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Screening cervical spine MRI after normal cervical spine CT scans in patients in whom cervical spine injury cannot be excluded by physical examination
The American Journal of Surgery (2008) 196, 857– 863
The Southwestern Surgical Congress
Screening cervical spine MRI after normal cervical spine CT scans in patients in whom cervical spine injury cannot be excluded by physical examination Megan Steigelman, M.D., Peter Lopez, M.D.*, Daniel Dent, M.D., John Myers, M.D., Michael Corneille, M.D., Ronald Stewart, M.D., Stephen Cohn, M.D. Division of Trauma, University of Texas, Health Sciences Center, San Antonio, TX, USA KEYWORDS: Cervical spine MRI; Cervical spine CT; Obtunded trauma patients; Cervical spine injury
Abstract BACKGROUND: Cervical spine injuries can occur in as many as 10% of patients with blunt trauma with mental status changes from closed head injuries. Despite normal results on cervical spine computed tomography (CT), magnetic resonance imaging (MRI) is often recommended to exclude ligamentous or soft tissue injury. METHODS: A retrospective review was conducted of trauma patients admitted to a level I trauma center from 2002 to 2006, in whom cervical spine injuries could not be excluded by physical examination. All patients with normal results on cervical spine CT followed by cervical spine MRI were included in the analysis. RESULTS: One hundred twenty patients underwent MRI to examine their cervical spines. Seven patients had abnormal MRI findings suggestive of acute traumatic injury. No MRI studies led to operative intervention. Screening MRI increased from 1% of comatose patients in 2002 to 18% in 2006. CONCLUSIONS: The use of MRI in patients with normal results on cervical spine CT does not appear to alter treatment. © 2008 Elsevier Inc. All rights reserved.
Cervical spine injuries occur in about 3% of all patients with blunt trauma.1 Several studies have demonstrated that injuries to the cervical spine can be safely excluded in conscious and cooperative trauma patients on physical examination alone.2 However, the incidence of cervical spine injuries may be as high as 10% in patients who arrive at emergency departments with altered mental status from brain injuries.3 These patients are usually left in a semirigid cervical collar until they can be clinically or radiographically examined and injuries excluded. Semirigid cervical collars used to immobilize the cervical spine contribute to * Corresponding author. Tel.: ⫹1-210-567-3623; fax: ⫹1-210-567-0003. E-mail address: [email protected] Manuscript received May 3, 2008; revised manuscript July 3, 2008
0002-9610/$ - see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.amjsurg.2008.07.040
morbidity by limiting central venous access, complicating airway management, and decreasing pulmonary toilet, and they can lead to pressure ulcers in as little as 5 days.3 Therefore, a quick and effective method for the exclusion of cervical spine injuries in obtunded trauma patients could decrease morbidity. Because a missed cervical spine injury may lead to permanent disability, a reliable, noninvasive radiologic method for evaluating the cervical spine is needed. For the detection of acute bony abnormalities, 3-view x-rays have largely been replaced with multidetector computed tomography (CT) at level I trauma institutions in adults.4 In trauma patients who remain unconscious or intubated or have distracting injuries and who have normal results on CT of the cervical spine, the performance of cervical spine
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magnetic resonance imaging (MRI) has been suggested as a method to diagnose soft tissue injury. Cervical spine MRI has been reported to have better sensitivity than CT for detecting soft tissue and ligamentous injuries that could contribute to an occult instability of the cervical spine.5 However, MRI carries a high false-positive rate of 24% to 40%, which may lead to overtreatment, both surgical and nonsurgical.6 Patients who experience unnecessary delays in the exclusion of cervical spine injuries may have further morbidity from cervical collar complications.7 Furthermore, although the increasing availability of MRI is leading to its increased use in traumatic cervical spine evaluation, the abnormalities detected on MRI are not predictive of cervical spine instability.8 On the basis of the availability of new studies endorsing the high negative predictive value of the newest generation computed tomographic scanners,9 and the indeterminate benefits of MRI in comatose patients, we hypothesized that the addition of cervical spine MRI to the evaluation of trauma patients is unnecessary after normal results on cervical spine CT.
Materials and Methods This retrospective review was approved by the university institutional review board and was compliant with the Health Insurance Portability and Accountability Act.
Study group From January 2002 to December 2006, trauma patients with altered mental status or unreliable physical examination results on admission to the emergency department were considered. All patients with normal results on cervical spine CT in whom cervical spine injuries could not be excluded by physical exam alone and who underwent cervical spine MRI during their initial hospital admissions were included. Patients were excluded if they (1) had reliable physical examination results at the time of admission, (2) had abnormal results on cervical spine CT or clinical examination results consistent with cervical spine injuries, or (3) did not undergo screening cervical spine MRI for the purposes of identifying a ligamentous or soft tissue cervical spine injuries.
CT and MRI imaging Cervical spine CT was performed using either a singlerow-detector or a 4-row-detector system (GE Healthcare, Chalfont St Giles, UK). Most of the patients’ initial computed tomographic cervical spine imaging was performed using the single-row-detector system because this scanner was in close proximity to the emergency room. In the few remaining patients, the 4-row-detector system was used for
CT of their cervical spines because the single-row system was unavailable. In September 2006, both imaging systems were upgraded to a 16-row-detector system (Philips Medical Systems, Best, the Netherlands), used only for the last 2 months of the study period. The standard computed tomographic protocol included noncontrast 1-mm multiple axial images from the skull base through C3 and 2-mm slices through the remainder of the cervical spine to the thoracic inlet, with sagittal and coronal reformations. Cervical spine magnetic resonance images were obtained using either 1.5-T or 3.0-T systems (Philips Medical Systems). The standard MRI protocol included T1, T2, short T1 inversion recovery, and axial T1-weighted and T2-weighted sequences that were obtained from the base of the skull through the entire cervical spine.
Cervical spine evaluation Both conscious patients at risk for acute cervical spine injury and neurologically unresponsive or uncooperative patients underwent cervical spine CT for the evaluation of acute injuries after admission to the trauma service. Patients with Glasgow Coma Scale scores of 15 and negative results on CT of the cervical spine underwent physical examinations, including full range of motion and palpation of the cervical spine, to exclude injuries before removal of the cervical collar. Patients who remained unresponsive remained in cervical spine precautions in a semirigid Aspen collar (Aspen Medical Products, Irvine, CA) until injury to the cervical spine was excluded. If a patient continued to have an unevaluable cervical spine by physical examination with normal results on cervical spine CT, he or she underwent cervical spine MRI to assess for a ligamentous or soft tissue injury. If MRI could not be performed and cervical spine injuries could not be excluded by physical exam, patients remained in semirigid collars for 6 weeks. All MRI studies were reviewed and approved by a staff neuroradiologist. A negative final reading of an MRI study by the staff neuroradiologist allowed for removal of the cervical collar and cervical spine injury precautions. Neurosurgery was consulted in all cases of abnormal cervical spine MRI results for further evaluation and treatment.
