Acute Nontraumatic Back Pain: Infections and Mimics

HomeRadioGraphicsVol. 39, No. 1 PreviousNext Trauma/Emergency RadiologyFree AccessRadioGraphics Fundamentals | Online PresentationAcute Nontraumatic Back Pain: Infections and MimicsOlga Laur , Jacob C. Mandell, David S. Titelbaum, Charles Cho, Stacy E. Smith, Bharti KhuranaOlga Laur , Jacob C. Mandell, David S. Titelbaum, Charles Cho, Stacy E. Smith, Bharti KhuranaAuthor AffiliationsFrom the Departments of Emergency Radiology (O.L., B.K.), Musculoskeletal Radiology (J.C.M., S.E.S.), and Neuroradiology (C.C.), Brigham and Women's Hospital, Harvard Medical School, 75 Francis St, Boston, MA 02115; and Department of Radiology, Shields Health Care, Brockton, Mass (D.S.T.).Address correspondence to O.L. (e-mail: [email protected]).Olga Laur Jacob C. MandellDavid S. TitelbaumCharles ChoStacy E. SmithBharti KhuranaPublished Online:Jan 8 2019https://doi.org/10.1148/rg.2019180077MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In AbstractThe full digital presentation is available online. Acute nontraumatic back pain has a broad differential diagnosis, but the primary concern in the emergent setting is the accurate and timely identification of spinal infection. Prompt diagnosis facilitates optimal medical and/or surgical management and can reduce the risk of long-term musculoskeletal and neurologic complications. MRI is the mainstay imaging modality for assessing a suspected infection. Diagnosing infection can be challenging owing to subtle imaging findings and because several noninfectious entities can mimic infection.This online presentation reviews the anatomy, pathophysiology, and characteristic appearances of spinal infections and noninfectious mimics involving the vertebral column, facet joints, and epidural space (Fig 1). Helpful imaging clues and the use of diffusion-weighted imaging (DWI) are described to help establish the correct diagnosis. Several cases are presented in a quiz-based format to allow the reader to determine if the presented case demonstrates an infection or a mimic.Figure 1. Illustration of a lumbar vertebral body shows the anatomy of the spine, including the disk-endplate complex, facet, and epidural and paraspinal regions. The potential sites of infection (green areas) are also indicated. As an infection can have a contiguous spread, psoas muscle involvement may serve as a helpful diagnostic imaging clue. CSF = cerebrospinal fluid.Figure 1.Download as PowerPointOpen in Image Viewer Imaging findings of infection involving the vertebral column include endplate destruction, iliopsoas edema, and epidural phlegmon. In particular, edema or fluid in the psoas musculature (MRI psoas sign) is a finding consistent with early spondylodiscitis, which may precede osseous destructive changes and if present serves as a feasible biopsy target to confirm infection and guide antibiotic treatment (Fig 2).Figure 2a. Methicillin-resistant Staphylococcus aureus (MRSA) infection in a 73-year-old man with a history of back pain. Sagittal short inversion time inversion-recovery (a) and axial T2-weighted (b) MR images of the lumbar spine show edema in the right aspect of the disk at L3-L4, with endplate irregularity (arrow in a) and a hyperintense T2-weighted signal extending along the right psoas muscle (arrows in b), findings concerning for discitis-osteomyelitis. The results of a subsequent blood culture analysis confirmed MRSA.Figure 2a.Download as PowerPointOpen in Image Viewer Figure 2b. Methicillin-resistant Staphylococcus aureus (MRSA) infection in a 73-year-old man with a history of back pain. Sagittal short inversion time inversion-recovery (a) and axial T2-weighted (b) MR images of the lumbar spine show edema in the right aspect of the disk at L3-L4, with endplate irregularity (arrow in a) and a hyperintense T2-weighted signal extending along the right psoas muscle (arrows in b), findings concerning for discitis-osteomyelitis. The results of a subsequent blood culture analysis confirmed MRSA.Figure 2b.Download as PowerPointOpen in Image Viewer DWI is helpful for assessing suspected infection. The DWI claw sign (paired clawlike hyperintense regions in adjacent vertebral bodies) has a high negative predictive value for excluding infection. In contrast, restricted diffusion centered in the endplate edema is highly suspicious for infection. DWI can help differentiate postoperative soft-tissue paraspinal abscess from noninfectious seroma. Noninfectious mimics of infectious discitis-osteomyelitis include Modic type 1 endplate edema, acute Schmorl node, Andersson lesion pseudarthrosis in ankylosing spondylitis, radiation osteitis, longus colli calcific tendinitis, Paget disease, and SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome.Facet septic arthritis is uncommon, characterized by facet effusion, bone destruction, thickened peripheral enhancement of the joint, edema, and phlegmon and/or abscess development within the adjacent paraspinal muscles. In contrast, noninfectious acute osteoarthritis of the facet joint represents an extremely common noninfectious cause, characterized by edematous changes in the facet joint and surrounding soft tissue, without bone destruction. In addition, metastases to the facet joint or articular processes are rare but can mimic acute infection. Infection may spread to the epidural space hematogenously or by contiguous spread from adjacent spondylodiscitis or from recent instrumentation. Noninfectious causes with overlapping imaging appearances include epidural hematoma and neoplastic and nonneoplastic masses with epidural extension.This online presentation reviews the imaging appearance of spinal infection and noninfectious mimics involving the disk-endplate complex, facet joints, and epidural space.Disclosures of Conflicts of Interest.