the identification of risk factors together with the frequency data, patient subsets were identified who may be considered “high risk” for ISCI. These patients include older patients, those with high grade tumor causing compression, severe rigid deformity requiring multiple osteotomies, those with structural pathologies causing myelopathy such as OPLL and those undergoing revision surgery. Table 1 summarises these patient subsets. The overall quality of evidence for risk factors for ISCI assessed as per GRADE was low or very low for most factors across the surgical conditions.
Table 1.
High-Risk Patients for Intra-operative Spinal Cord Injury.
| High Risk Deformity: Rigid Thoracic Curve with High Deformity Angular Ratio (dAR) |
| Revision congenital deformity with significant cord compression and myelopathy |
| Extrinsic lesion with cord compression and myelopathy |
| Intramedullary tumor |
| Unstable fractures: Bilateral facet dislocation and disc herniation |
| Extension distraction injury with ankylosing spondylitis |
| OPLL with severe cord compression and moderate to severe myelopathy |
Results for Meta-Analysis of the Role of Neuromonitoring for Detecting Intraoperative Spinal Cord Injury During Spinal Surgery
In the literature review addressing the diagnostic test accuracy meta-analysis for IONM to detect ISCI, a total of 163 studies were included. Specifically, for multimodal monitoring with data from 69 studies and 17,968 patients, the overall sensitivity, specificity, diagnostic odds ratio and area under the curve were found to be 83.5% (81-85.7), 93.8% (90.6-95.9), 60 (35.6-101.3) and .895, respectively. Using the QUADAS-2 ROB analysis for multimodal monitoring, 14 (20.3%) were high-risk, 13 (18.8%) were moderate-risk and 42 (60.7%) were low-risk.
Results for the Management of Intraoperative Spinal Cord Injury – A Scoping Review
The results of the literature review of management pathways for the intraoperative care pathways were summarised and divided into sections, including (i) surgical management, (ii) neurophysiology and technical measures, (iii) anaesthetic management, and (iv) considerations for ongoing events.
Surgical Management
Traction and Correction, Hardware Malposition and Compressive Forces, Interruption of Procedure (definite/temporary), Staging of Procedure, Correction of Spinal Instability, Repeat Testing of Evoked Potentials, Team Communication, Local Irrigation, Other Surgical Considerations (leaning on patient).
Neurophysiological and Technical Measures
Electrode Set-Up, Stimulation Parameters, Patient Positioning, Other Management Strategies (peripheral nerve issues).
Anaesthetic Systemic Management
Blood Pressure, Anesthetics, Body Temperature, Blood Volume and Hematocrit, Blood Gases, Wake Up Test, Other Management Strategies (blood glucose, electrolytes).
Considerations for Ongoing Events
Steroids, Peer Consultation, Pharmacological Management.
This was reviewed by the study team, and the responses as well as steps required for an appropriate response to an ISCI episode have been detailed in the intraoperative checklist as per Figure 1 modified from Vitale et al, 2014. 27 The modifications were as follows to incorporate the further findings of the literature review:
- having three distinct categories of (i) surgical, (ii) neurophysiological and technical and (iii) anaesthetic and systemic by combining “gain control of room” with “surgical”
- extra additions under surgical: more reversing actions suggested and local irrigation with saline
- extra additions under neurophysiological and technical: different attributes of signal change listed, rule out electrical interference, adjust stimulation parameters, repeat testing/shortening of assessment intervals and patient positioning clarified further
- extra additions under anaesthetic and systemic; more categories were placed for optimisation
Figure 1.
Intraoperative checklist for management of neuromonitoring signal changes modified from Vitale et al 2014.
Figure 2 is the overall AO Spine Praxis care pathway that was devised by the study team for the management of patients at high risk of intraoperative spinal cord deterioration. Through the GRADE process a final recommendation that intraoperative neurophysiologic monitoring be employed for “high risk” patients was achieved with 93% agreement.
Figure 2.
Overall AO spine and Praxis care pathway for intra-operative spinal cord injury.
Discussion
The narrative literature review was performed regarding the management of ISCI events, and a recommended overall care pathway is presented with an intra-operative checklist modified from Vitale et al, 2014. 27
The use of IONM is recommended in high-risk cases but there is understanding of the resource limitations in certain institutions and regions, so we recommend in the interests of patient safety that surgery is not delayed if there is an acute admission with evolving neurology and inability to arrange IONM.
It must be highlighted that before the operation there are preventative measures that can be taken to reduce the likelihood of an ISCI occurring highlighted in Steps 1, 2 and 3 of the care pathway. Step 1 is the initial clinical assessment and includes the identification of the high-risk patient as mentioned previously in Table 1. Documentation as per The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) 28 is important as a baseline to assess, and informed consent with the patient is required.
Step 2 of pre-operative planning includes multidisciplinary discussion, planning intraoperative neurophysiology monitoring, agreeing on an intraoperative checklist to be used, and ensuring a monitored bed is available post-op to increase patient safety. If there are other medical co-morbidities, then these should ideally be optimized pre-operatively.
