Beyond infancy the spinal cord in humans ends in the conus medullaris at about the level of L1. The position of the conus below L2 is consistent with a congenital tethered spinal cord. For normal humans as the spine flexes and extends, the spinal cord is free to move up and down within the spinal canal. If the spinal cord is fixed at any point, this movement is restricted and the spinal cord and associated nerve roots become stretched. This fixing of the spinal cord, regardless of the underlying cause of the fixation, is called a tethered cord. When severe pain or neurologic deterioration occurs in response to the fixation, it is called the tethered cord syndrome.

In its simplest form the tethered cord syndrome results from a thickened filum terminale, which normally extends as a thin, very mobile structure from the tip of the conus to the sacrococcygeal region where it attaches. When this structure is thickened and shortened, the conus is found to end at levels below L2. This stretching between 2 points is likely to cause symptoms later in life. Fatty infiltration is often seen in the thickened filum (Fig. 598-1).

Figure 598-1 Sagittal MRI showing thickening of the filum terminale in a patient with a symptomatic tethered spinal cord.

(Used with permission from Barrow Neurological Institute.)

Any condition that fixes the spinal cord can be the cause of the tethered cord syndrome. Conditions that are well established to cause symptomatic tethering include various forms of occult dysraphism such as lipomyelomeningocele, myelocystocele, and diastematomyelia. These conditions are associated with cutaneous manifestations such as midline lipomas often with asymmetry of the gluteal fold (Fig. 598-2), and hairy patches called hypertrichosis (Fig. 598-3). Probably the most common type of symptomatic tethered cord involves patients who had previously undergone closure of an open myelomeningocele and later become symptomatic with pain or neurologic deterioration. Tethered cord syndrome can also be associated with attachment of the spinal cord in patients who undergo surgical procedures that disrupt the pial surface of the spinal cord.

Figure 598-2 Child with a lipomyelomeningocele demonstrating an extraspinal mass and an asymmetry of the gluteal fold indicative of underlying occult dysraphism.

(Used with permission from Barrow Neurological Institute.)

Figure 598-3 Hairy patch or hypertrichosis usually associated with diastematomyelia.

(Used with permission from Barrow Neurological Institute.)

Clinical Manifestations

Patients at risk for the subsequent development of the tethered cord syndrome can often be identified at birth by the presence of an open myelomeningocele or by cutaneous manifestations of dysraphism. It is important to examine the back of the newborn for cutaneous midline lesions (lipoma, dermal sinus, tail, hair patch, hemangioma, port-wine stain) that may signal an underlying form of occult dysraphism. Dermal sinuses are usually located above the gluteal fold. Cutaneous abnormalities are not found in patients with an isolated thickened filum terminale. Patients who become symptomatic later in life often exhibit an asymmetry of the feet (i.e., one is smaller than the other). The smaller foot will show a high arch and clawing of the toes (Fig. 598-4). Characteristically, there is no ankle jerk on the involved side and the calf is atrophied. This condition is termed the neuro-orthopedic syndrome.

Figure 598-4 Example of the neuro-orthopedic syndrome involving a larger left foot than right foot, a high arch, and absent ankle jerk frequently associated with tethered cord regardless of the etiology.

(Used with permission from Barrow Neurological Institute.)

Three clinical syndromes can occur at the time of deterioration. The most likely clinical presentation is increasing urinary urgency and, finally, incontinence. Deterioration of motor and sensory function in the lower extremities is a compelling reason for intervention. Finally, severe generalized back pain, often radiating into the lower extremities, can occur, particularly in older adolescents and adults.

Syringomyelia is a cystic distension of the spinal cord caused by obstruction of the flow of spinal fluid from within the spinal cord to its point of absorption. There are 3 recognized forms of syringomyelia depending on the underlying cause. Communicating syringomyelia implies that cerebrospinal fluid (CSF) from within the ventricles communicates with the fluid within the spinal cord and is assumed to be the source of the CSF that distends the spinal cord. Noncommunicating syringomyelia implies that ventricular CSF does not communicate with the fluid within the spinal cord. It primarily occurs in the context of intramedullary tumors and obstructive lesions. In the final form of syringomyelia, that is, post-traumatic syringomyelia, spinal cord injury results in damage and subsequent softening of the spinal cord. This softening, combined with the scarring of the surrounding spinal cord tissue, results in progressive distension of the cyst.

Diagnostic Evaluation

MRI is the radiologic study of choice (Figs. 598-6 and 598-7). The study should include the entire spine and should include gadolinium-enhanced sequences. Specific attention should be paid to the craniovertebral junction due to the frequent association of syringomyelia with Chiari I and II malformations. Obstruction to the flow of CSF from the 4th ventricle can cause syringomyelia; therefore, most patients also should undergo imaging of the brain.

