Imaging of Back Pain in Children

Conventional Radiography

Spine radiography may not be recommended initially in patients who have had benign findings on physical and neurologic examination and whose symptoms are of short duration.¹⁸ When indicated, radiographs are a good initial diagnostic tool for the evaluation of back pain in children and should include both anteroposterior and lateral views of the spine. Collimation to the precise area of interest often helps. Oblique views are not routinely obtained in children, however, in part because of concerns regarding exposure to radiation and in part because subtle fractures are often missed on radiography. In the recent study by Feldman et al,¹¹ plain radiography demonstrated a high diagnostic yield. Among patients who had a specific diagnosis in his study, 68% were diagnosed by plain radiographs.

Nuclear Medicine, CT, and MR imaging

After plain radiography, the imaging technique best suited for imaging back pain in children is subject to debate. The clinician must be especially mindful of the amount of radiation exposure associated with each diagnostic technique—an important consideration in imaging children. The use of CT in children, for example, has increased significantly in the past 2 decades. Although CT is an excellent diagnostic tool, there is some evidence that repeated scanning (and associated ionizing radiation) may place some children at risk for fatal cancers. The principles of ALARA should be applied to reduce radiation exposure.²⁹ As a rule, the use of CT in children should be kept to a minimum, and when indicated, imaging should be restricted to the smallest FOV necessary.³⁰ When possible, imaging modalities that do not emit ionizing radiation, such as MR imaging, should be used in the pediatric population.

In the setting of persistent back pain with negative findings on plain radiographs, ^99mTc-MDP SPECT has been the criterion standard. However, the use of ¹⁸F with PET has been shown recently to provide exquisite detail.³¹ Radionuclide imaging can detect abnormalities (eg, spondylolysis, stress fractures)³² or bone lesions (eg, osteoid osteoma). In a study by Auerbach et al, ¹⁹ negative findings on a SPECT scan were 100% predictive of MBP in patients with <6 weeks of pain. MBP was diagnosed when there was no demonstrable cause of back pain and findings on all imaging studies (SPECT, CT, MR imaging) were negative. Spondylolysis, however, was more often detected by SPECT compared with MR imaging.

Achieving an effective radiation dose with SPECT is also of paramount importance, especially in cases in which a fracture requires further CT evaluation and exposes the child to yet more radiation.³³ In addition, SPECT may not identify other organic causes of back pain such as bone tumors, soft-tissue tumors, or soft-tissue infections. Until recently at our institution, back pain in the young athlete has been evaluated by a SPECT bone scan followed by CT of the affected area. These patients are now evaluated by MR imaging, and in cases in which there is some evidence of spondylolysis, the extent of healing is assessed by follow-up CT for up to 4 months following the initial diagnosis. This approach has recently been explored by Dunn et al,³³ who concluded that MR imaging should be used as the first-line imaging technique for evaluating adolescents with back pain, specifically when acute spondylolysis is suspected, because the presence of marrow edema is detected with great clarity on both sagittal STIR and fat-saturated T2 images.

CT is widely accepted as the criterion standard for the evaluation of osseous structures, and it is considered the imaging technique of choice for characterizing fractures, monitoring healing, and detecting progression.^23,33 CT alone fails, however, to detect early stress reaction and other relevant spinal abnormalities. In such cases, helical imaging is performed through the area of interest followed by 2D reconstruction of the images generated with this technique. 3D reconstruction models have become increasingly important in the preoperative evaluation of spinal trauma and scoliosis and in presurgical orthopedic planning.

MR imaging is the technique of choice in diagnosing intraspinal or paraspinal pathology, especially in younger children whose clinical histories and physical examinations are characterized by the several red flags mentioned previously. Indeed, increasing numbers of institutions use MR imaging as the first-line imaging technique when serious underlying pathology is suspected in a child with back pain.¹⁵ MR imaging is useful in evaluating soft tissue, bone marrow, and intraspinal contents, including disk disease, spinal tumors, infection, and congenital anomalies. More recently, it has been favored for evaluating bone marrow edema (evident, for example, in stress fractures) or for assessing spondylolysis.³³ On the basis of the suspected underlying abnormality, the examination is tailored accordingly. In all cases, the decision to use MR imaging must be weighed carefully against the relatively high cost of this type of study, the need to sedate younger children before and during a given examination, and the potential for adverse reactions to anesthesia and/or side effects arising from its administration.