Chart review The trauma database at the University of Texas Health Sciences Center at San Antonio was cross-referenced with the radiology database to identify all trauma patients with initial unreliable physical examinations who underwent complete cervical spine MRI for the exclusion of soft tissue or ligamentous injuries. All radiology reports of cervical spine MRI performed to examine unevaluable trauma patients were reviewed. The final staff reading of each MRI study was used to determine the positive or negative findings of acute cervical spine trauma on MRI. Patients with MRI results positive for acute injuries underwent further
M. Steigelman et al. Table 1
Cervical spine screening in obtunded patients
859
Demographics, MOIs, GCS scores, MRI results, and treatments resulting from each MRI study by patient
Patient age (y)/gender
MOI
Initial GCS score
ISS
MRI results
Treatment
58/female 16/male 23/male 83/male
MVA MVA MVA MVA
3 4 3 4
22 38 45 10
Cervical collar for 6 wk No additional treatment No additional treatment Cervical collar for 12 wk
43/female
MVA
3
45
79/female
Fall
3
13
15/female
Hanging
3
16
Chronic C5–C6 interspinous ligament injury Prevertebral soft tissue edema Contusion of ligamentum nuchae from C3–C5 Spinal cord contusion at C3–C4, C4–C5, paraspinous soft tissue edema Increased T2 signal adjacent to C7–T1 neuroforamina Spinal canal stenosis C4–C7 with central disk protrusion Interspinous ligament injury at C7–T1
No additional treatment No additional treatment Negative flexion/extension films, collar removed
No additional treatment indicates that the cervical collar was removed after neurosurgical consultation and trauma staff review. GCS ⫽ Glasgow Coma Score; ISS ⫽ injury severity score; MOI ⫽ mechanism of injury; MVA ⫽ motor vehicle accident.
chart review for outcomes and management of the cervical spine abnormalities. Outcome measures that were identified included clearance of the cervical spine by neurosurgery, recommended continued use of a semirigid cervical collar for 6 to 12 weeks, or surgical intervention of the cervical spine injury. An unstable cervical spine on MRI was defined as the complete rupture of 3 ligamentous columns in the cervical spine.
Cervical spine injury definitions Abnormalities on MRI included high signal intensity on T2-weighted imaging involving the posterior interspinal ligaments, facet joints, or disc spaces. In our study, abnormal cervical spine MRI results included ligamentous injuries, prevertebral soft tissue edema, spinal cord signal alteration without evidence of fracture, or spinal canal stenosis with associated alterations in spinal cord signal.
four percent (113 of 120) of these patients had negative MRI results for acute injury. Five percent (7 of 120) of these obtunded patients had abnormal findings consistent with acute injuries on MRI not seen on CT, with an annual incidence of 0.04% over the 5-year study period (range, 0%– 0.08% per year). Abnormal findings on cervical spine MRI included 3 patients with single-column ligament injuries, 1 patient with prevertebral soft tissue edema, 1 patient with spinal cord edema, 1 patient with spinal canal stenosis and significant disc protrusion, and 1 patient with edema surrounding a neuroforamina. These 7 patients consisted of 4 female and 3 male patients. The average age was 45 years (range, 15– 83 years), and the average injury severity score was 27 (range, 10 – 45). The average Glasgow Coma Scale score was 3 (range, 3– 4), and the average time until MRI was 8.3 days (range, 1–15 days) (Table 1). The distribution of the incidence of screening cervical spine MRIs is shown in Figure 1. The percentage of MRI studies performed for obtunded patients solely for cervical
Results Study group From January 2002 to December 2006, 338 trauma patients with altered mental status underwent cervical spine MRI. Of these, 120 patients with documented normal results on cervical spine CT underwent MRI to exclude soft tissue or ligamentous injury. This group consisted of 81 male and 39 female patients (mean age, 33 years; range, 0 –91 years). All 120 patients sustained blunt trauma. Fifty-three percent of these patients (63 of 120) experienced injuries in motor vehicle or motorcycle collision, while the other blunt causes of trauma included falls, pedestrian-vehicle impact, and assault. The mean injury severity score was 24 (range, 1–50). On average, patients underwent cervical spine MRI 7.7 days after their initial injuries (range, 0 –37 days). Ninety-
Figure 1 Although the number of patients with altered mental status unable to be evaluated with physical examinations alone remained approximately 300 each year, the number of those patients undergoing screening MRI increased from ⬍1% in 2002 to 18% in 2006, without a protocol in place.
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spine screening purposes steadily increased from 1.3% of obtunded trauma patients in 2002 to 18% in 2006, although the overall obtunded patient admission averaged 300 patients/year.
Post-MRI management One patient who was status post hanging with prevertebral soft tissue edema was cleared using flexion and extension films, and the collar was removed before discharge. Two patients were treated with continued immobilization in cervical collars; 1 patient with a spinal canal contusion, disk protrusion, and degenerative joint disease remained in a collar for 12 weeks. The other patient, with a chronic interspinous ligament injury and degenerative joint disease, remained in a collar for 6 weeks. On follow-up 1 year later, the patient in a collar for 6 weeks had no further treatment. No neurosurgical intervention was initiated on the basis of abnormal MRI results in 4 patients, and no further documented actions were taken after the positive MRI results were reviewed with trauma and neurosurgery staff members. These patients required no further treatment or had any cervical spine complaints after discharge to a rehabilitation, acute care, nursing home, or residential facility. Six of the 7 patients in our study had no documented follow-up after discharge from these facilities.
Comments In our study, the 0.04% annual incidence of abnormalities seen on cervical spine MRI in the absence of fractures on CT is equal to that seen in other similar studies.1 What remains unclear is what injuries detected solely on MRI are clinically significant, and how these findings affect clinical management and outcomes. We found no instances of clear instability of the cervical spine after MRI suggested acute soft tissue abnormalities, despite the increasing number of patients with altered mental status who underwent cervical spine MRI screening.
Increased incidence of screening MRI Although there was no policy mandating the performance of a screening MRI on obtunded trauma patients, the number of MRI studies performed for that reason steadily increased over the 5 years of the study, from 1% to 18%, despite a lack of compelling evidence that supports this practice. Although the number of trauma patients with altered mental status remained approximately 300 per year from 2002 to 2006, the number of patients undergoing MRI to clear cervical spines increased by an average of 4% per year. Despite this increase, only 0.04% of patients having initially negative results on CT had abnormal MRI results. In December 2007, the trauma multidisciplinary committee at our institution halted this trend by endorsing the
findings of normal cervical spine CT as the only radiologic study required for removal of cervical collars in patients with clinically unevaluable cervical spines. The committee excluded patients aged ⱕ16 years, elderly patients (aged ⬎65 years), and those with degenerative joint disease or previous cervical spine injuries, given the higher incidence of occult injuries that could be missed with CT alone in this population. From the review of our data, the patients at high risk for injuries who might benefit from screening MRI include children aged ⬍16 years, those with mechanisms for high risk for cervical spine injury, those with previous cervical spine injuries, and those with preexisting significant degenerative changes of the cervical spine.
Computed tomographic scanning resolution Recently, at our institution, the single-row and 4-row computed tomographic scanners were replaced by newer generation 16-row to 64-row scanners with 3-dimensional reconstruction. These scanners offer high-resolution cervical spine reconstructions that have 98% to 100% negative predictive value for detecting acute cervical spine bony abnormalities or misalignment.9 The increasing resolution and reconstructed images produced by advanced computed tomographic scanners call into question the applicability of recent studies published comparing MRI with CT performed on first-generation scanners. Despite this recent increase in resolution, our study used the single-row and 4-row scanners with no clinically significant missed cervical spine injuries, and we anticipate this to continue as the newer generation of computed tomographic scanners offers better resolution and even higher sensitivity.
