Imaging of Back Pain in Children and Adolescents Nabil J. Khoury, MD, Mukbil H. Hourani, MD, Mohammad M.S. Arabi, MD, Faysal Abi-Fakher, MD, and Maurice C. Haddad, MD, FRCR Purpose: To present the imaging findings of the wide spectrum of musculoskeletal diseases causing back pain in children and adolescents. Discussion: Back pain in children is a rare condition but may denote a serious health problem; hence, full clinical history, physical examination, and appropriate laboratory studies should be obtained. In this scientific exhibit, we present the imaging findings of the variable musculoskeletal diseases that are associated with back pain in children and adolescents. These disease processes include scoliosis of various causes; spondylolysis; spondylolisthesis; traumatic injuries; disc degeneration and herniation; Scheuermann s disease; spondylodiscitis; tumors (primary, secondary, hematogenous); and miscellaneous conditions (eg, metabolic disorders, sickle cell disease, osteoporosis). Conclusion: A wide spectrum of diseases causing back pain in children is presented. Radiologists should be aware of the imaging findings of this rather uncommon entity to help in reaching the appropriate diagnosis. Back pain in the pediatric age group is a rare clinical presentation and is significantly less common than in adults. In the absence of traumatic insult, back pain in children and adolescents frequently denotes serious underlying disease; hence, careful and thorough investigation should be performed by clinical, laboratory, and imaging examinations. In this pictorial review we will discuss and present the imaging findings of variable diseases that cause back pain in children and adolescents. The diseases are categorized in Table 1 and include the following: (1) various traumatic injuries; (2) diseases secondary to specific growth disturbance such as disc degeneration, From the Department of Diagnostic Radiology, American University of Beirut Medical Center, Beirut, Lebanon. Reprint requests: N. J. Khoury, MD, Department of Diagnostic Radiology, American University of Beirut Medical Center, PO Box 113-6044 Beirut, Lebanon. E-mail: nk01@aub.edu.lb. Curr Probl Diagn Radiol 2006;35:224-44. 2006 Mosby, Inc. All rights reserved. 0363-0188/2006/$32.00 0 doi:10.1067/j.cpradiol.2006.07.007 TABLE 1. Classification of diseases causing back pain in children and adolescents A. Traumatic 1. Mechanical or sports injury 2. Discogenic herniation 3. Traumatic spondylolysis and secondary spondylolisthesis 4. Ring apophyseal fracture B. Diseases related to growth disturbance 1. Disc degeneration 2. Spondylolysthesis without spondylolysis 3. Scoliosis 4. Scheuermann s disease C. Infections/Inflammation 1. Tuberculous 2. Nontuberculous 3. Inflammatory spondyloarthropathy D. Neoplastic disorders 1. Benign a. Osteoid osteoma b. Osteoblastoma c. Aneurysmal bone cyst 2. Malignant a. Langerhans cell histiocytosis b. Osteosarcoma c. Ewing s sarcoma d. Leukemia e. Lymphoma f. Metastases E. Hematological disorders 1. Sickle cell disease F. Metabolic disorders 1. Osteoporosis 2. Alkaptonuria G. Miscellaneous 1. Osteopetrosis nontraumatic spondylolisthesis, Scheuermann s disease, scoliosis; (3) progressive diseases such as infections, inflammations, benign and malignant neoplasia (both primary and secondary), bone marrow infiltrative tumors; (4) chronic or systemic diseases including hematological and metabolic diseases. Relevant imaging findings are summarized in Table 2. Diseases related to the nervous system (eg, spinal cord lesions) will not be discussed in this article. 224 Curr Probl Diagn Radiol, November/December 2006
TABLE 2. Summary of relevant and characteristic clinical and imaging findings of diseases causing back pain in children and adolescents Disease process Clinical findings Relevant imaging findings A. Trauma History of trauma 1. Mechanical Muscle spasm 2. Disc bulge/herniation Sciatica 3. Spondylolysis/spondylolisthesis Sports injury 4. Ring apophyseal fracture Sports injury, sciatica B. Growth disturbance 1. Disc degeneration 2. Spondylolisthesis without spondylolysis 3. Scoliosis Low back pain, self-limiting or recurrent Back pain Straight back, fractures, bone marrow edema Disc bulge or herniation by MRI Pars edema or defect, anterior translation Posteriorly avulsed bone fragment off vertebral body Disc of low-signal intensity on T2W MRI Absent or deficient facets, elongated pars Idiopathic Postural deformity, with or without pain Rotoscoliosis without other abnormalities Congenital Pain, associated congenital diseases (neurological, cardiac, urogenital) Abnormality in vertebral segmentation and formation 4. Scheuermann s disease Pain mainly lumbar, increased thoracic kyphosis in adolescents Vertebral wedging, endplate irregularity, Scmorl s nodes, disc space narrowing C. Infectious/Inflammatory 1. Tuberculous spondylodiscitis Insidious back pain, neurological deficit, increased kyphosis, fever, Osteitis discitis, paravertebral and/or epidural abscess, bone destruction or sclerosis night sweats 2. Nontuberculous spondylodiscitis Pain, stiff gait, fever, irritability Discitis with disc space narrowing, irregular enplate, and vertebral loss of height MRI: vertebral bodies: low signal on T1W, high signal on T2W Disc: high signal on T2W 3. Inflammatory arthritides Back pain and stiffness Sacroiliitis, vertebral squaring. MRI: edema or erosions at vertebral corners D. Neoplastic disorders 1. Benign Osteoid osteoma Osteoblastoma Aneurysmal bone cyst Painful scoliosis at night Painful scoliosis Pain, neurologic symptoms Nidus calcification, surrounding sclerosis Lytic expansile lesion, soft-tissue component Lytic expansile lesion, fluid fluid levels on MRI 2. Malignant Langerhans cell histiocytosis Back pain Vertebral body collapse Osteosarcoma Back pain Posterior elements vertebral body destructive mixed lytic and sclerotic Ewing sarcoma Back pain, neurological symptoms, Vertebral body lytic, sclerotic, or mixed fever Leukemia Back pain, fever, fatigue Generalized decreased bone