In the sections that follow, imaging sequences are presented as they relate to specific conditions associated with back pain. Some of the common etiologies of back pain are described in the sections below. This discussion is not meant to be exhaustive and is summarized in Table 2.

Spondylolysis and Spondylolisthesis

Spondylolysis is a defect or disruption in the pars interarticularis of the vertebral arch. Bilateral spondylolysis is more frequent than unilateral spondylolysis, and L5 is the most commonly affected vertebral level.³⁵ A large prospective study of spondylolysis reported a prevalence of 4.4% in children and 6% in the general population.³⁶ The etiology of spondylolysis is controversial, with both developmental defects and trauma proposed as risk factors.^23,37 Most frequently, spondylolysis is associated with repetitive microtrauma, occurring in the adolescent during spinal growth. An increased incidence of spondylolysis is seen in adolescent athletes who practice sports with repetitive and excessive hyperextension such as gymnastics, diving, ballet, and soccer.^38,39 In the general population, spondylolysis is more frequent in males, though young female athletes are also at risk for spondylolysis.³⁹ Other risk factors include spina bifida occulta, sacral anatomy, and family history.^37,40,41

Vertebral Body Fractures

Thoracolumbar fractures are more common in older children and adolescents, while cervical fractures are more common in younger children. In athletes, acute fractures of the thoracolumbar spine are rare.²³ Plain films are useful in assessing the degree of compression of the vertebral body. Compression of <25% indicates stability, with a single anterior column involvement. CT is indicated if the compression approaches 50%, which may be indicative of anterior and middle column involvement. In children, injury may be present without evidence of radiographic abnormality. In these situations, diagnosis is often elusive, and MR imaging is indicated for evaluation of intraspinal abnormalities.

Disk Degeneration and Herniation

Intervertebral disk degeneration, a fairly common finding in children with low back pain, is seen in approximately 50% of symptomatic patients, compared with 20% in asymptomatic patients.⁴⁶ MR imaging shows loss of disk height and decreased signal intensity on T2-weighted images. The finding of disk degeneration has no impact on treatment, however.

Intervertebral disk herniations in children are similar to those in adults with 3 exceptions: 1) The size of disk herniations is larger in children than adults, 2) traumatic disk herniation in adolescents is frequently accompanied by a fracture of the adjacent vertebral endplate (apophyseal ring fracture), and 3) pediatric disk herniations are often calcified.⁴⁷ Most children with disk herniation are asymptomatic, and most patients recover completely without surgical intervention. As mentioned previously, disk herniations may be associated with apophyseal ring fractures. Apophyseal ring fractures, also known as endplate avulsion fractures, are more frequently seen in the lumbosacral spine and are best appreciated on CT and MR imaging. On CT, there is an arc-shaped or rectangular bone fragment posterior to the dorsal endplate margin.⁴⁸ On MR imaging, apophyseal fractures manifest as bone marrow edema in the donor vertebral body with the disk extending into the defect. On T2-weighted images, the disk between the fragment and the vertebral body is hyperintense. The bone fragment appears hypointense on T1-weighted images. Disk desiccation can occur with time, appearing hypointense on T2-weighted images.⁴⁹ Surgical intervention depends on clinical symptoms.^48–50

Scheuermann Kyphosis (Juvenile Kyphosis)

Scheuermann kyphosis is an osteochondrosis presenting as an abnormality of the vertebral epiphyseal growth plates.¹⁸ This condition presents as a form of adolescent thoracic or thoracolumbar kyphosis characterized by anterior wedging of 3 or more contiguous vertebrae of 5° or greater resulting in a thoracic kyphosis greater than 35°, with the apex more commonly seen between T7 and T9. Other radiologic criteria for the diagnosis of Scheuermann kyphosis include irregular upper and lower endplates with Schmorl nodes, disk-height loss, and associated apophyseal ring fractures (Fig 4). Etiologies for this condition include genetic factors, repetitive microtrauma, osteoporosis, osteochondrosis, necrosis ring apophysis, and tight hamstrings.²³

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Fig 4.

