Todd Ellingson
EPIDEMIOLOGY
The incidence of spinal cord injuries (SCIs) has been estimated at 40 cases per million population at risk. The mean age is 40 years with a male-to-female predominance of 4 to 1.
Forty-two percent of SCIs are related to motor vehicle crashes, 27% to falls, and 15% to acts of violence.
PATHOPHYSIOLOGY
Three main vertebral columns provide stability to the spine.
The anterior column is made up of the anterior wall of the vertebral body, the anterior annulus, and the anterior longitudinal ligament.
The middle column consists of the posterior wall of the vertebral body, the posterior annulus fibrosus, and the posterior longitudinal ligament.
The posterior column includes the bony complex of the posterior vertebral arch and the posterior ligamentous complex.
For a vertebral injury to be considered unstable, disruption of two or more of these columns must be present.
While >25% compression from the third to seventh cervical vertebrae is considered unstable, the same status for the thoracic and lumbar vertebrae occurs with >50% compression.
Damage to the spinal cord results in two phases of injury. Initially, a direct mechanical injury may result in hemorrhage, edema, and ischemia. Within hours, a secondary tissue degeneration phase begins with release of membrane-destabilizing enzymes and inflammatory mediators, which induces lipid peroxi-dation and hydrolysis.
There are three main spinal cord tracts. The corti-cospinal tract fibers decussate in the lower medulla and descend through the lateral aspect of the spinal cord. Damage to the corticospinal tract (upper motor neurons) results in ipsilateral muscle weakness, spas-ticity, increased deep tendon reflexes, and Babinski’s sign.
The spinothalamic tracts transmit pain and temperature sensation and decussate shortly after entering the vertebral column. Injury to the spinothalamic tract causes contralateral loss of pain and temperature sensation.
The dorsal (or posterior) columns transmit vibration and proprioception sensation. The neurons in this tract do not synapse until they reach the medulla, where they then decussate. Injury to a dorsal column will cause ipsilateral loss of vibration and proprioception sensation.
Light touch is transmitted through both the spinotha-lamic and dorsal tracts. Light touch is not lost unless there is damage to both of these tracts.
CLINICAL FEATURES
Not all patients with SCI have neurologic deficits on initial presentation. Many unstable spinal fractures may present without spinal cord or nerve root trauma.
Symptomatic patients may complain of paresthesias, dysesthesias, weakness, or other sensory disturbances with or without specific physical examination findings. More severely injured patients may have an obvious neurologic deficit on physical examination.
Spinal cord injuries or lesions are considered incomplete if sensory, motor, or both are partially present below the neurologic level of injury. Complete lesions include total absence of both below the injury.
Incomplete lesions have some level of recovery, while complete lesions have minimal chance of recovery.
Spinal shock is the temporary loss or depression of spinal reflex activity below a complete or incomplete injury. It may cause incomplete injuries to appear complete and may persist for days to weeks.
Patients may present with neurogenic shock, in which hypotension and relative bradycardia are commonly seen due to loss of sympathetic tone.
Hypovolemic shock must be considered the cause of the hypotension until proven otherwise. Patients with neurogenic shock generally have pink, warm extremities, and adequate urine output.
DIAGNOSIS AND DIFFERENTIAL
The mechanism of injury is helpful in predicting the potential type of cervical injury along with its subsequent stability (Table 163-1).
TABLE 163-1 Cervical Spine Injuries
Any neurologic complaints, even if transitory, must raise suspicion for an SCI. Palpation of the entire spine will identify any potential areas of injury.
A complete neurologic examination should include motor strength and tone (corticospinal tract), pain and temperature sensation (spinothalamic tract), proprioception and vibration sensation (dorsal columns), and reflexes. Each sensory dermatome should be evaluated (Fig. 163-1).
FIG. 163-1. Dermatomes for sensory examination.
Incomplete injuries or lesions of the spinal cord with different involvment of these tracts result in various spinal cord syndromes (Table 163-2).
TABLE 163-2 Incomplete Spinal Cord Syndromes
Preserved anogenital reflexes, such as bulbocaverno-sius reflex, the cremaster reflex, and contraction of anal musculature (“anal wink”), denote an incomplete spinal cord lesion.