density, geographic permeative lesion Lymphoma Back pain, neurological symptoms Destructive lesion MR: low signal on T1W, high or low signal on T2W Metastases Back pain neurological symptoms Lytic or blastic lesions, vertebral collapse History of primary tumor E. Hematologic disorders Sickle cell disease Back pain, symptoms related to sickle crisis and organ infarction Central endplate depression ( H vertebrae) F. Metabolic disorders Osteoporosis (Primary or secondary) Back pain, repetititive fractures Diffuse decreased bone density, vertebral collapse Symptoms related to chronic diseases in the secondary form Alkaptonuria Back pain Disc space narrowing, disc and interosseous ligament calcifications Increased kyphosis G. Miscellaneous Osteopetrosis Back pain, fractures, diffuse pain of the involved bones Osteosclerosis, sandwich vertebrae, bone within bone appearance Trauma The injuries implicated in spine trauma are mostly due to overuse and microtrauma, with the most common bone injury being spondylolysis. In athletes, back pain may have several causes that may be 1 (1) mechanical (most common) with strain on the paravertebral liga- Curr Probl Diagn Radiol, November/December 2006 225
FIG 2. Traumatic fracture. A 5-year-old boy with compression fracture of L1 vertebral body resulting in minimal depression of the superior endplate and anterior wedging (arrows). FIG 1. An 11-year-old boy with muscle spasms following trauma. There is straightening of the lumbar lordosis (straight back syndrome). ments and muscles as well as on the facet joints; (2) discogenic with the herniated lumbar disc being uncommon; (3) vertebral apophyseal fractures involving the vertebral growth plate; and (4) spondylolysis (pars injury and fracture). Mechanical and Sport Injuries Children have great elasticity of their spinal column that increases the incidence of cord injuries without bone or joint injury. 2 When present, bone and ligament injuries have high incidence of pain, 2 with the latter presenting with acute self-limiting episodes. 3 Most spine injuries are mild, resulting in bone marrow contusion, ligament sprain, or muscle strain. Commonly, the injury results in straight back syndrome caused by muscle spasm and pain (Fig 1). 2 Vertebral body fractures and dislocations are infrequent (Fig 2). 3 Disc Bulge and Herniation Bulging discs may be painful, frequently occurring without disc degeneration (Fig 3). Disc protrusion is more common in symptomatic patients, although Scheuermann s disease contributes also to the risk of recurrent low back pain. 4 In adolescents, disc herniation is more commonly traumatic than degenerative (Figs 4 and 5). 3,5 The herniation is usually sudden and occurs after significant extension of the spine (Fig 4). It might also be associated with excess loading, resulting in disc herniation and/or degeneration. 5 Associated vertebral fractures may occur (Fig 5). In disc 226 Curr Probl Diagn Radiol, November/December 2006
FIG 4. A 3-year-old girl with acute traumatic back pain after being aggressed by her older brother from the back, resulting in hyperextension of the spine. Sagittal T2W image showing a large annular tear and disc protrusion at L5-S1. Bone marrow contusion is noted at the lower posterior corner of L5 body seen as an area of high signal intensity. FIG 3. A 15-year-old girl with low back pain. Sagittal T2-weighted image of the lumbar spine showing bulging discs between L3 and S1 (arrows). herniation, two-thirds of the patients have localized pain and one-third has sciatica. 3 Other reports state that about 92% of the patients have sciatica, 58% have sciatica with back pain, and 2% have isolated back pain. 6 In adolescents, the herniated disc material is usually larger than in adults. Disc bulge and herniation is best diagnosed by magnetic resonance imaging (MRI) (Figs 3-5). Traumatic Spondylolysis and Secondary Spondylolisthesis Spondylolysis is a defect in the pars interarticularis, which is the weakest point of the vertebra. 3 It sometimes results in anterior translation of the affected vertebra, so-called spondylolisthesis. The cause of spondylolysis is usually repetitive microtrauma or mechanical fatigue typically seen in athletic young adolescent boys. 1,3 Complete fracture from single trauma is less common. 7 Congenital defect is unlikely. 6,8 Sports activities implicated in spondylolysis include mainly gymnastics (typically with hyperextension), contact sports (eg, soccer), and dancing. 3,6,9 There is seldom history of severe trauma. 10 The most commonly affected area is the lower lumbar spine, mainly L5. 6,10 Spondylolysis is one of the commonest causes of low back pain but may be asymptomatic. 6 The degree of slipping may or may not correlate with the degree of pain. The most common affected age group is 10 to 15 years. On imaging, the lateral and oblique radiographs of the spine readily show moderate size defect with or without compensatory sclerosis (Fig 6). 1 However radiographs may be initially normal since spondylolysis starts as a stress phenomenon that progresses later into a fracture. Single-photon emis- Curr Probl Diagn Radiol, November/December 2006 227
FIG 6. A 15-year-old boy with low back pain. Conventional radiograph shows spondylolysis of L5 (arrow) with grade I spondylolisthesis of L5 over S1. FIG 5. A 16-year-old boy with traumatic fracture of L3 vertebral body. Sagittal T2W MR image. There is L3 fracture with posterior bulging of the L2-L3 disc (black arrow). In addition, a thin hypointense fracture line (white arrows) is noted within L2 vertebral body not seen on radiograph (image not shown). Both L2 and L3 fractures are surrounded by high signal intensity bone marrow edema. sion computed tomography (SPECT) plays an important role in detection of such stress injuries and has higher sensitivity than planar bone scan and radiographs (Fig 7A). 7-9 Normal SPECT scan excludes pars injuries. Computed tomography (CT) scan has a higher sensitivity than conventional radiographs in detecting pars fractures but may be still normal when only bone marrow edema is present. MRI is not usually used to diagnose spondylolysis but can show large defects or pars edema that may evolve to a defect (Fig 7B). Ring Apophyseal Fracture Ring apophyseal fracture is a fracture of the posterior vertebral endplate, most commonly seen in the lumbar spine, mainly the inferior rim of L4. 11,12 It very commonly results in low back pain and sometimes sciatica. 13 It is frequently seen along with disc degeneration and disc herniation that usually does not protrude beyond the dissociated bone fragment. The small fractured osseous fragments are frequently separated from the vertebra with interposition of disc material. Injury to the ring apophysis may be produced by both traction (annulus fibrosis, longitudinal ligaments, psoas muscle) and compression (shear injury 228 Curr Probl Diagn Radiol, November/December 2006
