Peak age incidence 15 to 30 years of age. Infection can develop from direct extension from bony source such as otitis or mastoiditis. Can also develop from retrograde septic thromboplebitis.
Inflammation involves the subarachnoid space which often leads to cerebritis.
May remain localized within subdural space or can spread. Loculations are common. Historically, subdural empyemas were considered universally fatal. Advances in antibiotic treatment have resulted in a marked improvement in survival although the clinical course tends to be rapid and requires emergency treatment. Focal cortical inflammation.