Cervical Spine Trauma and Spinal Cord Emergencies

Cervical Spine Trauma and Spinal Cord Emergencies
E. Megan Callan
Charles M. Andrews
THE CLINICAL CHALLENGE
The vast majority of spinal cord injuries occur from trauma, although other causes must be considered (Table 13.1). The mean age at the time of injury is 37 years and there is a bimodal age distribution, with the first peak between 16 and 30 years of age and the second peak older than 60 years.1 The ratio of males to females is approximately 4:1. In descending order of prevalence, the greatest causes for acute spinal trauma are motor vehicle accidents (˜40%), followed by falls (˜20%), violence, and sporting injuries. The level of spinal cord injury most often occurs in cervical spine (˜60%), thoracic (˜32%), and lumbosacral (˜9%). Injury to the spine in the setting of trauma can occur in isolation, or in polytrauma with other potential life-threatening injuries. Spinal immobilization is always an important consideration in these patients.
Spinal cord compression due to a structural abnormality is a neurosurgical emergency. Signs of injury must be recognized and urgent imaging obtained to direct treatment. About 20% of patients with a major spine injury have a second injury at a noncontiguous level; therefore, complete spine imaging with computed tomography (CT) or magnetic resonance imaging (MRI) is recommended.
PATHOPHYSIOLOGY
Trauma to the spine may involve damage to the bones, ligaments, vascular structures, and/or spinal cord. The discoligamentous complex includes the anterior longitudinal ligament, posterior longitudinal ligament, ligamentum flavum, facet capsule, and interspinous and supraspinous ligaments. The strongest component of the anterior structures is the anterior longitudinal ligament; the strongest component of the posterior structures is the facet capsule. The vertebral arteries travel through the transverse foramina of C2 to C6 and then converge to create the basilar artery.
Primary and Secondary Injury
Primary spinal cord injury encompasses the initial traumatic insult that occurs with its resulting disruption of neuronal axons. Secondary injury follows the primary insult, and can lead to ongoing progressive tissue damage for weeks after the initial injury. Secondary injury may occur because of inflammation, free radicals and oxidative stress, hypotension, hypoxia, ischemia, edema, or further mechanical disturbance of the spine. In blunt trauma, the extent of both primary and secondary injury to the cord may be directly related to the energy impact delivered at onset. A syrinx (fluid-filled cavity) may develop in some patients and lead to further neurologic deficits. Cystic cavities due to neuronal degeneration that occur ex vacuo and glial scarring from activated microglia and astrocytes can make it very difficult for damaged axons to regenerate. Even if neurites are able to regrow, oftentimes the myelin white matter surrounding them has been substantially damaged and oligodendrocyte remyelination attempts are often impaired.
Spinal shock refers to a transient loss of all neurologic function (motor, sensory, and autonomic pathways) below the level of initial spinal cord injury. Patients often have flaccid paralysis and areflexia, including loss of the bulbocavernosus reflex, from the level of the lesion down. In a select few patients, the spinal cord reflexes even above the level of injury might be depressed, known as the Schiff-Sherrington phenomenon. The duration of spinal shock most commonly dissipates within 72 hours of injury, but can persist in some patients up to 1 to 2 weeks.
Mechanism of Injury
Blunt injury is the most common mechanism for spinal trauma. Motor vehicle crashes and falls account for the majority of blunt trauma. With low-speed impacts, there may only be posterior neck muscle strain (ie, whiplash). Patients with preexisting spine disease (eg, due to degenerative spondylosis) or spine instability (eg, due to rheumatoid arthritis, Down syndrome) may develop more significant injury even at low speeds. Higher speed accidents have increased risk for spinal cord injury. Mobile parts of the spine (eg, cervical spine) and transition zones (eg, cervicothoracic and thoracolumbar) are at greatest risk for injury. Different mechanistic forces (ie, flexion, extension, distraction, compression) tend to be associated with specific injuries (Figure 13.1).