FIG 7. A 16-year-old athletic boy presenting with left-sided low back pain of 2 months duration. Conventional radiographs were normal. (A) SPECT bone imaging showing an increased uptake at the level of the left pars interarticularis of L5 (arrows), denoting active process causing the pain. (B) Axial T2W MR image showing high signal on T2W involving the left pars interarticularis of L5 representing edema (arrow) due to a stress phenomenon, an early stage of spondylolysis. accumulating between the vertebral body and ring apophyses). 5 Almost all affected patients are involved in sports secondary to repetitive or acute trauma. 11 Some authors suggest the combination of congenital insufficiency of the rim plate with injury to the lumbar spine. 13 On imaging, lateral radiographs are characteristic and show the posteriorly avulsed bone fragment (Fig 8A). The best diagnostic modality is CT scan that can differentiate avulsed bone fragment from calcified herniated disc (Fig 8B). 12,13 MRI has low sensitivity in detecting such fractures. 14 Diseases Related to Growth Disturbance Disc Degeneration The relationship between lumbar disc abnormalities and low back pain remains controversial. FIG 8. A 16-year-old adolescent with trauma to back. (A) Lateral radiograph shows a faint bone fragment posterior to the lower endplate of L4 (arrow). (B) Axial CT scan reveals the fragment representing an avulsion fracture of the endplate rim, on the right (arrow) (courtesy of Dr. George Y. El-Khoury, Iowa City, IA). Curr Probl Diagn Radiol, November/December 2006 229
FIG 10. A 12-year-girl with back pain. Lateral radiograph shows elongated L5 pars interarticularis (arrow) with grade III spondylolisthesis of L5 over S1 (courtesy of Dr. George El-Khoury, Iowa City, IA, USA). FIG 9. A 12-year-old girl complaining of chronic mid dorsal pain. Sagittal T2W MR image shows loss of the normal high-signal intensity of mid thoracic discs (arrows) compatible with degeneration. Endplate high signal intensity degenerative changes are also noted at one of these levels. During growth, disc degeneration may develop, with or without vertebral endplate changes, in association with Scheuermann s disease, Schmorl s nodes, and limbus vertebrae. 5,15,16 It may occur with or without prolapse 3,5,15 but is frequently associated with disc bulge and protrusion. 16 Pain is not always present. 5 In fact, 26% of asymptomatic patients have disc degeneration by MRI and only 38% of patients with low back pain have disc degeneration without any other abnormality (Fig 9). 16 Some authors have shown however increased association between disc degeneration and back pain, in particular, in the rapid physical growth period. 4,17 In one report, 50% of all children with disc degeneration by MRI have one or more episodes of self-limiting low back pain. Patients with disc degeneration, even if asymptomatic, have increased risk of recurrent and frequent back pain beyond growth spurt, up to early adulthood. 4,5,17 The diagnosis of disc degeneration is best made by MRI that shows low signal intensity on T2-weighted images (Fig 9). 230 Curr Probl Diagn Radiol, November/December 2006
FIG 12. A 4-year-old boy with painful scoliosis. AP radiograph of the spine. There is L4 hemivertebra (arrow), incomplete segmentation of L5, and lumbarization of S1. FIG 11. A 16-year-old girl with chronic back pain. AP radiograph taken in standing position shows rotoscoliosis of the lumbar spine convex to the left. No vertebral abnormalities were present. Spondylolisthesis Without Spondylolysis Painful spondylolisthesis may be caused by disease processes other than spondylolysis. 6,18 These include mainly (1) congenital absence or deficiency of the facet joints leading to dysplastic spondylolisthesis and (2) elongated pars interarticularis. 18 Elongation of the pars without pars defect may be either congenital or the consequence of repetitive trauma and microfractures. These fractures result in a continuity of bony callus that leads to an elongated thin pars. The diagnosis of these processes is made by radiographs (Fig 10) and CT scan with reformatted sagittal images. Scoliosis Scoliosis in the pediatric age group may be idiopathic or congenital or may result from variable disease processes. 19 Most cases of scoliosis are idiopathic 3 and consist of a lateral and rotational scoliosis (Fig 11). It has a prevalence of 2% in the adolescents when a curvature of more than 10 is used. Idiopathic scoliosis does not cause symptoms except for postural deformities. 20 Back pain in the general population and in patients with idiopathic scoliosis have equal inci- Curr Probl Diagn Radiol, November/December 2006 231
