Written by: M. Terese Whipple, MD (NUEM PGY-3) Edited by: Quentin Reuter, MD (NUEM ‘18) Expert commentary by: Matthew Levine, MD
We have excellent decision rules for clinically clearing cervical spine injury in low risk patients without imaging. However, a frustrating situation arises when a CT of their c-spine is obtained and negative, but they are having persistent midline pain. What do we do then? Are we forced to order an MR of the c-spine even when they have no neurological deficits and our gestalt tells us there is no clinically significant injury? MR often means admission, worsening of already overwhelming ED crowding, and unhappy patients when they cannot remove the c-collar for at least several more hours. Recent data and recommendations suggest that this may not be the case; a negative CT may be enough to rule out clinically significant injury. This blog post will explore some of the historical and recent data on the subject of cervical spine clearance after CT scan alone.
There has been great historical debate over the best management for patients with persistent midline pain after negative CT, however that evidence is beyond the scope of this post. Current common practice and the recommendation of the American College of Radiology leads down the path of cervical spine MR when this situation arises [1]. Due to the cumbersome logistics of MR, much work has been done to determine if MR truly adds value to the patient’s workup. Is MR catching clinically significant injury missed by CT that changes clinical management? The majority of studies have concluded that the answer to that question is no.
In 2015 the Eastern Association for the Surgery of Trauma (EAST) sought to tackle this question by reviewing all studies to date examining C-spine evaluation in obtunded patients [2]. They evaluated 11 studies with a total of 1718 obtunded patients who underwent C-Spine imaging with CT. None were ultimately found to have unstable fractures or unstable ligamentous injury missed by CT. There was a 9% incidence of stable injuries missed on CT and found on follow up MR, flex-x, upright XR, or clinical follow up. They found a cumulative 100% NPV for unstable C-Spine injury with CT and 91% NPV for stable injury. They did rate the quality of evidence as low for various reasons, including non-comparable imaging protocols, inconsistently reported and variable outcomes, publication bias, and an overall inability to perform a meta-analysis with the data. However, they rated the data from which they derived the NPV as moderate quality as the NPV was consistently 100% throughout all of the trials. Based on their analysis they provided the following recommendation for obtunded blunt trauma patients:
“We conditionally recommend cervical collar removal after negative high-quality c-spine CT scan results alone.”
They went on to further clarify,
“It should be acknowledged that cervical collar removal can result in neurological change and even paralysis, although this may be underreported in the literature. However we cannot continue indiscriminate two-stage sequential screening for C-spine injuries if the injury rate is near 0% for the first test and the second adjunctive test results in false positives and inconsistent treatment plans.”
But the real question that is more pertinent to us as EM physicians (obtunded MR’s are usually dealt with upstairs), is: if we can remove the c-collars of obtunded patients after negative CT, why couldn’t that be extrapolated to awake patients? Well, they commented on that too:
“Therefore, if collars are to be removed in a high risk obtunded population […] cervical collar removal can be logically argued for any population-obtunded or not.” [2]
They finally call for multicenter prospective research on the subject, again citing the low quality of evidence that they used for their recommendation. That call was answered in 2017 by the Western Trauma Association. The group completed a multi institution trial with 10,000 patients who were getting a CT for evaluation of cervical spine injury prospectively enrolled at 17 centers [3]. They found only 3 CT scans that missed clinically significant injury (.03%). All of those patients had focal neurological abnormalities on exam. There was no clinically significant injury missed by CT and exam combined. CT scan alone had an NPV of 99.97%, and an NPV of 100% when combined with clinical exam. Therefore, they proposed this diagnostic algorithm:
Most trials have found similar results, with a few exceptions. Two trials prior to the publication of the Western Trauma Association (WTA) paper found that CT missed a few clinically significant injuries in patients with no neurological symptoms. Both trials enrolled significantly fewer patients than the WTA paper, and only enrolled patients with negative CT who would be evaluated with MR, meaning they couldn’t comment on the overall sensitivity of CT in unstable c-spine injury. The ReConect trial in 2016 found 5 of 767 patients (.6%) with injuries requiring surgical intervention that were missed on CT [4]. Another study with similar methods published in Annals of Emergency Medicine in 2011 evaluated those who had a negative CT but were MR’ed for persistent midline C-Spine tenderness [5]. They found that out of 178 patients, 5 had injury requiring operative management that was missed on CT but found on subsequent MR (2.8%) [5]. The Annals paper is certainly an outlier, with a considerably higher rate of missed clinically significant injury than the remainder of the literature, with rates usually between 0-1% [6-18]. The authors believe this may be due to more stringent methodology. For instance, they required MR to be performed within 48 hours when it is the most sensitive for edema, and only enrolled patients with midline tenderness rather than subjective pain [5]. While this may be true, the results have not been replicated in subsequent studies.