Penetrating traumatic spine injury is much less common than are blunt injuries, and can also be divided into low-impact (eg, knife stab) and high-impact (eg, gunshot wound) injuries. Lower impact penetration may lead to either incomplete or complete injury to the cord. High-impact penetrating spine injuries are often complete. An unstable vertebral column injury in gunshot wound patients with an intact spinal cord is very rare, and in these situations, immobilization typically offers little benefit. Gunshot wound injuries lead to damage not only by ballistic disruption of the cord but also because of blast injury forces.
The Subaxial Cervical Spine Injury Classification (SLIC) is a classification system for cervical spine injury; see Table 13.2.2 Scores of 1 to 3 are typically nonsurgical, whereas scores ≥5 are surgical. A score of 4 is indeterminate.
Anatomic Subclassifications and Injury
When thinking of spine injuries, there may be a predilection for specific anatomic regions, and therefore dividing the spine up into these regions can help with classification. The cervical spine can be subclassified into the occipital-cervical (O-C) junction and the subaxial cervical spine (Table 13.3). The cervical spinal cord is the most susceptible to injury because of its mobility, accounting for nearly half of all spinal injuries. The National Emergency X-Radiography Utilization Study Group (NEXUS) study evaluated 818 patients with cervical spine injuries, and, based on that data, the levels most commonly fractured are C2 (24%), C6 (20%), and C7 (19%).3
Occipital-Cervical Junction Injuries
Occipital condyle fractures typically arise from an axial loading type injury (Figures 13.2 and 13.3). There are three types of occipital condyle fractures: type 1—crush injury between the skull and C1 lateral mass; type 2 or Anderson Montesano—extension of a skull fracture to the condyle; and type 3—avulsion of the alar ligament pulling a fragment of bone from the condyle. These axial loading injuries are rarely unstable, except for type 3. Type 3 occipital condyle fractures often occur in the context of a severe distracting injury and should raise suspicion for atlanto-occipital dislocation.
Atlanto-occipital dislocation occurs with severe distracting injuries (significant flexion), and is most commonly due to high-speed motor vehicle collisions or car versus pedestrian accidents. This injury disrupts all the major stabilizers of the craniocervical junction: tectorial membrane, alar ligaments, apical ligament, transverse ligament, O-C1 joint, and often C1-C2 capsular ligaments. Atlanto-occipital dissociation is highly unstable, and oftentimes instantly fatal. Given the magnitude of force it takes for this dislocation to occur, there are often other associated injuries, for example, subarachnoid hemorrhage (SAH), epidural hematoma at the foramen magnum, and vertebral artery injury. Atlanto-occipital dislocation requires surgical stabilization with an O-C fusion.
C1 fractures include Jefferson fracture (or C1 burst fracture) and fractures to the C1 posterior arch. Jefferson fractures occur because of an axial loading-type injury, and there are generally two opposing fractures in the ring. About 33% of cases may have an associated C2 fracture as well. Often, there is a low incidence of neurologic injury because the C1 ring is so wide around the spinal canal. If the transverse ligament is disrupted (which may manifest as lateral displacement of the lateral masses on imaging), this is an unstable injury and surgical stabilization is indicated. Posterior C1 arch fractures occur because of extension injuries and are usually stable. However, an associated C2 fracture can occur in nearly 50% of cases, rendering this unstable.
C2 is one of the most common vertebrae fractured. There are four identified fracture types: C2 body fracture, lateral mass fracture, hangman’s fracture, and fractures of the dens (or odontoid process). Both C2 body fractures and lateral mass fractures are often benign, and may be treated simply with an external brace. The hangman’s fracture involves bilateral C2 pedicle and/or pars interarticularis fractures. This is the injury that is most classically described with judicial hangings, leading to a distraction and extension injury. However, this fracture type can often be seen with axial loading combined with flexion-type injuries. There is risk of disruption of the posterior longitudinal ligament with C2 subluxation, and C2-C3 disk rupture as well. The need for surgical stabilization may depend on the amount of angulation and displacement, but most of these fractures are unstable. There are three different fracture types of the dens. Type 1 is rare and consists of avulsion of the upper portion of the dens with an intact transverse ligament. It is often associated with a distraction-type injury. Because the ligament is intact, this injury is stable. Type 2 is the most common, and is a fracture of the dens at its base. About 10% of these patients may have rupture of the transverse ligament, which renders this injury unstable. Ligamentous injury will be seen best on MRI. Younger patients who have less displacement may be able to heal with a brace or halo; however, elderly individuals do not tolerate external bracing as well. Surgical stabilization consists typically of posterior C1-C2 fusion, but a small percentage may be amenable to stabilization anteriorly with an odontoid screw. A type 3 fracture of the dens involves extension into the C1-C2 joints bilaterally. The greater the surface area of the fractured bones, the more likely the injury is to heal with an external brace. Type 3 fractures are more stable.
