For this week's edition of Trauma Tuesday, let's talk about our systematic approach to C-spine imaging in trauma patients, specifically focusing on if/when an MRI is warranted. We all know the initial workup -- Patient arrives in a cervical collar after an MVA. Depending on our level of suspicion for serious c-spine injury based on mechanism and exam, and perhaps depending also on whether the trauma team was called, there are a few ways to proceed: 1) Really low suspicion (minor fender bender, pt was able to ambulate out of the vehicle): apply one of your clinical decision rules (i.e. NEXUS), and if all criteria fit, clear the collar yourself and be done. 2) Moderate suspicion (mechanism still low but pt maaaybe has some midline tenderness on your exam): CT C-spine (has basically replaced x-rays due to superior sensitivity and specificity for detecting C-spine injuries)
Let's say that you proceed with a CT C-spine, and it comes back negative. You go and reassess your patient, who continues to report cervical spine pain upon palpation. What now?
In a large multi-center prospective study published in Dec 2016 by the Western Trauma Association (attached here), the authors concluded that in patients with both a negative CT scan and a normal neurologic exam, the sensitivity was 100% for determining absence of clinically significant C-spine injury.
How did they reach this bold conclusion? Let's backtrack. They included a convenience sample of over 10,000 adult trauma patients who received a CT C-spine after failing NEXUS (breakdown: 45% failed due to distracting injuries, 49% failed due to persistent midline ttp, 5% failed due to abnormal neurologic findings) 90% of these patients ended up with a normal CT C-spine. Of these 90%, a portion ended up getting an MRI C-spine (decision was left up to the treating physician rather than formal protocol). In the end, only 3 patients total were found to have a C-spine injury on MRI when the CT had been negative (in stats-speak, a false negative!) Moreover, all 3 of those patients had an abnormal neurologic exam prompting the decision for MRI, and all 3 were diagnosed with central cord syndrome (classically symptoms worse in upper extremities than lower, often presenting as paresthesias). For CT C-spine imaging alone, this study showed a sensitivity of 98.5% for ruling out clinically significant C-spine injury. Add on the presence of a normal neurological exam, and there were absolutely ZERO patients with significant C-spine injuries who were overlooked with CT C-spine imaging alone.
How's that for evidence? Next time our trauma colleagues might request a knee-jerk MRI C-spine on a patient with iffy "persistent midline tenderness" and a normal CT, we can engage in a respectful and productive discussion about the true utility of such imaging.
TL;DR Take Home Points: Trauma patients who fail NEXUS should get a CT C-spine. CT C-spine alone has excellent sensitivity MRI is indicated in patients with neuro deficits, regardless of negative CT C-spine. Combining your clinical gestalt with evidence-based practice = formula for success.
References: EM:RAP June 2017 https://www.ncbi.nlm.nih.gov/pubmed/27438681