What causes calcific ligamentum flavum of the thoracic spine?

Causes of Calcific Ligamentum Flavum of the Thoracic Spine

Calcification of the ligamentum flavum (CLF) in the thoracic spine is primarily caused by calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, which typically occurs in middle-aged and elderly patients with degenerative changes of the spine.

Pathophysiology and Risk Factors

• CPPD Crystal Deposition: The primary mechanism involves accumulation of calcium pyrophosphate dihydrate crystals within a thickened and hypertrophic ligamentum flavum 1

• Age-Related Factors:

  • Most common in patients over 50 years of age
  • Prevalence increases with advancing age
  • Rare in younger populations 2

• Anatomical Considerations:

  • Occurs predominantly at the lower thoracic levels (T10-T11 most common)
  • More frequent at junctional areas with increased mobility (thoracolumbar junction)
  • The relative hypomobility of the thoracic spine compared to cervical and lumbar regions may contribute to the specific pattern of calcification 1

• Ethnic Predisposition:

  • Higher prevalence among individuals of Japanese descent
  • Less common in other ethnic groups 2

• Degenerative Changes:

  • Often associated with other degenerative spine conditions
  • Vacuum disc phenomenon may be present at affected levels 1
  • Mechanical stress at mobile segments may potentiate CLF formation 1

Clinical Significance

CLF can lead to thoracic myelopathy with symptoms including:

• Band-like pain around the chest or abdomen
• Sensory changes in affected dermatomes
• Motor weakness
• Gait difficulties
• Progressive neurological deterioration 3

Diagnostic Approach

• MRI: Shows posterior spinal cord compression by a hypo-signal intense mass; preferred initial imaging for thoracic radiculopathy or myelopathy 3, 1

• CT: More definitive for identifying calcification; reveals CLF and potentially associated degenerative changes like vacuum disc phenomenon 1

Treatment Considerations

For symptomatic patients with myelopathy due to CLF:

• Posterior decompression (laminectomy)
• Possible instrumented fusion if instability is present
• Early surgical intervention for moderate to severe myelopathy 3, 1

Related Conditions

CLF should be differentiated from other calcified spinal lesions:

• Ossification of the posterior longitudinal ligament (OPLL)
• Diffuse idiopathic skeletal hyperostosis (DISH)
• Giant thoracic osteophytes 4

Clinical Pitfalls

• CLF may be misdiagnosed as other causes of thoracic myelopathy
• Symptoms can improve unexpectedly and rapidly after surgical decompression 5
• Delayed diagnosis can lead to progressive myelopathy and potentially irreversible neurological deficits

Understanding the pathophysiology of CLF is crucial for proper diagnosis and timely intervention to prevent permanent neurological damage in affected patients.