Pediatric Osteomyelitis Discitis

  • Etiology:
    — Pyogenic: Most common etiology with Staphylococcus aureus and Streptococcus the most common organisms, Salmonella is common organism in patients with sickle cell anemia, pseudomonas is common organism in IV drug abusers
    — Fungal: Diabetics, immunosuppression
    — Viral: Spinal cord infection
    — Post trauma: Vertebral body fracture can become secondarily infected
    — Note: Segmental arteries provide blood supply to subjacent vertebral bodies and intervening disc space – note disc space is avascular in adults but vascularized in children, slower blood flow to end arterioles adjacent to the anterior longitudinal ligament makes these areas prone to infection
  • Imaging Radiograph:
    — Not sensitive for diagnosis as takes 2-4 weeks for disc space narrowing and end plate erosion to occur and 6-10 weeks for flattening of vertebral body
    — Usually in lumbar spine at L2-3 or L3-4
    — Endplate erosion
    — Progressive height loss
    — Deossification
    — Alignment abnormalities
  • Imaging Bone scan with SPECT: Positive earlier than plain films with increased uptake in disc spaces and vertebral bodies
  • Imaging CT:
    — Endplate erosion
    — Progressive height loss
    — Deossification
    — Alignment abnormalities
  • Imaging MRI:
    — Isointense T1 signal intensity and increased T2 signal intensity within disc and loss of intranuclear cleft (after age of 40)
    — Marrow signal decreased on T1WI and increased on T2WI at adjacent endplates representing marrow edema
    — Paravertebral soft tissue isointense on T1WI and hyperintense on T2WI and progressively enhances
    — Spinal cord involvement with hyperintensity on T2WI
    — Vertebral body enhancement after contrast administration
    — Diffusion abnormality within subdural or epidural fluid collections
  • Note: Imaging of fungal osteomyelitis discitis is similar to tuberculous infection
  • DDX: Degenerative disease, spondyloarthropathies – rhematoid arthritis or ankylosing spondylitis or neoplasms – chordoma or lymphoma or metastases
  • Complications:
    — Subligamentous extension and paraspinal abscess
    — Subdural abscess: Subdural space is a potential space, direct innoculation or secondary dissection of infection into this space, ring enhancing collection, purulent fluid isointense to hypointense on T1WI, heterogeneously hyperintense T2WI, diffusion positive
    — Epidural abscess: May have fluid component, signal intensity similar to subdural abscess
    — Venous compression and thrombophlebitis
    — Vascular congestion to cord – ischemia or infarct, usually irreversible injury
    — Spinal cord damage
    — Venous obstruction or thrombosis and secondary venous congestion of the cord leading to vascular ischemia or infarct
  • Treatment: Antibiotics
  • Clinical: Usually in less than 5 years old due to increased regional vascularity of vertebral endplates and intradiscal extension of end arteries

Radiology Cases of Osteomyelitis Discitis

MRI of osteomyelitis of the spine
Coronal T1 MRI without contrast of the lumbar spine (left above) shows areas of low signal intensity on the right side of the L4 and L5 vertebral bodies and a right-sided paraspinal mass all of which enhance after the administration of contrast (right above). Axial T2 MRI through the L5 vertebral body (below) shows high signal intensity in the right side of the vertebral body and in the right paraspinal mass. The disk spaces are not involved.
Radiograph and MRI of diskitis / osteomyelitis
Lateral radiograph of the lumbar spine shows loss of height of the L3-L4 intervertebral disc space. Sagittal T2 MRI of the lumbar spine shows (right top) loss of normal bright signal of the L3-L4 intervertebral disc and an epidural mass just posterior to the L4 vertebral body. Axial T1 MRI with contrast at the L4 level shows the epidural mass to be right sided and to also involve the right psoas muscle.
Radiograph and CT scan and MRI scan of diskitis / osteomyelitis of the spine
Lateral radiograph of the spine shows anterior wedging of the T12 vertebral body and loss of height of the T12-L1 intervertebral disk space. Axial CT through T12 shows destruction of the vertebral body anteriorly and an associated paraspinal abscess forming between the aorta and the vertebral body. Sagittal T2 MRI (left), T1 MRI without contrast (middle) and T1 MRI with contrast (right) demonstrate more clearly the irregular contour of the inferior endplate of T12, the loss of height of the T12-L1 intervertebral disk space, and the loss of the normal bright signal within that disk space on T2 weighted-imaging.