MRI as an additional tool MRI has proved valuable for the evaluation of ligaments and surrounding soft tissues of the cervical spine, but its use in trauma patients is not without consequences. First, transporting a severely injured patient to the MRI system requires numerous resources not always available. Our institution performs inpatient MRI studies at night only, when staffing is already limited and overextended. In addition, the equipment must be MRI compatible, patients must have no metal prostheses, and patients must be stable enough to endure the time necessary for an optimal study. Second, MRI studies are most accurate ⱕ72 hours after injuries.10 Often, patients who are severely injured are not stable enough to be transported to MRI scanners within this short time frame. The data gathered from a study ⬎72 hours after injury are questionable, and the value of MRI outside the 72-hour time frame has not been addressed in the literature. Our 7.7-day delay is equal to those of other institutions that have MRI protocols in place.9,11,12 The most recent publication by Menaker et al12 in 2008 discusses an institutional protocol whereby screening MRI is mandatory for patients who cannot have their cervical spines cleared by physical
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exam, and they took an average of 9.9 days after injury to undergo all testing. The reasons for delays in performing MRI included patient instability and continued need for monitors not compatible with MRI.12 Finally, the information offered by screening cervical spine MRI may not assist in identifying an unstable cervical spine. In a 2005 study, Horn et al8 determined that negative results on cervical spine CT reliably identified unstable spines in all 65 patients, and MRI did not identify any occult injuries leading to cervical spine instability. Menaker et al12 retrospectively compared 16-slice CT with reconstructions and 1.5-T MRI over a 1-year period. Despite findings in recent publications from this institution9 suggesting that MRI of the cervical spine is not warranted in patients after negative results on CT of the cervical spine, the protocol of obtaining MRI continued. The average length of obtaining MRI was almost 10 days from the original injury. In this group, without clearly defining what findings on MRI identified an unstable cervical spine, or by performing other dynamic studies to determine cervical spine instability, 2 of 18 patients underwent operations to stabilize their cervical spines after MRI found abnormalities that were missed by CT. A review of the list of injuries from that study shows only 1 patient with a 2-column rupture, which still does not meet the accepted definition of unstable cervical spine. Most authorities require that all 3 columns be disrupted to call a cervical spine unstable.13 Another problem seen in studies such as ours is that the treatment of positive MRI findings varies depending on the attending trauma surgeon and neurosurgeon coverage. For example, in the study reported by Menaker et al,12 2 patients with injuries similar to those treated with collars were cleared by attending physicians and suffered no ill effects. This suggests that overtreatment occurred in the 2 patients who remained in collars. Also in Menaker et al’s12 study, all of the remaining patients with positive MRI results were placed in collars, despite a 25% to 40% false-positive rate in screening cervical spine MRI that leads to overtreatment. Another recent study by Tomycz et al13 on the use of MRI to clear the cervical spine in obtunded trauma patients with negative results on CT found 38 injuries on screening MRI.
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None of these patients had unstable cervical spines by definition of a 3-ligament column rupture. Using this definition, the authors concluded that outside of its use in patients with neurologic deficits, MRI is unlikely to uncover unstable cervical spine injuries when advanced CT of the cervical spine is used to evaluate obtunded trauma patients with suspected cervical spine injuries.13 Combining these studies and ours, there is not a clear answer to this dilemma. Using a definition of an unstable cervical spine as the rupture of all 3-ligamentous columns helps identify severe injuries that should be treated but leaves the treatment of a majority of acute MRI findings to the discretion of the trauma and neurosurgical attending physicians. Currently, there has been no agreement on the surgical or nonsurgical treatment of these soft tissue injuries of the cervical spine found on MRI. No literature is published in a prospective manner randomizing the treatment of MRI findings to collar versus surgery versus no treatment, and it is doubtful that such a study could be performed. Therefore, continuing to retrospectively analyze the data with differing outcome measures and not addressing unstable and stable cervical spine soft tissue injuries seen on MRI in the discussion is not useful. Table 214,15 examines recent studies comparing the use of cervical spine MRI with CT and the unstable cervical spines that were identified from abnormal results on cervical spine MRI.
Missed cervical spine injuries The annual incidence of abnormal cervical spine MRI results in obtunded patients with previously negative results on cervical spine CT was 0.04% in this 5-year review. This incidence failed to increase even as the number of MRI studies increased. Our chart review further established that MRI did not alter surgical patient management, and the results did not provide information as to the stability of the cervical spine. An study in 2006 by Stassen et al5 showed that 13 of 52 patients with blunt obtunded trauma with negative results on CT had positive MRI results, but none of these ultimately required surgical intervention. Additionally, they failed to examine the clinical significance of any
Table 2 Summary of a literature review of the available studies evaluating the current use of MRI in identifying unstable cervical spines in trauma patients Study
Study population
Obtunded patients
Normal results on CT and abnormal results on MRI
Unstable cervical spine
Horn et al8 Como et al11 Stassen et al5 Ghanta et al14 Adams et al15 Hogan et al9 Menaker et al12 Tomycz et al13
166 115 52 124 97 1,400 734 690
36 115 52 51 29 366 203 245
22 6 13 10 0 12 18 38
0 0 NS NS 0 0 NS 0
NS ⫽ not specified (there was no definition or discussion of whether the abnormal MRI results indicated unstable cervical spines).
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of these positive MRI results regarding the stability of the cervical spine. Most studies that find MRI beneficial in obtunded trauma patients acknowledge the difficulties of making MRI part of a routine cervical spine evaluation, including cost, dangers of patient transport, and device compatibility.5 These same studies then fail to attribute clinical significance to abnormal results on screening MRI. Our 5-year review of ⬎14,000 trauma patients failed to identify any cervical spine injuries requiring surgical intervention after negative results on cervical spine CT and abnormalities on cervical spine MRI. We also identified an increasing trend at our institution to perform screening MRI that did not alter management or identify unstable cervical spine injuries. There were several limitations to this study. First, this was a retrospective review of a trauma patient database relying on chart review and without long-term follow-up. Second, our imaging methods from 2002 to 2006, using single-row and 4-row computed tomographic scanners, are outdated compared with the 16-row and 64-row scanners used today. Despite this limitation, we did not identify any unstable cervical spines with the addition of the screening MRI. As the computed tomographic scanners were upgraded from 1 to 16 rows, the imaging quality improved. This should improve the ability to identify more injuries using CT alone and decrease false-negative results in the future.
Conclusions Our study supports the practice of not performing screening cervical spine MRI in all obtunded, unevaluable trauma patients with negative results on cervical spine CT, because 95% of patients did not benefit from screening MRI. However, further study is required to support our conclusions, as well as to identify which obtunded trauma patients may benefit from screening cervical spine MRI. In our study, obtunded trauma patients at risk for soft tissue cervical spine injuries after negative results on CT included elderly patients, patients aged ⱕ16 years, and patients with degenerative changes of the cervical spine.
References 1. Grossman MD, Reilly PM, Gillett T, et al. National survey of the incidence of cervical spine injury and approach to cervical spine clearance in U.S. trauma centers. J Trauma 1999;47:684 –90. 2. Hoffman JR, Mower WR, Wolfson AB, et al; National Emergency X-Radiography Utilization Study Group. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. N Engl J Med 2000;343:94 –9. 3. Ajani AE, Cooper DJ, Scheinkestel CD, et al. Optimal assessment of cervical spine trauma in critically ill patients: a prospective evaluation. Anaesthesiol Intens Care 1998;26:487–91. 4. Barba CA, Taggert J, Morgan AS, et al. A new cervical spine clearance protocol using computed tomography. J Trauma 2001;51:652– 6.