dence. Painful scoliosis is usually secondary to the presence of vertebra or end of rib lesion. Congenital scoliosis is the most frequent congenital deformity of the spine. 19 It is related to an insult of the fetus during the embryological development of the spine. It may be classified into defects of formation and segmentation. Most of the malformations have both types of defects. The diagnosis is usually made during the prenatal period using sonography and patients are usually asymptomatic. Associated congenital diseases should however be looked for. On imaging, radiographs of the whole spine should be obtained in a standing position and Cobb s angle should be measured. These radiographs detect abnormalities of vertebral formation and segmentation (Fig 12). MRI detects associated spinal cord abnormalities, including tethered cord, diastematomyelia, syrinx, and others. Scheuermann s Disease Scheuermann s disease is a condition of adolescents and young adults less than 18 years of age. It is usually related to repetitive trauma where the nucleus pulposus migrates through the cartilaginous layer between the vertebral body and the ring apophysis resulting in its avulsion. It is characterized by vertebral wedging, endplate irregularity, narrowing of the disc space with or without disc herniation, 3 and intravertebral disc herniation (Schmorl s nodes). These findings result in increased kyphosis of the thoracic spine. Both thoracic and lumbar spine may be affected. At the thoracic level, it usually involves more than one level. At the lumbar level, the vertebral wedging is less severe and affects usually a single level, hence mimicking diskitis on radiographs. Back pain is present in 20 to 30% of the cases. Radiographs readily demonstrate the previously described findings (Fig 13). In addition, occasional anterior bridging from ossification of the anterior portions of the discs may be seen. MRI (Figs 14) is helpful by demonstrating the Schmorl s nodes and disc prolapse beneath the vertebral apophyses and to exclude diskitis. Scintigraphy usually shows increased uptake. Infectious (Spondylodiscitis)/Inflammatory Spondyloarthropathy Tuberculous Spondylodiscitis The spine is the most common site of osseous involvement by tuberculosis. 21 It is particularly seen in immunocompromised patients. The spine is in- FIG 13. Scheuermann s disease. Lumbar spine radiograph in a 16-year-old girl, presenting with back pain. There are vertebral wedging, endplate irregularities, Schmorl s nodes, and narrowing of some of the disc spaces. volved in up to 15% of patients with tuberculosis. The clinical presentation is mainly of insidious pain (42%). Neurological deficits and kyphosis are even more frequent (75 and 60%, respectively). 21 Sixty-nine percent of patients with spine tuberculosis have infectious sites outside the spine. The involvement pattern consists of a hematogenous spread, which evolves into subligamentous spread. It results in osteitis with or without diskitis or abscess formation. Soft-tissue spread can reach up to 98% of the cases. The vertebral bodies are more commonly involved than the posterior elements. More than one vertebral body is usually involved and in a contiguous manner. Classically tuberculosis affects the thoracolumbar junction. On imaging, radiographs and CT scan show bone destruction or sclerosis and sometimes disc space narrowing (Fig 15A). Later on, there is spine deformity with a lytic or sclerotic pattern with or without spinal fu- 232 Curr Probl Diagn Radiol, November/December 2006
FIG 14. Scheuermann s disease. Sagittal T1W MR image of the thoracic spine in a 17-year-old boy having back pain. Similar findings to those in Figure 13 are noted, involving the thoracic and lumbar spine. sion. 17 CT scan may show calcifications in the softtissue component. MRI is the best modality for the diagnosis and extent of infection. It shows bone marrow edema of the affected vertebra, frequently at 2 consecutive levels, along with subligamentous spread (Fig 15B and C), soft-tissue extent, and abscess with thick enhancing rim, particularly within the psoas muscle. 21-23 MRI is also excellent in assessing the infection extent into the spinal canal, degree of cord compression, and presence of myelitis. Intervertebral discs may remain normal 23 (Fig 16) or may be secondarily affected. Note that MR signals of infection in pediatric patients are different from adults. In tuberculosis-affected children, disc involvement is of low signal intensity on T2W images, whereas, in adults, it appears as high signal. 22 On T1-weighted sequences, vertebral body involvement is best seen FIG 15. A 14-year-old boy with tuberculous spondylodiscitis (Pott s disease). (A) Lateral spine radiograph. The L2-L3 disc space (arrow) is narrowed with irregularity of the endplates and significant sclerosis of the adjacent vertebral bodies. (B) Sagittal T1W MR image shows the abnormal low signal of the involved vertebral bodies. The disc loses its normal low signal and appears high signal. Prevertebral soft-tissue involvement is present (star). (C) Sagittal T2W MR image showing the abnormally high signal of the vertebrae. The disc loses its normal high signal intensity, appearing as an intermediate signal. Prevertebral soft-tissue swelling is again seen (star). following gadolinium contrast injection where the vertebrae enhance since the bone marrow is predominantly of low signal because of rich red marrow. Besides, on T2W and mainly STIR images, the vertebrae display a significantly high signal in comparison with the normal vertebra (Fig 16). Curr Probl Diagn Radiol, November/December 2006 233
