Spinal Trauma & Spinal Cord Injury: General Principles

 

 

Injuries to the spine – the vertebral bodies, their surrounding soft tissues, and the spinal cord itself – can cause devastating neurological consequences. Rapid evaluation of any patient with potential spinal trauma is crucial, especially to rule out damage to the spinal cord and nerve roots. Even without neurological involvement, spinal injuries can be painful and disabling. In this section the general principles of spine trauma will be presented. A selection of more specific traumatic spinal conditions will be considered in a separate chapter.

 


Structure and Function

The spinal column is divided into four main parts: cervical, thoracic, lumbar, and sacral (Figure 1). Twenty-four vertebral bodies (7 cervical, 12 thoracic, 5 lumbar) extend from the foramen magnum at the skull to the sacrum at the pelvis.

 

Figure 1: The spinal column. (From https://openstax.org/books/anatomy-and-physiology/pages/7-3-the-vertebral-column)

 

The first cervical vertebrae (C1) is known as the atlas, and the second (C2) is known as the axis. The atlas is the first cervical vertebra and articulates with the occiput of the head of the axis (C2). The morphology of these two markedly differ from the other vertebrae below them. The atlas has no vertebral body and no spinous process. Rather, there are lateral masses connected by the anterior and posterior arches. The C2 vertebra has an odontoid process (also known as the dens) which is a peg or protuberance that enters the C1 body, creating the atlanto-axial joint for rotation of the head (see Figure 2)

 

Figure 2: Lateral x-ray of the cervical spine, annotated at right. C1 is in blue, C2 in red (showing the projection of the odontoid into C1), and the lower cervical spine in yellow. (Courtesy of Wikimedia.org)

 

The vertebral bodies are draped front and back by the anterior and posterior longitudinal ligaments, respectively. The ligamentum flavum covers the posterior aspect of the spinal canal and connects the lamina while the interspinal and intertransverse ligaments connect the spinous processes and transverse processes of adjacent vertebrae, respectively. Discs are situated between each vertebral body to act as cushions.

The spinal cord travels through the spinal canal from the foramen magnum to until (approximately) the caudal aspect of the L1 vertebral body. It is bordered in the front by the vertebral bodies, to the sides by the pedicles, and to the back by the laminae. At each vertebral level, the dorsal and ventral rami come together to create the nerve roots, which exit the spine through a lateral foramen.

 

At its terminus, the cord forms the conus medullaris and gives off a collection of nerve roots called the cauda equina (as this collection is said to resemble a horse’s tail). These peripheral nerves travel through the spinal canal until their point of exit at a neural foramen.

 

In the cervical spine, the vertebral arteries pass through transverse foramina before entering the foramen magnum.

 

Different portions of the spinal column have different propensities for injury. Most of the thoracic spine, for example, is relatively protected by its articulation with the inherently stable rib cage through T10. On the other hand, the thoracolumbar region (T11-L2) has more flexibility and mobility. This property enhances daily utility, but makes the region more prone to injury in trauma – the classic musculoskeletal trade-off between stability and mobility. Indeed, at each of the regional junctions (occipitocervical, cervicothoracic, thoracolumbar, and lumbosacral), mobility is maximized at the cost of decreased stability.

 


Patient Presentation

Spinal trauma has a bimodal age distribution. Younger patients (those 30 years of age and younger) presenting with after high-energy trauma (e.g., motor vehicle collisions) form one group. The second group comprises mostly geriatric patients with low-energy trauma (e.g., falls) in the setting of osteoporosis and degenerative changes in the spine.

 

Approximately 75% of fractures in younger patients involve the thoracolumbar spine, most commonly at the thoracolumbar junction. Spinal cord injuries occur less frequently, with about 10,000 new cases per year, about half of which are in the cervical region and half in the thoracic or lumbar regions. The level of function after spinal cord injury can be assessed on physical examination by motor and sensory testing (see Table 1 and 2) and is more commonly assessed using the ASIA (American Spinal Injury Association) scoring system.