5. Stassen NA, Williams VA, Gestring ML, et al. Magnetic resonance imaging in combination with helical computed tomography provides a safe and efficient method of cervical spine clearance in the obtunded trauma patient. J Trauma 2006;60:171–7. 6. Richards PJ. Cervical spine clearance: a review. Injury 2005;36:248 – 69. 7. Muchow RD, Resnick DK, Abdel MP, et al. Magnetic resonance imaging (MRI) in the clearance of the cervical spine in blunt trauma: a meta-analysis. J Trauma 2008;64:179 – 89. 8. Horn EM, Lekovic GP, Feiz-Erfan I, et al. Cervical magnetic resonance imaging abnormalities not predictive of cervical spine instability in traumatically injured patients. Invited submission from the joint section meeting on disorders of the spine and peripheral nerves. J Neurosurg Spine 2004;1:39 – 42. 9. Hogan GJ, Mirvis SE, Shanmuganathan K, et al. Exclusion of unstable cervical spine injury in obtunded patients with blunt trauma: is MR imaging needed when multi-detector row CT findings are normal? Radiology 2005;237:106 –13. 10. Ackland HM, Cooper DJ, Malham GM, et al. Factors predicting cervical collar-related decubitus ulceration in major trauma patients. Spine 2007;32:423– 8. 11. Como JJ, Thompson MA, Anderson JS, et al. Is magnetic resonance imaging essential in clearing the cervical spine in obtunded patients with blunt trauma? J Trauma 2007;63:544 –9. 12. Menaker J, Philp A, Boswell S, et al. Computed tomography alone for cervical spine clearance in the unreliable patient—are we there yet? J Trauma 2008;64:898 –904. 13. Tomycz ND, Chew BG, Chang YF, et al. MRI is unnecessary to clear the cervical spine in obtunded/comatose trauma patients: the four-year experience of a level I trauma center. J Trauma 2008;64:1258 – 63. 14. Ghanta MK, Smith LM, Polin RS, et al. An analysis of eastern association for the surgery of trauma practice guidelines for cervical spine evaluation in a series of patients with multiple imaging techniques. Am Surg 2002;68:563–7. 15. Adams JM, Cockburn MI, Difazio LT, et al. Spinal clearance in the difficult trauma patient: a role for screening MRI of the spine. Am Surg 2006;72:101–5.
Discussion Roxie Albrecht, M.D. (Oklahoma City, OK): Dr Steigleman and her coauthors have added further evidence to the literature that CT scans with reconstructions may be the only evaluation needed to “clear” the cervical spine in the nonevaluable patient. They have retrospectively evaluated findings from patients undergoing CT scan with reconstructions and MRI of the cervical spine for diagnosis of significant or potential unstable cervical spine injuries. They have concluded that there were no instances of clear instability of the cervical spine after MRI suggested acute soft tissue abnormalities, despite increasing the numbers of altered mental status patients that underwent MRI testing and thus continued use of screening cervical spine MRI is not warranted, in the obtunded trauma population with a negative CT. This conclusion is based on the data that none of the 7 patients that had an abnormal MRI had significant instability or required surgery. However, only 1 patient was evaluated by a dynamic study, 2 remained in a collar for 6 weeks but we were not given follow-up data on these 2 and 4 patients had no further documentation of actions. This leads to my first set of questions. What happened to these 4 patients? What was your length of follow-up? Did the pa-
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Cervical spine screening in obtunded patients
tients that were treated in the collar have follow-up studies to ensure no consequences of the identified injuries? Studies done at the University of New Mexico identified 1 to 2 patients/year with major longitudinal ligament disruption that had subluxation in a collar when upright films or flexion extension films were done at 6 weeks and required surgical stabilization. I am in support of literature regarding adequacy of CT with reconstructions alone for clearance of the cervical spine in nonevaluable/obtunded patients. However given the lack of follow-up information in this study, the retrospective nature of the other studies and the lack of standardization of the definition of what is an unstable injury by MRI I still have some concerns using CT alone in these patients. Albeit this concern is becoming less with the advancement of CT technology and the support of spine surgeons, trauma radiologists and neuroradiologist for these protocols. My final comment and questions are in regards to the technique of the CT scan. In 2 studies comparing CT to dynamic flexion/extension, CT missed 3 significant injuries, 1 of which was an atlanto-occipital dissociation due to lack of calculation of a power’s ratio and the other 2 were due to the width of the slices or cuts. My questions are: Who reads the C-spine CTs at your institution—neuroradiology, trauma radiologist or is it whoever is available? What technique and reconstructions would you recommend to minimize missed significant injuries? Megan Steigelman, M.D. (San Antonio, TX): To answer your first question about the follow-up of these patients, it was a major limitation of our study. This was a retrospective review of our trauma registry which is very limited with respect to long-term follow-up. Your question concerning the definition of an unstable cervical spine in the MRI, it is a uniform definition in the literature. Our radiologists, neurosurgeons and trauma team generally use the 3 column model for spine stability. We defined unstable as a fracture involving all 3 columns, and that never occurred in our 5 years of MRI readings. Concerning the physician interpreting the images, predominantly the residents read our MRIs and our CTs at night, but they are always overread by a staff radiologist. Concerning dynamic flexion extension, this was not commonly done at our institution. Steve Smith, M.D. (Wichita, KS): My question is directed at the patients who had a negative screening MRI. Did that finding alter your management of those patients at your institution from that point on? For example, did you remove the cervical collar at that point? Were you able to mobilize those patients faster? Did they have a lower incidence of decubitus ulcers, earlier initiation of physical therapy or occupational therapy and was the DVT rate essentially the same? Were you able to look at in your retrospective database? Megan Steigelman, M.D. (San Antonio, TX): The patients in this study had an average of 7 days postinjury
863
before an MRI was obtained. So we were going off a 7 days difference—with a wide range from 24 hours to almost 30 days. We did remove the cervical collar of the patients after a negative MRI. Six months ago, we instituted a policy based on these data and other reports in the literature. In brief, for patients who cannot be evaluated on physical exam, we obtain a thin cut CT scan with sagittal and coronal reconstructions. If that study is normal and the patient is older than 16 and has no significant degenerative spine changes, we remove the cervical collar without obtaining an MRI or dynamic flexion-extension radiographs. Scott Petersen, M.D. (Phoenix, AZ): Very nice presentation. Your data are a little different from what is out there in the literature in terms of—the fact that you did 132 patients who had MRIs and normal CTs, yet you only had 7 that showed abnormalities. John Fildes and his group in Las Vegas showed that if they did MRIs in this same population, they showed almost a 40% incidence of at least some abnormality on MRI. We did the same thing with 30% to 40% of our patients who then had abnormalities. So now we are stuck leaving these people in collars. That is the other side of the coin. Can you explain why the sensitivity of your MRI was less—is it because of the way it is done? Do you use STIR imaging? Tell me about that. Megan Steigelman, M.D. (San Antonio, TX): We did find a lot of patients that had abnormalities in their MRI that were not related to trauma. In the review if they had an MRI that was specifically different because of trauma, then that was what we counted as positive. And that really only ended up in 7. We had a lot of patients with degenerative joint disease with spinal stenosis, and other nonacute findings. So we really made sure our criteria for positive MRI was something related to the acute trauma. Alicia Mangram, M.D. (Dallas, TX): Have there been any changes in your institution because of this study, ie, a patient that has a negative CT and you cannot clear them because of their state? Do you switch them and put them on a soft collar after a certain number of weeks or exactly what do you all do? Megan Steigelman, M.D. (San Antonio, TX): We now have a 16-row detector that we use and a 64-row detector for CTs. Six months ago, we instituted a policy based on these data and other reports in the literature. In brief, for patients who cannot be evaluated on physical exam, we obtain a thin cut CT scan with sagittal and coronal reconstructions. If that study is normal and the patient is older than 16 and has no significant degenerative spine changes, we remove the cervical collar without obtaining an MRI or dynamic flexion-extension radiographs. Alicia Mangram, M.D. (Dallas, TX): Even without a clinical exam? Megan Steigelman, M.D. (San Antonio, TX): Yes.
