1. MR Imaging of Spinal Trauma: What a Radiology Resident Needs to Know ? K Hooda, MBBS; Kochar P, MD; Sapire J, MD; Muro G, MD; Y Kumar, MD; D Hayashi, MBBS, PhD Department of Radiology Yale New Haven Health System at Bridgeport Hospital, CT

2. Introduction Spinal trauma is a major cause of disability and can be accompanied by a significant neurological damage or even death. Magnetic resonance imaging (MRI) has been playing an increasingly important role in the spinal trauma patients due to high sensitivity for detection of soft tissue and cord injuries including cord hemorrhage. Rapid diagnosis and treatment of lesions compressing the spinal cord such as fracture fragments and hematomas may be helpful in preventing progression to a cord injury. Thus, imaging plays a critical role in diagnosis and helps in initiating prompt and accurate treatment in these patients.

3. Learning objectives 1.To discuss the indications of MRI in spinal trauma. 2.To review the advantages and disadvantages of MRI over CT. 3.To describe the commonly used MR sequences and their specific roles in spinal trauma. 4.To review the normal MR anatomy of spine. 5.To discuss the common findings in spinal trauma and role of MRI in diagnosis and predicting prognosis. 6.To describe pitfalls of MRI in spinal trauma.

4. Indications The main indications of MRI in spinal trauma include : 1. 1.Radiographs or CT scan suggesting ligamentous injury such as prevertebral hematoma, spondylolisthesis, asymmetric disc space widening, facet joint widening or dislocations, and inter-spinous space widening. 2. 2.To look for epidural hematoma or disc herniation before attempting a closed reduction of cervical facet dislocations. 3. 3.To identify spinal cord abnormalities in patients with impaired neurological status.

5. Indications 4. 4.To exclude clinically suspected ligamentous or occult bony injuries in radiographically negative patients. 5. 5.To clear the cervical spine and assess the need for cervical collar in obtunded trauma patients. 6. 6.To differentiate between hemorrhagic and non- hemorrhagic spinal cord injuries for the prognostic significance as the presence of hemorrhage significantly worsens the final clinical outcome.

6. Technical considerations: T1W images are mainly used for depiction of anatomy and osseous fractures. STIR images are very sensitive for detection of edema which is helpful in diagnosing the soft tissue and ligamentous injuries, particularly in the interspinous or supraspinous ligaments. T2W images are very good in detecting the cord edema. Gradient recalled T2*W images are used to detect the hemorrhage in and around the cord.

7. Pathologic features Role of MRI Ligamentous injury Higher sensitivity as compared to CT. Complete tear (seen as discontinuity of ligaments) or partial tear (seen as abnormal signal). Helpful in guiding management by differentiating stable from unstable injuries. Disc damages and herniations Abnormal signal related to traumatic damage with or without disc herniations. Important to diagnose before closed reduction as undetected disc herniations can cause worsening cord injury. Extra medullary hemorrhage Extradural hematoma most common and can lead to cord compression and injury. MRI shows extent of hematoma to help in surgical planning. Vascular injuries Vertebral artery is the most commonly involved artery. May have intimal flap, pseudoaneurysm, complete occlusion or active extravasation. Undetected vascular injuries can cause infarctions. Cord injuries Can be hemorrhagic or non hemorrhagic. Single most important role of MRI in spinal trauma. Seen as abnormal cord signal with hemorrhage best seen on gradient recalled echo (GRE) type sequences. Presence of hemorrhage single most important poor prognostic factor. Acute vs old vertebral fracture Age indeterminate fractures identified on radiography and CT can be classified into acute and old based on the presence or absence of bone marrow edema, respectively. Benign vs malignant fracture Benign fractures show horizontal band of marrow edema, concave appearance of posterior vertebral margin and lack of soft tissue mass. Malignant fractures show almost complete involvement of vertebral body, convex posterior margin and associated soft tissue mass.

8. Normal Anatomy ab Sagittal T2W image (a) shows normal anterior longitudinal ligament (smaller arrow), posterior longitudinal ghted ligament (double arrows) and ligamentum flavum (larger arrow). Sagittal T2 weighted image (b) shows normal wavy supraspinatous ligament (smaller arrow), and normal striated interspinous ligament (larger arrow).

