Etiology and Pathogenesis

According to the Centers for Disease Control and Prevention, spina bifida, the most common neural tube defect, occurs at a rate of two in 10,000 live births and results in varying degrees of disability from clinically normal to paraplegia. Traumatic spinal cord injury occurs at a rate of about 40 cases per million people per year and annually costs $9.7 billion in health care costs. Of these cases, it is estimated that up to half occur in adolescence and young adulthood. To diagnose and treat the disorders of the spinal cord, an understanding of its anatomy and how to examine for dysfunction of the spinal cord is imperative. The spinal cord is divided into four sections: cervical, thoracic, lumbar, and sacral (C, T, L, and S). It terminates at vertebral body level L2–L3 in infants, and in grown children and adults, it terminates at level L1–L2, where the cauda equina, the collection of nerves exiting the cord, begins. The spinal cord itself is sectioned in to a central H-shaped region of gray matter and surrounding white matter tracts (Figure 80-1).

The anterior horn of the gray matter contains motor nuclei, which receive information from the descending motor tracts. The axons of the motor neurons leave the ventral horn via the ventral root and synapse at the neuromuscular junction. The dorsal horn of the gray matter processes sensory information. It contains afferents from muscle spindles that participate in spinal cord reflexes. It also contains second-order neurons that mediate the various sensory inputs from the body.

There are three major white matter tracts of clinical importance when assessing myelopathy. The major descending tract is the lateral corticospinal tract (located posterolaterally within the cord). This tract contains the upper motor neurons originating from the primary motor cortex. The descending fibers cross at the cervicomedullary junction and descend, innervating the side of the body opposite the cortex. Within the tract, fibers that carry information to the upper extremities are located medially, and fibers that control the lower extremity movement are located laterally. The dorsal columns contain ascending proprioceptive and vibratory information and decussate in the medulla. These fibers are arranged so that information from the upper body is carried most laterally, in the fasciculus cuneatus, and that from the lower half is most medially, in the fasciculus gracilis. The spinothalamic tract (located anterolaterally in the cord) carries pain, temperature, and crude touch sensory information. These tracts decussate within a few levels of entering the spinal cord; therefore, they contain primarily contralateral sensory information. Within the spinothalamic tract, upper body information is carried medially, and lower body information is carried laterally.

The vascular anatomy of the spinal cord is divided into anterior and posterior circulations, arising from the vertebral arteries in the neck. The anterior spinal artery supplies the anterior two-thirds of the spinal cord. The two posterior spinal arteries primarily supply the posterior columns.

Clinical Presentation and Differential Diagnosis

The clinical examination is extremely helpful in localizing lesions within the spinal cord and can help determine the pathophysiology of spinal cord disease depending on the pattern of deficits. When examining a patient with suspected spinal cord disease, a thorough history and neurologic examination are essential to localizing the problem and generating a differential diagnosis. Cranial nerve examination can be helpful in distinguishing pure spinal cord disease from disease that involves the brainstem as well. It is important to perform a detailed motor, coordination, and reflex examination, including muscle bulk tone and strength, to determine patterns of weakness and elicit upper and lower motor neuron signs. Upper motor neuron signs include weakness, hypertrophy, spasticity, hyperreflexia, clonus, and a positive Babinski’s sign. Lower motor neuron signs include weakness, flaccidity, atrophy, fasciculations, and hyporeflexia. Tenderness along the spine can help with localization, and a sensory examination should detail the pattern of reported sensory loss and always include sensory level elicited by determining pinprick sensation and light touch along both sides of the spinal cord. Assessment of rectal tone and bowel and bladder function is critical. Respiratory function should be evaluated with vital capacity and negative inspiratory force. Importantly, an acute spinal cord lesion can present with signs of “spinal shock,” which includes reduced tone (or flaccidity in the extreme situation), hyporeflexia distal to the lesion, and reduced rectal sphincter tone. Only later will the upper motor neuron signs evolve. The sensory examination takes on greater emphasis toward localizing a spinal cord lesion in the acute setting.

There are common patterns of motor and sensory involvement depending on the localization of disease within the spinal cord. Table 80-1 describes the features of some typical patterns or spinal cord disease and their common causes (Figure 80-2).

Table 80-1 Features of Typical Patterns or Spinal Cord Disease and Common Causes

Localization	Common Pattern of Weakness and Sensory Loss	Common Causes in Pediatric Patients
Cervical spinal cord	Neck pain Lower motor neuron signs in the upper extremities at the level of the lesion Upper motor neuron signs in the lower extremities Sensory level: all sensory modalities Bowel or bladder involvement

Thoracic or lumbar spinal cord Ventral cord syndrome Dorsal cord syndrome Central cord syndrome Brown-Séquard syndrome (hemi-cord syndrome) Pure motor spinal cord syndrome Cauda equina syndrome Conus medullaris syndrome

The time course of the presentation can suggest the cause. Whereas traumatic injury such as transection or ischemic injury is usually sudden in onset, symptoms of spinal cord contusion develop over hours. Epidural abscesses, hematomas, transverse myelitis, and infectious myelopathy can have an acute to subacute course, which progress over hours to days. Tumors usually are very gradual in progression, over days to months, and neurodegenerative conditions typically change over months to years.