 

Table 1: Upper extremity root levels.
 

Table 2: Lower extremity root levels.
 
Figure 3: The 2019 revision of the International Standards for Neurological Classification of Spinal Cord Injury. (Reproduced with permission of the American Spinal Injury Association (ASIA))

 

In general, the higher (more rostral/proximal) the level of injury, the greater the functional loss. If the injury is at C5 or above, the patient is apt to be ventilator independent, and will lack wrist extension or supination. If the functional injury is at the C6 level, wrist extension and supination are preserved and patients can thus often feed themselves. When C7 function is retained, patients can power a manual wheelchair or perform transfers from chair to bed, since they have retained triceps function. Note that T1 function is needed to have full manual dexterity, since this level supplies the hand intrinsic muscles. Injuries in the lumbar spine cause lower extremity dysfunction and commonly urinary/fecal continence.        

 

Cord injury can further be categorized as complete or incomplete. Incomplete injury leads to some measure of voluntary distal motor and/or perianal sensation. Neurological impairment can be classified using the American Spinal Injury Association Impairment Scale (see Table 3),

 

Table 3: American Spinal Injury Association Impairment Grade.

 

In cases of incomplete spinal cord damage, symptoms will vary based on the portion of the cord affected. There are also specific regions within the spinal cord itself that might be affected more than others. Central cord syndrome is the most common incomplete spinal cord injury syndrome, most frequently seen in elderly patients after a fall, especially with a history of cervical spondylosis and spinal stenosis. Central cord syndrome results from a spinal cord contusion, usually the result of hyperextension in the cervical spine causing axonal disruption to lateral columns selectively. Central cord syndrome affects fine motor control of the hands but may be seen distally as well, including loss of bladder control.

 

Anterior cord syndrome is characterized by motor and sensory dysfunction below the level of injury, caused either by direct compression or indirect injury to the anterior spinal artery. The region affected includes the descending corticospinal tract, ascending spinothalamic tract, and autonomic fibers. It is characterized by a corresponding loss of motor function, loss of pain and temperature sensation, and hypotension. This is incomplete spinal cord syndrome with the worst prognosis as only about 15% of patients regain motor recovery.

 

Brown-Séquard syndrome, is seen after damage to one side of the spinal cord, left or right, usually after penetrating trauma. It is associated with loss of function or impaired function on the side of the injury and altered pain and temperature loss on the opposite side of the injury. Among the incomplete spinal cord syndromes, Brown-Séquard has the best prognosis for functional recovery.

 

 

Objective Evidence

In any suspected spinal trauma, radiographic imaging is crucial. In most cases, CT scanning will be indicated for detailed assessment of the bony anatomy. MRI provides additional details about the spinal cord and surrounding soft tissues. In general, both studies are usually warranted: CT to provide information about the bones, and MRI to provide detailed information about the soft tissues, including the spinal cord and discs.

 

A whole spine radiograph should be obtained to evaluate for any vertebral fractures. In the cervical spine, there are four parallel lines that should be assessed (see Figure 4): the anterior and posterior vertebral lines, at the margin of the vertebral bodies front and back; the spinolaminar line which is the posterior margin of the spinal canal, and the posterior spinous line at the tips of the spinous processes. These lines should be smooth. Any so-called “step-off” is suspicious for ligamentous injury.

 

Figure 4: Cervical spine radiograph showing the vertebral lines. (From https://upload.wikimedia.org/wikipedia/commons/1/10/X-ray_of_vertebral_lines.jpg)

 

For suspected instability of the cervical spine, patients who can move their heads on their own may have radiographs made in flexion/extension (see Figure 5) to assess stability.


Figure 5: Flexion and extension radiographs of the cervical spine. Positioning and imaging are shown. These studies are normal: there is no step off in any of the four lines (See text) as the head is moved. (Modified from Radiopaedia.org, rID: 10338 and Radiopaedia.org, rID: 80305)

 

The open mouth view allows assessment of the odontoid process of C2 (see Figure 6).