Scheuermann kyphosis in a 15-year-old boy. A, Sagittal 2D CT reconstruction image demonstrates midthoracic kyphosis with anterior wedging of at least 3 consecutive vertebrae with presence of Schmorl nodes. B, Sagittal 3D CT reconstruction image demonstrates midthoracic kyphosis with anterior wedging of at least 3 consecutive vertebrae with the presence of Schmorl nodes.

Patients present with pain typically localized to the midscapular region located over the kyphotic deformity. The pain usually intensifies gradually, though without an episode of precipitating trauma; it generally worsens after activity and improves with rest. Conservative treatment is strongly recommended in patients who have spinal growth remaining and who have responded well to therapy (ie, physical therapy and sometimes the use of a brace).^22,23

The initial diagnostic imaging evaluation consists of plain radiographs. CT and MR imaging may be indicated to confirm or further delineate disease (Fig 5). They may also be helpful in detecting associated apophyseal ring fractures. Atypical Scheuermann kyphosis (lumbar type) occurs at the thoracolumbar level with the apex situated between T10 and T12. There is a greater incidence reported in males²² and among athletes who participate in sports requiring repetitive flexion such as wrestling and football.²²

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Fig 5.

Scheuermann kyphosis in a 14-year-old boy. Sagittal T2-weighted image demonstrates thoracic kyphosis with mild anterior wedging of the T10–T12 vertebral bodies with slight disk space irregularity and Schmorl nodes. Minimal annular bulges slightly indent the ventral aspect of the thecal sac.

Disk Calcification

Intervertebral disk calcification is a rare entity in childhood. The etiology remains unknown, though inflammation and trauma have been suggested as possible causes. Intervertebral disk calcification can be an incidental finding or can present with symptoms such as pain, stiffness, decreased range of motion, muscle spasm, tenderness, and torticollis. Some patients present with fever and increased ESR.^51–53 In general, the symptoms are relatively brief, rarely lasting longer than several weeks.⁵² Neurologic complications may occur, however, when the calcification herniates through the fibrous annulus, causing nerve root or spinal cord compression. Anterior or posterior herniation of the calcified intervertebral disk material may also develop. Dysphagia associated with anterior disk protrusion has been described.⁵⁴

Disk calcification is most frequently found in the cervical spine, less frequently in the thoracic spine, and only rarely in the lumbar spine.⁵² Symptoms are seen most frequently with calcification of the cervical spine, typically at the level of C7–T1, though multiple levels can be affected.⁵¹ Boys seem to be slightly more often affected than girls.^52,53,55 The average age at diagnosis is 7–8 years, with a range of 7 days to 20 years.^51,53,56

Disk calcification in children can be seen as part of a syndrome or disease, such as Morquio syndrome, I cell disease, Patau syndrome, congenital or acquired vertebral fusion, hyperparathyroidism and other hypercalcemic states, osteomyelitis, tuberculosis, and diskitis.⁵⁶

Disk calcification, while often difficult to identify, is usually seen on plain film or CT as an attenuated, round, oval, flattened, or fragmented calcification in the nucleus pulposus (Fig 6). CT or MR imaging may also demonstrate an associated disk herniation. On MR imaging, calcification can appear as decreased signal intensity on T2-weighted images or as hyperintense on T1-weighted images.

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Fig 6.

Disk calcification in a 6-year-old boy. A, Axial CT image demonstrates posterior extrusion of a calcified disk. B, Sagittal 2D CT reconstruction image demonstrates calcification in the central portion of the disk.

Disk calcification in children is considered a self-limiting condition with a good prognosis. Dai et al⁵² have reported that in a series of 17 cases of disk calcification, the calcific deposits had completely resolved. While the severity of the symptoms is often not correlated with the radiographic findings, conservative treatment is generally recommended, even in the setting of disk herniation.⁵² At times, however, surgery is a preferable course, especially in patients with intractable pain and progressive neurologic deficit.⁵⁷

Diskitis

Diskitis is an inflammatory process or infection of the intervertebral disk. Diskitis has a bimodal distribution occurring in young children between 6 months and 4 years of age, with a second subtler peak from 10 to 14 years of age.⁶¹ Although the pathophysiology of diskitis is not entirely understood, it is thought to be related to the presence of vascular channels that terminate in the cartilaginous portion of the disk and disappear later in a life, thus making the disk susceptible to infection. Abundant intraosseous arterial anastomoses during childhood are thought to promote clearance of micro-organisms or entrapped emboli, making the vertebral body less susceptible to infarction from septic emboli.^62,63 Most experts attribute the etiology to an infectious process.

