Pediatric Spinal Cord and Spinal Column Trauma

Author: Doug Brockmeyer, MD

Objectives

1. Understand the anatomical and biomechanical differences between the pediatric and adult spines.
   
   
2. Understand the unique mechanisms of injury associated with pediatric spine trauma.
   
   
3. Identify different injury types based on age and anatomy.
   
   
4. Understand the principles behind treatment of pediatric spinal cord and spinal column injury.
   
   
5. Understand basic principles associated with the rehabilitation of pediatric spinal cord injury.
   
   
6. Identify measures which can be taken to prevent pediatric spinal cord and spinal column injury.

Introduction

Injuries to the pediatric spinal column and spinal cord have received increasing attention over the last two decades. Much has been learned in that period of time, but our knowledge about the fundamental differences between pediatric and adult spinal column and spinal cord injuries remains incomplete. Nevertheless, this brief primer will attempt to outline some of the important principles concerning pediatric spinal column and spinal cord injury, as well as describe different types of treatment and rehabilitation. As part of this discussion, measures which can be taken to prevent pediatric spinal column and spinal cord injury will also be discussed.

Although less frequently encountered than spinal trauma in other age groups, pediatric spinal injuries are not rare. The overall incidence of pediatric spine trauma within the overall population of spinal injuries varies between 1% and 11%, depending on the study examined. This variability presumably is dependent upon the volume of spinal trauma at a given medical center and different referral patterns between trauma systems. A reasonable estimate at most major pediatric trauma centers is that 5% of spinal column and spinal cord injuries will occur in the age group between 0 and 16 years of age.

Males more frequently sustained spinal column and spinal cord injuries than females. This fact, however, is influenced by an increased likelihood of vertebral column injury in the "more active" adolescent males in the 10 to 16 year old age group. Some studies have reported a higher incidence of spinal cord and spinal column injuries in females in the 0 to 5 year old age group.

All of these figures, however, must be looked at with some skepticism. Differences between referral patterns, injury grading and treatment and outcome measures between physicians all mask the true incidence and severity of pediatric spinal cord and spinal column injury. The lack of a standardized nationwide database for these injuries has hampered our understanding of this disease process. Until strict guidelines and a national database are established, a complete understanding of injury patterns and injury types will be impossible.

Anatomy and Biomechanical Considerations

There are significant anatomical and biomechanical differences between the pediatric spine and its adult counterpart. Many of the anatomical differences explain the different injury patterns seen in various age groups. The infant spine, defined as that between 0 and 2 years of age, has tremendous mobility and elasticity due to underdevelopment of the neck muscles, incompletely calcified, wedge-shaped vertebrae, and shallow, horizontally oriented spine (facet) joints. In addition to these features, the relatively large size of the head with respect to the torso in young patients, increases the likelihood of cervical spine injuries, especially between the skull and first cervical vertebrae.

The anatomical differences described develop a more mature configuration over time. Between the ages of 2 and 10, tremendous changes occur in the spinal column. Muscles and ligaments strengthen, bones grow and reach a mature shape and size, and areas of cartilage and soft bone are replaced with normal calcified bone. In addition, the body habitus changes so that the head is smaller in proportion to the torso. These changes shift the focus of injury from the upper cervical spine (skull-C1-C2) to the lower cervical spine (C5-C6). It appears that the age related maturation that occurs in the upper pediatric cervical spine is usually completed by approximately age 10 and the maturation of the lower cervical spine occurs by approximately age 14.

The elasticity of the pediatric spinal column probably allows some protection against spinal cord trauma that might cause fracture in older patients. This mobility and elasticity in the infant spine explains the relatively low incidence of spinal column injuries and the proportionately high incidence of spinal cord injuries without radiographic abnormalities (discussed later). In essence, the young spine will stretch, but not break, but this places the spinal cord at increased risk for stretching and disruptive injuries.