Figure 598-6 Sagittal MRI of patient with a Chiari I malformation and a holocord syrinx.

(Used with permission from Barrow Neurological Institute.)

Figure 598-7 T1-weighted MRI scan of upper spinal cord showing an extensive syringomyelia (arrow).

Tumors of the spine and spinal cord are rare in children. Different types of tumors have different relationships with the spinal cord, meninges, and bony elements of the spine (Fig. 598-8). Intramedullary spinal cord tumors arise within the substance of the spinal cord itself (Fig. 598-9). They represent between 5% and 15% of primary central nervous system tumors. This percentage may well reflect the total volume of spinal cord as opposed to brain. About 10% of intramedullary spinal cord tumors are malignant astrocytic tumors, but most are World Health Organization grade I or II tumors of glial or ependymal origin. In children, low-grade astrocytomas and gangliogliomas represent the most common tumor types with ependymomas being less common than in adults. Ependymomas in children are frequently associated with neurofibromatosis (NF 2).

Figure 598-8 Diagram of the relationship of various tumors to the spine, nerve roots, and spinal cord.

(Used with permission from Barrow Neurological Institute.)

Figure 598-9 T1-weighted MRI scan of a spinal cord tumor (arrow). The fusiform expansion of the cervical cord enhances after intravenous gadolinium injection.

Except in the context of NF 1 and NF 2, intradural extramedullary tumors are extremely rare in children. Most are nerve sheath tumors, either schwannomas or, in the case of NF 2, neurofibromas. Intraspinal meningiomas in children are essentially found only in patients with NF 2. The intradural extramedullary compartment is also a site for metastatic tumors from primary cancers such as leukemia or primitive neuroectodermal tumors.

Extradural spinal tumors characteristically begin in the bones of the spine. Primary tumors in this location include aneurysmal bone cysts, Langerhans cell histiocytosis (formerly called eosinophilic granuloma), and giant cell tumors. In infants the extradural space is often the site of neuroblastomas or ganglioneuroblastomas, which tend to be present in the epidural space and in the paraspinous tissue through the intervertebral foramen. In older patients the bones of the spine may be the site of multiple myeloma and metastases from common malignant tumors.

Spine and spinal cord injuries are very rare in children, particularly in young children. The spine of a small child is very mobile, and fractures of the spine are exceedingly rare. This increased mobility is not always a positive feature. Transfer of energy leading to spinal distortion can maintain the structural integrity of the spine but lead to significant injuries of the spinal cord. Spinal cord injury without radiographic bone (vertebral) abnormalities, called SCIWORA, is more common in children than adults. There seem to be 2 distinct forms. The infantile form involves severe injury of the cervical or thoracic spine. These patients have a poor likelihood of complete recovery. In older children and adolescents, SCIWORA is more likely to cause a less severe injury and the likelihood of complete recovery over time is high. The adolescent form is assumed to be a spinal cord concussion or mild contusion as opposed to the severe spinal cord injury related to the mobility of the spine in small children.

Although the mechanisms of spinal cord injury in children include birth trauma, falls, and child abuse, the major cause of morbidity and mortality remains motor vehicle injuries. While the mechanisms of injury and diagnosis are distinct in very small children, adolescents incur spinal cord injuries with epidemiology similar to that of adults, including significant male predominance and a high likelihood of fracture dislocations of the lower cervical spine or thoracolumbar region. In infants and children under the age of 5 yr, fractures and mechanical disruption of spinal elements are limited to the upper cervical spine between the occiput and C3.

Transverse myelitis is a condition characterized by rapid development of both motor and sensory deficits (Table 598-1). It has multiple causes and tends to occur in 2 distinct contexts. Small children, 3 yr of age and younger, develop spinal cord dysfunction over hours to a few days. They have a history of an infectious disease, usually of viral origin, or of an immunization within the few weeks preceding the 1st development of their neurologic difficulties. The clinical loss of function is often severe and may seem complete. Although a slow recovery is common in these cases, it is likely to be incomplete. The likelihood of independent ambulation in these small children is about 40%. The pathologic findings of perivascular infiltration with mononuclear cells imply an infectious or inflammatory basis. Overt necrosis of spinal cord can be seen.

In older children, the syndrome is somewhat different. Although the onset is also rapid with a nadir in neurologic function occurring between 2 days and 2 wk, recovery is more rapid and more likely to be complete. Pathologic or imaging examination shows acute demyelination.