In a patient presenting with acute or sub‑acute spinal cord dysfunction (weakness, sensory level, bowel or bladder disturbance), what is the recommended initial diagnostic work‑up and empiric treatment for suspected infectious myelitis?

Infectious Myelitis: Diagnostic Work-Up and Empiric Treatment

Immediate Diagnostic Approach

Obtain urgent contrast-enhanced MRI of the entire spine as the first-line imaging study, followed immediately by lumbar puncture for cerebrospinal fluid analysis, while simultaneously drawing blood cultures and inflammatory markers before initiating any antimicrobial therapy. 1

Critical First Steps (Within Hours)

• Perform contrast-enhanced MRI of the spine (ideally whole spine, minimum affected region) to distinguish infectious myelitis from compressive myelopathy, epidural abscess, or other structural causes that require emergency surgical intervention 1
• Obtain two sets of blood cultures from separate sites before any antibiotics are administered 2, 3
• Draw inflammatory markers: ESR and CRP are more sensitive than white blood cell count for spinal infections; CRP >100 mg/L strongly suggests active infection 1, 2, 3
• Perform lumbar puncture for CSF analysis including cell count with differential, protein, glucose, Gram stain, bacterial culture, viral PCR panel (HSV-1/2, VZV, enteroviruses, West Nile virus), mycobacterial stain and culture, and fungal studies 4, 5, 6

Why MRI with Contrast Is Essential

• MRI demonstrates spinal cord edema, enhancement patterns, and longitudinal extent that help differentiate infectious from autoimmune or demyelinating causes 1, 7
• Contrast enhancement is mandatory for initial evaluation to identify abscess formation, meningeal involvement, or characteristic enhancement patterns of infection 1
• Whole-spine imaging is recommended when infectious myelitis is suspected, as multilevel involvement occurs in 51% of spinal infections with skip lesions in 8% 2, 3
• MRI can identify epidural abscess or spinal cord compression requiring emergency neurosurgical intervention 1

Laboratory Evaluation Beyond Initial Studies

• Send CSF for additional testing: oligoclonal bands, IgG index, cytology, VDRL (syphilis), cryptococcal antigen if immunocompromised 5, 6
• Obtain serology for endemic pathogens if patient is from or has traveled to tuberculosis-endemic regions (South Asia, Africa, Turkey, Egypt) or areas with coccidioidomycosis, schistosomiasis 1, 2
• Test for Mycoplasma pneumoniae with specific IgA, IgG, and IgM antibodies, as this pathogen can cause myelitis with negative routine serologies 8
• Check HIV status, diabetes screening, and immunosuppression markers as these are major risk factors for infectious myelitis 1, 2

Empiric Treatment Strategy

When to Start Empiric Antibiotics

Do not initiate empiric antimicrobial therapy until after blood cultures and CSF are obtained, unless the patient has:

• Hemodynamic instability, severe sepsis, or altered mental status requiring immediate intervention 3
• MRI evidence of epidural abscess with neurologic compromise 1, 3
• Rapid neurologic deterioration with weakness, sensory loss, or bowel/bladder dysfunction 3, 4

Empiric Antibiotic Regimen

When empiric treatment is required before pathogen identification:

• Vancomycin (to cover Staphylococcus aureus including MRSA) PLUS
• Third- or fourth-generation cephalosporin (ceftriaxone or cefepime for gram-negative coverage) PLUS
• Acyclovir (for HSV/VZV coverage, as viral myelitis is common and treatable) 3, 5, 6

Special Pathogen Considerations

• If tuberculosis is suspected (endemic region, immunocompromised, characteristic imaging with large paraspinal abscess disproportionate to bone destruction): perform image-guided biopsy before starting anti-tubercular therapy; standard regimen is 2 months of isoniazid, rifampicin, pyrazinamide, and ethambutol followed by 4 months of isoniazid and rifampicin 2
• If Mycoplasma pneumoniae is suspected (respiratory prodrome, young patient): add doxycycline 100 mg daily for 14 days 8
• If fungal infection is suspected (immunocompromised, endemic area): add amphotericin B pending culture results 5, 6

Critical Pitfalls to Avoid

• Do not delay MRI to wait for laboratory results; imaging must be performed urgently to exclude surgical emergencies 1, 3
• Do not rely on normal white blood cell count to rule out infection; up to 40% of spinal infections have normal WBC 2, 3
• Do not start antibiotics before obtaining cultures and CSF unless there is hemodynamic instability or rapid neurologic decline, as this markedly reduces diagnostic yield 2, 3
• Do not assume atelectasis or "normal postoperative course" in any patient with fever and neurologic symptoms; infectious myelitis must be excluded first 3
• Do not perform single-level imaging; whole-spine MRI is needed to detect multilevel or skip lesions 2, 3

Escalation Triggers Requiring Immediate Neurosurgical Consultation

• New or progressive motor weakness, sensory level, or bowel/bladder dysfunction 3, 4
• MRI showing epidural abscess or significant spinal cord compression 1
• Spinal instability or significant kyphotic deformity 2
• Failure to improve after 1-2 weeks of appropriate antimicrobial therapy 2

Monitoring During Treatment

• CRP declines more rapidly than ESR and correlates with clinical improvement; CRP >2.75 mg/dL after 4 weeks suggests treatment failure 2
• Serial MRI is essential to assess disease response and detect complications 2
• Monitor for drug toxicity: liver function tests for anti-tubercular drugs, visual acuity for ethambutol, renal function for vancomycin and acyclovir 2