Mechanisms of Injury

Numerous mechanisms responsible for the patterns of pediatric spinal cord and spinal column injury have been described. Flexion, extension, rotation, axial (top), loading and distraction (pulling) have all been implicated. Lack of blood flow to the spinal cord either by compression or disruption has also been documented. Compression of the spinal cord from blood clots, fractured bones, bending or buckling of ligaments, and angulation of the spinal column have all been described. It is also possible that underlying diseases that the patient is either born with or develops may also contribute to the risk of spinal cord injury. These problems include, but are not limited to, os odontoideum, Down's syndrome, Chiari malformations, congenital bone abnormalities, rheumatoid arthritis, ankylosing spondylitis, and other underlying infections or tumors may all play a part in the predisposition to spinal column or spinal cord injury.

The actual type of injury responsible for the mechanism varies according to the age of the patient. The youngest age group patients (0 to 10 years) have a high incidence of falls and pedestrian/automobile accidents, while their older counterparts have a higher incidence of motor vehicle accidents, motorcycle accidents and sports related injuries. Obviously, these observations are overgeneralized, but the different reasons responsible for pediatric spinal cord and spinal column injuries according to age do hold true in large studies.

Specific Injuries

• Fractures and Dislocations
  As described above, different patterns of spinal cord and spinal column injuries are seen between adult and pediatric patients. This section will expand on these differences in light of specific injury types. A fracture encompasses all types of disruption of the bony vertebral column. There is a wide variety of fracture types, ranging from simple linear fractures affecting the vertebral bodies or posterior portion of the spine, to complex fractures involving several elements of the spine or possibly several vertebral levels. A fracture may or may not make the spinal column unstable, depending on its type and severity. In addition, a fracture may or may not compress the spinal cord an cause spinal cord injury. A dislocation, otherwise known as subluxation, refers to abnormal position and motion between vertebral levels in the spine. Typically, dislocations are caused by injuries of the ligaments that traverse between each vertebral level. In addition to ligamentous injuries, disruption of the intervertebral disks may also contribute to spinal dislocation. Obviously, fractures and dislocations may exist either independently or in combination with each other. Complex fracture/dislocations are typically the worst type of vertebral column injury and imply both bony and ligamentous disruption. These patients usually have the most severe neurological injuries as well.
  
  
• Injuries Seen in Younger Children
  Young children tend to sustain soft tissue injuries without incurring "true fractures", a finding that reflects hypermobility and skeletal immaturity. Most of the spinal injuries in the first decade of life affect the upper segments of the cervical spinal column.
  
  Cervical sprain is perhaps the most common type of spinal injury, but has been poorly documented due to its "trivial" status. Serious ligamentous injuries and dislocations have a higher incidence in the upper cervical spine in younger children. Dislocation between the skull and the first cervical vertebrae is typically due to injury of the strong ligaments that normally keep this joint intact. Injuries in this area usually result in extreme instability at the craniocervical junction. Unfortunately, many of these injuries are fatal and their overall incidence is probably underreported. Dislocations between the first and second cervical vertebrae (atlanto-axial joint) are less often fatal, but are many times just as serious. Various types of dislocations, including rotatory dislocation, as well as fracture, can occur.
  
  Young children are prone to dislocation without fracture. In these instances, a higher rate of persistent instability can occur in comparison to instability associated with fracture dislocation injuries. As stated above, fracture characteristics among children change with skeletal maturation. Young children typically suffer growth plate fractures and separations. This mechanism is thought to be the etiologic factor behind "os odontoideum", a condition where part of the second cervical vertebrae is separate from the vertebral body. This separation leads to chronic instability and an increased risk of spinal cord injury.
  
