SACRAL LESIONS: Differential diagnosis for the general radiologist

Transcription

1 SACRAL LESIONS: Differential diagnosis for the general radiologist Poster No.: C-2147 Congress: ECR 2017 Type: Educational Exhibit Authors: M. R. Campos Arenas, M. C. Sánchez-Porro, J. Garrido Rull ; CADIZ/ES, Cádiz/ES, 11010/ES Keywords: Trauma, Neoplasia, Congenital, Diagnostic procedure, MR, CT, Musculoskeletal spine DOI: /ecr2017/C-2147 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 23

2 Learning objectives Knowledge of certain pathologies that could affect the sacrum is important for general radiologists because they could find a sacral lesion even when studies are performed for any other reason (CT scan for abdominal pathologies, MRI for low back pain ) A very wide range of lesions can be found in and around the sacrum, which might be the only structure involved or perhaps a part of a systemic disease that may affect the remainder spine. Background INTRODUCTION Conventional radiography is the first-line modality in most instances and serves as a useful baseline for future comparison. However, the absence of radiographic features do not exclude an underlying disease. Many patients will proceed to further imaging. Cross-sectional imaging with computed tomography (CT) and magnetic resonance (MR) as well as skeletal scintigraphy play a crucial role in identifying, localizing, and characterizing sacral lesions. ANATOMY The sacrum is a large, triangular bone located between the lumbar and coccygeal portions of the caudal spinal axis. It articulates superiorly with L5, inferiorly with the coccyx, and bilaterally with the iliac bones at the sacroiliac joints. The sacrum consists of five vertebrae, which are fused both anteriorly and posteriorly. The sacral canal is the caudal continuation of the lumbar spinal canal. The epidural space terminates at the sacral hiatus. Four pairs of foramina with openings on the anterior and posterior surfaces of the sacrum transmit the ventral and dorsal rami of the sacral nerve roots (S1-S4), respectively. Page 2 of 23

3 Findings and procedure details 1. CONGENITAL LESIONS 1.a) TRANSITIONAL VERTEBRA Transitional vertebrae are frequently encountered developmental variants of the spine. They often involve the sacrococcygeal and lumbosacral junctions. The L5 vertebra can be incorporated into the sacrum ("sacralized"), or the S1 vertebra can be incorporated into the lumbar spine ("lumbarized"). The most clinically important aspect of transitional vertebrae is the potential for confusion over the labeling or assignment of vertebral levels during medical or surgical treatment planning. 1.b) SACRAL AGENESIS (CAUDAL REGRESSION SYNDROME) This rare condition is a severe form of abnormal sacral development. There is an increased frequency of spinal cord abnormalities (syrinx, tethered cord, lipoma, and lipomyelomeningocele). We can classify sacral agenesis into four types: - Type 1: partial unilateral agenesis. - Type 2: there are partial but bilaterally symmetric defects. - Type 3: there is total sacral agenesis and the iliac bones articulate with the lowest available segment of the lumbar spine. - Type 4: there is total sacral agenesis and the iliac bones are fused posteriorly along the midline. 1.c) MENINGOCELE Protrusions of the membrane-lined spinal canal contents through a ventral or dorsal osseous defect in the vertebral colum. - Anterior meningoceles: asymptomatic or symptomatic pelvic masses. Page 3 of 23

4 - Posterior meningoceles (more common): myeloceles, myelomeningoceles and lipomyelomeningoceles according to the contents of the herniated sac. They are frequently associated with a tethered spinal cord. 1.d) MENINGEAL CYSTS Abnormal dilatations of the meninges within the sacral canal or foramina. They are referred to as: - Perineural or Tarlov cysts: When the meningeal cyst communicate freely with the subarachnoid space. - Sacral meningeal cyst: There is not free communication with the subarachnoid space. Although the cysts are usually asymptomatic, large cysts can manifest as neurologic symptoms. Furthermore, symptomatic cysts tend not to communicate with the subarachnoid space. 2. NEOPLASTIC LESIONS The diagnosis of sacral tumors is often delayed because they show symptoms only when they become large enough to compress adjacent nerves or pelvic organs (unexplained or atypical sciatica, gastrointestinal or urinary tract disorders). Patients often present with nonspecific low back pain. For staging, CT and MRI evaluate intraosseous and extraosseous extension essential for treatment planning. Tumour staging classifies lesions into three groups: - High midline lesions: situated above S3. - Low midline lesions: not ascending above S3. - Lateral lesions involving the sacroiliac joint arising from either the sacral bone or the iliac bone. 2.a) SACRAL CANAL TUMORS Schwannomas and neurofibromas (rare): These benign, slowly-growing tumours arise from the myelin sheath of nerve roots. It is often not possible to reliably distinguish between schwannomas and isolated neurofibromas Page 4 of 23