9. Cases 1. 1.Ligamentous injuries 2. 2.Disc injury and herniations 3. 3.Extradural and subdural hematoma 4. 4.Vertebral artery injury 5. 5.Cord injuries: hemorrhagic and non-hemorrhagic contusions 6. 6.Acute vs old vertebral fractures 7. 7.Benign vs malignant fractures

10. 45-year-old man with MVC: Sagittal STIR images show complete anterior longitudinal ligament tear (arrow) (a), complete posterior longitudinal ligament tear (smaller arrow) and ligamentum flavum tear (larger arrow)(b), facet capsular injury (arrow)(c), and interspinous ligament injury (arrow)(d). Also note the presence of interspinous ligament injury in figure (b) and thoracic vertebrae contusions in figure (d). ab c d Ligamentous Injuries

11. 36 year-old man following a motor vehicle accident - Axial GRE (a) and sagittal T1 weighted image (b) show the presence of disc herniation (arrows). Also note the presence of paraspinal muscle edema. ab Disc Injuries and Herniations

12. 76 year-old woman with MVC- Sagittal T1 weighted image (a) and axial GRE image (b) shows presence of epidural hematoma (arrows), and axial T2 weighted image (c) shows subdural hematoma (larger arrow) deep to the dura (smaller arrow). abc Extra medullary hemorrhage

13. 56 year-old man with MVC- Axial T2 weighted image (a) shows presence of post traumatic vertebral artery dissection with double lumen (arrow). Subsequent CTA (b) confirms of the finding of vertebral artery injury. Follow-up angiography next day (c) shows presence of pseudo aneurysm formation (arrow). abc Vertebral artery injury

14. 45 year-old woman with MVC- Sagittal T2 weighted (a) and axial GRE image (b) shows presence of non hemorrhagic contusion in the spinal cord (arrows). ab Non-hemorrhagic cord contusion

15. 64 year-old woman with MVC- Sagittal T2 weighted (a) and axial GRE image (b) shows presence of hemorrhagic contusion in the spinal cord characterized by susceptibility artifact on GRE image (arrows). ab Hemorrhagic cord contusion

16. 46 year-old man following a fall from a height: Sagittal bone window CT image (a) did not show any fracture. But sagittal STIR MR image (b) shows bone marrow edema in the superior aspects of multiple vertebrae (arrow) suggesting bone contusions. ab Occult vertebral compression fractures

17. 67-year-old man with fall: Sagittal image shows prevertebral edema/hemorrhage (smaller arrow) and paraspinal muscle edema suggesting muscle injury (larger arrow). Soft tissue injuries

18. 70-year-old woman with fall and back pain: Sagittal bone window CT image (a) of spine shows age indeterminate compression fracture which showed bone marrow edema on sagittal STIR MR image (b) suggestive of acute injury. a b c d Acute vs chronic compression fractures 67-year-old woman with back pain: Sagittal bone window CT image of spine (c) from another patient also shows age indeterminate compression fracture without bone marrow edema on sagittal STIR MR image (d) suggestive of chronic injury.

19. Sagittal T1 weighted (a) and sagittal T2 weighted image (b) shows compression fracture with horizontal band of abnormal bone marrow edema in the superior half of vertebra without associated soft tissue mass suggesting benign compression fracture. cbda Benign vs malignant compression fractures Sagittal T1 weighted (c) and sagittal T2 weighted image (d) in a patient with multiple metastases shows compression fracture with diffuse involvement of vertebral body and associated epidural soft tissue mass. Note the presence of multiple other vertebral involvement.

20. Sagittal MRI image (a) in a patient with stable cervical spine injury involving interspinous ligaments suggesting single column injury. Sagittal MRI image (b) in a patient with unstable cervical spine injury with complete posterior longitudinal ligament tear (smaller arrow) and ligamentum nuche tear (larger arrow) suggesting two column involvement. ab Stable vs unstable spine injury

21. Pitfalls 1. 1.Susceptibility artifacts due to metallic hardware, especially in GRE sequences, which can be reduced by using – –The spin echo sequences with short TE – –Large receiver bandwidth, – –STIR rather than chemically selective fat suppression, and – –swapping the phase and frequency-encode directions. 2. 2.Saturation pulses used in MRI can sometimes mask the prevertebral hematoma. 3. 3.Lower sensitivity of MRI for detection of fractures of the posterior elements of the spine due to minimal edema associated with avulsion injuries.

22. Axial GRE image (a) shows marked susceptibility artifact due to dental implants which might obscure the prevertebral soft tissues. Sagittal T2 weighted image (b) shows the presence of fluid in the esophagus which may mimic the prevertebral edema. ab Susceptibility artifacts and fluid in the esophagus

23. Sagittal MR image of cervical spine (a) shows the presence of vessels in the interspinous space which are seen as well defined high signal (arrow) as compared to ill defined high signal intensity (arrow) in interspinous ligament injury in seen on sagittal MR image (b) in another patient. ab Veins in the interspinous space vs interspinous ligament injury

24. Conclusions In conclusion, MRI is more sensitive than other imaging modalities in the diagnosis of soft tissue and spinal cord injuries. MRI can help in guiding the surgical treatment by diagnosing stable vs unstable injuries due to its ability to diagnose ligamentous injuries when compared with CT. MRI is also helpful in predicting the prognosis by demonstrating the hemorrhagic and non hemorrhagic cord injuries. MRI also helps in differentiating acute from chronic, and benign from malignant compression fractures.