  Due to factors involving the maturing spine, fractures and dislocations of the lower cervical spine are relatively rare. Fractures involving the thoracolumbar spine in young children tend to involve the junction between the thoracic and lumbar spine where the relatively rigid thoracic segments join the more mobile lumbar segments. Again, the injuries of younger children tend to involve the soft tissues and ligaments resulting in cartilage or growth plate injuries. In automobile accidents with frontal impact, children restrained by standard rear seat lap belts can sustain mid lumbar spine fractures. Clues to an injury include lap belt abrasions across the abdomen or lower thorax.
  
  
• Adolescent Injuries
  Adolescents and young adults in the 16 to 24 year old age group have the highest incidence of spinal injury in many studies. Once the patient age reaches 15 to 16 years old, injury mechanisms and patterns closely resemble those of adults. Specifically, a fractured bone is seen more often than soft tissue injuries alone. Combination fracture and dislocation injuries are seen more often also. The level of injury in the cervical spine is more evenly distributed throughout the entire neck. The most common level of injury in the adolescent age group is at the C5 and C6 level. Spinal column injuries to the thoracic and lumbar levels assume greater importance in the adolescent age group.
  
  Obviously, changes in lifestyle patterns among adolescents account for a large part of the injury pattern differences. Drugs, alcohol and motor vehicles are all important causative factors in this age group. In addition, sports related accidents assume a higher prominence in the adolescent age group. In the United States, organized tackle football has the highest incidence of spinal column and spinal cord injury of any sport. In other countries, rugby accounts for a significant amount of sports related spinal column and spinal cord injuries. Other "at risk" sports include wrestling and boxing. A more detailed discussion of sports related spinal column injuries in adolescents is beyond the scope of this discussion and further reference should be obtained by interested persons.
  
  
• Spinal Cord Injury without Radiographic Abnormality (SCIWORA)
  SCIWORA is defined as the occurrence of a spinal cord injury despite normal plain radiographic studies. In addition, flexion/extension films of the cervical spine and CT scans are also normal. There are wide differences in the reporting of SCIWORA and its incidence ranges from 5% and 70% of all pediatric spinal cord injuries, depending on the study examined. A true incidence is probably close to 20% of all pediatric spinal cord injuries. SCIWORA occurs almost exclusively among younger children and 2/3 of the cases occur in patients 8 years or younger. SCIWORA is very uncommon in adolescents and rare among adults. Cervical and thoracic spinal levels are injured with almost equal frequency and lumbar levels are rarely involved. There are important differences in SCIWORA injury patterns between younger age groups (0 to 8 years) and older children (9 to 16 years). Younger patients account for 2/3 of all SCIWORA injuries and have a higher porportion of complete neurological injuries. Adolescents show a far less frequent incidence of complete spinal cord injury due to SCIWORA. Upper cervical spine injuries typically involve young children more than adolescents. Due to insufficient data regarding injury patterns, it is difficult to make other general statements regarding the completeness of SCIWORA injuries or injury level. Further experience and information is necessary for this analysis.
  
  SCIWORA is due to the ligamentous flexibility and elasticity of the immature spine. A young child's vertebral column can withstand elongation without evidence of deformity while the spinal cord is injured. The infant spine and cadaver specimens can withstand up to two inches of stretch without disruption. In contrast, the spinal cord ruptures only after 1/4 inch of stretching. This mismatching of elasticity response between the spinal column and spinal cord is the major factor contributing to the high incidence of SCIWORA injuries in young children.
  
  In all cases of suspected SCIWORA injury, an MRI should be performed. It is possible that compressive, treatable lesions may be identified that were not seen on plain films. Examples of such lesions include hematomas or hidden ligamentous instability not shown on other studies. Some authors have reported that a delayed onset of neurological deficits may predispose to a worse outcome. Further data is needed to substantiate this claim.
  
