What are myelopathy and myelomalacia?

Understanding Myelopathy and Myelomalacia

Myelopathy refers to any pathologic process affecting the spinal cord, while myelomalacia specifically describes softening of the spinal cord tissue due to chronic compression or injury, best visualized on MRI as signal changes representing irreversible damage to neural tissue. 1, 2

Myelopathy: Definition and Classification

Myelopathy encompasses a broad spectrum of spinal cord pathologies that can be classified based on time course:

• Acute myelopathy: Symptoms progress to maximum deficit within 21 days
• Subacute myelopathy: Intermediate progression
• Chronic/progressive myelopathy: Slow, gradual worsening over months to years

Common Causes of Myelopathy

1. Extrinsic compression:

   • Degenerative disease (spondylotic myelopathy) - most common, especially in cervical spine
   • Disc herniations
   • Epidural lipomatosis
   • Spinal malalignment
   • Congenital spinal stenosis
   • Ossification of posterior longitudinal ligament

2. Post-surgical complications:

   • Seromas
   • Pseudomeningoceles
   • Hematomas
   • Epidural abscesses

3. Neoplastic causes:

   • Primary or metastatic tumors (extradural, intradural extramedullary, intramedullary)

4. Inflammatory/demyelinating conditions:

   • Multiple sclerosis (MS) - affects cervical cord in 80-90% of MS patients
   • Neuromyelitis optica (NMO)
   • Acute disseminated encephalomyelitis (ADEM)
   • Autoimmune myelitis (including paraneoplastic)

5. Vascular causes:

   • Spinal cord ischemia
   • Arteriovenous malformations/fistulas
   • Hematomyelia

6. Metabolic/nutritional causes:

   • Vitamin B12 deficiency
   • Copper deficiency
   • Nitrous oxide exposure

7. Infectious causes:

   • HTLV myelitis
   • Tuberculosis
   • Schistosomiasis
   • HIV vacuolar myelopathy
   • Tertiary syphilis

8. Other causes:

   • Radiation-induced myelopathy
   • Hirayama disease (cervical flexion myelopathy)
   • Dorsal arachnoid webs
   • Ventral cord herniation

Myelomalacia: Definition and Characteristics

Myelomalacia specifically refers to softening of the spinal cord tissue, representing irreversible damage:

• Typically develops as part of chronic/progressive myelopathy
• Results from prolonged compression causing ischemia, edema, and eventual necrosis
• Most commonly seen in cervical spondylotic myelopathy
• Often accompanied by gliosis (scarring of neural tissue)

Imaging Features of Myelomalacia

MRI is the gold standard for diagnosing myelomalacia 1, 2:

• Hyperintense signal on T2-weighted images
• Cord thinning/atrophy in advanced cases
• May show cystic changes within the cord
• Often associated with evidence of extrinsic compression

Clinical Significance of Myelomalacia

The presence of myelomalacia has important prognostic implications:

• Indicates irreversible spinal cord damage
• Serves as a prognostic factor for neurosurgical outcomes 1
• Often requires surgical intervention when progressive neurological deficits are present 2
• Even with profound neurological deficits, remarkable recovery is possible with appropriate surgical decompression 3

Diagnostic Approach

MRI is the imaging modality of choice for evaluating both myelopathy and myelomalacia 1, 2:

• MRI without contrast: Initial evaluation for most cases
• MRI with contrast: Recommended for:
  • Suspected demyelinating disease
  • Suspected infection or inflammation
  • Suspected neoplasm
  • Post-surgical evaluation
  • Vascular malformations

Key Pitfalls to Avoid

1. Delayed diagnosis: Dorsalgia (back pain) often precedes profound myelopathy and should prompt early imaging 3

2. Inadequate imaging: The entire spinal cord may need evaluation, particularly with demyelinating diseases

3. Misattribution to age-related changes: Not all degenerative findings cause myelopathy; clinical correlation is essential

4. Missing dynamic causes: Some myelopathies worsen with certain positions (e.g., Hirayama disease with neck flexion)

5. Overlooking systemic causes: Always consider metabolic, inflammatory, and infectious etiologies when extrinsic compression is not evident

Remember that early diagnosis and appropriate treatment are crucial for preventing irreversible spinal cord damage, as myelomalacia represents permanent injury to the spinal cord tissue.