Septic facet arthropathy with epidural abscess

Findings:

Sagittal T2 weighted images of the lumbar spine with fat saturation demonstrate extensive signal abnormalities within the paraspinal soft tissues at lower lumbar levels, with fluid collections within the facet joints, epidural space, and paravertebral soft tissues. There is abnormal marrow signal of the pedicles and facets at these levels. Postcontrast images confirm abnormal enhancement associated with this process with multiple fluid collections. An additional fluid collection with peripheral enhancement projects from the left L5 S1 facet, compatible with epidural abscess causing left thecal sac compression.

Discussion:

nDifferential diagnosis
nSeptic facet arthropathy w abscess, complex synovial cyst with reactive changes, infiltrative neoplasm
nFeatures
nFacet joint destruction, extensive soft tissue enhancement, fluid collections
nEpidural inflammatory changes may be abscess, phlegmon, or combination
nLook for fluid signal pockets for abscess
nLook for cord edema/infarction (septic thrombophlebitis)
nSubdural empyema and epidural abscess difficult to distinguish
nClinical
n45% staph aureus, hematogenous
nUsually dorsal

 

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