Diskitis occurs typically in the lumbar region, most often at the L2–L3 and L3–L4 levels. Clinical presentation varies widely, making the diagnosis difficult. Symptoms and signs may include, among others, fever, back pain, irritability, and refusal to walk or sit up. Mild leukocytosis and an elevated ESR and C-reactive protein level are usually present; results of blood cultures can often be negative.⁶⁴ In one-third to one-half of patients, however, results of blood cultures or biopsy materials are positive and the infectious agent is almost always Staphylococcus aureus.⁶⁰

While findings of radiographs of the spine are usually normal in the early stages of disease, findings of bone scintigraphy can be positive as soon as 1–2 days after the onset of symptoms, demonstrating increased uptake in the intervertebral bodies on each side of the disk involved. However, bone scintigraphy is not specific and cannot differentiate diskitis from other causes of back pain. The earliest time interval between the onset of symptoms and a positive radiograph has been 12 days. In the series of Fernandez et al,⁶⁰ of 33 children with diskitis, 76% had abnormalities detected on spine radiographs and the most frequent finding was decreased height of the disk space and erosion of adjacent vertebral endplates.

MR imaging is the study of choice because it can detect diskitis early on. MR imaging findings include loss of the normal hyperintense signal intensity of the disk on T2-weighted images, narrowing or complete absence of the disk, and abnormal increased T2-weighted signal intensity in the adjacent vertebral bodies, consistent with marrow edema (Fig 7A).⁶⁵ There may be contrast enhancement of the disk and adjacent vertebral body (Fig 7B). MR imaging detects disk extrusion and the formation of paraspinal and epidural abscesses. Any evaluation for suspected diskitis should exclude spinal cord compression.^58,65,66 Follow-up radiographs will show persistent narrowing of the intervertebral disk space and sclerosis at adjacent vertebral bodies weeks or months after the initial diagnosis. Most patients, moreover, will be asymptomatic within 3 weeks following antibiotic treatment, and in such cases, disk space height can sometimes be restored.

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Fig 7.

Vertebral osteomyelitis and diskitis in a 7-year-old boy. A, Sagittal T2-weighted image with fat saturation shows marked disk space narrowing at L2–L3 with hypointense T2 signal intensity within the disk. There is increased T2 prolongation in adjacent vertebral bodies. B, Sagittal T1-weighted MR image with fat saturation with gadolinium shows diffuse enhancement in the L2–L3 vertebral bodies and intervening disk space.

Vertebral Osteomyelitis

In children, osteomyelitis occurs more frequently in the long bones than it does in the spine. When it does present in the spine (vertebral osteomyelitis), it is thought to occur when micro-organisms lodge in the low-flow end-organ vasculature adjacent to the subchondral plate region. A history of trauma has been associated with vertebral osteomyelitis and diskitis.^67,68 Possible infectious causes include bacteria (S aureus)⁶⁰ and tuberculosis in endemic areas.⁶⁹ Other etiologies include coccidioidomycosis, blastomycosis, and actinomycosis. The clinical presentation of the older child with vertebral osteomyelitis includes fever and back pain in the lumbar, thoracic, or cervical regions. Initially, plain radiographs may demonstrate localized rarefaction of 1 vertebral body and, later, destruction of bone, usually anteriorly with osteophytic formation.^60,63

Diskitis and vertebral osteomyelitis often, however, cannot be differentiated in the early stage of the disease process. Nuclear medicine bone scans and CT are not useful in providing a specific diagnosis of vertebral osteomyelitis. MR imaging is the technique of choice for the assessment of vertebral osteomyelitis, with high sensitivity and specificity. MR imaging should include T1-weighted images and T2-weighted images with fat saturation (or STIR) in the sagittal and axial planes. Bone marrow edema, an early nonspecific finding, presents as low signal intensity on T1-weighted and high signal intensity on STIR or T2-weighted images with fat saturation (Fig 7A).⁶⁴ Fat-suppressed T1-weighted images with contrast can detect early cases of spinal infection and can determine accurately the extent of disease (Fig 7B).⁶⁴

It is often difficult to differentiate osteomyelitis from leukemia/lymphoma or metastatic disease. These entities usually affect several noncontiguous vertebral bodies, do not involve the disk space, and may not produce a paraspinal mass.³⁵

Primary Neoplasms

Osteoid Osteoma.

