What is the most appropriate immediate test for a patient with systemic lupus erythematosus (SLE) on hydroxychloroquine (Plaquenil) 200 mg/day, prednisone (Deltasone) 5 mg/day, and azathioprine (Imuran) 100 mg/day, presenting with sudden onset of lower limb weakness, urinary incontinence, paraplegia, and hyperreflexia?

Immediate Diagnostic Approach for SLE Patient with Acute Myelopathy

The most appropriate immediate test is C: Lumbar puncture and MRI spinal cord. This patient presents with classic signs of acute transverse myelitis—a neurological emergency in SLE that requires urgent spinal cord imaging to guide immediate treatment and exclude cord compression.

Clinical Reasoning

Why Spinal Cord MRI is Essential

This patient's presentation of sudden-onset paraplegia, hyperreflexia, and urinary incontinence indicates upper motor neuron dysfunction consistent with SLE myelopathy 1. The clinical picture demands immediate spinal cord evaluation because:

• Contrast-enhanced spinal cord MRI is the recommended imaging modality for suspected SLE myelopathy, with sensitivity of 70-93% for detecting T2-weighted hyperintense lesions 1
• Spinal cord MRI excludes cord compression, which is a critical differential diagnosis requiring different management 1
• Timing is critical: Factors associated with severe neurological deficit include delay (>2 weeks) in initiation of therapy, making immediate diagnosis essential 1

Role of Lumbar Puncture

CSF analysis is important but non-specific in SLE myelopathy 1:

• Mild-to-moderate CSF abnormalities occur in 50-70% of cases 1
• Microbiological studies are crucial to exclude infectious myelitis, particularly given this patient's immunosuppression with azathioprine and prednisone 1
• An intensely inflammatory CSF resembling bacterial or HSV meningitis necessitates antimicrobial/antiviral therapy while awaiting MRI confirmation 1

Why Brain Imaging is Not the Priority

Brain MRI should only be performed when other neuropsychiatric SLE symptoms co-exist 1. In this case:

• The patient has isolated spinal cord syndrome without cerebral manifestations
• Brain MRI has modest sensitivity (50-70%) and specificity (40-67%) for neuropsychiatric lupus, primarily useful for psychosis and cognitive symptoms 1
• The clinical localization clearly points to spinal cord pathology, not brain involvement

Treatment Implications of Prompt Diagnosis

Early diagnosis directly impacts morbidity and mortality 1:

• High-dose glucocorticoids may be given early while awaiting MRI confirmation if infection is ruled out 1
• Combination of intravenous methylprednisolone and cyclophosphamide is effective if used promptly within the first few hours, with neurological response occurring within days to 3 weeks 1
• Delay in treatment initiation (>2 weeks) is associated with severe neurological deficit 1
• Factors predicting poor outcome include extensive spinal cord MRI lesions, reduced muscle strength, sphincter dysfunction at presentation, and antiphospholipid antibodies 1

Additional Diagnostic Considerations

Once spinal cord MRI is obtained:

• Involvement of >3 spinal cord segments indicates longitudinal myelopathy, which may warrant testing for serum NMO IgG (aquaporin) antibodies to diagnose co-existing neuromyelitis optica 1
• Antiphospholipid antibodies should be evaluated as they are associated with ischemic/thrombotic myelopathy and may require anticoagulation 1

Common Pitfalls to Avoid

• Do not delay spinal cord imaging to obtain brain imaging first—the clinical syndrome localizes to the spinal cord
• Do not perform lumbar puncture before imaging if there is any concern for cord compression, as this could worsen neurological status
• Do not wait for complete diagnostic workup before initiating treatment—high-dose glucocorticoids can be started once infection is excluded 1