FIG 16. A 15-year-old girl presenting with severe diffuse back pain. Sagittal T2W MR image of the spine. There is an abnormally high signal intensity of an upper lumbar vertebra (arrow), which is low on T1W images (not shown). There is loss of height of the affected lumbar vertebral body. The adjacent discs are preserved. Tuberculous spondylitis was proven by biopsy. Nontuberculous Spondylodiscitis Nontuberculous discitis and spondylodiscitis may be either nonspecific (nonpyogenic, traumatic) or infectious (mainly bacterial). 6 In this latter instance primary focus may be detected (ear, throat). The commonest causal agents are staphylococcus, streptococcus, and coxiella. 24,25 Sometimes, the organism is not cultured. The spine is involved by infectious organisms through hematogenous spread or from a contaminated contiguous source. 24 Spine infection represents about 2 to 4% of all osteomyelitis cases. The diagnosis is often delayed 3 and the mean age at diagnosis is 7.5 years. There are three clinical forms according to age. In patients less than or 1 year of age, there is a serious form with septicemia. The infantile form (1 to 4 years) is associated with stiff gait and limping. After 4 years of age, spondylodiscitis is associated with back pain and has a benign course, more so in the younger. 6 Besides, the symptoms may include fever, malaise, weight loss, bone pain, irritability, and a refusal to walk. 25,26 The early focus of infection may be within either the disc or the anterior subchondral region. 24,25 The lumbar level is the most commonly involved region. On imaging, conventional radiographs show disc space narrowing, decreased vertebral height, and irregular endplates with lucencies (Fig 17A). In late phase, kyphosis, scoliosis, or sclerotic changes occur. MRI is the modality of choice to detect and assess this condition. The signal intensity is similar to what is seen in tuberculous spondylitis. MRI shows abnormal signal intensity of the disc (mainly high on T2W) and increased signal intensity in the vertebral body on long TR/long TE sequences (Fig 17B) and decreased signal on short TR/short TE sequences. 24 Abscess formation and soft-tissue involvement may be present. In fungal infections (eg, candida, aspergillus), the increased signal on T2- weighted sequence within the disc is much less intense than in bacterial infections and may sometimes be absent. 24 The intranuclear cleft may be preserved. Inflammatory Arthritides Seronegative spondyloarthropathies (SPA) are the most common inflammatory disorders that affect the thoracic and lumbar spine in the pediatric age group. Juvenile rheumatoid arthritis very rarely affects the spine or causes back pain. The juvenile form of SPA occurs in patients who are less than 16 years of age and is characterized by the presence of sacroiliitis. These SPA include ankylosing spondylitis, psoriatic arthritis, Reiter s syndrome, and arthritis associated with inflammatory bowel disease. In all these SPA, disease of the spine (spondylitis) is a late gradual manifestation that follows sacroiliitis. 27,28 On imaging, findings of sacroiliitis may be delayed on radiographs. CT scan is a better modality to assess earlier changes. Bone marrow edema is readily seen by MRI, denoting very early inflammation. 27 In the spine, the findings are subtle with some erosions or sclerosis at the anterior vertebral corners. Facet joint involvement and vertebral squaring may occur. There is sometimes loss of the lumbar lordosis with stiff back. Syndesmophytes and bamboo spine are rare in children. 27 Neoplastic Disorders Spinal bone tumors may be benign or malignant (both primary and secondary). Infiltrative bone marrow tumors may also occur. Primary tumors of the thoracic and lumbar spine are very rare. 3 The most common 234 Curr Probl Diagn Radiol, November/December 2006
clinical presentation of vertebral tumors is back pain (86%) followed by neurological symptoms in 55% of patients. The most common tumors are 3 osteoid osteoma and osteoblastoma; aneurysmal bone cyst (ABC); Langerhans cell histiocytosis; Ewing sarcoma; leukemia; and lymphoma and metastases. FIG 17. Bacterial spondylodiscitis in a 1.5-year-old child with fever and irritation. (A) Lateral spine radiograph shows narrowing of the L3-L4 disc space with lucencies at both endplates (circle). (B) Sagittal T2W MR image. The involved vertebrae display slight increased signal. A focus of significant increased signal is seen in the posterior aspect of the disc due to discitis (circle). The rest of the disc is of abnormal low signal intensity when compared with other normal discs. Benign Osteoid Osteoma Osteoid osteoma is a common benign bone-forming tumor, consisting of a central core of vascular connective tissue and osteoid nidus (usually 1 to 2 cm) with reactive sclerosis of the surrounding bone. The nidus is not calcified early on, but shows calcifications with maturation. 29 Osteoid osteoma is mostly prevalent between 7 and 25 years of age (90% of the cases). It is rare (3%) under the age of 5 years. 29 Spinal osteoid osteoma occurs in 10 to 18% of all cases. It involves mainly the posterior elements. Vertebral bodies lesions are unusual. 3,6 Spinal involvement by osteoid osteoma presents usually with painful scoliosis, mainly at night, which can be relieved by salicylates intake. 3,6,29 Referred pain to the lower extremities may also occur. 6 On imaging, radiographs show dense sclerotic areas obscuring the nidus, 3 usually at the concave side of the scoliosis. 29 CT scan is the method of choice for the diagnosis. It should be performed using thin collimation. It accurately localizes the nidus, which usually has central calcification. 29 Surrounding reactive sclerosis is frequently observed (Fig 18). MR shows bone marrow edema with overlying soft-tissue edema that may resemble malignant processing. 29 However the nidus may be visualized by dynamic Gadolinium-enhanced study. 30 Bone scan shows that increased uptake within the lesion is very helpful in localizing the lesion, in particular in the spine, where the anatomy is complex. 6,29 The sensitivity is higher when SPECT scan is used. Osteoblastoma Osteoblastoma is a benign bone-forming lesion that has similar histopathology to osteoid osteoma. 29 It is however equal or larger than 1.5 to 2 cm in size. 6,29 Osteoblastoma may be aggressive. In occurs before 30 years of age in 90% of the cases and is most commonly seen between 10 and 15 years of age. 29 One-third of all osteoblastomas occur in the spine with nearly all of them involving the posterior elements. 3,29 In the spine, it causes painful scoliosis Curr Probl Diagn Radiol, November/December 2006 235