5 only on the basis of imaging criteria. The presence of multiple nerve sheath tumors suggests the diagnosis of neurofibromatosis. Intraosseous schwannoma (or neurilemmoma) is rare, but the sacrum is the most frequent site after the mandible. Meningiomas (very rare). Ependymomas rarely involve the distal filum terminale. Drop metastases from malignant primary central nervous system neoplasms (PNET, germinomas, choroid plexus tumors and glioblastoma multiforme) can accumulate within the dependent portion of the sacral spinal canal. 2.b) BENIGN BONE LESIONS AND TUMORS Giant cell tumor is the second most common primary sacral tumor after chordoma. Giant cell tumors are most common in the 2nd-4th decades of life. Giant cell tumor is locally aggressive and rarely may metastasize. On CT and MR images the typical feature is a lytic, expansile, and destructive process that is often eccentrically located. At CT it may contain a thin sclerotic rim. At MR these lesions show intermediate signal intensity on both T1- and T2-weighted images. They demonstrate significant enhancement at both techniques, and may contain areas of hemorrhage or necrosis, and they may show growth across the sacroiliac joint to the ilium. Aneurysmal bone cysts are expansile lesions with blood-filled cystic areas that are encountered by the age of 20 years. These lesions are probably reactive lesions, not true neoplasms. They may result from trauma or coexist with other bone lesions. They are relatively rare in the sacrum. The presence of fluid-fluid or hematocrit levels suggests the diagnosis but is not pathognomonic. Cavernous hemangiomas: Despite being the most common primary tumor of the spine, they rarely involve the sacrum. Osteoid osteoma and osteoblastoma are rarely found within the sacrum. These lesions usually occur in males in the 2nd decade of life. Patients may present with the classic clinical history of night pain, which is relieved by salicylates. Osteoblastoma manifests as neurologic symptoms and tend to be expansile involving the posterior vertebral elements. The differential diagnosis essentially concerns osteosarcoma. 2.c) MALIGNANT BONE LESIONS AND TUMORS The sacrum, as a site of hematopoietic or red marrow in the adult, is a common site for metastatic disease as well as hematologic malignancies. The presence of multiple lesions involving the sacrum and the rest of the spine suggests the diagnosis of metastatic disease or multiple myeloma. Page 5 of 23

6 Metastases are the commonest malignant tumours of the sacrum. Lung, breast, kidney, and prostate carcinoma are the most frequent causes. Metastatic lesions are usually osteolytic, although sclerotic lesions can be observed, especially from prostate or breast carcinoma. Plasmacytoma and myeloma: they have a predominantly lytic pattern with peripheral sclerosis or purely lytic lesions with a "soap bubble" appearance. The majority of patients with multiple myeloma and plasmacytoma are >60 years of age. Plasmocytoma is an isolated, osteolytic, space-occupying lesion, considered to be an early stage of multiple myeloma. Bone lymphoma can be either primary and isolated or part of multifocal bone disease, possibly associated with other lymph node and visceral sites of lymphoma. Three signs, although nonspecific, are suggestive of lymphoma: the intensity and extent of uptake on scintigraphy, massive bone marrow invasion on MRI, despite normal radiography findings, and a large soft tissue mass with no visible cortical lesion on CT. Chordomas arise from notochordal rests and therefore almost always occur in a midline or paramedian location in relation to the spine. Chordoma is the most common primary malignant sacral tumor, usually situated very low in the sacrum (S3 to S5). A chordoma manifests as a destructive, lytic lesion with internal calcifications and a large presacral soft-tissue component. These tumors are capable of extending across the adjacent disk space and the sacroiliac joint. Although chordomas are relatively low-grade malignancies that metastasize infrequently, they are locally aggressive. Radiotherapy is used for partially resected or inoperable tumours, but only has a palliative and analgetic effect Teratomas: The sacrococcygeal region is the most common location of teratomas discovered in infancy. They are composed of a variable mixture of solid and cystic components. Although the majority of teratomas in infancy and childhood are benign, there is a tendency toward malignant transformation as the child gets older. Ewing sarcoma:it is an aggressive malignant tumor that manifests between the ages of 5 and 30 years. The sacral ala is the most common site for primary Ewing sarcoma of the spine, despite the fact that the spine represents only 3-10% of cases. The typical feature is a lytic and destructive lesion, often with an accompanying soft-tissue mass, that may spread to adjacent bones. Other uncommon primary tumors: chondrosarcoma (Calcified and osteolytic lesion associated with a soft tissue mass), fibrosarcoma, osteosarcoma, and primitive neuroectodermal tumor. Chondrosarcoma, which generally occurs in adults, may manifest as a lytic lesion with an associated soft-tissue mass and calcifications. TREATMENT Lateral lesions with sacroiliac joint involvement are treated by vertical sacrectomy. Page 6 of 23

