Initial Assessment (Including Imaging) of Cervical Spinal Cord Injury

h1 class=”calibre8″>4 Initial Assessment (Including Imaging) of Cervical Spinal Cord Injury

Justin Iorio and Todd J. Albert

Abstract

The initial management of cervical spinal cord injuries includes following the ABCDEs: evaluation of airway, breathing, and circulation, followed by an assessment for disability/neurological deficits, and exposure of the patient. Immobilization should be performed in all patients with a spinal injury to prevent further neurological injury. A neurological examination as outlined by the American Spinal Injury Association (ASIA) must be performed. ASIA requires a detailed examination of 28 dermatomes (C2–S5) and 10 myotomes (C5–T1 and L2–S1) on each side of the body. An examination of upper extremity, lower extremity, and bulbocavernosus reflexes must be performed. Imaging of the spinal column is done to identify the location(s) of injury, fracture morphology, presence of dislocation, spinal instability, soft-tissue abnormalities, epidural hematoma, and neurological injury. Computed tomography (CT) and magnetic resonance imaging (MRI) are the most commonly utilized imaging modalities. Radiography, although less sensitive and specific than advanced techniques, has traditionally been used as the initial imaging in the awake patient. However, radiography is not necessary if CT imaging is available. In addition, a newer MRI technique known as diffusion tensor imaging has demonstrated improved ability to characterize spinal cord injury by providing detailed information about white matter tracts, which are responsible for the functional deficits following spinal cord injury. Early recognition of cervical spine injuries by thorough history, examination, and imaging may prevent neurological decline, improve outcomes, and mitigate the risk of delayed diagnosis and treatment.

Keywords: trauma, examination, assessment, cervical spine, fracture, spinal cord injury, imaging, MRI, CT

4.1 Introduction

Approximately 150,000 cervical spine injuries and 12,000 spinal cord injuries (SCIs) occur each year in the United States. Nearly half to three-fourths of SCIs are due to cervical spine trauma, ¹ with incomplete quadriplegia being the most common diagnosis. ²^,³ The majority of cervical injuries are sustained in the subaxial region with about 65% of fractures and more than 75% of dislocations occurring below C2. ⁴ Fractures and dislocations at the occipitocervical junction (OCJ) are more likely to result in death than subaxial trauma. Early recognition of cervical spine injuries by thorough history-taking, examination, and imaging may prevent neurological decline, improve outcomes, and mitigate the risk of delayed diagnosis and treatment, which occurs in nearly 33% of cervical spine patients. ⁵^,⁶

4.2 Initial Assessment

A systematic evaluation is performed on all trauma patients. The initial management is guided by the protocol set forth by The American College of Surgeons Advanced Trauma Life Support. The primary survey follows the ABCDEs: evaluation of airway, breathing, and circulation, followed by an assessment for disability/neurological deficits, and exposure of the patient. Spinal immobilization is applied in the field and strict adherence to spinal precautions (immobilization and log rolling) is required until mechanical spinal stability can be assured by clinical and radiographic evaluation. Immobilization should be performed in all patients with a spinal injury, or if a patient sustains an injury which has the potential to result in SCI. However, immobilization is not required for penetrating cervical trauma because of the risk of mortality from delayed resuscitation, ⁷ relatively low incidence of spinal instability, and high risk of airway compromise. ⁸ In unique situations, preexisting conditions, such as ankylosing spondylitis, will affect the position of the spine during immobilization. In such conditions, extension of the cervical spine can cause neurological deficits because it produces an opening wedge osteotomy in a normally kyphotic cervicothoracic spine. ⁹ Maintaining the normal cervicothoracic kyphosis is recommended during immobilization and imaging which can be done with the use of pillows or other supports.

A thorough history should be obtained from the patient, if possible, or from family members or witnesses to the injury. A detailed history involving medical comorbidities, prior surgeries, description of the injury, time of occurrence, presence and location of pain, severity and description of pain, neurological symptoms in the trunk and extremities (both transient or sustained), and prior spinal pathology is relevant to the management of the patient. A determination of underlying cardiopulmonary comorbidities including chronic obstructive pulmonary disease and heart disease is crucial, especially in the setting of chest wall or lung injury. Respiratory compromise may indicate the level of SCI. However, if family members or witnesses are not available to supplement the history of an unconscious patient, then the evaluation relies primarily on physical examination and imaging studies.

