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Subdural empyema

Summary

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  • Subdural empyema is a life-threatening intracranial infection characterised by purulent material accumulation between the dura mater and arachnoid membrane
  • Most commonly results from complications of sinusitis, otitis media, or neurosurgical procedures
  • Rapid diagnosis and treatment are crucial due to high morbidity and mortality rates1

Pathophysiology

  • Infection typically spreads from contiguous structures (e.g., sinuses, middle ear) or hematogenously
  • Bacteria invade the subdural space, leading to:
    • Inflammatory response
    • Increased intracranial pressure
    • Potential brain parenchyma compression
    • Venous thrombosis and infarction
  • Common pathogens:
    • Streptococcus species
    • Staphylococcus aureus
    • Anaerobic bacteria

Demographics

  • More common in males (2:1 male to female ratio)
  • Peak incidence in second and third decades of life
  • Higher prevalence in developing countries
  • Risk factors:
    • Recent sinusitis or otitis media
    • Neurosurgical procedures
    • Head trauma
    • Immunocompromised state

Diagnosis

  • Clinical presentation:
    • Fever
    • Headache
    • Altered mental status
    • Focal neurological deficits
    • Seizures
  • Laboratory findings:
    • Elevated white blood cell count
    • Increased C-reactive protein and erythrocyte sedimentation rate
  • Lumbar puncture (if not contraindicated):
    • Elevated protein
    • Pleocytosis
    • Normal or low glucose levels
  • Blood cultures may be positive in some cases

Imaging

  • Computed Tomography (CT):
    • Hypodense, crescentic collection along the cerebral convexity
    • Mass effect with midline shift
    • Enhancement of the dura and leptomeninges
  • Magnetic Resonance Imaging (MRI):
    • Superior to CT for diagnosis and extent evaluation
    • T1-weighted: iso- to hypointense collection
    • T2-weighted: hyperintense collection
    • Diffusion-weighted imaging: restricted diffusion
    • Contrast-enhanced T1: rim enhancement
  • Follow-up imaging is essential to monitor treatment response

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Treatment

  • A neurosurgical emergency: urgent surgical drainage plus antibiotics and treatment of the source (usually sinusitis). Restricted diffusion within the crescentic collection distinguishes it from a bland effusion or subdural haematoma

Differential diagnosis

Differential Diagnosis Differentiating Feature
Brain abscess Typically round or oval lesion on imaging, while subdural empyema is crescent-shaped
Epidural abscess Located between dura and skull, not beneath dura; often associated with osteomyelitis
Subdural haematoma No restricted diffusion; blood products showing T1 hyperintensity (subacute) or mixed signal; no rim enhancement
Meningitis No localised extra-axial fluid collection on imaging; leptomeningeal rather than rim enhancement
Cerebral venous thrombosis No pus collection; different imaging appearance with venous filling defects
Empyema-associated hydrocephalus Ventricular enlargement present; empyema may be a secondary finding
Subgaleal abscess Located outside the skull; no intracranial involvement on imaging
Cerebritis Ill-defined area of cerebral oedema without discrete fluid collection
Encephalitis Diffuse brain involvement; no localised fluid collection
Subdural effusion No enhancement on contrast imaging; usually sterile fluid collection

  1. Stephanov et al. Intracranial subdural empyema and its management. A review of the literature with comment. 2002. Swiss surgery = Schweizer Chirurgie = Chirurgie suisse = Chirurgia svizzera - Open in new tab. ↩