Evaluation and Management

Evaluation of spinal cord disease typically depends on clinical presentation. In a trauma patient, assessment of the patient’s airway, breathing, and circulation should take precedence. A transection above C3 can be rapidly fatal because it can involve the cessation of respiration. The cervical spine should be immobilized in a collar to prevent or minimize damage.

In all patients who present with an acute or subacute spinal cord process, urgent or emergent imaging is indicated. Typically, magnetic resonance imaging (MRI) is done with and without contrast of the suspected area, including diffusion-weighted imaging if the clinical history is suspicious for ischemia. MRI evaluation is always preferable to computed tomography for imaging the spinal cord.

If the injury is traumatic, there is some evidence in the adult literature that supports the use of steroids also in the emergent setting. In blunt traumatic spinal cord injury, one steroid has been the most extensively studied: methylprednisolone sodium succinate. This medication, when administered within 8 hours of injury, has been shown to improve neurologic outcome up to 1 year postinjury. The regimen used in the Second National Acute Spinal Cord Injury Study (NASCIS II) was a bolus of 30 mg/kg administered over 15 minutes with a maintenance infusion of 5.4 mg/kg/h infused for 23 hours. In the Third National Acute Spinal Cord Injury Study (NASCIS III), this regimen was administered if the patient presented within 3 hours, and if the patient presented with 3 to 8 hours, the methylprednisolone infusion was continued for a total of 47 hours. In this study, there was improvement in the functional mobility scores, which was not statistically significant at 6 months. There was also increased morbidity in the group that received the 47-hour infusion, with these patients having a higher incidence of severe sepsis and pneumonia. These data did not include pediatric patients younger than 13 years old; therefore, the use of steroids in this setting should be determined on an individual basis, with the involvement of the neurosurgeon. Steroids should not be used in the setting of penetrating traumatic injury.

For other causes of spinal cord injury, treatment depends on the etiology. In the nontraumatic setting, obtaining MR imaging, is crucial to establishing the diagnosis. If the clinical course or imaging suggests an abscess as the cause, early empiric antibiotic administration that treats Staphylococcus aureus infection is important to prevent extension of the infection and further cord damage. With any compressive lesions, early decompressive neurosurgical intervention can minimize the damage to the spinal cord and may benefit functional recovery. When cord compression is caused by cancer, the use of dexamethasone may reduce swelling and compression of the spinal cord. In the adult literature, the dosage of dexamethasone was given as a 20 mg IV bolus followed by 10 mg IV every 6 hours. These data did not include pediatric patients and should be considered on an individual basis in conjunction with an oncologist and a neurosurgeon.

Because the etiology of transverse myelitis is so diverse, from demyelinating and inflammatory or autoimmune disease to infections to nutritional and metabolic derangements, the evaluation of these patients is similarly broad. The evaluation for transverse myelitis should include an MRI of the brain to look for lesions above the foramen magnum that would suggest multiple sclerosis (see Chapter 78). It should also include serum tests such as inflammatory markers, vitamin levels (such as B12, folate, vitamin D, and copper), a rheumatologic evaluation (including autoantibody seen in systemic lupus erythematosus, Sjögren’s syndrome, sarcoidosis, and other autoimmune disease), as well as serum infectious evaluation as indicated (Lyme disease, Mycoplasma, HIV, Epstein-Barr virus, cytomegalovirus). If there are risk factors, the patient should have evaluation for tuberculosis. Finally, cerebrospinal analysis including cell count, glucose, protein, culture, cytology, oligoclonal bands, myelin basic protein, immunoglobulin G, and viral polymerase chain reaction tests (enterovirus, herpesviruses) as indicated are important for determining diagnosis and treatment. For viral myelitis, treatment is typically supportive.

In the setting of spinal cord infarction, treatment is typically supportive. Minimizing risk factors, such as hypercoagulability, and evaluating for the source of ischemia, such as an embolism, vasculitis, or venous thrombophlebitis, are important to reduce the chances of further ischemic events. In adult populations in which spinal cord infarction is more common, particularly after aortic surgeries, there is some evidence that suggests lumbar drain placement to augment spinal perfusion pressure improves functional outcome. This has not been studied in pediatric patients.

Future Directions

Spinal cord diseases, although uncommon in children, are often very disabling conditions. At this point in time, there is only one treatment option that has been used extensively in traumatic spinal cord injury with evidence of benefit. Steroids have also been used with some success in inflammatory conditions, but this medication is not without its consequences, and it is far from curative.

Currently, there are two major approaches actively being studied focusing on improving functional outcome in spinal cord disease. The first is neuroprotection, which attempts to reduce the tissue loss by mediating secondary intracellular cascades that cause neuronal tissue damage. These neuroprotective agents being studied include mediators of excitotoxicity such as pregabalin and mediators of lipid metabolism. The second strategy involves promoting regeneration of axons, such as stem cell transplant and growth factors, to improve functional outcomes. These strategies seem promising to help treat a multitude of conditions that have a very high financial cost to the health care system and immeasurable physical and emotional cost to the patient.