The Southwestern Surgical Congress
Screening cervical spine MRI after normal cervical spine CT scans in patients in whom cervical spine injury cannot be excluded by physical examination Megan Steigelman, M.D., Peter Lopez, M.D.*, Daniel Dent, M.D., John Myers, M.D., Michael Corneille, M.D., Ronald Stewart, M.D., Stephen Cohn, M.D. Division of Trauma, University of Texas, Health Sciences Center, San Antonio, TX, USA KEYWORDS: Cervical spine MRI; Cervical spine CT; Obtunded trauma patients; Cervical spine injury
Abstract BACKGROUND: Cervical spine injuries can occur in as many as 10% of patients with blunt trauma with mental status changes from closed head injuries. Despite normal results on cervical spine computed tomography (CT), magnetic resonance imaging (MRI) is often recommended to exclude ligamentous or soft tissue injury. METHODS: A retrospective review was conducted of trauma patients admitted to a level I trauma center from 2002 to 2006, in whom cervical spine injuries could not be excluded by physical examination. All patients with normal results on cervical spine CT followed by cervical spine MRI were included in the analysis. RESULTS: One hundred twenty patients underwent MRI to examine their cervical spines. Seven patients had abnormal MRI findings suggestive of acute traumatic injury. No MRI studies led to operative intervention. Screening MRI increased from 1% of comatose patients in 2002 to 18% in 2006. CONCLUSIONS: The use of MRI in patients with normal results on cervical spine CT does not appear to alter treatment. © 2008 Elsevier Inc. All rights reserved.
Cervical spine injuries occur in about 3% of all patients with blunt trauma.1 Several studies have demonstrated that injuries to the cervical spine can be safely excluded in conscious and cooperative trauma patients on physical examination alone.2 However, the incidence of cervical spine injuries may be as high as 10% in patients who arrive at emergency departments with altered mental status from brain injuries.3 These patients are usually left in a semirigid cervical collar until they can be clinically or radiographically examined and injuries excluded. Semirigid cervical collars used to immobilize the cervical spine contribute to * Corresponding author. Tel.: ⫹1-210-567-3623; fax: ⫹1-210-567-0003. E-mail address: [email protected] Manuscript received May 3, 2008; revised manuscript July 3, 2008
0002-9610/$ - see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.amjsurg.2008.07.040
morbidity by limiting central venous access, complicating airway management, and decreasing pulmonary toilet, and they can lead to pressure ulcers in as little as 5 days.3 Therefore, a quick and effective method for the exclusion of cervical spine injuries in obtunded trauma patients could decrease morbidity. Because a missed cervical spine injury may lead to permanent disability, a reliable, noninvasive radiologic method for evaluating the cervical spine is needed. For the detection of acute bony abnormalities, 3-view x-rays have largely been replaced with multidetector computed tomography (CT) at level I trauma institutions in adults.4 In trauma patients who remain unconscious or intubated or have distracting injuries and who have normal results on CT of the cervical spine, the performance of cervical spine
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magnetic resonance imaging (MRI) has been suggested as a method to diagnose soft tissue injury. Cervical spine MRI has been reported to have better sensitivity than CT for detecting soft tissue and ligamentous injuries that could contribute to an occult instability of the cervical spine.5 However, MRI carries a high false-positive rate of 24% to 40%, which may lead to overtreatment, both surgical and nonsurgical.6 Patients who experience unnecessary delays in the exclusion of cervical spine injuries may have further morbidity from cervical collar complications.7 Furthermore, although the increasing availability of MRI is leading to its increased use in traumatic cervical spine evaluation, the abnormalities detected on MRI are not predictive of cervical spine instability.8 On the basis of the availability of new studies endorsing the high negative predictive value of the newest generation computed tomographic scanners,9 and the indeterminate benefits of MRI in comatose patients, we hypothesized that the addition of cervical spine MRI to the evaluation of trauma patients is unnecessary after normal results on cervical spine CT.
Materials and Methods This retrospective review was approved by the university institutional review board and was compliant with the Health Insurance Portability and Accountability Act.
Study group From January 2002 to December 2006, trauma patients with altered mental status or unreliable physical examination results on admission to the emergency department were considered. All patients with normal results on cervical spine CT in whom cervical spine injuries could not be excluded by physical exam alone and who underwent cervical spine MRI during their initial hospital admissions were included. Patients were excluded if they (1) had reliable physical examination results at the time of admission, (2) had abnormal results on cervical spine CT or clinical examination results consistent with cervical spine injuries, or (3) did not undergo screening cervical spine MRI for the purposes of identifying a ligamentous or soft tissue cervical spine injuries.
CT and MRI imaging Cervical spine CT was performed using either a singlerow-detector or a 4-row-detector system (GE Healthcare, Chalfont St Giles, UK). Most of the patients’ initial computed tomographic cervical spine imaging was performed using the single-row-detector system because this scanner was in close proximity to the emergency room. In the few remaining patients, the 4-row-detector system was used for
CT of their cervical spines because the single-row system was unavailable. In September 2006, both imaging systems were upgraded to a 16-row-detector system (Philips Medical Systems, Best, the Netherlands), used only for the last 2 months of the study period. The standard computed tomographic protocol included noncontrast 1-mm multiple axial images from the skull base through C3 and 2-mm slices through the remainder of the cervical spine to the thoracic inlet, with sagittal and coronal reformations. Cervical spine magnetic resonance images were obtained using either 1.5-T or 3.0-T systems (Philips Medical Systems). The standard MRI protocol included T1, T2, short T1 inversion recovery, and axial T1-weighted and T2-weighted sequences that were obtained from the base of the skull through the entire cervical spine.
Cervical spine evaluation Both conscious patients at risk for acute cervical spine injury and neurologically unresponsive or uncooperative patients underwent cervical spine CT for the evaluation of acute injuries after admission to the trauma service. Patients with Glasgow Coma Scale scores of 15 and negative results on CT of the cervical spine underwent physical examinations, including full range of motion and palpation of the cervical spine, to exclude injuries before removal of the cervical collar. Patients who remained unresponsive remained in cervical spine precautions in a semirigid Aspen collar (Aspen Medical Products, Irvine, CA) until injury to the cervical spine was excluded. If a patient continued to have an unevaluable cervical spine by physical examination with normal results on cervical spine CT, he or she underwent cervical spine MRI to assess for a ligamentous or soft tissue injury. If MRI could not be performed and cervical spine injuries could not be excluded by physical exam, patients remained in semirigid collars for 6 weeks. All MRI studies were reviewed and approved by a staff neuroradiologist. A negative final reading of an MRI study by the staff neuroradiologist allowed for removal of the cervical collar and cervical spine injury precautions. Neurosurgery was consulted in all cases of abnormal cervical spine MRI results for further evaluation and treatment.
