Spinal cord injuries are most commonly caused by motor vehicle accidents. The next most frequent causes are falls and acts of violence. Sports-related spinal cord injuries occur more commonly in children and teenagers, while work-related injuries (especially from construction work) predominate in adults.
Most spinal cord injury patients are in their teens or twenties. Approximately 80% are male. This male preponderance decreases beyond age 65, at which age falls become the most common mechanism of spinal cord injury. More than half of all spinal cord injuries occur in the cervical area, i.e., in the neck. Almost a third occur in the thoracic area (where the ribs attach to the spine). The remainder occur in the lumbar area, i.e., the lower back.
TYPES OF SPINAL INJURY
Bony or Ligamentous Injury.
Fortunately, most injuries to the spine are not associated with injury to the spinal cord itself. Some of these fractures may require only immobilization, such as a rigid collar for cervical spine fractures or some type of brace or body jacket for fractures lower in the spine. Even if the bones and ligaments are not damaged, the muscles and other soft tissues of the neck may sustain injury that can be painful but is usually not serious (Figure 1).
Figure 1. MRI scan from a patient with an incomplete spinal cord injury. The hash marks and arrow on the right side of the picture indicate an area of injury to the soft tissues just in back of the spine.(Click on the image for a larger image) However, other bony or ligamentous injuries may require surgery to stabilize the spine. In these cases, the spine may be so unstable that abnormal movement of the spine may produce damage to the spinal cord itself or to the nerves arising from the cord (Figures 2 and 3). If left untreated, some bony and ligamentous injuries may eventually cause chronic pain or may result in progressive deformity of the spine. Early surgery to fuse the injured area of the spine may promote proper healing, greatly reducing the risk of such future problems.
Figure 2. CT scan reconstructed in the sagittal plane, i.e., as if the viewer were standing at the patient's side. Arrow points to a fracture.(Click on the image for a larger image)
Figure 3. CT scan of fracture from Figure 2, showing reconstruction in the coronal plane, i.e., as if the viewer were standing directly in front of the spine.(Click on the image for a larger image)
Complete Spinal Cord Injury.
A complete spinal cord injury produces total loss of all motor and sensory function below the level of injury. Almost one half of all spinal cord injuries are complete.
Even in complete spinal cord injuries, the spinal cord is rarely cut or transected (Figures 4 and 5). More commonly, loss of function is caused by a contusion or bruise in the spinal cord or by compromise of blood flow to the injured part of the spinal cord.
Figure 4. MRI scan through the damaged area in a patient with a complete spinal cord injury. The view is as if one were looking up from below at a cross-section. The arrow points to the spinal cord, which is damaged but not disrupted. Compare to Figure 5.(Click on the image for a larger image)
Figure 5. MRI scan through an uninjured area from patient in Figure 4. Same view as Figure 4. Arrow points to spinal cord, which is not compressed at all.(Click on the image for a larger image) Incomplete Spinal Cord Injury.
Incomplete spinal cord injuries often fall into one of several patterns.
The anterior cord syndrome results from injury to the motor and sensory pathways in the anterior parts of the spinal cord. These patients can feel some types of crude sensation via the intact pathways in the posterior part of the spinal cord, but movement and more detailed sensation are lost.The central cord syndrome is caused by injury to nerve cells and pathways located in the center of the cervical spinal cord. This produces weakness or paralysis of the arms, as well as some sensory deficits in the arms. Strength and sensation in the legs are affected much less than in the arms.
Brown-Sequard syndrome results from injury to the right or left half of the spinal cord. Movement and some types of sensation are lost below the level of injury on the injured side, but pain and temperature sensation are lost on the side of the body opposite the injury because these pathways cross to the opposite side shortly after they enter the spinal cord.
Other Types of Injuries. Injuries to a specific nerve root may occur either by themselves or together with a spinal cord injury. Because each nerve root supplies motor and sensory function to a different part of the body, the symptoms produced by this injury depend upon the pattern of distribution of the specific nerve root involved.
So-called spinal concussions can also occur. These consist of complete or incomplete spinal cord dysfunction that is transient, generally resolving within one or two days.
DIAGNOSIS
The key to detecting spinal injury in the acute setting is a high index of suspicion. The possibility of injury to the spine and spinal cord must be considered in anyone with significant trauma to the head and/or neck. The safest strategy is to assume that such patients have an unstable spine fracture until proven otherwise.