FIG 18. A 12-year-old boy with painful scoliosis. Axial CT scan with bone window setting. Subperiosteal lytic lesion of the right lamina of a mid thoracic vertebra is seen with severe surrounding reactive sclerosis consistent with osteoid osteoma. The nidus is faintly calcified (arrow). due to muscle spasm. However, the pain is less frequent than in osteoid osteoma. On imaging, the radiographs and CT scan typically show a lytic expansile lesion and rarely an osteoblastic tumor. Some lesions may be intact surrounding sclerotic rim or cortical thinning with soft-tissue mass. The tumor matrix has varying degrees of mineralization. Surrounding bone sclerosis is rare. On MRI, the findings are nonspecific. Aneurysmal Bone Cyst ABC is a benign cystic bone lesion of debatable origin. It is accepted that it represents either true primary tumor or may develop within preexisting lesions (eg, giant cell tumor, chondroblastoma). A solid variant of ABC is described on histopathology that lacks the cystic component. Patients with ABC usually present before 20 years of age. The spine is involved in about 11% of cases, occurring more at the lumbar level. 3 The posterior elements are always involved with infrequent extension to the vertebral bodies or ribs. 3,31 Spinal lesions frequently present with neurological symptoms. Pain is invariably present and either is localized in the back or is secondary to involvement of a nerve root or the FIG 19. Aneurysmal bone cyst (ABC) in a 16-year-old girl. (A) Thoracolumbar radiograph shows an expansile lytic lesion of the right transverse process of D12 (arrows) associated with scoliosis concave to the lesion side. (B) Axial CT scan showing to better advantage the expansile lesion with thinning and destruction of the cortex, flecks of destroyed bone, and minimal epidural extension. cord. 31 Imaging radiographs and CT scan show a lytic expansile lesion associated with cortical thinning or loss 3 (Fig 19). The lesion margins are 236 Curr Probl Diagn Radiol, November/December 2006
usually well defined and preserved but appear poor in 14% of the cases. Internal trabeculae and septae are very frequent. Fluid fluid levels are seen on MRI or CT scan. MR imaging better assesses extension into the spinal canal and degree of cord compression. 3 Enhancing septae may also be seen on MRI following IV administration of gadolinium DTPA (diethylenetriamine pentaacetic acid). Angiography is performed if presurgical embolization is planned. Malignant Langerhans Cell Histocytosis Langerhans cell histocytosis (LCH) is an uncommon disease caused by inappropriate proliferation and infiltration of various tissues by a unique type of histiocytes called the Langerhans cell. LCH presents in three main forms 29 : (1) eosinophilic granuloma, the localized form, usually occurs at 5 to 15 year of age. On conventional radiograph and CT scan, eosinophilic granuloma appears as an aggressive lesion at an early stage. Later on, the lesion is cyst-like in appearance. (2) Hand Schüller Christian disease, which is a chronic form associated with diabetes insipidus, exophthalmoses, and skull involvement. The presentation in two-thirds of the patients is before 5 years. (3) Letterer Siwe, which is an acute fulminant form encountered in 10% of the cases. In the spine, LCH most commonly involves the vertebral bodies, frequently in a multifocal manner. 32 The thoracic spine is a more frequent site than the lumbar spine. Involvement of the posterior vertebral elements is very rare. 32 On imaging, spine involvement results in variable degrees of collapse with the most severe appearance being complete vertebra plana. 32 Epidural extension is seen in 15% of the cases. This is better assessed by MRI, where the lesion appears of low signal on T1-weighted and high signal on T2-weighted images (Fig 20A). On CT scan, the lesion is lytic and destructive (Fig 20B). Osteosarcoma Osteosarcoma is the most common malignant bone tumor in children and young adults, occurring mainly between 10 and 30 years of age. 29 However, it involves the vertebral column in only 4% of the cases (33.3% at the thoracic level and 32.3% at the lumbar level). 33 It is a mesenchymal tumor with several subtypes: the osteoblastic type is the most FIG 20. A 9-year-old girl with Langerhans cell histiocytosis presenting and subacute dorsal back pain. (A) Sagittal T1W MR image showing abnormal low signal intensity replacing the bone marrow of T7 vertebral body (arrow) associated with minimal vertebral collapse. A similar smaller focal lesion is seen in the T6 body. (B) Axial CT section of T7. The lesion is lytic and ill defined. Curr Probl Diagn Radiol, November/December 2006 237
FIG 21. Ewing sarcoma of S1 vertebra in a 15-year-old girl. (A) Axial T1W MR image. A large hypointense tumor of S1 is present (asterisk) with right presacral soft-tissue component (star). The tumor is invading the sacral canal. (B) T2W MR image. The tumor is of heterogeneous signal intensity including low signal intensity areas due to hypercellularity seen in Ewing sarcomas and/or sclerosis. common followed by the chondroblastic type. 29 No surface sarcomas are seen in the spine. Most commonly, vertebral osteosarcoma involves the posterior elements (79%) with variable extent into the vertebral body. The lesion is confined only to the body in 21% of the cases. Two-level involvement occurs in 17% of the cases. 33 On radiographs and CT scan, osteosarcoma is a destructive lesion with variable degrees of mineralization leading to a mixture of permeative lytic pattern and sclerosis. Marked mineralization is less common. 29 Pure lytic patter may also occur (20%). 33 Spinal canal invasion is seen in high-grade tumors and is best assessed by means of MRI. On MRI, the tumor is nonspecific and is usually low on T1-weighted FIG 22. A 6-year-old girl with known lymphoblastic leukemia. (A) Axial CT scan showing a permeative lesion of L3 vertebral body. (B) Sagittal STIR MR image showing very high signal intensity of the involved L3 vertebra. images and high on T2-weighted images. If significant blastic pattern is present, decreased signal on all sequences may be then seen. 238 Curr Probl Diagn Radiol, November/December 2006
