Intracranial Epidural Abscess

Epidemiology

  • Far less common than spinal epidural abscess
  • Intracranial epidural abscess is the third most common type of focal intracranial infection, after brain abscess and subdural empyema
  • Historically, most cases of intracranial epidural abscess were associated with spread from contiguous cranial infections (such as otitis, mastoiditis, and sinusitis), but currently, neurosurgery is the most common etiology

Etiology

  • Contiguous Focus of Intracranial Infection: direct extension into the epidural space
  • Fetal Monitoring Probes: used obstetrically
  • Neurosurgery: surgical invasion of the epidural space
  • Trauma: direct inoculation into the epidural space

Physiology

  • Anatomic Relationships: the intracranial dura forms the inner lining of the skull (and is firmly adherent to the skull bone): in normal anatomy, the epidural space is only a virutal space
    • Epidural space can be “opened” by invasion by tumor cells, blood, inflammatory masses (granulation tissue), or pus
    • Due to firm adherence of dura to the skull bone, invasion and creation of the epidural space is typically a gradual process (with dissection of the dura away from the bone), forming a rounded and well-localized collection
    • Spread from the intracranial space caudally into spinal epidural space is rare, as the dura is tightly adherent around the foramen magnum

Diagnosis

  • Culture
    • Microaerophilic/Anaerobic Strep: associated with sinusitis and otitis cases
    • Propionibacterium (anaerobe): associated with sinusitis and otitis cases
    • Peptostreptococcus (anaerobe): associated with sinusitis and otitis cases
    • Gram-Negative Rods: occasionally isolated
    • Haemophilus species
    • Staph Epi/Staph Aureus: associated with neurosurgical cases
    • Fungi: occasionally isolated
  • Head CT: typically rounded (lenticular) collection
    • May be surrounded by inflammatory reaction
    • May be calcified
  • CT-Guided Aspiration: may be performed
  • Brain MRI: preferred imaging modality

Clinical

  • Slowly-Expanding Intracranial Mass
    • Focal neurologic signs
    • Increased intracranial pressure
  • Fever/Headache: common
  • Nausea/Vomiting: common
  • Purulent Drainage from Nose/Ear: may occur in sinusitis-associated cases

Treatment

  • Burr Hole/Craniotomy for Drainage: usually required
    • If dura is breached, may require dural repair with a fascial graft
  • Management of Sinusitis: sinus drainage may be adequate without surgery in some childhood sinusitis-associated cases without intracranial mass effect
  • Antibiotics: directed against the isolated organism

Prognosis:

  • Mortality: <;10%

References

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