Osteoid osteoma, a benign osteoblastic lesion of unknown etiology, was first described by Jaffe in 1935.⁸⁰ This lesion consists of a nidus of osteoid matrix and a stroma of loose vascular connective tissue. The nidus may be calcified and surrounded by sclerotic reactive bone, usually measuring <15 mm. Of all osteoid osteomas, 10% are localized in the spine. Osteoid osteoma is more frequently found in boys; most affected children are 10–12 years of age at the time of diagnosis.

Back pain in children with osteoid osteoma is more intense at night and can be alleviated by aspirin. This lesion often presents as painful scoliosis of the thoracic and lumbar spine secondary to muscle spasm, which differs from nonpainful idiopathic juvenile scoliosis localized in the thoracic spine. The lesion is usually on the concave side of the curve.^81,82

The radiologic appearance of spinal osteoid osteoma is similar to that of other parts of the skeleton characterized by a radiolucent nidus, which may contain central calcification surrounded by sclerotic bone. These lesions are usually localized to the posterior elements, most often in the lamina and pedicles, but can also occur in the transverse and spinous processes (Fig 8).^81,83

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Fig 8.

Osteoid osteoma in a 14-year-old girl. A, ^99mTc-MDP SPECT scan demonstrates mild increased uptake in the spinous process of L5. B, Axial CT image shows a lucency in the tip of the spinous process of L5 with surrounding sclerosis and a tiny sclerotic nidus. C, Axial T1-weighted MR image with gadolinium demonstrates homogeneous enhancement of the lesion at the tip of the spinous process of L5.

Although bony sclerosis in osteoid osteoma can be detected on conventional radiography, targeted CT is the preferred cross-sectional technique for the demonstration and precise localization of the lucent nidus (Fig 8B).^{84 99m}Tc bone scintigraphy is accepted as the most accurate technique for detection of suspected osteoid osteoma, showing marked uptake of the bone tracer (Fig 8A).^81,85

On MR imaging, osteoid osteoma can have a very heterogeneous and variable appearance. The nidus appears isointense on T1-weighted images and hypointense on T2-weighted FSE sequences. Matrix mineralization can present as a focal signal-intensity void. Perinidal edema is usually present and is graded according to location and extension.⁸⁶ MR imaging is also useful in determining any involvement of the spinal canal and cord.¹¹ Dynamic gadolinium-enhanced MR imaging can often improve the conspicuity of osteoid osteomas over thin-section CT (Fig 8C).^87,88 Before surgical or percutaneous treatment (ie, excision, laser treatment, or thermocoagulation), precise localization of the lesion must be determined. CT-guided RFA, a minimally invasive and safe method, has been proved an effective treatment for spinal osteoid osteoma.^89,90 Surgery is usually reserved for lesions causing nerve root compression. Another therapeutic approach is gamma probe−guided surgery, which is typically used when RFA is not applicable and complete resection is difficult.⁹¹

Osteoblastoma.

Osteoblastoma, also known as giant osteoid osteoma, contains a fibrovascular stroma with numerous osteoblasts, osteoid tissue, well-formed woven bone, and giant cells. Osteoblastoma is usually >2 cm in diameter. Forty percent of all osteoblastomas occur in the spine, specifically in the neural arch, and can often extend to the vertebral body. An associated soft-tissue mass can be present. A neurologic deficit also may be present in approximately 25%–50% of cases. On imaging, osteoblastoma can show progression and aggressive features with bone destruction and a soft-tissue mass but no surrounding bone edema. Osteoblastomas can recur.⁹²

In patients with osteoblastoma, pain at night is not as severe as it is in osteoid osteoma and is not relieved by aspirin. Neurologic deficits occur more frequently in osteoblastomas. CT can demonstrate a geographic lesion with sclerotic borders (Fig 9A). On MR imaging, most lesions have T2-weighted hypointense areas consistent with immature chondroid matrix, hypercellularity, calcifications, and hemosiderin on histologic analysis. Enhancement with gadolinium is often present, which may be lobular, marginal, or septal (Fig 9B).⁹³ Treatment is curettage with bone graft or methylmethacrylate placement. Preoperative embolization may be extremely helpful.^92,94

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Fig 9.

