IS Case 439: Extensive spinal epidural abscess

Lisa Siripun, MD

University of Rochester

Imaging Sciences URMC 2010
Publication Date: 2010-08-30

History

Patient is a 60-year-old male with progressive back pain for 3 weeks.

Findings

There was an anterior epidural fluid collection which extends from the level of foramen magnum to the level of L2 with peripheral enhancement. There was mild compression to the spinal cord. Diffuse dural enhancement was seen from the anterior aspect of the medulla to the lumbar spinal cord.

Diagnosis

Extensive spinal epidural abscess

Discussion

Spinal epidural abscess (SEA) can cause marked neurologic morbidity by compression of the spinal cord or cauda equina or lead to life threatening sepsis. Frequently, diagnosis is understandably delayed because the initial presentation may be only back pain. It usually occurs in patients with chronic illness such as diabetes mellitus or immunodeficiency and in those with intravenous drug abuse. The patients usually present with back pain, fever, radicular pain, neck stiffness, weakness, bowel and bladder dysfunction and paralysis. The duration of symptoms can range from a few days to more than a month.

Hematogenous spread with seeding of the epidural space is the suspected source of infection in most children and is thought to occur in many adults as well. Direct extension of infection from vertebral osteomyelitis or discitis occurs in adults and rarely in children. The most common infectious agent is staphylococcus aureus. Mycobacterium tuberculosis is the second most common pathogen. Eighty percent of SEA occurs in the posterior epidural space, and 20% anteriorly. Most common site is at the lower thoracic and lumbar spine.

MRI with gadolinium (Gd-MRI) has a specificity and sensitivity above 90% to detect SEA, and being superior to other imaging modalities, is therefore the diagnostic method of choice. On T1 pre-contrast studies, the SEA appears hypo- to isointense to the spinal cord. In case of diffuse SEA, the signal of the CSF in the subarachnoid space may not visualized at the involved segments due to total encasement and displacement of the thecal sac. On T2W, the collection is hyperintense to the spinal cord and therefore difficult to differentiate from CSF. However, T2W help demonstrate areas of discitis and osteomyelitis. On post-contrast study, there may be enhancement of solid component of the SEA either homogeneous or heterogeneous fashion, peripheral enhancing necrotic abscess, diffuse dural enhancement in extensive SEA and enhancing prominent anterior epidural vein or basivertebral venous plexus above/ below the abscess.

Other imaging modality include

CT which may show enhancing epidural mass narrowing the central canal
Myelography may show epidural mass impeding CSF flow
Gallium scan for evaluation of vertebral osteomyelitis The treatment for SEA includes emergent surgical decompression and abscess drainage, and long-term antibiotic therapy.

References

Numaguchi Y, Rigamonti D, Rothman MI, et al. Spinal epidural abscess: evaluation with gadolinium-enhanced MR imaging. Radiographics. 1993 May;13(3):545-59; discussion 559-60. PMID: 8316663
Huff JS. Spinal epidural abscess. eMedicine. March 17, 2010. http://emedicine.medscape.com/article/1165840-overview
Sendi P, Bregenzer T, Zimmerli W. Spinal epidural abscess in clinical practice. QJM. 2008 Jan;101(1):1-12. PMID: 17982180