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Paget Disease of the Spine



 

 General Considerations

Sites of involvement

  • Usually polyostotic and asymmetric
    • Pelvis (75%) most common, followed by
      • Lumbar spine
      • Thoracic spine
      • Proximal femur
      • Calvarium
      • Scapula
      • Distal femur
      • Proximal tibia
      • Proximal humerus

Imaging Findings

  • Classical triad
    • Thickening of the cortex
    • Accentuation of the trabecular pattern
    • Increased size of bone
  • Cyst-like areas
  • Skull (involvement in 29-65%)
    • Inner and outer table involved
      • Leads to diploic widening
    • Osteoporosis circumscripta is well-defined lysis, most commonly in frontal bone producing well-defined geographic lytic lesion in skull
      • Represents early destructive phase of disease active stage)
    • "Cotton wool" appearance represents mixed lytic and blastic pattern of thickened calvarium (later stage)
    • Basilar invagination with encroachment on foramen magnum
    • Deossification and sclerosis in maxilla
    • Sclerosis of skull base
  • Long bones (almost invariably starts at end of bone)
    • "Candle flame" or "blade of grass" pattern of lysis is the advancing tip of V-shaped lytic defect in diaphysis of long bone originating in subarticular site
    • Lateral curvature of femur
    • Anterior curvature of tibia (commonly resulting in fracture)
  • Pelvis
    • Thickened trabeculae in sacrum, ilium
    • Rarefaction in central portion of ilium (looks like a large lytic lesion)
    • Thickening of iliopectineal line
    • Acetabular protrusio with secondary degenerative joint disease
  • Spine (upper cervical, low dorsal, midlumbar most common sites)
    • Coarse trabeculations at periphery of bone
    • "Picture-frame vertebra" mimics bone-within-bone appearance
      • Enlarged vertebral body with reinforced peripheral trabeculae and more lucent center, typically in lumbar spine
    • "Ivory vertebra" is a blastic vertebra with increased density
    • Ossification of spinal ligaments, paravertebral soft tissue, disk spaces can occur

MRI Findings

  • Hypointense area / area of signal void on T1WI + T2WI (cortical thickening, coarse trabeculation)
  • Widening of bone
  • Reduction in size and signal intensity of medullary cavity due to replacement of high-signal-intensity fatty marrow by medullary bone formation
  • Focal areas of higher signal intensity than fatty marrow (from cyst-like fat-filled marrow spaces)
  • Areas of decreased signal intensity within marrow on T1WI and increased intensity on T2WI (= fibrovascular tissue resembling granulation tissue)

DDx

  • Depends on the bone in which it occurs
  • Skull
    • Osteolytic or osteoblastic metastases
  • Long bones
    • Metastases
    • Chronic osteomyelitis (thickened cortex)
    • Old trauma (thickened cortex)
    • Hodgkin’s disease
  • Spine
    • Hemangioma
    • Metastases

 

Paget Disease of Spine

 
Paget Disease of Spine. The lumbar vertebral body has thickened cortices which outline the body ("picture-frame appearance") (red arrows). The vertebral body is slightly larger than the body above and below it (white double arrow). The trabecular pattern is thickened and coarsened (yellow arrow).