With the publication of the WTA paper, evidence certainly seems to be tipping in favor of CT clearance of cervical spine in neurologically intact patients. However, a few questions remain. In every study discussed here, MR resulted in discharge with hard collar in a portion of patients. Indications ranged from stable injury to persistent pain with no evidence of injury on MR. It is unclear whether hard collar placement makes a difference in the clinical course of these patients, if their stable injuries would have become unstable without it, or if it has any long term impact on outcomes such as chronic pain. This is an important question not yet adequately addressed in the literature. The majority of these trials were also completed at trauma centers with radiologists well trained in reading c-spine imaging and high quality CT scanners. It could be difficult to generalize this data to centers with older scanners or whose radiology departments are not as expert in trauma radiology.
Incredibly high quality and reproducible evidence is required to change practice when high stakes, such as potentially missed cervical spine injury, are involved. So far we have multiple trials showing an NPV of close to 100% when CT and good neurological exam are combined, and the conditional recommendation by the EAST group. Time will tell if recommendations in the future remove the “conditional” portion as CT technology continues to improve, further studies with stringent methodologies are conducted, and the results of the WTA paper are hopefully replicated.
Expert Commentary
Thank you Dr Whipple for that really practical review of a real-life common clinical question we face all the time: Can we remove the collar? Some important takeaways are:
There is a robust and growing body of evidence that removing the collar after a negative high-quality CT is safe if the patient is neurologically intact.
This practice is endorsed by two major trauma organizations, EAST and WTA.
The endorsement by respected major trauma societies is important in translating evidence into practice. It seems like all that is left at this point for widespread implementation is overcoming culture. This would likely require addressing the outlier studies listed by Dr Whipple to win over those still skeptical. Part of overcoming culture would involve buy-in from neurosurgical societies. What do neurosurgical societies say regarding clearing these patients? There are many instances in which a patient is discharged with recommendations from the neurosurgeon to wear a hard collar despite a negative CT and MRI. On the surface this seems like defensive medicine and impractical for the patient. Is the patient really going to comply with this until follow up? Is this collar really protecting them and preventing further injury which, after negative CT and MRI and with a normal neuro exam, seems exceedingly unlikely? Does evidence support this practice?
In the end, decision rules should be used when you want evidence to support your clinical decisions, such as removing the C collar after negative imaging in a neurologically intact patient. Do not use decision rules, however, to overturn or replace sound clinical judgement. If there is something about a case that makes you still feel like you could be missing an outlier injury by removing the collar, listen to that voice inside of you. It is that sound clinical judgement that will guide you through your career, not decision rules.
Matthew Levine, MD
Northwestern Medicine, Assistant Professor of Emergency Medicine
How To Cite This Post
[Peer-Reviewed, Web Publication] Whipple T, Reuter Q. (2019, May 13). C-spine clearance with negative CT: Are we there yet? [NUEM Blog. Expert Commentary by Levine M]. Retrieved from http://www.nuemblog.com/blog/cspine-clearance-ct
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References:
American College of Radiology. ACR appropriateness criteria on suspected spine trauma. Available at: http://www.acr.org.
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