What are the causes and treatment options for myelitis?

Causes of Myelitis

Myelitis is most commonly caused by demyelinating diseases, infections, autoimmune disorders, and spinal cord compression, with specific treatment approaches required for each etiology to reduce morbidity and mortality.

Major Etiological Categories

1. Extrinsic Compression Causes

• Degenerative disease (spondylotic myelopathy) - most common cause of chronic/progressive myelopathy, especially in cervical spine 1
• Disc herniations and osteophyte complexes 1
• Epidural lipomatosis 1
• Spinal malalignment 1
• Post-surgical complications - seromas, pseudomeningoceles, hematomas, epidural abscesses 1
• Primary or metastatic tumors - affecting extradural and intradural extramedullary spaces 1
• Rare conditions - Hirayama disease (cervical flexion myelopathy), dorsal arachnoid webs, ventral cord herniation 1

2. Non-Compressive Inflammatory Causes

Demyelinating Disorders

• Multiple sclerosis (MS) - affects 80-90% of MS patients, predominantly in cervical cord 1
• Neuromyelitis optica spectrum disorder (NMOSD) - characterized by AQP4-IgG antibodies 2
• MOG-IgG-associated encephalomyelitis (MOG-EM) - typically without oligoclonal bands 2
• Acute disseminated encephalomyelitis (ADEM) 1

Infectious Causes

• Viral - poliomyelitis, coxsackieviruses, enterovirus-71, West Nile virus, HIV, HTLV-1 3, 4
• Bacterial - tuberculosis, syphilis 1
• Parasitic - schistosomiasis (requires praziquantel plus dexamethasone) 2, 3
• Fungal infections 3

Autoimmune/Inflammatory Causes

• Paraneoplastic myelopathy 1
• Systemic autoimmune diseases 1
• Immune checkpoint inhibitor-related myositis - can affect spinal cord 1
• Post-infectious or post-vaccinal processes 5

Metabolic Causes

• Vitamin B12 (cobalamin) deficiency - causes subacute combined degeneration 1
• Copper deficiency 1
• Nitrous oxide inhalation 1

3. Vascular Causes

• Spinal dural arteriovenous malformations/fistulas 1
• Spinal cord ischemia - from atherosclerosis, aortic surgery complications 1
• Systemic hypotension 1
• Thoracoabdominal aneurysms or dissection 1
• Sickle cell disease 1
• Fibrocartilaginous embolic disease 1

4. Other Causes

• Radiation-induced myelopathy - rare dose-dependent complication 1
• Idiopathic transverse myelitis - diagnosis of exclusion 6

Diagnostic Approach

Clinical Presentation

• Sensory alterations - often with clear sensory level 2, 6
• Motor weakness - variable severity 2, 6
• Autonomic dysfunction - bowel/bladder problems, temperature dysregulation 2, 6
• Reflex abnormalities - hyperreflexia below lesion level, possible hyporeflexia at lesion level 2

Essential Diagnostic Tests

1. MRI spine with and without contrast - gold standard for evaluation 1, 2

   • Look for T2 hyperintensity, possible gadolinium enhancement
   • Cigar-like shape in sagittal view, wedge-shaped in axial view
   • Assess for compressive vs. non-compressive causes

2. Cerebrospinal fluid analysis

   • Cell count, protein, glucose
   • Oligoclonal bands (present in MS, rare in MOG-EM)
   • Infectious studies as indicated

3. Serum studies

   • AQP4-IgG and MOG-IgG antibodies
   • Vitamin B12, copper levels
   • Inflammatory markers (ESR, CRP)
   • Specific infectious testing based on clinical suspicion

Treatment Approach

Acute Management

1. Rule out compressive causes requiring surgical intervention 1, 6

2. For inflammatory/demyelinating myelitis:

   • High-dose intravenous methylprednisolone (1g/day for 3-5 days) as soon as possible 2
   • Plasma exchange (5-10 sessions) if inadequate response to steroids 2
   • IVIG (2 g/kg divided over 5 days) as alternative 2

3. For specific etiologies:

   • AQP4-IgG positive: Consider rituximab or cyclophosphamide 2
   • Infectious causes: Pathogen-specific antimicrobial therapy 3, 4
   • Metabolic causes: Correct deficiencies (B12, copper) 1

Maintenance Therapy

• Immunosuppressive therapy for autoimmune causes to prevent relapses 2
• Consider AHSCT (autologous hematopoietic stem cell transplantation) in severe refractory MS or NMOSD 1

Symptomatic Management

• Neuropathic pain: Pregabalin, gabapentin, or duloxetine 2
• Spasticity: Baclofen, tizanidine, physical therapy 2
• Autonomic dysfunction: Monitor for cardiac arrhythmias, blood pressure fluctuations 2
• Respiratory support: Early intubation if vital capacity falls below 15 ml/kg 2

Prognostic Factors

Favorable Prognostic Factors

• Early treatment initiation
• Prompt neurological response
• Absence of extensive MRI lesions 2

Poor Prognostic Factors

• Extensive lesions on spinal MRI
• Reduced muscle strength or sphincter dysfunction at onset
• Positive antiphospholipid antibodies
• Delayed initiation of treatment 2

Special Considerations

• Pregnancy: IVIG may be preferred over steroids 2
• Secondary complications: Monitor for scoliosis in pediatric cases 7
• Rule out infectious causes before starting immunosuppression 2