Osteoblastoma in a 12-year-old boy. A, Axial CT image demonstrates an expansile lytic lesion in the pedicle of the C5 vertebra, which involves the C4–C5 facet joint and the left transverse foramen. B, Axial T1-weighted image with gadolinium and fat saturation demonstrates extensive enhancement in the adjacent bone and the left paraspinal soft tissues of the cervical spine, with extension into the epidural space.

LCH.

LCH (previously termed “histiocytosis X”) comprises a group of rare disorders of unknown etiology, characterized by abnormal proliferation of histiocytes in a variety of organs, causing tissue destruction. This cellular infiltration can affect the bone, skin, and internal organs. Traditionally, LCH has been classified according to certain clinical manifestations, on the age of presentation, and on the severity and distribution of disease. Three main forms described in the order of severity are the following: eosinophilic granuloma, Hand-Schüller-Christian disease, and Letterer-Siwe disease. Eosinophilic granuloma, the most frequent and benign, can manifest as a unifocal or multifocal osseous lesion, with or without soft-tissue involvement, presenting at any age. Hand-Schüller-Christian disease presents in children or young adults; it manifests with the characteristic triad of exophthalmos, osteolytic skull lesions, and diabetes insipidus. Acute disseminated LCH (Letterer-Siwe disease), usually seen in children <3 years of age, can affect multiple organs and systems with a lethal outcome.⁹⁵

When the spine is involved, LCH most frequently presents with local back pain; the thoracic vertebrae is the most commonly affected region (54%), followed by the lumbar spine (35%) and cervical spine (11%). There may be associated leukocytosis and fever. On conventional radiography, LCH can present as a lytic nonsclerotic destructive vertebral lesion; as a vertebra plana (with preserved adjacent disks and posterior elements rarely involved); or as scoliosis, which is far less common. On CT, the nonsclerotic destructive osseous lesion can present with a paraspinal enhancing soft-tissue mass. Epidural extension may occur. A collapsed vertebra plana is a typical form of presentation (Fig 10A).

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Fig 10.

LCH−vertebra plana in an 18-month-old boy. A, Sagittal 2D CT reconstruction image of the lumbar spine shows a collapsed L3 vertebral body. B, Sagittal T2-weighted MR image of the lumbar spine demonstrates a vertebra plana deformity with significant decreased height of the L3 vertebral body and preservation of the adjacent intervertebral disks.

MR imaging is the technique of choice for staging LCH and monitoring response to therapy.⁹⁶ LCH may manifest as a homogeneously enhancing soft-tissue mass that is hypointense on T1-weighted images and hyperintense on T2-weighted images, with or without a pathologic fracture. When a vertebra plana is present, the classic appearance is 2 vertebral disks in apposition without an intervening normal vertebral body (Fig 10B). The differential diagnosis for vertebra plana includes histiocytosis; tumors; and infections such as tuberculosis, leukemia, lymphoma, trauma, Gaucher disease, and neurofibromatosis.

Treatment for histiocytosis varies and can include conservative management, curettage with allograft implantation, chemotherapy, steroids, and external beam radiation therapy. Spontaneous regression of single spinal lesions with conservative treatment also has been described.⁹⁷

Ewing Sarcoma.

Ewing sarcoma most commonly affects the spine as metastatic disease from a primary tumor elsewhere in the body but can also present as a primary osseous lesion that is centered in the vertebral body, in the posterior elements, or in the sacrum. Spinal canal invasion is common.⁹⁸ Rarely, Ewing sarcoma can present as an extraosseous lesion located in the epidural region.⁹⁹ Clinically, Ewing sarcoma can present with local pain. Neurologic deficits, including muscle weakness and sensory deficiencies, can be present at the time of initial presentation. Bladder and bowel dysfunction are usually late manifestations. Constitutional symptoms, however, are rare.^98,100

On conventional radiography and CT, Ewing sarcoma presents as a permeative osteolytic lesion with a “moth-eaten” appearance. An extraosseous noncalcified soft-tissue mass can be present in 50% of cases (Fig 11A). Although CT can differentiate Ewing sarcoma from osteosarcoma by confirming the absence of a tumor matrix, it may also underestimate soft-tissue involvement. MR imaging is an excellent tool for delineating soft-tissue extension and invasion into the spinal canal. Ewing sarcoma appears T1-hypointense to normal bone; and on T2-weighted images, it varies from hypointense to hyperintense. Moderate enhancement of the lesion is present with areas of necrosis (Fig 11B).¹⁰¹ Lymphoma and neuroblastoma can have a similar radiographic appearance.

