Cause: paranasal sinusitis, otitis media, calvarial osteomyelitis, infection after craniotomy or ventricular shunt placement, penetrating wound, contamination of meningitis-induced subdural effusion
- rim-enhancing purulent collection
- restricted diffusion on DWI (DDx: simple effusion of acute bacterial meningitis is WITHOUT diffusion restriction)
20% of all intracranial bacterial infections
Location: frontal + inferior cranial space in close proximity to paranasal sinuses; 80% over convexity extending into interhemispheric fissure or posterior fossa
- hypo- / isodense crescentic / lentiform zone adjacent to inner table
- may show mass effect (sulcal effacement, ventricular compression, shift)
- thin curvilinear rim of enhancement (7–10 days later) adjacent to brain
- severe sinusitis / mastoiditis (may be most significant indicator)
Mortality: 30% (neurosurgical emergency)
Cx: venous thrombosis (= thrombophlebitis), infarction, seizures, hemiparesis, hemianopia, aphasia, cerebritis, brain abscess
- Subdural >>epidural empyema more likely to cause complications requiring urgent neurosurgery!
DDx: subacute / chronic subdural hematoma
- NO neurologic deficits (dura minimizes pressure exerted on brain)
- thick enhancing rim