SPINE IMAGING 1862 Nontraumatic Spinal Cord Com- pression: MRI Primer for Emer- gency Department Radiologists The occurrence of acute myelopathy in a nontrauma setting consti- tutes a medical emergency for which spinal MRI is frequently or- dered as the first step in the patient’s workup. The emergency depart- ment radiologist should be familiar with the common differential di- agnoses of acute myelopathy and be able to differentiate compressive from noncompressive causes. The degree of spinal cord compression and presence of an intramedullary T2-hyperintense signal suggestive of an acute cord edema are critical findings for subsequent urgent care such as surgical decompression. Importantly, a delay in diagno- sis may lead to permanent disability. In the spinal canal, compressive myelopathy can be localized to the epidural, intradural extramedul- lary, or intramedullary anatomic spaces. Effacement of the epidural fat and the lesion’s relation to the thecal sac help to distinguish an epidural lesion from an intradural lesion. Noncompressive myelopa- thy manifests as an intramedullary T2-hyperintense signal without an underlying mass and has a wide range of vascular, metabolic, inflammatory, infectious, and demyelinating causes with seemingly overlapping imaging appearances. The differential diagnosis can be refined by considering the location of the abnormal signal intensity within the cord, the longitudinal extent of the disease, and the clinical history and laboratory findings. Use of a compartmental spinal MRI approach in patients with suspected nontraumatic spinal cord injury helps to localize the abnormality to an epidural, intradural extramed- ullary, or intramedullary space, and when combined with clinical and laboratory findings, aids in refining the diagnosis and determining the appropriate surgical or nonsurgical management. Online supplemental material is available for this article. © RSNA, 2019฀•฀radiographics.rsna.org Olga Laur, MD, MHS Hari Nandu, MD 1 David S.Titelbaum, MD Diego B. Nunez, MD, MPH Bharti Khurana, MD Abbreviations: ADEM = acute disseminated encephalomyelitis, AQP4-IgG = aquaporin-4 immunoglobulin G, CSF = cerebrospinal fluid, DAVF = dural arteriovenous fistula, MS = multi- ple sclerosis,NMO = neuromyelitis optica,STIR = short τ inversion-recovery RadioGraphics 2019; 39:1862–1880 https://doi.org/10.1148/rg.2019190024 Content Codes: From the Departments of Radiology (O.L., D.B.N.), Neuroradiology (H.N., D.B.N.), and Emergency Radiology (B.K.), Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115; and Department of Radiology, Shields Health Care, Brockton, Mass (D.S.T.). Recipi- ent of a Certificate of Merit award for an educa- tion exhibit at the 2018 RSNA Annual Meeting. Received February 15, 2019; revision requested April 29 and received June 28; accepted July 25. For this journal-based SA-CME activity, the au- thor B.K. has provided disclosures (see end of article); all other authors, the editor, and the re- viewers have disclosed no relevant relationships. Address correspondence to O.L. (e-mail: olga.laur@bwh.harvard.edu). 1 Current address: CP Advanced Imaging, New York, NY. © RSNA, 2019 After completing this journal-based SA-CME activity, participants will be able to: ■ Describe the anatomy of the spinal canal compartment and localize com- pressive lesions to an epidural, intradural extramedullary, or intramedullary space. ■ Differentiate common compressive causes of acute myelopathy according to compartment location and characteristic imaging findings. ■ List common causes of noncompressive myelopathy and refine the differential diagnosis according to the location and longitudinal extension of abnormal signal intensity within the spinal cord, neural tracts involved, and ancillary clinical his- tory and laboratory data. See rsna.org/learning-center-rg. SA-CME LEARNING OBJECTIVES Introduction Acute compressive myelopathy in the setting of minimal to no trauma is a medical emergency for which timely intervention is es- sential to minimize irreversible loss of neurologic function. Decom- pression of the spinal cord within the first 24 hours after the onset of myelopathy has been shown to improve neurologic outcomes (1–3). As a result, MRI of the spine is frequently performed on an emer- gent basis, including after hours, to assess suspected cord compres- sion. Thus, it is imperative that emergency department radiologists have a good understanding of the common differential diagnoses of acute myelopathy and be able to differentiate the compressive versus noncompressive causes. The anomalies commonly included in the differential diagnosis of acute myelopathy and the compressive and noncompressive causes of this disease are described in this review. This copy is for personal use only. To order printed copies, contact reprints@rsna.org