Sunday, December 16, 2012

MRI for C-spine

Motivation: An elderly man trips on ice and falls.  He complains of neck pain in the ED.  He gets a cervical spine CT, which is normal. He still complains of neck pain.  What do you do now?  I think that many doctors would follow different strategies.  Some would take off the cervical collar and provide ibuprofen.  Others would continue imaging with MRI.  What is the right approach?

As way of background, for cervical spine injury, potentially dangerous ligamentous injuries remain on the differential even after a negative CT.  What is less clear is the incidence of these injuries and the clinical significance of these findings.

Paper: Schoenfeld, A.J., Bono, C.M., McGuire, K.J. et. al. "Computed Tomography Alone versus Computed Tomography and Magnetic Resonance Imaging in the Identification of Occult Injuries to the Cervical Spine: A Meta-Analysis" J. Trauma. (2010); 68(1): 109.

Methods: Meta-analysis of prospective and retrospective studies of MRI after negative CT.  True positive MRI was defined as change in clinical management per clinician judgement.

Results:
Studies: Eleven studies were identified evaluating 1,550 blunt trauma patients evaluated initially by CT and then by MRI.  None of the trials were randomized controlled trials.

Abnormalities: Of the entire cohort, 194 MRI abnormalities were detected in 182 patients (12% of cohort) with negative CT scans.  Of these abnormalities, majority (86, 47% of abnormalities) were ligamentous injuries.  Other significant injuries detected were: degenerative changes (47, 24% of abnormalities),  cord contusion (16, 8.2% of changes), fracture (3, 1.5% of changes), and cord contusions (16, 8.2% of changes).

Clinical Outcomes: As a result of MRI, 84 patients (5% of cohort) required prolonged use of collar, and 12 patients (1% of cohort) required cervical stabilization.  In 86 patients (5.5% of patients), MRI findings were judged clinically insignificant.  For MRI, the pooled sensitivity was 100%, and the pooled specificity was 94%.

Discussion: This paper surprised me with the number of clinically significant injuries missed on CT scanning. About 1% of patients required operative intervention after an apparently normal CT scan.  Similarly, about 1% of patients had cervical cord contusions despite a negative CT scan.  What is not apparent from this paper though are the factors predictive of positive MRI findings with a negative CT scan.  In the absence of clear prospective data, I would think that persistent neck pain or any neurological findings calls for an MRI scan despite a negative CT scan.  So, in summary, if an elderly man continues to complain of neck pain even with a negative CT, I would recommend a cervical MRI.

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