MRI Findings in Acute Transverse Myelitis
MRI of the spine with and without IV contrast is the reference standard for diagnosing acute transverse myelitis, typically showing centrally located T2 hyperintensity extending 3-4 vertebral segments and occupying more than two-thirds of the cord's cross-sectional area. 1, 2, 3
Key Imaging Protocol
Obtain MRI spine with and without IV contrast as the initial diagnostic study. 1 The American College of Radiology recommends contrast-enhanced imaging for initial evaluation of suspected inflammatory myelopathy, as enhancement patterns help distinguish transverse myelitis from other etiologies. 1
- Include diffusion-weighted imaging (DWI) in the protocol, as it can detect spinal cord signal abnormalities earlier than T2-weighted sequences. 1
- Obtain brain MRI concurrently to evaluate for demyelinating lesions elsewhere and help differentiate between idiopathic transverse myelitis, multiple sclerosis, neuromyelitis optica, and ADEM. 1
Characteristic MRI Features
T2-Weighted Imaging Findings
- Central cord hyperintensity occupying more than two-thirds of the cross-sectional area (88% of cases). 3
- Longitudinal extent of 3-4 vertebral segments is most common (53% of cases). 3
- Small central area of normal signal intensity within the hyperintense lesion core (47% of cases). 3
- Cord expansion is present in approximately half of cases (47%). 3
Contrast Enhancement Patterns
- Focal, peripheral cord enhancement occurs in 53% of cases, particularly when cord expansion is present. 3
- Enhancement typically appears within the first 4-6 weeks of lesion formation, representing inflammatory infiltrates causing blood-brain barrier breakdown. 1
- Absence of enhancement in early phases suggests spinal cord ischemia rather than inflammatory myelitis and should prompt consideration of alternative diagnoses. 1
Distinguishing Features by Etiology
Idiopathic Transverse Myelitis
- Centrally located lesion with symmetric involvement. 3
- Slow regression of T2 hyperintensity with enhancing nodule on follow-up. 3
- Limited to spinal cord without brain lesions. 3, 4
Multiple Sclerosis
- Shorter lesions (typically <2 vertebral segments). 1
- Peripheral cord location affecting less than half the cross-sectional area. 1
- Cervical cord most commonly affected (80-90% of MS patients have spinal involvement). 1
- Concurrent brain lesions meeting MAGNIMS criteria for dissemination in space. 1
Neuromyelitis Optica Spectrum Disorders (NMOSD)
- Longitudinally extensive transverse myelitis (LETM) extending ≥3 contiguous segments. 1, 5
- Central cord involvement with predilection for gray matter. 1
- Optic nerve involvement on brain/orbit MRI showing T2 hyperintensity extending over half the optic nerve length. 1
- Periependymal brainstem or area postrema lesions may be present. 1
Acute Disseminated Encephalomyelitis (ADEM)
Critical Pitfalls to Avoid
Do not diagnose transverse myelitis based on imaging alone—clinical correlation and follow-up MRI are essential, as MR findings alone cannot definitively distinguish transverse myelitis from cord tumors or other inflammatory conditions. 3
Contrast enhancement presence in early acute myelopathy strongly suggests inflammatory or infectious etiology rather than ischemia. 1 If enhancement is absent and vascular risk factors exist, consider spinal cord ischemia and obtain MRA to evaluate for vertebral artery dissection or anterior spinal artery occlusion. 1
Order complete spine imaging, not just the symptomatic level, as lesions may extend beyond the clinically apparent level and additional asymptomatic lesions help establish the diagnosis. 1, 2
Follow-Up Imaging Considerations
- Repeat MRI shows slow regression of T2 hyperintensity in idiopathic transverse myelitis with clinical improvement. 3
- Persistent or new lesions on follow-up suggest recurrent demyelinating disorder or progression to multiple sclerosis. 4
- Complete spine MRI helps assess disease burden in demyelinating disorders and differentiate NMOSD from MS. 1