Intervertebral Disc/Endplate Irregularity

Jeffrey S. Ross, MD

DIFFERENTIAL DIAGNOSIS

Common

Degenerative Disc Disease
Degenerative Endplate Changes (Modic Changes)
Schmorl Node
Accelerated Degeneration
Scheuermann Disease
Pyogenic Disc Space Infection
Tuberculous Disc Space Infection
Fungal Infection (Coccidiomycosis)
Rheumatoid Arthritis

Less Common

Neurogenic (Charcot) Arthropathy
Ankylosing Spondylitis
Brucellosis
Bone Infarcts
- Sickle Cell
- Gaucher
Post-Treatment: Bone Morphogenetic Protein
Hemodialysis Spondyloarthropathy

Rare but Important

Gout
Spondyloepiphyseal Dysplasia
Ochronosis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Primary consideration is infection vs. other
- Classic pattern of disc space infection includes
  - Endplate irregularity
  - Loss of distinction of disc margin and endplate on T1 weighted images
  - Abnormal T2 signal disc hyperintensity
  - Abnormal T2 vertebral body hyperintensity
  - Abnormal irregular enhancement of the disc
- Epidural enhancing soft tissue (phlegmon) or rim-enhancing mass (abscess) definitive findings
- Fat-suppressed T2 images &/or fat-suppressed post-contrast T1 images especially useful for evaluation of paraspinal and epidural soft tissues
- Severe degenerative endplate changes may be associated with endplate irregularity and fluid within disc giving T2 hyperintensity
  - Should not see epidural soft tissue or paraspinal soft tissue
- Definite overlap in MR findings between early disc space infection and severe degenerative endplate changes ⇒ biopsy required

Helpful Clues for Common Diagnoses

Degenerative Disc Disease/Endplate Changes
- Disc hypointense on T1WI and T2WI
- Endplates may be irregular, with Schmorl nodes, but margin between disc and vertebral body preserved
- Mild post-gadolinium enhancement, often linear along endplate margins in horizontal direction
- No paravertebral or epidural soft tissue to suggest infection
Schmorl Node
- Well-defined, smoothly marginated endplate herniation
- May see variable marrow signal around it, depending upon age of insult
  - Acute shows ↑ STIR, chronic shows normal or fatty marrow halo
Accelerated Degeneration
- Aberrant biophysical stresses from altered normal spinal motion/fusion
- Wolff law; living tissue responds to chronic changes in stresses & strains
- Increased mobility in remaining mobile segments is hypothesized to cause accelerated degenerative pathologic changes
Scheuermann Disease
- Kyphosis secondary to multiple Schmorl nodes → vertebral body wedging
- Three or more wedged thoracic vertebrae with irregular endplates
- Thoracic spine pain and tenderness worsened by activity in teenager, young adult
Pyogenic Disc Space Infection
- Severe endplate irregularity with loss of distinction of disc from endplate
- ↑ T2 signal from disc, endplate, ± vertebral body
- Paravertebral and epidural soft tissue
Tuberculous Disc Space Infection
- Endplate irregularity and osteolysis
- Multiple (non) contiguous vertebrae involved, including posterior elements
- Migration of phlegmon underneath all with erosion of vertebral body corners
- May mimic metastatic disease
Fungal Infection (Coccidiomycosis)
- Variable appearance from small focal body involvement ⇒ gross vertebral body/disc destruction
- Multiple bodies involved, similar to TB
Rheumatoid Arthritis
- C1-C2 instability in 33% of all RA patients
- Facet and uncovertebral joint erosions
- Multilevel subluxations, uncommon disc and adjacent vertebral body destruction

Helpful Clues for Less Common Diagnoses

Neurogenic (Charcot) Arthropathy
- 4 of classic “5 Ds” related to spine: Normal density bone, destruction, disorganization, debris
Ankylosing Spondylitis
- Endplate irregularity with acute inflammation phase, or chronic with fusions and Schmorl node formation
- Irregularity with chronic fracture and pseudoarthrosis development
Brucellosis
- Granulomatous osteomyelitis pattern
- May see pattern mix similar to pyogenic w/disc involvement, + skip lesions like TB
Bone Infarcts
- Sickle cell & Gaucher disease: “H-shaped” vertebral bodies
- May see only vertebral collapse with Gaucher
Post-Treatment: Bone Morphogenetic Protein
- Bone morphogenetic protein (rhBMP-2) bone lytic resorption defects occur at fusion sites in up to 1/3 patients
- Transforming growth factor acts as signaling molecule to attract mesenchymal stem cells
  - Binds to receptors and causes stem cells to differentiate into osteoblasts with bone formation
Hemodialysis Spondyloarthropathy
- Peridiscal destructive arthritis in patient on long-term hemodialysis