  It is important to understand that once a SCIWORA injury is diagnosed, the child is at increased risk for recurrence of this episode. Recurrent injuries are typically more severe than initial injuries and may have permanent sequelae. Many centers maintain patients in external braces such as a stiff cervical collar for several months in order to prevent further injury. However, strict guidelines regarding treatment of this injury are lacking and there is significant variability between physicians regarding the type of treatment necessary. In general, once a diagnosis of SCIWORA is made, most practitioners are very conservative in their approach and some type of external immobilization is usually necessary for at least one to two months.
  
  
• Birth Injuries
  Spinal cord injury due to birth related trauma is probably underdiagnosed and underreported. This is most likely due to the lack of radiographic findings seen in most instances. Typically the upper cervical spine or cervicothoracic junction is affected. However, any level of the spinal cord can be involved and involvement in multiple levels is not uncommon. Two thirds of all birth injuries accompany breech presentation and 1/3 occur with cephalic presentation or transverse lie. There have been a wide variety of factors implicated in birth related spinal cord trauma including mechanical repositioning, breech presentation and forceps extraction. The mortality for birth related spinal cord injury is high and survivors may have a poor prognosis. Improved prenatal monitoring and obstetrical techniques have helped reduce these injuries over time.
  
  
• Treatment of Pediatric Spinal Cord Injury
  The principles involved in treatment of pediatric spinal cord injury are similar to those established in adults. Spinal cord injury in the pediatric age group is usually accompanied by a traumatic insult and varying degrees of neurological deficit occur. The deficit may range from an incomplete spinal cord injury where partial loss of function in the arms or legs is present to complete spinal cord injuries where all function below the level of injury is lost.
  
  Injuries in the high cervical spinal cord affect muscles required for respiration as well as nerves responsible for motor strength and sensation in the arms or legs. In addition, bowel and bladder function is lost if the lesion is complete. Injuries to the lower cervical cord have varying degrees of sparing of arm strength depending on the level of the lesion. In these instances, lower extremity and bowel and bladder function are also lost. Injuries in the thoracic spine or in the upper lumbar areas have sparing of the upper extremities, but loss of function in the lower extremities and bowel and bladder. Injuries lower down in the lumbar spine can show incomplete and patchy loss of function in the lower extremities as well as incomplete loss of function in the bowel and bladder. In thinking of these injury patterns, it is sometimes useful to consider the spinal cord and nerve roots as a large electrical system and disruption of the "wires" lead to loss of function downstream from the injury.
  
  The treatment of traumatic spinal cord injury should begin in the field shortly after the accident and continue through the prehospital transport stages as well as through the Emergency Room and Intensive Care Unit. Modern techniques of resuscitation and transport include complete spine immoblization, including placement of a rigid cervical collar, as well as early administration of medication to prevent further injury to the spinal cord. One such medication is methylprednisolone, also known as SoluMedrol, which has been shown in studies to improve the overall outcome in certain patients with spinal cord injury. Any patient with a neurological deficit due to spinal cord injury should be started on this medication and it should be followed according to protocol. Any Level 1 Trauma Center or children's hospital should be aware of this protocol and use methylprednisolone appropriately.
  
  The evidence of administration of methylprednisolone in very minor or incomplete injuries is less substantiated and most physicians err on the side of overtreatment in the hopes of regaining any lost neurological function. However, the evidence for improvement in these lesions is not available at this time and treatment decisions are basically left up to the judgment of the managing physician. In the Intensive Care Unit setting, treatment should be based at maintaining adequate blood flow to the spinal cord. Compressive lesions along the cord should be identified and surgically addressed. There are certain instances where compressive lesions may be managed non-operatively and this is best left up to the judgement of the treating surgeon.
  
  
• Treatment of Pediatric Spinal Column Injury
  The treatment of pediatric spinal column injury is large and complex and is well beyond the scope of this discussion. However, there are several general treatment principles that are followed in the management of spinal column injuries. The first principle is identification of the proper level and injury affecting the spinal column. This includes identification of the fracture type, if any, recognition of dislocation and instability, identification of mass lesions that may be compressing the spinal cord (such as hematomas or ruptured disks) and identification of spinal cord injury. This principle is firmly based on adequate history and clinical examination as well as the acquisition of proper radiographic studies. Radiographic studies include plaine films with or without dynamic (flexion/extension) views, tomograms, CT scans and MRI scans. All of the following principles are based on this first step.
  
