Spinal Subdural Empyema¶
Definition¶
Spinal subdural empyema is a rare collection of pus between the dura mater and the arachnoid membrane. It is far less common than spinal epidural abscess and carries significant morbidity due to its close proximity to the spinal cord and nerve roots. Most cases result from hematogenous spread or contiguous extension from adjacent infection.
Imaging Findings¶
MRI¶
- Location — Subdural space, often dorsal, which may extend over multiple segments
- T1-weighted — Isointense to slightly hypointense collection in the subdural space
- T2-weighted — Hyperintense
- Post-contrast — Thin rim enhancement of the collection margins. The enhancement pattern may help distinguish from epidural abscess — subdural empyema is more closely applied to the cord surface and may extend along the nerve root sleeves.
- DWI — Restricted diffusion within the collection
- Cord compression — May be present depending on the size of the collection
Distinguishing from Epidural Abscess¶
| Feature | Subdural Empyema | Epidural Abscess |
|---|---|---|
| Location | Between dura and arachnoid | Between dura and periosteum |
| Shape | Crescent, conforms to cord surface | Biconvex or lenticular |
| Dural margin | Internal to the dura | External to the dura |
| Extension | May track into nerve root sleeves | Respects the dural boundary |
| Associated spondylodiscitis | Less common | Common (50–80%) |
Clinical Pearl
Spinal subdural empyema is rare and difficult to distinguish from epidural abscess on imaging. The key clue is the relationship to the dura — subdural collections are more intimately applied to the cord surface and may insinuate into the nerve root sleeves, while epidural collections are separated from the cord by the dura. In practice, the distinction is often made at surgery.
Management¶
- Urgent surgical drainage (laminectomy with durotomy)
- Prolonged IV antibiotics
- Treatment of the underlying source of infection
Key Points¶
- Rare but serious infection in the subdural space
- MRI shows a rim-enhancing subdural collection with restricted diffusion
- Difficult to distinguish from epidural abscess on imaging
- More closely applied to the cord than epidural abscess
- Urgent surgical drainage is usually required
References¶
- Hall WA, De Jesus O. Subdural Empyema. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2024 Oct 6. https://www.ncbi.nlm.nih.gov/books/NBK557829/
- Subdural empyema. Radiopaedia.org. https://radiopaedia.org/articles/subdural-empyema
- Levy ML, Wieder BH, Schneider J, Zee CS, Weiss MH. Subdural empyema of the cervical spine: clinicopathological correlates and magnetic resonance imaging. Report of three cases. J Neurosurg. 1993;79(6):929-935. https://pubmed.ncbi.nlm.nih.gov/7902429/
- Sandler AL, Thompson D, Goodrich JT, et al. Infections of the spinal subdural space in children: a series of 11 contemporary cases and review of all published reports. A multinational collaborative effort. Childs Nerv Syst. 2013;29(1):105-117. https://pubmed.ncbi.nlm.nih.gov/23053357/
- Thiruvengadam S, Khoo B, Saha S. Spinal subdural empyema in an immunocompetent patient: illustrative case. J Neurosurg Case Lessons. 2024;8(16):CASE24464. https://pubmed.ncbi.nlm.nih.gov/39401455/
- Ramos AD, Rolston JD, Gauger GE, Larson PS. Spinal subdural abscess following laminectomy for symptomatic stenosis: a report of 2 cases and review of the literature. Am J Case Rep. 2016;17:476-483. https://pmc.ncbi.nlm.nih.gov/articles/PMC4944552/
- Expert Panel on Neurological Imaging, Ortiz AO, Levitt A, Shah LM, et al. ACR Appropriateness Criteria® Suspected Spine Infection. J Am Coll Radiol. 2021;18(11S):S488-S501. https://pubmed.ncbi.nlm.nih.gov/34794603/