The physical examination begins with a visual inspection of the spine for malalignment, swelling, bruising, lacerations, and other lesions. Palpation of the spine from the skull to sacrum is performed for identifying tenderness, step-offs, gapped spinous processes, and other significant findings. Pain at the affected area is the most common presenting symptom after cervical trauma. ¹⁰ The International Spinal Cord Injury Pain Basic Data Set (ISCIPBDS) is a reliable and valid measure of SCI-related pain and should be used in conjunction with the ASIA scoring system. ¹¹^,¹² The ISCIPBDS contains several domains for assessing pain related to the musculoskeletal and visceral systems, at and below the level of cord injury, and pain unrelated to SCI or without any identifiable etiology. An examination for other nonspinal musculoskeletal and nonorthopedic injuries is routinely completed as part of a thorough clinical analysis.

A neurological examination as outlined by the ASIA must be performed. The ASIA impairment scale is a standardized assessment for SCI patients to determine the neurological level. ASIA requires a detailed examination of 28 dermatomes (C2–S5) and 10 myotomes (C5–T1 and L2–S1) on each side of the body. Identifying a nerve root injury versus SCI can be difficult. Generally, multiple myotomal involvement suggests an SCI whereas unilateral, single myotome weakness represents a nerve root injury. However, high-energy injuries with unilateral, multiple myotomal involvement can result from brachial plexopathy. The sensory examination includes evaluation of light touch and pin prick and is categorized as absent (0), impaired (1), or normal (2). Myotomes in the extremities are graded as total paralysis (0), palpable or visible contractions (1), movement with gravity eliminated (2), movement against gravity only (3), movement against gravity with some resistance (4), and normal strength (5). The assessment of sacral sensation at the perianal area and deep sensation with digital rectal examination is a critical aspect of the physical examination because of its prognostic significance. Sacral sparing, which is the retention of sacral sensation, in the setting of absent motor indicates an incomplete injury.

Patients should also be evaluated for disproportionate weakness of the extremities because central cord syndrome is the most common SCI. ¹³ Hyperextension injuries have been traditionally associated with central cord syndrome, but fracture-dislocations and acute disc herniations can also result in upper extremity weakness with relative sparing of the bilateral lower extremities. Sensory loss and bladder dysfunction are variable after traumatic central cord syndrome. However, if the patient develops progressive neurological deficits after a stable interval, then an epidural hematoma must be ruled out with an MRI. Signs of an epidural hematoma include progression of ascending weakness and weakness within hours of an injury. ¹⁴ Other spinal cord syndromes include: Brown-Séquard, anterior spinal cord, posterior spinal cord, conus medullaris, and cauda equina syndromes.

An examination of upper extremity, lower extremity, and bulbocavernosus reflexes is critical. Initial flaccid paralysis, complete loss of sensation, and absent reflexes after a traumatic injury is referred to as spinal shock. In the absence of spinal shock, reflexes in the extremities are useful for differentiating a nerve root injury from a cord injury. Motor weakness in the presence of reflexes is common in SCI whereas weakness and areflexia is indicative of nerve root lesion. Altered reflexes occur in approximately 20% of injuries to the proximal cervical spine. ¹⁰ A critical reflex is the bulbocavernosus reflex because it is useful for the determination of spinal cord shock. The maneuver is performed by pinching the glans penis (clitoris in females) or tugging the Foley catheter and monitoring for involuntary contraction of the anal sphincter. An absent response indicates spinal shock. In contrast, contraction of the anal sphincter indicates the end of spinal shock. If the bulbocavernosus reflex does not return after 72 hours, the patient is presumed to be out of spinal shock. Clinical examination at the end of spinal shock is pertinent to the determination of incomplete versus complete SCI: presence of the bulbocavernosus reflex in the setting of complete motor and sensory loss indicates a complete SCI and poor prognosis for neurological recovery.

Cranial nerve function may provide additional information regarding the level of injury. The incidence of cranial nerve dysfunction is low after occipitocervical trauma (3.6%) ¹⁰ but aids in the localization of the lesion during clinical assessment. Occipital condyle fractures, for instance, may result in hypoglossal nerve dysfunction because the hypoglossal canal is positioned medially and superiorly to the condyles. Occipitocervical fractures can cause injury to the brainstem in which the nuclei of cranial nerves three to eight are located. Injury to the medulla can produce dysfunction of cranial nerves nine through twelve.

An evaluation for a source of hemorrhagic shock is warranted because both hemorrhagic and neurogenic shock may be present. Neurogenic shock occurs in patients who have sustained SCI to the cervical or upper thoracic region (above T6). Autonomic dysfunction inhibits the normal physiologic responses to blood loss: tachycardia and peripheral vasoconstriction. Patients with cervical SCI have lower baseline heart rates, systolic blood pressures, and mean arterial pressures while supine compared to patients without cervical SCI; blood pressure and mean arterial pressure may not increase during upright posture as expected. ¹⁵ The lack of sympathetic response to hypotension does not correlate with the severity of cervical SCI (i.e., incomplete vs. complete).