  The next principle is correction of any spinal column deformity and decompression of the spinal cord if present. This step may include the application of cranial tongs and placing the patient in traction. Many times such a maneuver may help correct a bony spinal deformity compressing on the spinal canal. This step may also include the planning and execution of the removal of blood clots pressing on the spinal cord.
  
  The next treatment principle involves the recognition and management of unstable segments of the spinal canal. Spinal instability almost uniformly results in progressive spinal deformity over time and early treatment of instability is important in protecting the spinal cord and nerve roots from further damage. Instability may be treated in a variety of ways. Fractures without spinal cord compression and involving only bone many times are managed by an external brace such as a halo device. This device consists of a metal ring which is affixed to the skull and connected to a rigid plastic vest with rigid bars. These devices are useful in treatment fractures in a variety of age groups and vertebral levels. Other ways of managing this problem include surgical fusion, with or without the application of rigid metal devices, also known as instrumentation. These new techniques have the advantage of many times being able to avoid the placement of a halo vest, but are not necessarily indicated in all cases. The decision of how to treat the problem in an operative way is best left up to the judgement of the treating physician.
  
  A final principle is close follow-up of the patient after treatment. For example, an occasional patient who has been treated with an external brace may develop a progressive instability over time that was not immediately detected. Careful serial follow-up examination are important in this instance to make sure that proper treatment is instituted. In the example mentioned above, this patient would probably go on to require operative fusion.
  
  Using the above principles, the vast majority of spinal column injuries can be managed successfully. It must be emphasized that practice patterns vary across the country and treatment philosophies differ from physician to physician. This must be kept in mind when individual patients are being treated and comparisons are being made between institutions or physicians.
  
  
• Rehabilitation of Spinal Cord Injury
  Once a spinal cord and spinal column injury has been diagnosed and treated, rehabilitation begins. Some patients are lucky enough to have no neurological deficit and will just require close follow-up by their physicians. Other patients have significant neurological deficits and require intensive rehabilitation programs in order to maximize their potential for recovery of function or learn to function with their new neurological status. Many pediatric hospitals have in-house rehabilitation units where this may be facilitated. Rehabilitation includes physical therapy, occupational therapy, speech and dysphasia therapy as well as close follow-up by physiatrists and rehabilitation medicine specialists. The rehabilitation doctors typically work closely with the treating surgeons. Other rehabilitation centers are freestanding and offer many, if not all, of the same features of inhospital rehab centers. Many times the decision is automatic which rehabilitation center should be used, but when there is a choice, it is wise for the parents to investigate the different centers so they are comfortable with the facility and the services available.
  
  

Prevention of Pediatric Spinal Cord and Spinal Column Injury

Needless to say, once a spinal cord or spinal column injury occurs in a child, preventive measures are a moot point. The affected parents are then left wondering what preventive measures could have been taken in order to avoid the injury. Fortunately, there are several organizations, both at local and national levels, that are directed toward the prevention of spinal cord and spinal column injuries in the pediatric age group. One example of such an organization is ThinkFirst for Kids, a non-profit organization organized by national neurosurgical organizations. This and other programs offer school-based instruction on preventative behaviors that ultimately lead to the decreased risk of head and spinal cord injuries. The key feature of these programs is reaching children when they are in grade school and delivering the message while they are still developing their behavior patterns. Research suggests that these behavior patterns are maintained through the adolescent years when the children are at greatest risk. Only through comprehensive and systematic prevention programs will the incidence of tragic spinal cord injuries decrease. The medical community extends its wholehearted support to these programs and the work behind these significant and sometimes tragic injuries.