Chart review The trauma database at the University of Texas Health Sciences Center at San Antonio was cross-referenced with the radiology database to identify all trauma patients with initial unreliable physical examinations who underwent complete cervical spine MRI for the exclusion of soft tissue or ligamentous injuries. All radiology reports of cervical spine MRI performed to examine unevaluable trauma patients were reviewed. The final staff reading of each MRI study was used to determine the positive or negative findings of acute cervical spine trauma on MRI. Patients with MRI results positive for acute injuries underwent further
M. Steigelman et al. Table 1
Cervical spine screening in obtunded patients
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Demographics, MOIs, GCS scores, MRI results, and treatments resulting from each MRI study by patient
Patient age (y)/gender
MOI
Initial GCS score
ISS
MRI results
Treatment
58/female 16/male 23/male 83/male
MVA MVA MVA MVA
3 4 3 4
22 38 45 10
Cervical collar for 6 wk No additional treatment No additional treatment Cervical collar for 12 wk
43/female
MVA
3
45
79/female
Fall
3
13
15/female
Hanging
3
16
Chronic C5–C6 interspinous ligament injury Prevertebral soft tissue edema Contusion of ligamentum nuchae from C3–C5 Spinal cord contusion at C3–C4, C4–C5, paraspinous soft tissue edema Increased T2 signal adjacent to C7–T1 neuroforamina Spinal canal stenosis C4–C7 with central disk protrusion Interspinous ligament injury at C7–T1
No additional treatment No additional treatment Negative flexion/extension films, collar removed
No additional treatment indicates that the cervical collar was removed after neurosurgical consultation and trauma staff review. GCS ⫽ Glasgow Coma Score; ISS ⫽ injury severity score; MOI ⫽ mechanism of injury; MVA ⫽ motor vehicle accident.
chart review for outcomes and management of the cervical spine abnormalities. Outcome measures that were identified included clearance of the cervical spine by neurosurgery, recommended continued use of a semirigid cervical collar for 6 to 12 weeks, or surgical intervention of the cervical spine injury. An unstable cervical spine on MRI was defined as the complete rupture of 3 ligamentous columns in the cervical spine.
Cervical spine injury definitions Abnormalities on MRI included high signal intensity on T2-weighted imaging involving the posterior interspinal ligaments, facet joints, or disc spaces. In our study, abnormal cervical spine MRI results included ligamentous injuries, prevertebral soft tissue edema, spinal cord signal alteration without evidence of fracture, or spinal canal stenosis with associated alterations in spinal cord signal.
four percent (113 of 120) of these patients had negative MRI results for acute injury. Five percent (7 of 120) of these obtunded patients had abnormal findings consistent with acute injuries on MRI not seen on CT, with an annual incidence of 0.04% over the 5-year study period (range, 0%– 0.08% per year). Abnormal findings on cervical spine MRI included 3 patients with single-column ligament injuries, 1 patient with prevertebral soft tissue edema, 1 patient with spinal cord edema, 1 patient with spinal canal stenosis and significant disc protrusion, and 1 patient with edema surrounding a neuroforamina. These 7 patients consisted of 4 female and 3 male patients. The average age was 45 years (range, 15– 83 years), and the average injury severity score was 27 (range, 10 – 45). The average Glasgow Coma Scale score was 3 (range, 3– 4), and the average time until MRI was 8.3 days (range, 1–15 days) (Table 1). The distribution of the incidence of screening cervical spine MRIs is shown in Figure 1. The percentage of MRI studies performed for obtunded patients solely for cervical
Results Study group From January 2002 to December 2006, 338 trauma patients with altered mental status underwent cervical spine MRI. Of these, 120 patients with documented normal results on cervical spine CT underwent MRI to exclude soft tissue or ligamentous injury. This group consisted of 81 male and 39 female patients (mean age, 33 years; range, 0 –91 years). All 120 patients sustained blunt trauma. Fifty-three percent of these patients (63 of 120) experienced injuries in motor vehicle or motorcycle collision, while the other blunt causes of trauma included falls, pedestrian-vehicle impact, and assault. The mean injury severity score was 24 (range, 1–50). On average, patients underwent cervical spine MRI 7.7 days after their initial injuries (range, 0 –37 days). Ninety-
Figure 1 Although the number of patients with altered mental status unable to be evaluated with physical examinations alone remained approximately 300 each year, the number of those patients undergoing screening MRI increased from ⬍1% in 2002 to 18% in 2006, without a protocol in place.
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spine screening purposes steadily increased from 1.3% of obtunded trauma patients in 2002 to 18% in 2006, although the overall obtunded patient admission averaged 300 patients/year.
Post-MRI management One patient who was status post hanging with prevertebral soft tissue edema was cleared using flexion and extension films, and the collar was removed before discharge. Two patients were treated with continued immobilization in cervical collars; 1 patient with a spinal canal contusion, disk protrusion, and degenerative joint disease remained in a collar for 12 weeks. The other patient, with a chronic interspinous ligament injury and degenerative joint disease, remained in a collar for 6 weeks. On follow-up 1 year later, the patient in a collar for 6 weeks had no further treatment. No neurosurgical intervention was initiated on the basis of abnormal MRI results in 4 patients, and no further documented actions were taken after the positive MRI results were reviewed with trauma and neurosurgery staff members. These patients required no further treatment or had any cervical spine complaints after discharge to a rehabilitation, acute care, nursing home, or residential facility. Six of the 7 patients in our study had no documented follow-up after discharge from these facilities.
Comments In our study, the 0.04% annual incidence of abnormalities seen on cervical spine MRI in the absence of fractures on CT is equal to that seen in other similar studies.1 What remains unclear is what injuries detected solely on MRI are clinically significant, and how these findings affect clinical management and outcomes. We found no instances of clear instability of the cervical spine after MRI suggested acute soft tissue abnormalities, despite the increasing number of patients with altered mental status who underwent cervical spine MRI screening.
Increased incidence of screening MRI Although there was no policy mandating the performance of a screening MRI on obtunded trauma patients, the number of MRI studies performed for that reason steadily increased over the 5 years of the study, from 1% to 18%, despite a lack of compelling evidence that supports this practice. Although the number of trauma patients with altered mental status remained approximately 300 per year from 2002 to 2006, the number of patients undergoing MRI to clear cervical spines increased by an average of 4% per year. Despite this increase, only 0.04% of patients having initially negative results on CT had abnormal MRI results. In December 2007, the trauma multidisciplinary committee at our institution halted this trend by endorsing the
findings of normal cervical spine CT as the only radiologic study required for removal of cervical collars in patients with clinically unevaluable cervical spines. The committee excluded patients aged ⱕ16 years, elderly patients (aged ⬎65 years), and those with degenerative joint disease or previous cervical spine injuries, given the higher incidence of occult injuries that could be missed with CT alone in this population. From the review of our data, the patients at high risk for injuries who might benefit from screening MRI include children aged ⬍16 years, those with mechanisms for high risk for cervical spine injury, those with previous cervical spine injuries, and those with preexisting significant degenerative changes of the cervical spine.
Computed tomographic scanning resolution Recently, at our institution, the single-row and 4-row computed tomographic scanners were replaced by newer generation 16-row to 64-row scanners with 3-dimensional reconstruction. These scanners offer high-resolution cervical spine reconstructions that have 98% to 100% negative predictive value for detecting acute cervical spine bony abnormalities or misalignment.9 The increasing resolution and reconstructed images produced by advanced computed tomographic scanners call into question the applicability of recent studies published comparing MRI with CT performed on first-generation scanners. Despite this recent increase in resolution, our study used the single-row and 4-row scanners with no clinically significant missed cervical spine injuries, and we anticipate this to continue as the newer generation of computed tomographic scanners offers better resolution and even higher sensitivity.
