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
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