Vertebral artery injuries (VAIs) may occur during cervical trauma. Many VAIs are clinically silent, but symptomatic injuries have a wide range of manifestations. Patients may present with vertebrobasilar insufficiency (dizziness, ataxia, and vision changes), dysphagia, facial numbness, vertigo, Horner syndrome, or signs of anterior spinal cord ischemia (complete motor paralysis, loss of pain and temperature, autonomic dysfunction, areflexia, urinary retention, and retained proprioception and vibratory sensation). The screening protocol for VAI is controversial with some authors recommending an investigation in all cervical trauma patients, ¹⁶^,¹⁷ and others recommending screening for patients with high-risk injuries. Guidelines by Biffl et al ¹⁸ proposed screening for VAIs in the setting of midface fractures, basilar skull fractures, cervical hematomas, neurological changes, Glasgow coma scale scores of less than 6 or 8, facet subluxations, cervical fractures between C1 and C3, fractures through the foramen transversarium, vertebral body fractures, or fractures causing ligamentous injury. ¹⁹ Members of the Cervical Spine Research Society (CSRS) have advocated for screening in patients with cervical injuries who have neurological symptoms reflective of a vascular etiology. ²⁰ A significant, positive correlation between the incidence of VAI and ASIA grade has been reported. ²¹ In a study of 632 cervical fracture patients with or without SCI, 59% of vertebral artery thrombosis patients had an SCI. The incidence of VAI was significantly different between motor complete (20%) and neurologically intact patients (11%), but not between motor-incomplete (10%) and intact patients. ²¹

4.3 Imaging

Imaging of the spinal column after a suspected injury is performed to identify the location(s) of injury, fracture morphology, presence of dislocation, spinal instability, soft tissue abnormalities, epidural hematoma, and neurological injury. Computed tomography (CT) and magnetic resonance imaging (MRI) are the two most commonly utilized imaging modalities. Radiography, although less sensitive and specific than the advanced techniques, has traditionally been used for initial imaging in awake patients. Radiographic assessment of symptomatic patients includes X-rays supplemented with CT to better define areas that are not easily visualized, such as the occipitocervical and cervicothoracic junctions. However, plain radiographs are not currently required in the awake, symptomatic patient if CT imaging is available. If CT imaging is not readily available, a 3-view radiographic series should be performed and supplemented with CT imaging when available. Obtunded patients should similarly undergo CT imaging of the cervical spine; radiographs are not necessary in this situation. In addition, a newer MRI technique known as diffusion tensor imaging (DTI) has demonstrated an improved ability to characterize SCI.

4.3.1 Radiography

The standard radiographs for the initial evaluation of cervical trauma are the anteroposterior, lateral, and open-mouth odontoid views. Dynamic views have been advocated in the awake, cooperative, symptomatic patient with normal static X-rays to exclude discoligamentous injuries. ²² However, dynamic views in the setting of fractures or dislocations are not recommended and may place the obtunded patient at risk of neurological injury. The occipitocervical and subaxial spine is assessed for occipitocervical injury, atlantoaxial fractures and instability, facet dislocations, vertebral body fractures, listhesis, and posttraumatic kyphosis, among other injuries. Injury to the OCJ is often fatal at the time of injury. Radiographs can be used to identify atlanto-occipital dissociation; however, the sensitivity for identifying pathology is poor. ²³

Visualization of the midcervical region is superior to the upper and lower segments because parallax and mastoid air cells affect the identification of anatomy in the upper cervical region and the shoulder girdle obscures the lower cervical spine. ²⁴ Important information about the vertebral bodies, pedicles, facets, canal diameter, and spinous processes can be gathered from lateral radiography. Vertebral bodies should be analyzed for radiolucencies indicating fracture lines, height loss, subluxation, facet pathology, and angulation. Distraction of spinous processes on lateral radiographs indicates a hyperflexion mechanism. Soft-tissue injury anterior to the cervical spine is represented by prevertebral soft-tissue swelling, which is measured between the anterior surface of the vertebral bodies and the air shadow of the airway. Various limits of normal have been reported from approximately 3 to 10 mm between C2 and C4. ²⁵^,²⁶

Anteroposterior views of vertebral bodies are similarly inspected for radiolucencies, height loss, interpedicular widening, and lateral listhesis. In addition to traumatic injuries, underlying degenerative changes and congenital stenosis of the cervical spine are important to recognize because of their contribution to cord injuries, such as central cord syndrome. ²⁷ Approximately 50% of patients with traumatic central cord syndrome do not sustain fractures or dislocations. ²⁷ Severe congenital stenosis is a risk factor for SCI. ²⁸ In a study of 52 patients who sustained acute SCI, a disc-level canal diameter of ≤ 8 mm was the greatest risk factor for SCI after minor cervical trauma. ²⁹