—J.C.M.Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: royalties from Cambridge University Press. Other activities: disclosed no relevant relationships. D.S.T.Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: fees for independent medical-legal consulting. Other activities: disclosed no relevant relationships.Recipient of a Cum Laude award for an education exhibit at the 2017 RSNA Annual Meeting.The authors J.C.M. and D.S.T. have provided disclosures; all other authors have disclosed no relevant relationshipsSuggested ReadingsCapps EF, Kinsella JJ, Gupta M, Bhatki AM, Opatowsky MJ. Emergency imaging assessment of acute, nontraumatic conditions of the head and neck. RadioGraphics 2010;30(5):1335–1352. Link, Google ScholarChang CY, Simeone FJ, Nelson SB, Taneja AK, Huang AJ. Is biopsying the paravertebral soft tissue as effective as biopsying the disk or vertebral endplate? 10-year retrospective review of CT-guided biopsy of diskitis-osteomyelitis. AJR Am J Roentgenol 2015;205(1):123–129. Crossref, Medline, Google ScholarHong SH, Choi JY, Lee JW, Kim NR, Choi JA, Kang HS. MR imaging assessment of the spine: infection or an imitation? RadioGraphics 2009;29(2):599–612. Link, Google ScholarLedbetter LN, Salzman KL, Shah LM. Imaging psoas sign in lumbar spinal infections: evaluation of diagnostic accuracy and comparison with established imaging characteristics. AJNR Am J Neuroradiol 2016;37(4):736–741. Crossref, Medline, Google ScholarPatel KB, Poplawski MM, Pawha PS, Naidich TP, Tanenbaum LN. Diffusion-weighted MRI "claw sign" improves differentiation of infectious from degenerative Modic type 1 signal changes of the spine. AJNR Am J Neuroradiol 2014;35(8):1647–1652. Crossref, Medline, Google ScholarArticle HistoryReceived: Mar 11 2018Revision requested: Apr 26 2018Revision received: May 23 2018Accepted: June 1 2018Published online: Jan 8 2019Published in print: Jan 2019 FiguresReferencesRelatedDetailsCited BySpinal InfectionsHajimeYokota, E. TurgutTali2023 | Neuroimaging Clinics of North America, Vol. 33, No. 1Imaging assessment of deep neck spaces infections: an anatomical approachSimoneCaprioli, AlbertoTagliafico, MartinaFiannacca, FabioBorda, RiccardoPicasso, CristinaConforti, AlessandroCasaleggio, GiuseppeCittadini2022 | La radiologia medicaImaging Spectrum of Infections in the Setting of Immunotherapy and Molecular Targeted TherapyMariaZulfiqar, ChristineMenias, AnupShetty, Daniel R.Ludwig, Sana Saif UrRehman, HilaryOrlowski, VincentMellnick2022 | Current Problems in Diagnostic Radiology, Vol. 51, No. 1Axial Spondyloarthritis: Mimics and Pitfalls of Imaging AssessmentAntónio ProençaCaetano, Vasco V.Mascarenhas, Pedro M.Machado2021 | Frontiers in Medicine, Vol. 8MRI of the SpineM. K.Jesse, Corey K.Ho2020Spine MRI: A Review of Commonly Encountered Emergent ConditionsAaronWinn, AdamMartin, IvanCastellon, AllenSanchez, Efrat SarafLavi, FelipeMunera, DiegoNunez2020 | Topics in Magnetic Resonance Imaging, Vol. 29, No. 6Radiopaedia.orgJoachimFeger, HamishSmith2019Radiopaedia.orgFrancisDeng, HamishSmith2019Radiopaedia.orgJoachimFeger, JackRen2014Radiopaedia.orgHenryKnipe, BehrangAmini2008Accompanying This ArticleAcute Nontraumatic Back Pain: Infections and MimicsJan 8 2019Default Digital Object SeriesRecommended Articles Spinal Neuroarthropathy: Pathophysiology, Clinical and Imaging Features, and Differential DiagnosisRadioGraphics2016Volume: 36Issue: 3pp. 783-799Differential Diagnosis of Facet Joint DisordersRadioGraphics2021Volume: 41Issue: 2pp. 543-558Injuries to the Rigid Spine: What the Spine Surgeon Wants to KnowRadioGraphics2019Volume: 39Issue: 2pp. 449-466Case 234: Neuropathic SpondyloarthropathyRadiology2016Volume: 281Issue: 1pp. 314-319Spinal Injections for Pain ManagementRadiology2016Volume: 281Issue: 3pp. 669-688See More RSNA Education Exhibits Pocket Guide to Key Findings of Differential Diagnoses of Facet Joints DisordersDigital Posters2019Things That Go "Splat" on the Spine: Bugs, Blood, and Other Imitators — An Anatomical Compartment ApproachDigital Posters2019Lumbar Facet Joint Septic Arthritis: CT and MRI Findings of an Important and Commonly Missed PathologyDigital Posters2019 RSNA Case Collection Early spine infectionRSNA Case Collection2022Facet joint synovial cystRSNA Case Collection2020Pyogenic spondylodiscitis RSNA Case Collection2020 Vol. 39, No. 1 Slide PresentationAbbreviations Abbreviation: DWI diffusion-weighted imaging Metrics Altmetric Score PDF download