What is the diagnostic approach for transverse myelitis?

Diagnostic Approach to Transverse Myelitis

The diagnosis of transverse myelitis requires MRI of the spine with and without contrast as the first-line investigation, followed by cerebrospinal fluid analysis and comprehensive blood tests to identify the underlying etiology. 1

Imaging Studies

• MRI of the spine with thin axial cuts through the suspected abnormal region is essential to detect T2-weighted hyperintense lesions that appear wedge-shaped on axial views and cigar-shaped on sagittal views 1
• Contrast-enhanced spinal cord MRI is necessary to exclude cord compression and to detect T2-weighted hyperintense lesions (70-93% sensitivity) 2
• The involvement of more than three spinal cord segments indicates longitudinal myelopathy, which may suggest neuromyelitis optica spectrum disorder (NMOSD) 2, 1
• Brain MRI should be performed to evaluate for demyelinating lesions suggestive of multiple sclerosis or other CNS disorders 1
• In cases with additional neurological symptoms or signs, brain MRI helps in differential diagnosis of demyelinating disorders 2

Cerebrospinal Fluid Studies

• Lumbar puncture is crucial for analyzing cell count, protein, glucose, oligoclonal bands, and ruling out infectious causes 1
• CSF typically shows mild-to-moderate abnormalities (50-70%) including pleocytosis, but these findings are non-specific 2
• An intensely inflammatory CSF resembling bacterial meningitis or HSV infection requires antimicrobial/antiviral therapy while awaiting confirmation 2
• Microbiological studies are important to exclude infectious myelitis 2, 1
• Oligoclonal bands help distinguish transverse myelitis from multiple sclerosis 1

Blood Tests

• Aquaporin-4 IgG antibodies should be tested to evaluate for NMOSD, particularly when longitudinally extensive transverse myelitis is present 1
• MOG-IgG (myelin oligodendrocyte glycoprotein) antibodies should be tested using cell-based assays (current gold standard) 2, 1
• Cell-based assays must employ full-length human MOG as target antigen with Fc-specific secondary antibodies 2
• Autoimmune panel including antinuclear antibodies, anti-Ro/La antibodies, and antiphospholipid antibodies should be performed 1
• Infectious disease screening including HIV, HTLV1, and syphilis (RPR) is necessary 2, 1
• Vitamin B12 levels and thyroid function tests should be checked to rule out metabolic causes 1

Diagnostic Algorithm

1. First-line testing: 1

   • MRI spine with and without contrast
   • Lumbar puncture for CSF analysis
   • Basic blood tests (CBC, CMP, B12, folate, TSH)

2. Second-line testing: 1

   • Aquaporin-4 IgG and MOG-IgG antibodies
   • Brain MRI with and without contrast
   • Expanded autoimmune panel
   • Infectious disease screening

3. Third-line testing: 1

   • Electrodiagnostic studies
   • Specialized antibody testing
   • Additional imaging as indicated

Differential Diagnosis

• Multiple sclerosis: Look for Dawson's finger-type lesions, juxtacortical U fiber lesions, or lesions adjacent to lateral ventricles on brain MRI 2
• Neuromyelitis optica: Test for aquaporin-4 antibodies and look for longitudinally extensive lesions 2, 1
• MOG encephalomyelitis: Consider in patients with bilateral acute optic neuritis, OCB-negative myelitis, or ADEM-like presentation 2
• Systemic lupus erythematosus and other autoimmune conditions: Test for relevant autoantibodies 2, 1
• Infectious causes: HTLV1, Lyme disease, syphilis, and viral infections can present with similar symptoms 2, 1
• Paraneoplastic disorders: Cerebellar ataxia with elevated IgG in CSF may suggest this diagnosis 2
• Acute disseminated encephalomyelitis (ADEM): Consider especially in post-vaccination or post-infectious settings 2

Clinical Pearls and Pitfalls

• Monophasic demyelinating diseases like ADEM, postviral Devic's syndrome, and acute transverse myelitis present diagnostic challenges; a diagnosis of multiple sclerosis should not be made unless new symptoms/signs or imaging abnormalities appear more than three months after clinical onset 2
• The presence of increased deep tendon reflexes helps distinguish transverse myelitis from conditions with flaccid paralysis like Guillain-Barré syndrome 1
• Longitudinally extensive transverse myelitis (≥3 vertebral segments) should raise suspicion for NMOSD or MOG-associated disease 2, 1
• Biopsy is rarely needed but can confirm inflammatory and demyelinating lesions when performed 2

Special Considerations

• For patients on immune checkpoint inhibitor therapy, consider immune-related adverse events as a potential cause 1
• Evaluation for urinary retention and constipation is important as these are common autonomic manifestations 1
• Relapses are common (50-60%) during corticosteroid dose reduction, highlighting the need for maintenance immunosuppressive therapy in some cases 2