B. EPIDURAL AND SUBDURAL ABSCESS OR EMPYEMA
- Abscesses are localized collections of pus. Pyogenic organisms
are the infectious agent involved with abscess formation. Empyema
describes the accumulation of pus within a space or cavity, again, typically
secondary to pyogenic organism infection. Epidural and subdural infections
can be called either abscess or empyema
2. Pathogenesis of Subdural Abscess/Empyema:
- a. Direct inoculation secondary to trauma, usually of organisms
resident in the sinuses (often pneumococcus).
- b. Secondary to middle ear infections; organisms may erode directly
into either space or spread via venous sinuses.
3. Etiologic agents:
- Usually bacteria; streptococcus and staphylococcus are the most common.
4. Pathological changes:
- Acutely a purulent exudate; organization later; reactive leptomeningitis;
cerebral veins in the subdural space may be affected.
5. Spinal fluid changes:
- Reactive meningitis occurs; CSF changes include elevation of protein
levels, PMN count, and sometimes pressure. No organisms can be cultured,
unless the empyema is accompanied by infection of leptomeninges.
- Space-occupying effects plus edema of brain may lead to herniation and
midline shift. Infection may spread into leptomeninges and contaminate cerebrospinal
fluid in subarachnoid space.