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Fig 11.

Ewing sarcoma of the lumbar spine in a 17-year-old boy. A, Post-contrast-enhanced axial CT image demonstrates a large partially calcified mass in the paraspinal musculature at the L3–L5 levels. The mass involves the adjacent spinous process and extends into the spinal canal. B, Axial T1-weighted postgadolinium MR image shows extensive enhancement of the mass with epidural extension.

Lymphoma and Leukemia

Spinal involvement of lymphomas and leukemias in children is relatively rare. More often the spine is involved in disseminated disease. Metastases are typically located in the epidural or paravertebral space, though bony and leptomeningeal spread can occur.¹⁰² In 4% of all patients with lymphoma, an epidural lesion can be the initial site of presentation.¹⁰³ Primary spinal lymphoma, most often non-Hodgkin disease, has been reported in children.^104,105 Children with acute myelogenous leukemia can present with a solid spinal tumor in the epidural compartment, known as granulocytic sarcoma (chloromas).^106,107 Several cases of granulocytic sarcomas have been reported in patients without leukemia.^108,109 Chloromas are highly vascularized lesions composed of immature granulocytes.¹¹⁰ On MR imaging, these lesions are isointense to hyperintense on T1-weighted images and isointense to hypointense on T2-weighted images (Fig 12 ) and may demonstrate moderate-to-marked contrast enhancement.¹¹⁰ These tumors tend to respond rapidly to first-line therapies (ie, chemotherapy and radiation).¹⁰⁸

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Fig 12.

Lymphoblastic lymphoma in a 15-year-old boy. Sagittal T2-weighted MR image demonstrates an intraspinal extradural well-circumscribed hypointense lesion at the T2–T4 level with compression of the spinal cord with hypointensity diffusely in the vertebral bodies.

Unlike the high T1 signal intensity seen in the bone marrow of healthy children, the bone marrow in children with lymphoma and leukemia is low in signal intensity on T1-weighted images (Fig 13). It is unclear if this is the result of leukemic infiltration and/or increased activity of the bone marrow or is secondary to treatment.⁴⁷ Low signal intensity, however, is not a reliable marker in children younger than 5 years of age because bone marrow in toddlers and infants may still have active hematopoiesis (red marrow), which typically exhibits low signal intensity on T1-weighted images.¹¹¹ Moreover, following the administration of gadolinium, bone marrow in young children can enhance heterogeneously and should not be confused with tumor infiltration.⁴⁷ Pathologic vertebral compression fractures can be a manifestation of acute lymphoblastic leukemia in childhood,^112,113 secondary to severe osteoporosis and occurring in 1%–7% of patients diagnosed with this cancer.¹¹²

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Fig 13.

Acute lymphoblastic leukemia in a 3-year-old boy. A, Sagittal T1-weighted MR image demonstrates diffuse abnormal low signal intensity in the lumbar spine bone marrow consistent with a diffuse infiltrative process. B, Sagittal T1-weighted image of a healthy 3-year-old boy with normal higher T1 signal intensity of the vertebral body marrow relative to the intervertebral disks.

Intramedullary Spinal Cord Tumors

Astrocytoma.