MRI as an additional tool MRI has proved valuable for the evaluation of ligaments and surrounding soft tissues of the cervical spine, but its use in trauma patients is not without consequences. First, transporting a severely injured patient to the MRI system requires numerous resources not always available. Our institution performs inpatient MRI studies at night only, when staffing is already limited and overextended. In addition, the equipment must be MRI compatible, patients must have no metal prostheses, and patients must be stable enough to endure the time necessary for an optimal study. Second, MRI studies are most accurate ⱕ72 hours after injuries.10 Often, patients who are severely injured are not stable enough to be transported to MRI scanners within this short time frame. The data gathered from a study ⬎72 hours after injury are questionable, and the value of MRI outside the 72-hour time frame has not been addressed in the literature. Our 7.7-day delay is equal to those of other institutions that have MRI protocols in place.9,11,12 The most recent publication by Menaker et al12 in 2008 discusses an institutional protocol whereby screening MRI is mandatory for patients who cannot have their cervical spines cleared by physical
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exam, and they took an average of 9.9 days after injury to undergo all testing. The reasons for delays in performing MRI included patient instability and continued need for monitors not compatible with MRI.12 Finally, the information offered by screening cervical spine MRI may not assist in identifying an unstable cervical spine. In a 2005 study, Horn et al8 determined that negative results on cervical spine CT reliably identified unstable spines in all 65 patients, and MRI did not identify any occult injuries leading to cervical spine instability. Menaker et al12 retrospectively compared 16-slice CT with reconstructions and 1.5-T MRI over a 1-year period. Despite findings in recent publications from this institution9 suggesting that MRI of the cervical spine is not warranted in patients after negative results on CT of the cervical spine, the protocol of obtaining MRI continued. The average length of obtaining MRI was almost 10 days from the original injury. In this group, without clearly defining what findings on MRI identified an unstable cervical spine, or by performing other dynamic studies to determine cervical spine instability, 2 of 18 patients underwent operations to stabilize their cervical spines after MRI found abnormalities that were missed by CT. A review of the list of injuries from that study shows only 1 patient with a 2-column rupture, which still does not meet the accepted definition of unstable cervical spine. Most authorities require that all 3 columns be disrupted to call a cervical spine unstable.13 Another problem seen in studies such as ours is that the treatment of positive MRI findings varies depending on the attending trauma surgeon and neurosurgeon coverage. For example, in the study reported by Menaker et al,12 2 patients with injuries similar to those treated with collars were cleared by attending physicians and suffered no ill effects. This suggests that overtreatment occurred in the 2 patients who remained in collars. Also in Menaker et al’s12 study, all of the remaining patients with positive MRI results were placed in collars, despite a 25% to 40% false-positive rate in screening cervical spine MRI that leads to overtreatment. Another recent study by Tomycz et al13 on the use of MRI to clear the cervical spine in obtunded trauma patients with negative results on CT found 38 injuries on screening MRI.
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None of these patients had unstable cervical spines by definition of a 3-ligament column rupture. Using this definition, the authors concluded that outside of its use in patients with neurologic deficits, MRI is unlikely to uncover unstable cervical spine injuries when advanced CT of the cervical spine is used to evaluate obtunded trauma patients with suspected cervical spine injuries.13 Combining these studies and ours, there is not a clear answer to this dilemma. Using a definition of an unstable cervical spine as the rupture of all 3-ligamentous columns helps identify severe injuries that should be treated but leaves the treatment of a majority of acute MRI findings to the discretion of the trauma and neurosurgical attending physicians. Currently, there has been no agreement on the surgical or nonsurgical treatment of these soft tissue injuries of the cervical spine found on MRI. No literature is published in a prospective manner randomizing the treatment of MRI findings to collar versus surgery versus no treatment, and it is doubtful that such a study could be performed. Therefore, continuing to retrospectively analyze the data with differing outcome measures and not addressing unstable and stable cervical spine soft tissue injuries seen on MRI in the discussion is not useful. Table 214,15 examines recent studies comparing the use of cervical spine MRI with CT and the unstable cervical spines that were identified from abnormal results on cervical spine MRI.
Missed cervical spine injuries The annual incidence of abnormal cervical spine MRI results in obtunded patients with previously negative results on cervical spine CT was 0.04% in this 5-year review. This incidence failed to increase even as the number of MRI studies increased. Our chart review further established that MRI did not alter surgical patient management, and the results did not provide information as to the stability of the cervical spine. An study in 2006 by Stassen et al5 showed that 13 of 52 patients with blunt obtunded trauma with negative results on CT had positive MRI results, but none of these ultimately required surgical intervention. Additionally, they failed to examine the clinical significance of any
Table 2 Summary of a literature review of the available studies evaluating the current use of MRI in identifying unstable cervical spines in trauma patients Study
Study population
Obtunded patients
Normal results on CT and abnormal results on MRI
Unstable cervical spine
Horn et al8 Como et al11 Stassen et al5 Ghanta et al14 Adams et al15 Hogan et al9 Menaker et al12 Tomycz et al13
166 115 52 124 97 1,400 734 690
36 115 52 51 29 366 203 245
22 6 13 10 0 12 18 38
0 0 NS NS 0 0 NS 0
NS ⫽ not specified (there was no definition or discussion of whether the abnormal MRI results indicated unstable cervical spines).
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of these positive MRI results regarding the stability of the cervical spine. Most studies that find MRI beneficial in obtunded trauma patients acknowledge the difficulties of making MRI part of a routine cervical spine evaluation, including cost, dangers of patient transport, and device compatibility.5 These same studies then fail to attribute clinical significance to abnormal results on screening MRI. Our 5-year review of ⬎14,000 trauma patients failed to identify any cervical spine injuries requiring surgical intervention after negative results on cervical spine CT and abnormalities on cervical spine MRI. We also identified an increasing trend at our institution to perform screening MRI that did not alter management or identify unstable cervical spine injuries. There were several limitations to this study. First, this was a retrospective review of a trauma patient database relying on chart review and without long-term follow-up. Second, our imaging methods from 2002 to 2006, using single-row and 4-row computed tomographic scanners, are outdated compared with the 16-row and 64-row scanners used today. Despite this limitation, we did not identify any unstable cervical spines with the addition of the screening MRI. As the computed tomographic scanners were upgraded from 1 to 16 rows, the imaging quality improved. This should improve the ability to identify more injuries using CT alone and decrease false-negative results in the future.
Conclusions Our study supports the practice of not performing screening cervical spine MRI in all obtunded, unevaluable trauma patients with negative results on cervical spine CT, because 95% of patients did not benefit from screening MRI. However, further study is required to support our conclusions, as well as to identify which obtunded trauma patients may benefit from screening cervical spine MRI. In our study, obtunded trauma patients at risk for soft tissue cervical spine injuries after negative results on CT included elderly patients, patients aged ⱕ16 years, and patients with degenerative changes of the cervical spine.
References 1. Grossman MD, Reilly PM, Gillett T, et al. National survey of the incidence of cervical spine injury and approach to cervical spine clearance in U.S. trauma centers. J Trauma 1999;47:684 –90. 2. Hoffman JR, Mower WR, Wolfson AB, et al; National Emergency X-Radiography Utilization Study Group. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. N Engl J Med 2000;343:94 –9. 3. Ajani AE, Cooper DJ, Scheinkestel CD, et al. Optimal assessment of cervical spine trauma in critically ill patients: a prospective evaluation. Anaesthesiol Intens Care 1998;26:487–91. 4. Barba CA, Taggert J, Morgan AS, et al. A new cervical spine clearance protocol using computed tomography. J Trauma 2001;51:652– 6.