This approach to trauma patients begins in the prehospital setting. Paramedics and other rescue workers receive extensive training in immobilizing the spine. This training is designed to prevent worsening of any neurological injury that may already be present and also to prevent spinal cord injury in patients who have no neurologic problems but who may have an unstable spinal column (Figure 6). Extricating a patient from automobile wreckage while protecting his or her spine may be quite difficult. After extrication, paramedics apply a rigid collar to the neck and secure the patient to a rigid backboard. These devices are kept in place until the patient has been evaluated in the emergency room, and sometimes even longer.
Figure 6. MRI scan from a patient with an incomplete spinal cord injury. The view is from the side. Arrow indicates fracture compressing the spinal cord. If proper precautions and adequate immobilization had not been used, this injury might easily have become complete.(Click on the image for a larger image) Clinical Evaluation.
A physician may "clear" the cervical spine (i.e., decide that significant spinal injury does not exist) simply by examining a patient if the patient has no neck pain and if the patient meets the following criteria: no altered mental status, no neurological deficits, no intoxication from alcohol or other drugs or medications, and no other painful injuries that may divert his or her attention from a neck injury. These same criteria may be used to determine that the other parts of the spine are free of injury.
In other cases, such as when patients complain of neck pain, when they are not fully awake, or when they have obvious weakness or other signs of neurological injury, the cervical spine is kept in a rigid collar until appropriate radiologic studies are completed.
Radiologic Evaluation.
The radiologic diagnosis of spinal injury begins with x-rays (Figure 7). In many cases, the entire spine may be x-rayed. Patients with spinal injuries may go on to receive both computerized tomography (CT) and magnetic resonance imaging (MRI) of the spine. Indications for performing these additional radiologic studies include the further evaluation of areas of abnormality seen on plain x-rays and the investigation of neurological deficits. As shown by the illustrations in this brochure, the information provided by these two imaging techniques is not redundant, but rather complementary. MRI is most helpful for looking at the actual spinal cord itself, as well as any blood clots, herniated disks, or other masses that may be compressing the spinal cord. CT is quite helpful to visualize the bony anatomy, including any fractures.
Figure 7. X-ray of the cervical spine as viewed from the left side. Arrow indicates area of injury.(Click on the image for a larger image)
Even after all radiologic tests have been performed, a patient may still be kept in a collar for a variable period of time. There may be several reasons for this. If patients are awake and alert but still complaining of neck pain, a physician may send them home in a collar, with plans to repeat x-rays in the near future, such as one to two weeks. The concern in these cases is that muscle spasm caused by pain might be helping to mask an abnormal alignment of the bones in the spinal column. Once this period of spasm passes, repeat x-rays may reveal abnormal alignment or excessive motion that was not visible immediately after the injury. In patients who are comatose, confused, or not fully cooperative for some other reason, adequate radiographic visualization of parts of the spine may be difficult. This is especially true of the bones at the very top of the cervical spine. In these cases, the physician may keep the patient in a collar until the patient is more cooperative. Alternatively, the physician may repeat another imaging study to rule out injury.
TREATMENT
As mentioned above, treatment of spinal cord injury begins in the prehospital setting, with paramedics or other emergency medical services personnel carefully immobilizing the entire spine. In the emergency department, this immobilization is continued while more immediate life-threatening problems are identified and addressed. If the patient must go to emergency surgery because of trauma to the abdomen, chest, or other area, immobilization and alignment of the spine are maintained during the operation.
Intensive Care Unit Treatment.
If a patient has a spinal cord injury, he or she will usually be admitted to an intensive care unit (ICU). For many injuries of the cervical spine, traction may be indicated to help "reduce" the spine, i.e., bring the spine into proper alignment. Standard ICU care, including maintaining a stable blood pressure, monitoring cardiovascular function, ensuring adequate ventilation and lung function, and preventing and promptly treating infection and other complications, are also essential if patients with spinal cord injury are to achieve the best possible outcome.
Surgery.
Occasionally, a surgeon may wish to take a patient to the operating room immediately if the spinal cord appears to be compressed by a herniated disk, blood clot, or other lesion. This is most commonly done for patients with an incomplete spinal cord injury or with progressive neurological deterioration. The entire issue of the timing of surgical decompression of an acutely injured spinal cord is currently under intense debate. Traditionally, surgeons have felt that waiting for several days was the safest course of action, since there was some evidence that operating immediately may actually worsen outcome. However, more recently, some surgeons have begun advocating immediate early surgery, but this hypothesis has never been scientifically tested. A clinical trial to test this is currently in the planning stages. This trial is being organized by the Joint Sections on Neurotrauma and Critical Care and on Spine and Peripheral Nerves of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons.
