Walsh & Hoyt: Empyema

Empyema (from the Greek word meaning ""suppuration"") is pus that collects in a preformed space that is not confined by a capsule. Intracranial empyemas usually occur in the subdural or epidural spaces where the wide extent of these potential spaces and the relative avascularity of the dura are such that pus, once formed, normally spreads too rapidly for effective adhesions to develop. An epidural empyema is a relatively uncommon lesion; however, cranial subdural empyemas are the second most common cause of localized intracranial infection after brain abscesses. Subdural empyemas are much more common in men than in women, perhaps reflecting a higher incidence of frontal sinus disease and trauma in men than in women. Kaufman et al. suggested that young men have rapid growth of the frontal sinus, resulting in thinning of the sinus walls and an incomplete barrier to infection.