NEXUS criteria and Canadian Cervical Spine Rule for Radiograpy both seek to identify “low-risk” patients not requiring cervical spine imaging (Table 163-3 and Table 163-4).
TABLE 163-3 National Emergency X-Radiography Utilization Study Criteria: Cervical Spine Imaging Unnecessary in Patients Meeting These Five Criteria
Absence of midline cervical tenderness
Normal level of alertness and consciousness
No evidence of intoxication
Absence of focal neurologic deficit
Absence of painful distracting injury
TABLE 163-4 Canadian Cervical Spine Rule for Radiography: Cervical Spine Imaging Unnecessary in Patients Meeting These Three Criteria
CT is more sensitive and specific than plain radiography for cervical spine trauma and has become the current trend in most trauma centers for initial imaging.
For the cervical spine plain radiography, a minimum of three views (lateral, odontoid, and anteroposterior) are necessary.
Since occult fractures and ligamentous injuries may be missed on plain radiographs, clinical clearance of the cervical spine must be performed after a negative cervical spine series on alert and oriented patients without distracting injuries.
Flexion and extension views may reveal ligamentous injury in a patient who cannot be clinically cleared. A step-off of 3.7 mm or an angulation of greater than 11 degrees indicates cervical instability. Patients with persistent pain, including those with normal flexion/extension radiographs, can then be placed in a hard collar to follow up with a spine specialist in 3 to 5 days.
Ten percent of patients with spine fracture in one segment will have a second fracture in another. Therefore, determination of spinal column injury at one level mandates radiographic evaluation of the entire spine.
The mechanism, physical examination, and associated injuries help to identify patients needing imaging of the thoracic and lumbar spine after trauma (Table 163-5).
TABLE 163-5 Indications for Thoracic and Lumbar Imaging after Trauma
As with the cervical spine, CT has become more important for the thoracic and lumbar spine imaging at most trauma centers due to increased sensitivity and specificity.
Thoracic and lumbar vertebral fractures can be divided into minor and major injuries (Table 163-6).
TABLE 163-6 Thoracic and Lumbar Spine Fractures
Magnetic resonance imaging (MRI) offers better determination of neurologic, ligamentous, muscular, and soft tissue anatomy and injury. MRI is indicated in patients with neurologic findings or persistent pain without a clear explanation following radiographs and/or CT.
Spinal cord injury without radiographic abnormality (SCIWORA) is an entity that is most commonly seen in the pediatric population.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Airway assessment and management with in-line cervical immobilization is the first and most pressing priority in the ED.
For patients with cervical spine injury (especially for injuries of C5 and above) a low threshold for endotra-cheal intubation should be maintained. Diaphragmatic weakness or paralysis can lead to hypoventilation or hypoxemia.
Place the patient on high-flow oxygen and establish two large-bore IVs.
Fluid resuscitation facilitates spinal cord resuscitation; control obvious bleeding and rapidly assess other life-threatening injuries.
While maintaining in-line spinal immobilization that prevents secondary injury to the spine and preserves residual spinal cord function, logroll the patient to identify any obvious fractures or associated injuries.
Remove the patient off of a hard backboard in order to prevent skin breakdown and pressure sores. Standard hospital mattresses provide adequate spinal support.
Treat neurogenic shock with oxygen, IV fluids, and positive inotropic pressors as necessary.
The use of methyl lprednisolone remains an option for blunt spinal cord trauma with neurologic deficits; however, the current evidence suggesting harmful side effects of the medication may outweigh potential benefit. Consultation with a spinal surgeon prior to administration is recommended. Indications for use and administration guidelines can be found in Table 163-7.
TABLE 163-7 The National Acute Spinal Cord Injury Study Protocol
Methylprednisolone therapy has not been proven to be beneficial in penetrating spinal cord injury.
Patients with penetrating spinal injuries should receive empiric antibiotics in the ED.
Patients with progressive neurologic deterioration require operative intervention. Most injuries that do not progress are treated nonoperatively.
Admit any patient with a significant injury to the spine or spinal cord to the hospital.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 255, “Spine and Spinal Cord Trauma,” by Bonny J. Baron, Kevin J. McSherry, James L. Larson, Jr., and Thomas M. Scalea.