FIG 23. An 8-year-old boy with metastatic disease to the spine from a thigh rhabdomyosarcoma. He presented with severe back pain and urinary incontinence. Sagittal T1W MR image. There are low signal intensity lesions involving multiple thoracic and lumbar vertebral bodies, with a large epidural component at the lower lumbar level (star). Bone scintigraphy was normal. Ewing Sarcoma Ewing sarcoma is the second most common malignant bone tumor in children 29 following osteosarcoma. The tumor presents mainly at 5 to 25 years of age and is uncommon before the age of 5. 3 In the spine, the tumor typically involves the vertebral body. In addition to back pain, neurological signs may be seen due to intraspinal extension. Systemic symptoms may also occur, including fever and malaise. The radiographic and CT scan findings include destructive, permeative, and sclerotic or mixed tumor (Figs 25 and 26). On MRI, the findings FIG 24. A 4-year-old girl with sickle-cell disease and back pain. AP spine radiograph shows central squared-shape endplate depression typical of sickle-cell anemia. are nonspecific, but it shows good determination of the tumor extent (Fig 21). Leukemia Leukemia is usually encountered in childhood and adolescents with the acute forms representing more than one-third of pediatric malignancies. 34,35 The spine is one of the sites of pediatric leukemia. Radiographs show generalized decrease in bone density (which can be also either geographic permeative or moth-eaten). Decreased mineralization is Curr Probl Diagn Radiol, November/December 2006 239
FIG 26. A 14-year-old girl known to have congenital cirrhosis presenting with back pain with no history of trauma. (A) Lateral spine radiograph. There is diffuse osteoporosis related to hepatic failure. (B) Sagittal T2W MR image. There is a Schmorl s node at the upper endplate of L5 with surrounding edema compatible with acute intravertebral disc herniation. There is also edema and irregularity of the upper endplate of S1 posteriorly, with possible fracture, denoting an acute event. In addition, there is a posterior annular tear with protrusion of the L5-S1 disc (arrow). The L4-L5 and L5-S1 discs are degenerated. The endplate vertebral changes are due to bone softening resulting from osteoporosis. FIG 25. Osteogenesis imperfecta tarda in an 8-year-old boy presenting for exacerbation of chronic back pain. Lateral spine radiograph. There is diffuse decreased bone density and compression fracture of L2 vertebral body (arrow). seen in 90% of children with acute lymphoblastic leukemia and may cause compression fracture due to bone marrow infiltration by leukemia cells. 34 MRI shows low signal on T1-weighted sequence, and high signal on T2-weighted images. The abnormality is focal in myelocytic and diffuse in lymphocytic. Lymphoma Spinal involvement by lymphoma is presumed to be entirely due to hematogenous spread and is commonly more affected than the appendicular skeleton. 29 It is usually seen in advanced stages of the disease but this is rare. It can be secondary to both Hodgkin s disease and Non-Hodgkin s lymphoma. 6 Another method of infiltration of the spine is by direct invasion. 29 Primary lymphomatous involvement of the spine is extremely rare in the general population. However in children it is the third most common primary malignant bone tumor and is seen more in Non-Hodgkin s lymphoma. 36 The symptoms include back pain and neurological symptoms, depending on the extension within the spinal canal. On imaging, 29 radiographs and CT scan usually show destructive permeative lesions and rarely blastic lesions (Fig 22A). Lymphoma may not be detected by these modalities. MRI has a better sensitivity in detecting the lesions, which appear of low signal intensity on short TE sequences and of variable signal on long TE sequences (Fig 22B). It can be of low signal on T2-weighted images due to fibrosis or hypercellularity. 240 Curr Probl Diagn Radiol, November/December 2006
FIG 27. A 10-year-old girl known to have lymphoma on high doses of steroids (decadron). The patient had meningeal spread for which she received total spine radiation therapy. (A) Radiograph obtained because of exacerbation of chronic back pain reveals diffuse decreased bone density compatible with osteoporosis secondary to chemotherapy and radiation therapies. In addition, there is fracture of L4 body with depression of its upper endplate (arrows). Biconcave appearance of several lumbar vertebrae is seen due to softening of the endplates seen in osteoporosis. (B) Sagittal T1W MR image. The L4 fracture is well identified as a low signal intensity line. The remaining vertebrae show significantly increased signal due to fatty bone marrow replacement secondary to radiation therapy. Note again the biconcave appearance of the vertebral bodies. Metastases to the Spine Various types of metastases occur in the spine (lytic, blastic, or mixed) depending on the primary lesions. Primary soft-tissue tumors usually produce lytic metastatic lesions. Blastic metastases are produced by primary bone-forming tumors. Primary sites are variable and include mainly osteosarcoma, Wilm s tumor, embryonal rhabdomyosarcoma, and neuroblastoma. 37 MRI is the best modality to diagnose and assess the extent of metastatic disease in the spine (Fig 23). Hematological Disorders Sickle-Cell Disease In sickle-cell involvement of the spine, most of the marrow space tends to remain as red marrow, some- Curr Probl Diagn Radiol, November/December 2006 241
