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:
References