7 High or low midline tumours without sacroiliac joint involvement are treated by transverse sacrectomy. Follow-up MRI assesses changes in the residual lesions: 1. Decreased volume in response to chemotherapy-radiotherapy, or stability of a known residual tumour, constitute signs of efficacy of treatment. Certain changes such as ossification of an initially osteolytic lesion, may indicate stable disease. 2. An increase in size, modification of the residual tumour signal (such as the appearance of central necrosis or haemorrhage) indicate disease progression despite treatment. 3. INFECTIOUS LESIONS They may have their origin in: - Contiguous spread from adjacent infection. - Hematogenous spread (via the Batson plexus) from the bladder, intestines, or genitourinary tract or from intravenous injections in drug abusers. - Soft-tissue infections in the pelvis (decubitus ulcers, traumatic injuries ) - Iatrogenic injury from gluteal injections, sacral biopsy At imaging sacral osteomyelitis appears as a destructive lesion poorly marginated associated with soft-tissue swelling. 4. NONINFECTIOUS ARTHROPATHIES A number of inflammatory conditions can involve the sacrum by affecting the sacroiliac joints as part of a systemic or local inflammatory process. There is considerable overlap between these conditions but all are characterized by involvement of the SI joints. The pattern of involvement can be unilateral or bilateral and ranges in severity from mild to severe inflammation resulting in partial or complete ankylosis. Ankylosing spondylitis and inflammatory bowel disease cause bilateral symmetric sacroiliac joint involvement. Initial erosive changes are followed by repair, which leads to subchondral sclerosis and subsequent ankylosis. Psoriatic arthritis and Reiter syndrome can result in bilateral symmetric, bilateral asymmetric (more frequently), or unilateral sacroiliac joint involvement. Findings include erosions with subsequent repair, resulting in subchondral sclerosis but rarely ankylosis. Page 7 of 23

8 Osteoarthritis can cause bilateral symmetric, bilateral asymmetric, or unilateral sacroiliac joint involvement. Findings include absence of erosions, joint space narrowing, subchondral sclerosis, and osteophyte formation. Rheumatoid arthritis. Crystal deposition arthropathy (gout, calcium pyrophosphate deposition disease). The presence or absence of symmetry, the status of the joint space, the presence or absence of periarticular erosions or subchondral sclerosis, and the presence or absence of joint ankylosis allow characterization of sacroiliac joint arthropathies. 5. TRAUMATIC LESIONS Sacral fractures are difficult to diagnose and treat and may be associated with significant morbidity. Plain radiographs of the sacrum are particularly difficult to interpret due to overlying soft tissues. CT is the examination of choice for imaging suspected sacral fractures and dislocations. Classification of sacral fractures: - Zone 1: fractures are lateral to the sacral foramina. - Zone 2: fractures involve one or more of the foramina. Neurologic deficits uncommon. - Zone 3: fractures involve the central sacral canal with or without involvement of the other two zones. Significant bilateral neurologic damage is present in the majority of cases. - Lumbosacral junction injuries: when sacral fracture lines pass cranially through or medial to the S1 articular process. 5.a) INSUFFICIENCY STRESS FRACTURE It is a relatively common cause of lower back pain in elderly patients, particularly osteopenic women or after irradiation of the pelvis. There may be a history of minor recent low-impact trauma. Plain radiographs are very inaccurate for diagnosis of sacral insufficiency stress fractures. CT reveals vertical lucent lines in both sacral alae and a horizontal fracture line through the sacral body may be apparent on CT and MR imaging reveals bone marrow edema with or without discrete fracture lines. The presence of further fractures in characteristic locations such as the pubic rami support the diagnosis of insufficiency fractures. 5.b) FATIGUE STRESS FRACTURE Page 8 of 23

9 Sacral fatigue stress fractures are very uncommon and they may be underreported in the literature owing to the initial physical examination findings, which are often not localizing to the sacrum. Fatigue stress fractures are usually unilateral. Images for this section: Fig. 1: TRANSITIONAL VERTEBRA. Lumbarisation of S1. On conventional radiography and sagittal MR images there are six rib-free lumbar-type vertebrae. Page 9 of 23