However, radiographs are not required for the evaluation of SCI. Instead, CT imaging should be used as the initial screening method supplemented with MRI. Compared to advanced techniques, X-rays have not been found to identify additional fractures ³⁰ due to their lower sensitivity and specificity. ³¹^,³²^,³³^,³⁴ Plain radiography has a sensitivity of 60% for detecting cervical spine fractures in a patient with blunt trauma, ³⁵ and is insufficient for the screening of spine trauma patients. ³⁶^,³⁷^,³⁸

4.3.2 Computed Tomography

CT is the imaging modality of choice for evaluating bony anatomy. CT is accurate, efficient, and cost effective. Cervical CT imaging provides optimal evaluation of fracture location (i.e., vertebral body, pedicle, pars interarticularis, facet, lamina, and/or spinous process), injury morphology, vertebral translation, angulation, bony canal compromise, and facet dislocation (▶ Fig. 4.1). In addition, soft-tissue pathology and presence of a hematoma can be evaluated with the use of soft-tissue windows. Multidetector CT imaging permits the simultaneous acquisition of multiple sections of the spine and increases the speed of the study compared to conventional CT imaging. The advantages of CT imaging are, therefore, the rapid procurement of information and the ability to characterize bony injuries to a greater extent than plain radiography. ³⁹ A Level II study of cervical trauma patients found that CT had a sensitivity of 100% for identifying bony and ligamentous injuries. ⁴⁰

$Computed tomography (CT) of penetrating trauma to the cervicothoracic junction. The morphology of the fractured lamina and left pedicle is well visualized, as well as protrusion of bony fragments into$

Fig. 4.1 Computed tomography (CT) of penetrating trauma to the cervicothoracic junction. The morphology of the fractured lamina and left pedicle is well visualized, as well as protrusion of bony fragments into the spinal canal.

An assessment of the entire cervical spine from the occipitocervical to the cervicothoracic junction must be performed after cervical spine trauma. Visualization of the OCJ is important because of the high incidence of upper cervical injuries in cervical trauma patients. In a study of 34,069 trauma patients, 2.4% sustained cervical spine injuries and 34% of these injuries occurred at the OCJ; the axis was the most commonly fractured cervical vertebra. ⁴¹ Injuries to the upper cervical spine that can be identified by CT imaging include atlanto-occipital dissociations, occipital condyle fractures, atlas and axis fractures, traumatic spondylolisthesis of the axis, and combinations of these injury patterns. The condyle–C1 interval has the highest sensitivity and specificity for atlanto-occipital dissociation among all measurement parameters. ⁷ Fracture, translation, and angulation of the C2 pars interarticularis is visualized in the coronal and sagittal planes. Atypical hangman’s fractures involve the posterior vertebral body, either unilaterally or bilaterally, rather than the neural arch. Spinal cord compression against the posterior cortex of C2 and a high rate of neurological injury ⁴² occurs after these atypical fractures. Disc space widening and signal hyperintensity can often be seen on supplemental MRI. It is important to note that OCJ parameters (basion–dens interval, atlantodental interval, and atlanto-occipital interval) on CT imaging differ significantly from those measured on radiographs. ⁴³

Subaxial injuries are well-visualized by CT imaging. Fracture patterns are evaluated with sagittal and axial imaging to characterize the amount of retropulsion, translation, angulation, and canal compromise (▶ Fig. 4.2). Coronal imaging is useful for identifying horizontal fracture lines. Burst fractures with retropulsion may cause spinal cord or nerve root injury. In flexion–distraction injury patterns, axial CT imaging reveals a gradual loss of definition of the pedicles secondary to horizontal fracture lines. ⁴⁴ Translation or rotation of one vertebral body on another occurs with facet dislocation or fracture. Uncovering of facets on axial imaging is the result of vertical distraction (▶ Fig. 4.3). Fractures of the pars interarticularis can cause instability and SCI. Widening of the spinous processes is indicative of posterior element disruption.

$Sagittal (left) and axial (right) computed tomography (CT) images of a C5 vertebral body fracture with bony canal compromise and focal kyphosis. Prevertebral soft-tissue swelling is seen up to the bod$

Fig. 4.2 Sagittal (left) and axial (right) computed tomography (CT) images of a C5 vertebral body fracture with bony canal compromise and focal kyphosis. Prevertebral soft-tissue swelling is seen up to the body of C3.

$Sagittal and axial computed tomography (CT) images of left unilateral C4–C5 facet dislocation (left) and fracture (right).$