As mentioned above, even if surgery cannot reverse damage to the spinal cord, surgery may be needed to stabilize the spine to prevent future pain or deformity. The field of spinal surgery is currently enjoying an explosion of new surgical techniques, new equipment, and improved understanding, which has resulted in a variety of surgical approaches being available for many types of injuries (Figure 8). A detailed discussion of these techniques is beyond the scope of this brochure, but certainly the patient and family members should discuss in detail with the surgeon any planned operation, including risks, alternatives, likelihood of good outcome, and potential recovery time.
Figure 8. Postoperative x-ray of patient who had fusions performed on both the front and back of his neck. Fractured bones were removed and replaced with a piece of bone from his hip. Metallic plates and screws are seen at both the front and back of the spine.(Click on the image for a larger image) Pharmacologic Therapy.
In addition to high-quality ICU care, most patients with spinal cord injuries receive high doses of a steroid called methylprednisolone. This drug has been shown to improve outcome slightly after spinal cord injury. To be effective, administration of this drug must begin within eight hours after injury, so patients often begin receiving it in the emergency room. If the drug was begun within three hours of injury, it is generally continued for 24 hours. If the patient did not receive the drug until 3-8 hours after injury, then it may be best to continue the drug for 48 hours.
Penetrating Spinal Injuries.
Most of the above discussion has concerned so-called 'closed' spinal injuries, or those occurring after significant force causes abnormal and excessive movement of the spinal column, resulting in injury. However, 'open' or penetrating injuries to the spine and spinal cord, especially those caused by firearms, are being seen more and more frequently (Figures 9 and 10). Currently, gunshot wounds to the spine comprise roughly 10-15% of all spinal cord injuries seen in the United States. Most gunshot wounds to the spine are stable, i.e., they do not carry much risk of excessive and potentially dangerous motion of the injured parts of the spine. Depending upon the anatomy of the injury, the patient may need to be immobilized with a collar or brace for several weeks or months so that the parts of the spine that were fractured by the bullet may heal. In most cases, surgery to remove the bullet does not yield much benefit and may create additional risks, including infection, cerebrospinal fluid leak, and bleeding. However, occasional cases of gunshot wounds to the spine may require surgical decompression and/or fusion in an attempt to optimize patient outcome.
Figure 9. X-ray of patient with a gunshot wound to the cervical spine. Bullet and bone fragments (such as those indicated by the arrows) are widespread.(Click on the image for a larger image)
Figure 10. CT scan through the area of damage from patient in Figure 9. The damage caused by the bullet is seen on the left-hand side of the figure.(Click on the image for a larger image)
OUTCOME
Mortality.
Mortality from spinal cord injury is influenced by several factors. Perhaps the most important of these is the severity of associated injuries. Because of the force that is required to fracture the spine, it is not uncommon for the spinal cord-injured patient to suffer significant damage to the chest and/or abdomen. Many of these associated injuries are fatal. For isolated spinal cord injuries, the mortality after one year is roughly 5-7%. If a patient survives the first 24 hours after injury, the probability of survival for ten years is approximately 75-80%. Likewise, the ten-year survival rate for patients who survived the first year after injury is 87%. Not surprisingly, younger patients and those with incomplete injuries do better than older patients and those with complete injuries.
Neurologic Improvement.
Recovery of function depends upon the severity of the initial injury. Unfortunately, those who sustain a complete spinal cord injury are unlikely to regain function below the level of injury. If at least some recovery is to occur, a patient will usually begin showing some improvement within a few days.
Incomplete injuries usually show some degree of improvement over time, but this varies with the type of injury. Although full recovery may be unlikely in most cases, many patients can improve at least enough to ambulate and to control bowel and bladder function. Patients with an anterior cord syndrome tend to do poorly, but most of those with a Brown-Sequard syndrome can expect to reach these goals. Patients with a central cord syndrome often recover to the point of being ambulatory and controlling bowel and bladder, but they often are not able to perform detailed or intricate work with their hands.
PREVENTION
Despite the progress that has been made in understanding the cellular and biochemical events that occur after spinal cord injury, a tremendous amount of work remains to be done. It is also obvious that "an ounce of prevention is worth a pound of cure". One of the most successful prevention programs has been THINK FIRST, a program that was begun by North American neurosurgeons to educate the public (especially children, adolescents, and young adults, which are the age groups most likely to sustain spinal cord injuries) about the implications of head and spinal cord injury and about simple ways to minimize their chances of sustaining such injuries.