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Title: Spinal Trauma Authors: Sundgren PC, Philipp M, Maly PV Journal: Neuroimaging Clinics of North America Key Points • Injuries to the spinal column and spinal cord are a major cause of disability, affecting predominantly young, healthy individuals with almost half of spinal injuries result in neurologic deficits which can be severe or even fatal with reported mortality rates during hospital reported to be almost 10%.(Pope 1991; Hills and Deane 1993) • Careful evaluation and selection of appropriate imaging modalities is key to the initial diagnosis and management of these patients. Clinical Conclusions Multislice CT (MSCT) and MR imaging are the modalities of choice for the evaluation of bony spine injury (CT) and soft tissue injury including the ligamentous structures and the spinal cord itself (MRI). Section Highlights Introduction • The main cause for spinal injuries is blunt trauma, most commonly by motor vehicle accidents (48%), followed by falls (21%) and sports injuries (14.6%) although penetrating trauma accounts for an additional 10-20%. • Injury to the spinal cord occurs in 10-14% of spinal fractures and dislocations(Riggins and Kraus 1977) with cervical spine injuries accounting for 40% of cases. (Castellano and Bocconi 1970) • 85% of spinal cord injuries occur at the time of the initial trauma while 5-10% occur in the immediate post-injury period.(Rogers 1957) Imaging Modalities • Plain film radiography is useful when MSCT is unavailable but has an overall sensitivity of 39-94% and variable specificity in the overall diagnosis of spinal injuries; delay in diagnosis can occur in 5-23% of cases when radiology is used as the initial screening modality. • Today MSCT (or single slice helical CT) is the initial imaging modality of choice for bony injury of the cervical spine after blunt trauma as it allow whole spine examination in a very short time with fast reformatting of images in multiples planes. • Axial CT only is not useful due to its limitations in diagnosing such things as subluxation and dislocation (detection of these abnormalties in only 54% of cases using axial CT in one study).(Woodring and Lee 1992) • MR imaging is the modality of choice for assessing soft tissue injuries, spinal cord injury, intervertebral discs and ligaments, and vascular injuries. o MR imaging is the only method to differentiate between spinal cord hemorrhage and edema which may change treatment (Figure 1) and allows for better differentiation between acute and chronic compression fractures and bone marrow abnormalities and improved visualization of post-traumatic sequelae (syrinx, myelomalacia, cord atrophy or tethering). o MR should be used with caution in assaulted patients and those with penetrating trauma as retained metal fragments close to the spinal canal may move and cause additional spinal cord trauma.(Teitelbaum, Yee et al. 1990; Smith, Hurst et al. 1991) Criteria for Imaging and Choice of Imaging Modality • The National Emergency X-Radiology Utilization Study (NEXUS) established five criteria to classify patients having low probability of injury (no midline tenderness, no focal neurologic deficit, normal alertness, no intoxication, absence of painful distracting injury). • Another, perhaps more sensitive method is the Canadian C-spine rule which divides patients into high or low risk categories. o High risk factors include age >65 years, dangerous mechanism, or paresthesias in the extremities o Low risk factors include simple rear-end motor vehicle collision, sitting position in the emergency department, ambulation since the trauma, delayed onset of neck pain, absence of midline tenderness. • CT or MR imaging is recommended to exclude suspected soft tissue injury or fractures of the craniocervical junction (C1 or C2). Types of Injuries • Cervical spine injuries o Cervical spine injuries are twice as likely in patients older than 70 and odontoid fractures are the most common, accounting for 20% of all fractures. o Hyperflexion injuries include anterior subluxation (stable), bilateral interfacetal dislocation (unstable), simple wedge fracture (stable), clay-shoveler’s fracture (stable), teardrop fracture (unstable), an odontoid fracture (stable or unstable). Figures 2-4 o Hyperextension injuries are less frequent, are usually secondary to direct impact on the front of the head or sudden deceleration, and are often associated with central cord syndrome. o Hyperextension injury can result in dislocation, avulsion fracture or fracture of the posterior arch of C1, teardrop fracture of C2, laminar fracture, or the Hangman’s fracture (unstable while the rest are generally stable). o The Jefferson fracture involves the atlas, is caused by vertical compression, and is considered unstable (Figure 5) while burst fractures are also caused by vertical compression, may be stable or unstable, and are associated with cord injury in up to 50% of cases. (Figure 6) • Thoracic and lumbar spine injuries o The most common fracture, accounting for 50% of all fractures is the simple compression or wedge fracture which is stable if angulation is <40 degrees; the remaining types of fractures are unstable. o The most common flexion-distraction injury is the so-called “seat belt injury” which includes the type I (Chance fracture) involving the posterior elements, type II (Smith fracture) involving the posterior ligaments, and type III involving a ruptured annulus fibrosis allowing for subluxation.(Rogers 1971) o Burst fractures account for 64-81% of fractures in this area and are associated with a high incidence of neurologic injury. (Gertzbein 1992) They are recognized by a combination of wedge compression of the anterior column and fractures of the posterior cortex with retropulsion of fracture fragments into the spinal canal. Figure 7 Trauma to the Spinal Cord and Spinal Content • Acute spinal cord injury occurs in an estimated 2.6% of blunt trauma patients. (Burney, Maio et al. 1993) o Spinal cord injury usually begins with direct compression of neural elements by fracture fragments, disc material, ligament injury, associated epidural hematoma, or penetrating trauma. o The spinal cord swells within minutes with secondary ischemia developing as the cord swelling exceeds venous pressure; the result is spinal shock as the disrupted neural membrane releases toxic chemicals. (McDonald and Sadowsky 2002) o Complete spinal cord transection is often caused by fracture with dislocation of the vertebral bodies but can also be secondary to penetrating trauma; Figure 8 o Incomplete spinal cord injuries can be further categorized as anterior cord syndrome, Brown-Sequard syndrome, central cord syndrome, conus medullaris syndrome, cauda equina syndrome, and spinal cord contusions; of these anterior cord syndrome has the worse prognosis with only 10-15% of patients demonstrating functional recovery. • Traumatic disc herniation is commonly caused by distraction and shearing in sudden extension but can also occur in flexion injuries; they are seen in 54-80% of facet dislocations. (Yue, Lawrence et al. 2004) Figure 9 • Ligamentous injury can be detected on plain film or CT in some cases but MRI is the modality of choice for evaluating ligamentous injury of the spine although the sensitivity of detecting these injuries can be relatively low, around 55-65%.(Weisskopf, Bail et al. 1999; Diaz, Aulino et al. 2005) o Disruption of the anterior longitudinal ligament is seen in hyperextension injuries while posterior longitudinal ligament injuries are caused by distraction and flexion forces. Figure 10 Trauma to the Pediatric Spine • Injuries to the spinal and spinal cord are relatively infrequent in the pediatric population and when they do occur they involve the cervical spine 40-60% of the time. • Spinal cord injury in children often occurs without evidence of fracture or dislocation due to the inherent elasticity of the pediatric vertebral column.(Pang and Wilberger 1982) Late Posttraumatic Changes in the Spinal Cord • Spinal cord atrophy and myelomalacia are the most common late findings after spinal cord injury (62% and 54%, respectively), followed by syrinx (22%), spinal cord cysts (9%), and transection of the cord (7%).(Imhof and Fuchsjager 2002) Summary • Injuries to the spine and spinal cord affect young, healthy individuals and are a major cause of disability with significant socioeconomic consequences. • MSCT is the imaging modality of choice for initial evaluation of these trauma patients. • MR is recommended to evaluate soft tissue structures including the spinal cord itself. 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