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 condi-tion but may denote a serious health problem; hence, full clinical history, physical examination, and appropriate labo-ratory 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 var-ious causes; spondylolysis; spondylolisthesis; traumatic inju-ries; disc degeneration and herniation; Scheuermann’s dis-ease; 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 inves-tigation 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, nontraumatic spondylolisthesis, Scheuermann’s dis-ease, scoliosis; (3) progressive diseases such as infec-tions, inflammainfec-tions, benign and malignant neoplasia (both primary and secondary), bone marrow infiltra-tive tumors; (4) chronic or systemic diseases including hematological and metabolic diseases. Relevant imag-ing findimag-ings are summarized in Table 2. Diseases related to the nervous system (eg, spinal cord lesions) will not be discussed in this article.
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
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 be1 (1) mechanical (most common) with strain on the paravertebral liga-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
2. Disc bulge/herniation
3. Spondylolysis/spondylolisthesis 4. Ring apophyseal fracture
Muscle spasm Sciatica⫾ Sports injury
Sports injury, sciatica⫾
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 B. Growth disturbance
1. Disc degeneration
2. Spondylolisthesis without spondylolysis
Low back pain, self-limiting or recurrent Back pain
Disc of low-signal intensity on T2W MRI Absent or deficient facets, elongated pars 3. Scoliosis
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, night sweats
Osteitis⫾ discitis, paravertebral and/or epidural abscess, bone destruction or sclerosis
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,
fever
Vertebral body—lytic, sclerotic, or mixed
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
ments and muscles as well as on the facet joints; (2) discogenic with the herniated lumbar disc being un-common; (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.2When 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. Com-monly, the injury results in straight back syndrome caused by muscle spasm and pain (Fig 1).2 Verte-bral 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 hernia-tion is more commonly traumatic than degenerative (Figs 4and5).3,5The 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 As-sociated vertebral fractures may occur (Fig 5). In disc
FIG 1. An 11-year-old boy with muscle spasms following trauma. There is straightening of the lumbar lordosis (straight back syndrome).
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).
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 some-times 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 un-likely.6,8Sports activities implicated in spondylolysis include mainly gymnastics (typically with hyperexten-sion), contact sports (eg, soccer), and dancing.3,6,9 There is seldom history of severe trauma.10The most commonly affected area is the lower lumbar spine, mainly L5.6,10Spondylolysis 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 moder-ate size defect with or without compensatory sclerosis (Fig 6).1However radiographs may be initially normal since spondylolysis starts as a stress phenomenon that progresses later into a fracture. Single-photon
emis-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).
FIG 4. A 3-year-old girl with acute traumatic back pain after being aggressed by her older brother from the back, resulting in hyperexten-sion 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.
sion computed tomography (SPECT) plays an impor-tant role in detection of such stress injuries and has higher sensitivity than planar bone scan and radio-graphs (Fig 7A).7-9Normal 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 poste-rior 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 some-times 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 sep-arated from the vertebra with interposition of disc material. Injury to the ring apophysis may be produced by both traction (annulus fibrosis, longitudinal liga-ments, psoas muscle) and compression (shear injury
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 sur-rounded by high signal intensity bone marrow edema.
FIG 6. A 15-year-old boy with low back pain. Conventional radio-graph shows spondylolysis of L5 (arrow) with grade I spondylolisthesis of L5 over S1.
accumulating between the vertebral body and ring apophyses).5Almost 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.13On imaging, lateral radiographs are character-istic 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 abnormal-ities and low back pain remains controversial.
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.
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).
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 prolapse3,5,15 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 epi-sodes of self-limiting low back pain. Patients with disc degeneration, even if asymptomatic, have in-creased 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).
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.
FIG 10. A 12-year-girl with back pain. Lateral radiograph shows elongated L5 pars interarticularis (arrow) with grade III spondylolisthe-sis of L5 over S1 (courtesy of Dr. George El-Khoury, Iowa City, IA, USA).
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.18Elongation 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 thatleads 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 idio-pathic or congenital or may result from variable disease processes.19 Most cases of scoliosis are idio-pathic3and 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.20Back pain in the general population and in patients with idiopathic scoliosis have equal
inci-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.
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.
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.19It 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 radio-graphs detect abnormalities of vertebral formation and segmentation (Fig 12). MRI detects associated spinal cord abnormalities, including tethered cord, diastem-atomyelia, 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 pulpo-sus 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 ante-rior bridging from ossification of the anteante-rior 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-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 infec-tious 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 ele-ments. More than one vertebral body is usually in-volved and in a contiguous manner. Classically tuber-culosis affects the thoracolumbar junction. On imaging, radiographs and CT scan show bone destruc-tion 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-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.
sion.17 CT scan may show calcifications in the soft-tissue 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 normal23 (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
following gadolinium contrast injection where the vertebrae enhance since the bone marrow is predomi-nantly 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).
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 inFigure 13are noted, involving the thoracic and lumbar spine.
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).