5. Stassen NA, Williams VA, Gestring ML, et al. Magnetic resonance imaging in combination with helical computed tomography provides a safe and efficient method of cervical spine clearance in the obtunded trauma patient. J Trauma 2006;60:171–7. 6. Richards PJ. Cervical spine clearance: a review. Injury 2005;36:248 – 69. 7. Muchow RD, Resnick DK, Abdel MP, et al. Magnetic resonance imaging (MRI) in the clearance of the cervical spine in blunt trauma: a meta-analysis. J Trauma 2008;64:179 – 89. 8. Horn EM, Lekovic GP, Feiz-Erfan I, et al. Cervical magnetic resonance imaging abnormalities not predictive of cervical spine instability in traumatically injured patients. Invited submission from the joint section meeting on disorders of the spine and peripheral nerves. J Neurosurg Spine 2004;1:39 – 42. 9. Hogan GJ, Mirvis SE, Shanmuganathan K, et al. Exclusion of unstable cervical spine injury in obtunded patients with blunt trauma: is MR imaging needed when multi-detector row CT findings are normal? Radiology 2005;237:106 –13. 10. Ackland HM, Cooper DJ, Malham GM, et al. Factors predicting cervical collar-related decubitus ulceration in major trauma patients. Spine 2007;32:423– 8. 11. Como JJ, Thompson MA, Anderson JS, et al. Is magnetic resonance imaging essential in clearing the cervical spine in obtunded patients with blunt trauma? J Trauma 2007;63:544 –9. 12. Menaker J, Philp A, Boswell S, et al. Computed tomography alone for cervical spine clearance in the unreliable patient—are we there yet? J Trauma 2008;64:898 –904. 13. Tomycz ND, Chew BG, Chang YF, et al. MRI is unnecessary to clear the cervical spine in obtunded/comatose trauma patients: the four-year experience of a level I trauma center. J Trauma 2008;64:1258 – 63. 14. Ghanta MK, Smith LM, Polin RS, et al. An analysis of eastern association for the surgery of trauma practice guidelines for cervical spine evaluation in a series of patients with multiple imaging techniques. Am Surg 2002;68:563–7. 15. Adams JM, Cockburn MI, Difazio LT, et al. Spinal clearance in the difficult trauma patient: a role for screening MRI of the spine. Am Surg 2006;72:101–5.
Discussion Roxie Albrecht, M.D. (Oklahoma City, OK): Dr Steigleman and her coauthors have added further evidence to the literature that CT scans with reconstructions may be the only evaluation needed to “clear” the cervical spine in the nonevaluable patient. They have retrospectively evaluated findings from patients undergoing CT scan with reconstructions and MRI of the cervical spine for diagnosis of significant or potential unstable cervical spine injuries. They have concluded that there were no instances of clear instability of the cervical spine after MRI suggested acute soft tissue abnormalities, despite increasing the numbers of altered mental status patients that underwent MRI testing and thus continued use of screening cervical spine MRI is not warranted, in the obtunded trauma population with a negative CT. This conclusion is based on the data that none of the 7 patients that had an abnormal MRI had significant instability or required surgery. However, only 1 patient was evaluated by a dynamic study, 2 remained in a collar for 6 weeks but we were not given follow-up data on these 2 and 4 patients had no further documentation of actions. This leads to my first set of questions. What happened to these 4 patients? What was your length of follow-up? Did the pa-
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tients that were treated in the collar have follow-up studies to ensure no consequences of the identified injuries? Studies done at the University of New Mexico identified 1 to 2 patients/year with major longitudinal ligament disruption that had subluxation in a collar when upright films or flexion extension films were done at 6 weeks and required surgical stabilization. I am in support of literature regarding adequacy of CT with reconstructions alone for clearance of the cervical spine in nonevaluable/obtunded patients. However given the lack of follow-up information in this study, the retrospective nature of the other studies and the lack of standardization of the definition of what is an unstable injury by MRI I still have some concerns using CT alone in these patients. Albeit this concern is becoming less with the advancement of CT technology and the support of spine surgeons, trauma radiologists and neuroradiologist for these protocols. My final comment and questions are in regards to the technique of the CT scan. In 2 studies comparing CT to dynamic flexion/extension, CT missed 3 significant injuries, 1 of which was an atlanto-occipital dissociation due to lack of calculation of a power’s ratio and the other 2 were due to the width of the slices or cuts. My questions are: Who reads the C-spine CTs at your institution—neuroradiology, trauma radiologist or is it whoever is available? What technique and reconstructions would you recommend to minimize missed significant injuries? Megan Steigelman, M.D. (San Antonio, TX): To answer your first question about the follow-up of these patients, it was a major limitation of our study. This was a retrospective review of our trauma registry which is very limited with respect to long-term follow-up. Your question concerning the definition of an unstable cervical spine in the MRI, it is a uniform definition in the literature. Our radiologists, neurosurgeons and trauma team generally use the 3 column model for spine stability. We defined unstable as a fracture involving all 3 columns, and that never occurred in our 5 years of MRI readings. Concerning the physician interpreting the images, predominantly the residents read our MRIs and our CTs at night, but they are always overread by a staff radiologist. Concerning dynamic flexion extension, this was not commonly done at our institution. Steve Smith, M.D. (Wichita, KS): My question is directed at the patients who had a negative screening MRI. Did that finding alter your management of those patients at your institution from that point on? For example, did you remove the cervical collar at that point? Were you able to mobilize those patients faster? Did they have a lower incidence of decubitus ulcers, earlier initiation of physical therapy or occupational therapy and was the DVT rate essentially the same? Were you able to look at in your retrospective database? Megan Steigelman, M.D. (San Antonio, TX): The patients in this study had an average of 7 days postinjury
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before an MRI was obtained. So we were going off a 7 days difference—with a wide range from 24 hours to almost 30 days. We did remove the cervical collar of the patients after a negative MRI. Six months ago, we instituted a policy based on these data and other reports in the literature. In brief, for patients who cannot be evaluated on physical exam, we obtain a thin cut CT scan with sagittal and coronal reconstructions. If that study is normal and the patient is older than 16 and has no significant degenerative spine changes, we remove the cervical collar without obtaining an MRI or dynamic flexion-extension radiographs. Scott Petersen, M.D. (Phoenix, AZ): Very nice presentation. Your data are a little different from what is out there in the literature in terms of—the fact that you did 132 patients who had MRIs and normal CTs, yet you only had 7 that showed abnormalities. John Fildes and his group in Las Vegas showed that if they did MRIs in this same population, they showed almost a 40% incidence of at least some abnormality on MRI. We did the same thing with 30% to 40% of our patients who then had abnormalities. So now we are stuck leaving these people in collars. That is the other side of the coin. Can you explain why the sensitivity of your MRI was less—is it because of the way it is done? Do you use STIR imaging? Tell me about that. Megan Steigelman, M.D. (San Antonio, TX): We did find a lot of patients that had abnormalities in their MRI that were not related to trauma. In the review if they had an MRI that was specifically different because of trauma, then that was what we counted as positive. And that really only ended up in 7. We had a lot of patients with degenerative joint disease with spinal stenosis, and other nonacute findings. So we really made sure our criteria for positive MRI was something related to the acute trauma. Alicia Mangram, M.D. (Dallas, TX): Have there been any changes in your institution because of this study, ie, a patient that has a negative CT and you cannot clear them because of their state? Do you switch them and put them on a soft collar after a certain number of weeks or exactly what do you all do? Megan Steigelman, M.D. (San Antonio, TX): We now have a 16-row detector that we use and a 64-row detector for CTs. Six months ago, we instituted a policy based on these data and other reports in the literature. In brief, for patients who cannot be evaluated on physical exam, we obtain a thin cut CT scan with sagittal and coronal reconstructions. If that study is normal and the patient is older than 16 and has no significant degenerative spine changes, we remove the cervical collar without obtaining an MRI or dynamic flexion-extension radiographs. Alicia Mangram, M.D. (Dallas, TX): Even without a clinical exam? Megan Steigelman, M.D. (San Antonio, TX): Yes.