10 Page 10 of 23

11 Fig. 2: CAUDAL REGRESSION SYNDROME. Partial sacral agenesis with tethered cord and syrinx. Fig. 3: MYELOMENINGOCELE. There is a posterior deffect with widened canal and protrusion of cerebrospinal fluid and meninges. It associates syrinx and tethered cord. Page 11 of 23

12 Fig. 4: LIPOMYELOMENINGOCELE. There is a posterior deffect with protrusion of softtissue density within fat, outside the canal space. There is also a tethered cord, which is displaced posteriorly, and syrinx. Page 12 of 23

13 Fig. 5: SACRAL SCHWANNOMA: T2W, T1W and post-gadolinium T1W sagittal and axial images. There is a solid tumor that occupies the sacral canal and extends through a foramen. It has a hypointense central image that corresponds to necrosis. Page 13 of 23

14 Page 14 of 23

15 Fig. 6: SACROCOCCYGEAL TERATOMA. Heterogeneus policystic mass arising from sacro-coccygeal region in an infant. Fig. 7: METASTASES from lung cancer. There are multiple lesions involving the sacrum and the rest of the spine, hypointense in both T1W and T2W images, and lytic-sclerotic on CT. Page 15 of 23

16 Fig. 8: MULTIPLE MYELOMA: There are multiple lesions involving the sacrum and the rest of the spine which present an heterogeneus signal intensity. Note the important edema of the 12º vertebral body with posterior displacement towards the central canal with signs of myelopathy. Page 16 of 23

17 Fig. 9: CHORDOMA: Sagittal T2W and T1W images showing a lobulated mass arising from the lower sacrum extending into the pre-sacral space. There is partial destruction of the sacrum associated. Fig. 10: CHONDROSARCOMA: In left sacral ala there is a lytic lesion with an associated soft-tissue mass and calcifications. Fig. 11: CHONDROSARCOMA: In left sacral ala there is a lytic lesion with an associated soft-tissue mass and calcifications. CT, Sagittal T1 and T2 weighted MR images. Page 17 of 23

18 Fig. 12: TUBERCULOUS OSTEOMYELITIS: Multiple hypointense (T1W) and hiperintense (STIR) lesions that affect vertebral bodies and sacrum in a patient with clinical symptoms and laboratory tests that prooved M. tuberculosis. Page 18 of 23

19 Fig. 13: TELANGIECTATIC OSTEOSARCOMA: There is a large sacral mass that involves massively the majority of sacrum's posterior elements and the vertebral bodies of S1 to S3. Fig. 14: SACROILIITIS. Coronal STIR image shows subtle areas of bone marrow oedema on both sides of the left sacroiliac joint with a trace amount of fluid along the left iliacus. Page 19 of 23

20 Fig. 15: SACROILIITIS. STIR axial images demonstrates signal hyperintensity and T1W image shows subtle erosions. Page 20 of 23

21 Page 21 of 23

22 Fig. 16: SACRAL INSUFFICIENCY FRACTURE. Coronal oblique image (T1W, STIR and CT). On MR images is shown an extensive bone marrow edema on both sacral wings. On T1W and CT is possible to delineate two fracture lines parallel to the sacroiliac joint and one transverse fracture line along with sclerosis on CT. Page 22 of 23

23 Conclusion The sacrum, often ignored as an important site of spinal pathologic conditions, is optimally imaged with cross-sectional techniques. The development of the sacrum, or failure thereof, reflects subsequent imaging manifestations of congenital and neoplastic sacral lesions. Unusual entities that have a predisposition for affecting the sacrum include sacral agenesis, primary tumors (particularly teratoma, chordoma, giant cell tumor and chondrosarcoma), sacroiliitis and stress fractures. Perineural cysts, metastases, and fractures of the sacrum are relatively common lesions. Familiarity with all of the entities that may affect the sacrum will enhance the ability of subspecialty radiologists and general radiologists not only to arrive at a specific diagnosis or appropriate differential diagnosis but also to contribute to the management of these conditions. Personal information References Diel J, Ortiz O, et al. The Sacrum: Pathologic spectrum, multimodality imaging approach). RadioGraphics (2001) 21:1, Gerber S, Ollivier L, Leclère J. et al. Sleletal Radiol (2008) 37: 277. doi: / s Kok, Hong Kuan et al. Imaging the patient with sacroiliac pain. Canadian Association of Radiologists Journal, Volume 67; Issue 1, Thornton E, Krajewski KM et al. Imaging features of primary and secondary malignant tumours of the sacrum. The British Journal of Radiology (2012) 85:1011, Page 23 of 23