Nontuberculous Spondylodiscitis
Nontuberculous discitis and spondylodiscitis may be either nonspecific (nonpyogenic, traumatic) or in-fectious (mainly bacterial).6 In this latter instance primary focus may be detected (ear, throat). The commonest causal agents are staphylococcus, strepto-coccus, and coxiella.24,25Sometimes, 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 delayed3 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.6Besides, the symptoms may include fever, malaise, weight loss, bone pain,
irrita-bility, and a refusal to walk.25,26 The early focus of infection may be within either the disc or the anterior subchondral region.24,25The 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 scle-rotic 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 in-volvement 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 imag-ing, findings of sacroiliitis may be delayed on radio-graphs. 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. Syndesmo-phytes 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 tu-mors may also occur. Primary tutu-mors of the thoracic and lumbar spine are very rare.3 The most common
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 spon-dylitis was proven by biopsy.
clinical presentation of vertebral tumors is back pain (86%) followed by neurological symptoms in 55% of patients. The most common tumors are3 osteoid os-teoma and osteoblastoma; aneurysmal bone cyst (ABC); Langerhans cell histiocytosis; Ewing sarcoma; leukemia; and lymphoma and metastases.
Benign
Osteoid Osteoma
Osteoid osteoma is a common benign bone-forming tumor, consisting of a central core of vascular connec-tive 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’ le-sions 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.6On imaging, radiographs show dense sclerotic areas obscuring the nidus,3 usually at the concave side of the scoliosis.29CT 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 Sur-rounding reactive sclerosis is frequently observed (Fig 18). MR shows bone marrow edema with overlying soft-tissue edema that may resemble malignant pro-cessing.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 sensi-tivity 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 oc-curs 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.3,29In the spine, it causes painful scoliosis
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.
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.3The 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
cord.31 Imaging radiographs and CT scan show a lytic expansile lesion associated with cortical thin-ning or loss3 (Fig 19). The lesion margins are
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).
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.
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). An-giography is performed if presurgical embolization is planned.
Malignant
Langerhans Cell Histocytosis
Langerhans cell histocytosis (LCH) is an uncommon disease caused by inappropriate proliferation and in-filtration of various tissues by a unique type of histiocytes called the Langerhans cell. LCH presents in three main forms29: (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, ex-ophthalmoses, and skull involvement. The presenta-tion 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, fre-quently in a multifocal manner.32The thoracic spine is a more frequent site than the lumbar spine. Involve-ment of the posterior vertebral eleInvolve-ments is very rare.32 On imaging, spine involvement results in variable degrees of collapse with the most severe appearance being complete vertebra plana.32Epidural 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.29However, 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.
common followed by the chondroblastic type.29 No surface sarcomas are seen in the spine. Most com-monly, vertebral osteosarcoma involves the poste-rior 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.29Pure lytic patter may also occur (20%).33 Spinal canal inva-sion 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
images and high on T2-weighted images. If signif-icant blastic pattern is present, decreased signal on all sequences may be then seen.
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.
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.
Ewing Sarcoma
Ewing sarcoma is the second most common malig-nant bone tumor in children29 following osteosar-coma. 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 25and26). On MRI, the findings
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 per-meative or moth-eaten). Decreased mineralization is
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.
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.
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 abnor-mality is focal in myelocytic and diffuse in lympho-cytic.
Lymphoma
Spinal involvement by lymphoma is presumed to be entirely due to hematogenous spread and is com-monly more affected than the appendicular skele-ton.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 involve-ment 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 symp-toms include back pain and neurological sympsymp-toms, depending on the extension within the spinal canal. On imaging,29 radiographs and CT scan usually show destructive permeative lesions and rarely blas-tic 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.
FIG 25. Osteogenesis imperfecta tarda in an 8-year-old boy present-ing for exacerbation of chronic back pain. Lateral spine radiograph. There is diffuse decreased bone density and compression fracture of L2 vertebral body (arrow).
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 intra-vertebral 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 soften-ing resultsoften-ing from osteoporosis.
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 meta-static 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-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.
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 end-plate depression due to microvascular endend-plate occlu-sion and overgrowth of the surrounding portions of the endplates that result in the H-shaped vertebral defor-mity (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 recov-ery (STIR) images. Sometimes, they show enhance-ment following IV gadolinium contrast injection. These MR findings may be encountered in both infarctions and osteomyelitis and hence the differen-tiation 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 osteopo-rosis is much more frequent and the etiologies include a large number of chronic diseases and therapies used in their management.39These 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), en-docrine diseases (eg, Cushing diseases), neuropsychi-atry 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 radio-graph absorption. The diagnosis of fracture is easily made using radiographs, CT scan, or MRI.
Alkaptonuria
Alkaptonuria is an autosomal-recessive genetic dis-order caused by deficiency of the enzyme homogenti-sate-1,2-dioxygenase, resulting in the accumulation of homogentisic acid and its metabolites in different structures of the body (eg, bone, cartilage, connective
tissues).40 In the spine, several abnormalities are encountered including disc-space narrowing, disc cal-cification, 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 conven-tional 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 interme-diate autosomal-recessive form, and the adult autoso-mal-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
FIG 28. An 11-year-old female known to have alkaptonuria present-ing with back pain. AP radiograph of the spine shows diffuse decreased bone density compatible with osteoporosis, scoliotic curva-ture, and calcified thoracic discs (arrows).
symptoms is present that depends on the form of disease.42Back pain may be present with or without obvious underlying fracture. On imaging, a variable degree of osteosclerosis is seen, along with accen-tuation of the vertebral endplates (“sandwich” ap-pearance) and typical “bone within bone” appear-ance (Fig 29).
Conclusion
We presented the imaging spectrum of disease pro-cesses 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.
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