Discitis and Osteomyelitis

• Usually the result of blood–borne agents
  • Especially from lung and urinary tract
  • Average age of onset is in children around 6 years
  • Most common pathogen is staphylococcus
  • Also Streptococcus
  • Gram-negative rods in IV drug abusers or immunocompromised patients
    • E. Coli
    • Proteus
    • Non-pyogenic
      • Tuberculosis
      • Coccidioidomycosis
• May occur as a result of invasive procedure
  • Surgery
  • Discography
  • Myelography
• Pathogenesis
  • In children, probably begins in still vascularized disc
  • In adults, in anterior inferior corner of vertebral body with spread across disk to adjacent vertebral endplate
• Site of involvement
  • L3/4
  • L4/5
  • Unusual above T9
  • Usually involvement of one disk space (occasionally 2)
• Bacteria destroy disk and both contiguous end-plates
• Imaging Findings
  • Narrowing and destruction of an intervertebral disk
    • Earliest plain film sign
  • Indistinctness of adjacent endplates with destruction
  • Often associated with bony sclerosis of the two contiguous vertebral bodies
  • Paravertebral soft tissue mass
  • Endplate sclerosis (during healing phase beginning anywhere from 8 weeks to 8 months after onset)
  • Bone fusion after 6 months to 2 years

Frontal and lateral radiographs of the thoracic spine demonstrate destruction of the endplates
of two contiguous vertebral bodies with considerable endplate sclerosis, findings characteristic of discitis

• MRI
  • Decreased marrow intensity on T1-weighted images in two contiguous vertebrae
  • High signal intensity on T2
    • Because of associated edema
  • Disk space and paravertebral soft tissues enhance on MRI
• Clinical
  • Pain is present if disease  is acute
  • Point tenderness
  • Malaise
  • Irritability in children
  • Referred hip pain
  • Inability to bear weight
  • Course of discitis is frequently more benign in children than adults
    • Disk space is narrowed but no destruction of contiguous vertebral bodies
• Osteomyelitis of the vertebral body
  • Usually the result of discitis
  • But can occur from direct involvement from hematogenous dissemination to body
  • MRI findings are similar to discitis
• Bone scan will be positive
• Gallium scan or Indium-111 scan will be positive
• Renal spondyloarthropathy
  • May resemble discitis
  • Usually involves cervical spine
  • Destruction of disk space and adjacent vertebral bodies
  • Signal on T2 is low rather than high
  • No clinical evidence of infection
• Complication of disease
  • Kyphosis
• Treatment
  • Bone fusion after 6 months to 2 years

Radiologic Clinics, Imaging of the Spine, 1991
The Requisites, Neuroradiology
Dahnert, 4^th Ed