Astrocytoma is the most common spinal cord tumor of childhood, comprising 30%–35% of intraspinal tumors and >60% of intramedullary tumors. Astrocytomas are classified pathologically into 4 grades based on the WHO classification: pilocytic astrocytoma (grade 1), fibrillary astrocytoma (grade 2), anaplastic astrocytoma (grade 3), and glioblastoma multiforme (grade 4). In children, 80%–90% of intramedullary astrocytomas are most often low-grade astrocytomas. The most common histologic types are pilocytic astrocytoma and fibrillary astrocytoma. Although uncommon, high-grade neoplasms (WHO grades 3 and 4) may also occur.¹¹⁴ Astrocytomas are slow-growing tumors that may present clinically with back pain, paresthesias, and spasticity. Subarachnoid dissemination may occur. Astrocytomas most often occur in the cervical and thoracic spinal cord and tend to be eccentrically located. Intramedullary astrocytomas affecting the entire cord (ie, holocord tumor) have also been reported (Fig 14).¹¹⁵

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Fig 14.

Astrocytoma in an 11-year-old boy. A, Sagittal T2 MR image of the cervical and upper thoracic spine demonstrates a partly cystic and solid intramedullary spinal cord tumor. B, Sagittal T2 MR image of the thoracic spine demonstrates a partly cystic and solid intramedullary spinal cord tumor. C, Sagittal T1-weighted postcontrast MR image shows enhancement of the solid portions of the tumor and peripheral enhancement of the cystic components.

On conventional radiography, occasionally enlargement of the spinal canal or scoliosis is seen. CT may show expansion and remodeling of the bone.

MR imaging is the technique of choice for evaluating intramedullary spinal cord tumors, effectively demonstrating cord expansion that typically spans fewer than 4 vertebral levels. Tumors of this type appear hypointense to isointense on T1-weighted images and hyperintense on T2-weighted images (Fig 14A, -B). Cysts, necrosis, and occasionally hemorrhage may be present. Edema or a syrinx may be seen above and below the level of the lesion. Contrast enhancement is usually intense and can be homogeneous, heterogeneous, partial, or total (Fig 14C).^72,102

Differential diagnoses of intramedullary lesions include ependymoma, ganglioglioma, and hemangioblastoma; autoimmune or inflammatory myelitis (acute transverse myelitis, multiple sclerosis, and infectious myelitis); and vascular diseases such as cord ischemia or infarction.

Ependymoma.

Ependymoma is uncommon in children except in association with neurofibromatosis type 2 and is usually a WHO grade 2 tumor. These tumors are slow-growing, presenting more often in adolescence with a slight male predilection. The origin of ependymomas is presumably from the ependymal cell remnants of the central canal. As a result, the extension of this tumor is circumferential and vertical along the central canal and centrally located in the cord, causing expansion of the gray matter.^72,102 On conventional radiography and CT, there may be spinal canal widening, posterior vertebral body scalloping, widened interpediculate distance with thinning of the pedicles, and scoliosis (though uncommon).

On MR imaging, ependymomas are T1 hypointense or isointense and T2 hyperintense with well-circumscribed lesions and are characterized by expansion of the spinal cord. Hemorrhage and cysts can be present. In ≤20% of cases, deposits of hemosiderin may be seen in the cranial and caudal margins of the lesion, a so-called “cap sign.”¹¹⁶ Cord edema can also be present. Enhancement of the solid component is usually intense and well-delineated.

Myxopapillary ependymomas, a distinct variant of spinal ependymomas, are categorized as WHO grade 1 lesions and occur most commonly in the lumbosacral region. These tumors originate within the terminal filum or the conus medullaris, are rare in children, and account for 13% of all spinal ependymomas. Although myxopapillary ependymomas are considered benign, they tend to be more aggressive in children than in adults. The most common symptom in the series of Bagley et al was pain.¹¹⁷ Other symptoms include motor, sensory, urinary, and gait abnormalities. Tumor spread may occur via the subarachnoid space, invade locally, or rarely metastasize outside the central nervous system. MR imaging findings in myxopapillary ependymomas are nonspecific; however, certain features may suggest this type of tumor, including an intradural extramedullary thoracolumbar mass spanning several vertebral levels in the lumbar and sacral canal. These tumors tend to be T1 hypointense and T2 hyperintense and almost always enhance homogeneously after intravenous contrast administration (Fig 15).¹¹⁷

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Fig 15.

Myxopapillary ependymoma in a 12-year-old boy. Sagittal T1-weighted postcontrast MR image demonstrates an intradural extramedullary mass lesion extending from the T12 to L3 levels and a second lesion at the L5–S2 level with diffuse enhancement. There is associated scalloping of the posterior aspects of the lumbar vertebral bodies.