Step 3 highlights how important surgical and anaesthetic planning is. This includes an informed detailed briefing to occur with the surgical team before starting these high-risk operations, safe fibreoptic intubation for unstable C-spine or extrinsic cervical cord compression, maintaining MAP targets, having neurophysiology monitoring in theatre, careful patient positioning, and intraoperative imaging/guidance available.
The logic of the intra operative sections in the checklist of Step 4 is as follows. In the surgical section, the initial recommendations of pausing, announcing to the team, and eliminating external distraction are to gain control of the operating room and to make everyone involved focus and prioritize the issue. Then, reversible surgical factors are explored (decrease/remove traction, remove rods, open/close osteotomies, confirm placement of hardware, widen decompression) to reverse the signal loss. Intraoperative imaging is suggested to highlight any malposition or compression that is not obviously visible. Also, consultation with a peer is recommended because having a fresh perspective as an outsider in a stressful situation can be beneficial in helping identify and resolve any reversible issues. In the consensus meeting, it was suggested that “irrigation with warm saline” be altered to “irrigation with saline”, as spinal cord injury may be worsened with increased temperature.
For the neurophysiology and technical section, correct interpretation of the features of the signal change is critical to determine if it is associated with a cord/nerve root (asymmetric changes) or anaesthetic/hypotension issues (symmetric changes). The next stages, if the signal change is not resolved, are to check the integrity of the equipment and electrode placement, stimulation parameters, repeat testing, modify anaesthetic agents, and verify the correct positioning of the patient.
For the anaesthetic section it was felt that there should be a dialogue between the surgeon and anaesthetist regarding optimal blood pressure, haemoglobin, respiratory issues including oxygenation/ventilation and pCO2, electrolyte imbalance, blood glucose, body temperature, neuro-muscular blocking agents and anaesthetic depth. However, the checklist does not prescribe specific management strategies to resolve this as the preferred standard operating procedures will vary between regions and institutional policies.
In a situation where despite working through the checklist there are ongoing signal changes then steroids, consultation with a colleague, wake-up test, and or aborting the procedure if it is safe and post-operative imaging can be considered.
Step 5 of post-operative management includes a monitored bed, documenting neurological function with serial examinations, considering pharmacological intervention with methylprednisolone, MAP parameters, and further post-operative imaging, which completes the care pathway for safe responsible management of an ISCI.
A final recommendation that intraoperative neurophysiologic monitoring be employed for “high risk” patients was achieved in the consensus meeting through the stringent GRADE process. The ISCI care pathway and intraoperative checklist can serve as an aid to surgeons to provide a clear structure to do the necessary checks, identify reversible elements in ISCI and improve patient safety. It may be helpful to have the checklist available in the operating room. A consensus on a care pathway for ISCI will allow for it to be prospectively evaluated in a clinical setting over multiple sites to obtain user feedback to help improve future versions.
Acknowledgments
MGF is supported by the Robert Campeau Family Foundation/Dr C.H Tator Chair in Brain and Spinal Cord Research at UHN. BKK is the Canada Research Chair in Spinal Cord Injury and the Dvorak Chair in Spinal Trauma. NH acknowledges support by the Research Fund of the University of Basel for Excellent Junior Researchers. The authors wish to thank the following for contributions to this work: Shelby Kantner for literature search, collation, summarization and organization of checklist/guideline information that informed creation of the pathway. This Focus Issue was reviewed by the Joint Guidelines Review Committee of the American Association of Neurological Surgeons and Congress of Neurological Surgeons as well as the North American Spine Society. However, this review process does not constitute or imply endorsement of this work product by these organizations.
Footnotes
The author(s) declared no potential conflicts of interest concerning the research, authorship, and/or publication of this article.
Funding: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was financially supported by the AO Foundation, AO Spine and Praxis Spinal Cord Institute. This study was jointly organized and funded by AO Foundation through the AO Spine Knowledge Forum Spinal Cord Injury (SCI) (https://www.aospine.org/kf-sci), a focused group of international SCI experts, and the Praxis Spinal Cord Institute (https://praxisinstitute.org/) through funding from Western Economic Diversification Canada. The funding bodies did not control or influence the editorial content of the articles or the guidelines process. Methodologic and analytic support for this work was provided by Aggregate Analytics, Inc, with funding from the AO Foundation and Praxis Spinal Cord Institute.
ORCID iDs
Nisaharan Srikandarajah https://orcid.org/0000-0001-9578-508X
Nader Hejrati https://orcid.org/0000-0001-8583-9849
Mohammed Ali Alvi https://orcid.org/0000-0002-7131-079X
Nathan Evaniew https://orcid.org/0000-0003-1974-5224
Paul M Arnold https://orcid.org/0000-0002-4622-7695
Michael G. Fehlings https://orcid.org/0000-0002-5722-6364
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