Subaxial Cervical Spine Fractures (C3-T1)
Fractures that occur with mild, pure axial loading-type injuries are typically due to compression. When the axial load is more significant, burst fractures, retropulsion of bone, and traumatic disk herniation with spinal cord compression may all occur (Figure 13.4). If the axial load is given in combination with either a flexion and/or rotational force, there may be disruption in the posterior ligamentous complex (including interspinous, interlaminar, joint capsules, and disk capsules) and facet fractures. This may lead to subluxation of the spine and possible spinal cord injury. The classic “diving injury” consists of an axial load with hyperflexion of the neck, leading to bilateral facet joint dislocation and spinal cord injury.
The stability of these fractures in the subaxial spine depends on the degree of displacement and angulation, and whether there is associated ligamentous-disk complex injury. The following fractures are typically considered stable: articular mass fracture, burst fracture, wedge fracture, spinous process fracture, unilateral facet fracture, and transverse process fracture.
PREHOSPITAL CONCERNS
The patient with a spine injury may have injuries at multiple levels. Between 25% and 50% of patients with a spinal cord injury have also sustained a head injury, whereas spinal cord injury is seen in 10% to 30% of polytrauma patients.4 The goal of prehospital management is to minimize secondary injury. After ensuring oxygenation and perfusion, a secondary evaluation includes enquiry about pain in the neck or back, tenderness to palpation, weakness or altered sensation, signs of incontinence, and other signs of injury. Given the mechanism of injury, prehospital providers are often tasked with removing patients from harmful situations before further evaluation and transport. Care must be taken to restrict motion of the patient’s spine as much as possible during patient movement and transport. It is recommended to place the patient in a rigid cervical collar with the head stabilized in a forward-facing position. A spine log roll may be used to keep the patient in a spine-neutral position to be placed on a rigid backboard with straps. These immobilization techniques have side effects of their own, including discomfort, pressure sores, restriction of respiration, and difficulty with maintaining airway protection; see section “Evidence.” In brief, there is only evidence to use restricted spine motion with a rigid backboard or similar device in a subset of patients: blunt trauma with altered level of consciousness, spinal pain or tenderness, neurologic disability (weakness or numbness), anatomic deformity of the spine, high-energy mechanism with either intoxication, inability to communicate, or other distracting injury.
Patients with high cervical spine injuries may have diaphragmatic weakness or respiratory accessory muscle weakness leading to respiratory failure and death. If bag mask ventilation is ineffective, an advanced airway intervention is indicated. Concomitant facial fractures or thoracic injuries (such as pneumothorax or aspiration) may confound the clinical picture. Trained emergency medical services personnel may use an advanced airway with in-line immobilization of the cervical spine. Hypotension may occur either due to hypovolemic/hemorrhagic shock or autonomic dysfunction (neurogenic shock). Crystalloid or colloid intravenous (IV) fluid volume resuscitation with at least two large-bore IVs can help maintain blood pressure until arrival at the hospital. The desired mean arterial pressure (MAP) is 90 mm Hg, and episodes of hypotension with systolic blood pressure below 90 mm Hg should be avoided because this can exacerbate neurologic injury.
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Jun 23, 2022 | Posted by in EMERGENCY MEDICINE | Comments Off on Cervical Spine Trauma and Spinal Cord Emergencies

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