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Subdural Abscess


KEY FACTS

Terminology

  • Spinal subdural abscess (SSA)

  • Intradural extramedullary ring-enhancing fluid collection of pus in “potential” space between dura and arachnoid

Imaging

  • Thoracolumbar region most common

  • Presence suggested by mass effect on cord and obliterated subarachnoid space

  • Cord displacement: ± impingement and edema

  • Increased subdural density on NECT

  • MR

    • T2 hyperintense/T1 hypointense

    • Heterogeneous, diffuse subdural enhancement

    • Rim-enhancing fluid collection

  • Best imaging modality

    • MR with contrast → ↑ sensitivity in detecting SSA

    • Axial sequences confirm subdural location (inside dural margin)

Top Differential Diagnoses

  • Abscess: Epidural, paravertebral

    • Typically associated with spondylodiscitis

  • Subdural hematoma

    • Predominantly hypointense on T2WI or gradient-echo

Pathology

  • Predisposing factors

    • Intravenous drug abuse, immunocompromised state, diabetes, cirrhosis, renal failure

Clinical Issues

  • Fever

  • Neck or back pain and tenderness

Diagnostic Checklist

  • Ring-enhancing intradural extramedullary collection outlined by epidural fat and cerebrospinal fluid on axial imaging

Sagittal T2WI MR shows a heterogeneously hyperintense collection
in the dorsal intradural extramedullary space, with hypointense rim causing marked mass effect on cervical cord
.

Sagittal CT shows a hyperdense spinal subdural abscess (SSA)
in the dorsal spinal canal. Osseous destruction of the L4 & L5 endplates
& intradiscal hypodense fluid
at this level are seen. This extensive SSA began as a lumbar spinal epidural abscess caused by Serratia marcescens.

Axial T1WI C+ MR depicts a rim-enhancing fluid collection
in the dorsal spinal canal, causing mass effect upon and anteriorly displacing the cervical cord
.

Sagittal T1 C+ MR exhibits a low-intensity collection with thick peripheral enhancement
spanning the cervical and thoracic dorsal spinal canal. The SSA causes severe impingement of the cord
. Initially, CT-guided drainage was attempted but with limited success. Subsequently, surgical decompression was performed.

TERMINOLOGY

Synonyms

  • Spinal subdural empyema

  • Spinal subdural abscess (SSA)

Definitions

  • Collection of pus in “potential” space between dura and arachnoid

IMAGING

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