 

Figure 6: The open mouth view for assessment of the odontoid. Normal anatomy is shown. In the annotated x-ray to the right, the lateral masses of C1 are in pink with C2 and its odontoid process in yellow. (Case courtesy Radiopaedia.org, rID: 48418)

 

Although x-rays have been of historical importance, over the last two decades, CT scans have replaced x-rays to evaluate bony injury, given their higher level of detail. CT scanning will detect most fractures (Figure 7 and 8). CT can also help evaluate for patency of the spinal canal throughout the imaged portions although direct visualization of the spinal cord is still poor.

 

Figure 7: A CT scan showing a small fracture (arrow) through an anterior/superior osteophyte of C5. (Courtesy of Radiopedia)

 

Figure 8: A CT scan of a thoracic fracture, seen in sagittal and axial CT images. The axial view to the right shows that the canal is patent. (Case courtesy of Radiopaedia.org, rID: 5274)

 

The main indications of MRI (see Figures 9 and 10) in spinal trauma include the following:

  • Investigating x-ray or CT scan findings suggestive of ligamentous injury (e.g. spondylolisthesis or asymmetric disc space widening),
  • Detecting epidural hematoma, disc herniation or occult fracture,
  • Identifying spinal cord abnormalities,
  • Assessing cervical stability in trauma patients who are obtunded or otherwise unable to pose for flexion/extension radiographs,
  • Radiographic confirmation of neurological injury detected on clinical examination.

 

Figure 9: MRI to identify soft tissue abnormalities not apparent on radiography. On the left is an MRI showing interspinous ligament injury (red arrows). On the right, the yellow arrow points to a nonhemorrhagic contusion in the spinal cord. (Courtesy of BMC Musculoskelet Disordv.17; 2016PMC4957861)

 

Figure 10: Sagittal CT image to the left did not show a fracture but MRI (STIR) image of this patient shows bone marrow edema in the superior aspect of multiple vertebrae (yellow lines) suggesting bone contusions. (Courtesy of BMC Musculoskelet Disordv.17; 2016PMC4957861)

 

 

 

Treatment Options

Non-operative treatment of spinal trauma often centers on immobilization. Various immobilization devices can be used (see Figures 11 and 12), including a Philadelphia collar, a thoraco-lumbosacral orthosis, a lumbosacral corset, or a halo vest.


Figure 11: Philadelphia (cervical) collar; thoraco-lumbosacral orthosis, and lumbosacral corset. (Courtesy of Effectiveness of orthoses for treatment in patients with spinal pain doi: 10.12701/yujm.2020.00150 PMCID: PMC7142031)

  

Figure 12: A halo vest is the most rigid form of external immobilization of the upper cervical spine. Fixation of the halo to a patient's head relies on pins spaced around a ring which are (after injection of a local anesthetic) tightened against the head above the orbits and ears.

 

Surgery for spinal trauma, in general, consists of decompressing the spinal cord (that is, relieving any pressure on it) and stabilizing the spine, usually by a spinal fusion with plates, screws, wires or rods. The construct can be supplemented with bone graft.

  

Figure 13: Preoperative CT midsagittal images of a right facet dislocation and left facet subluxation at the C5–C6 level. Post anterior cervical discectomy and fusion CT images show an anterior plate holding the normal alignment of the facet joints. (From https://www.asianspinejournal.org/journal/view.php?number=1193)

 

 Spinal trauma leading to spinal cord damage will require immediate administration of certain medications. These included prophylaxis for deep vein thrombosis and fluids and/or vasopressors to treat or prevent shock. Administration of steroids in an attempt to reduce spinal cord edema and compression is controversial, especially in the setting of polytrauma (additional injuries beyond the spine) or open fractures, where the infection rate is high and potentially worsened by administration of corticosteroids. According to a meta-analysis in the journal Neurology published in 2019, high-dose methylprednisolone early after acute spinal cord injury “does not contribute to better neurologic recoveries but may increase the risk of adverse events.”