times with expansion. The congested cellular marrow result impedes blood flow, which results in infarction or infection, bone infarction being more common. 38 Spine infarction results in central, square-shaped endplate depression due to microvascular endplate occlusion and overgrowth of the surrounding portions of the endplates that result in the H-shaped vertebral deformity (Fig 24). The incidence rate of such findings on radiographs is 10%. On MRI, the infarctions are of low signal intensity on T1-weighted and of variable signal on T2-weighted and short-tau inversion recovery (STIR) images. Sometimes, they show enhancement following IV gadolinium contrast injection. These MR findings may be encountered in both infarctions and osteomyelitis and hence the differentiation is sometimes difficult. Metabolic Disorders Osteoporosis Primary osteoporosis in childhood is very rare and is mainly due to osteogenesis imperfecta (Fig 25) or idiopathic juvenile osteoporosis. Secondary osteoporosis is much more frequent and the etiologies include a large number of chronic diseases and therapies used in their management. 39 These include diseases of the gastrointestinal tract (hepatobiliary and inflammatory bowel diseases) (Fig 26), nutritional diseases (eg, malabsorption), neoplasms (eg, leukemia, lymphoma), renal diseases, connective tissue diseases (eg, juvenile rheumatoid arthritis), lung diseases (eg, asthma), endocrine diseases (eg, Cushing diseases), neuropsychiatry diseases (eg, anorexia nervosa), and drug intake (eg, corticosteroids) (Fig 27). Childhood osteoporosis is usually asymptomatic but may be discovered after light trauma that leads to fracture that involves the spine in 44% of the cases. The symptoms include acute back pain and muscle spasm. The diagnosis of osteoporosis is usually confirmed by measuring the bone mineral density using mainly dual energy radiograph absorption. The diagnosis of fracture is easily made using radiographs, CT scan, or MRI. Alkaptonuria Alkaptonuria is an autosomal-recessive genetic disorder caused by deficiency of the enzyme homogentisate-1,2-dioxygenase, resulting in the accumulation of homogentisic acid and its metabolites in different structures of the body (eg, bone, cartilage, connective FIG 28. An 11-year-old female known to have alkaptonuria presenting with back pain. AP radiograph of the spine shows diffuse decreased bone density compatible with osteoporosis, scoliotic curvature, and calcified thoracic discs (arrows). tissues). 40 In the spine, several abnormalities are encountered including disc-space narrowing, disc calcification, and late disc fusion, calcifications of the interosseous ligaments leading to bone ankylosis. 40,41 Increased kyphosis is common. Other findings include osteophyte formation, osteoporosis, and loss of lumbar lordosis. 40 The findings are readily seen on conventional radiographs and CT scan (Fig 28). Miscellaneous Osteopetrosis Osteopetrosis is a rare complex skeletal disease characterized by increased bone density and caused by aberrant bone resorption due to osteoclast dysfunction. A spectrum of three clinical forms is known: the infantile autosomal-recessive lethal form, the intermediate autosomal-recessive form, and the adult autosomal-dominant form (Albers Schönberg disease). The disease is severe in the young and runs a more benign course in the adult form. A wide variety of clinical 242 Curr Probl Diagn Radiol, November/December 2006
Conclusion We presented the imaging spectrum of disease processes encountered in our institution, which result in back pain in children and adolescent patients. This spectrum includes a wide variety of diseases ranging from very benign conditions such as disc bulge to very significant conditions such as malignancy. Clinicians and radiologists should be aware of these conditions to orient the imaging studies and rule out first the presence of clinically significant diseases. FIG 29. A 14-year-old girl presenting with mild chronic back pain not previously investigated. AP radiograph of the lumbosacral spine shows areas of increased bone sclerosis with characteristic sandwich appearance of the vertebral bodies and bone-within-bone appearance in the pelvis diagnostic of osteopetrosis. symptoms is present that depends on the form of disease. 42 Back pain may be present with or without obvious underlying fracture. On imaging, a variable degree of osteosclerosis is seen, along with accentuation of the vertebral endplates ( sandwich appearance) and typical bone within bone appearance (Fig 29). REFERENCES 1. Papanicolaou N, Wilkinson R, Emans J, et al. Bone scintigraphy and radiography in young athletes with low back pain. AJR 1985;145:1039-44. 2. Rosenblum B, Rothman A. Low back pain in children. Mt. Sinai J Med 1991;58:115-9. 3. Afshani E, Kuhn J. Common causes of low back pain in children. Radiographics 1991;11:269-91. 4. Salminen J, Erkintalo M, Pentti J, et al. Recurrent low back pain and early disc degeneration in the young. Spine 1999;24: 1316-21. 5. Kujala U, Taimela S, Erkintalo M, et al. Low back pain in adolescent athletes. Med Sci Sports Exerc 1996;28:165-70. 6. Mason DE. Back pain in children. Pediatr Ann 1999;28: 727-38. 7. Ralston S, Weir M. Suspecting lumbar spondylolysis in adolescent low back pain. Clin Pediatr 1998;37:287-93. 8. Bodner R, Heyman S, Drummond D, et al. The use of single photon emission computed tomography (SPECT) in the diagnosis of low back pain in young patients. Spine 1988;13:1155-60. 9. Bella R, Summerville D, Treves S, et al. Low back pain in adolescent athletes: Detection of stress injury to the pars interarticularis with SPECT. Radiology 1991;180:509-12. 10. Hensinger RN. Current concepts review: Spondylolysis and spondylolisthesis in children and adolescents. J Bone Joint Surg Am 1989;71:1098-107. 11. Ikata T, Morita T, Katoh S, et al. Lesions of the lumbar posterior end plate in children and adolescents. J Bone Joint Surg Br 1995;77:951-5. 12. Wagner A, Albeck M, Madsen F. Diagnostic imaging in fracture of lumbar vertebral ring apophyses. Acta Radiol 1992;33:72-4. 13. Martinez-Lage J, Poza M, Arcas P. Avulsed lumbar vertebral rim plate in an adolescent: trauma or malformation? Child s Nerv Syst 1998;14:131-4. 14. Peh WC, Griffith JF, Yip DK, et al. Magnetic resonance imaging of lumbar vertebral apophyseal ring fractures. Australas Radiol 1998;42:34-7. 15. Swischuk L, John S, Allbery S. Disk degenerative disease in childhood: Scheuermann s disease, Schmorl s nodes, and the limbus vertebra: MRI findings in 12 patients. Pediatr Radiol 1998;28:334-8. Curr Probl Diagn Radiol, November/December 2006 243
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