Table of contents
Home CHAPTER FIVE
INFECTIONS OF THE NERVOUS SYSTEM
SUPPURATIVE INFECTIONS SUBDURAL EMPYEMA SUPPURATIVE MENINGITIS BRAIN ABSCESS ... PRION DISEASES SUPPURATIVE INFECTIONS The brain is protected from bacterial invasion from the environment by the skull, the dura, and the arachnoid membrane, the pia, and the glia limitans, which is a dense mesh of astrocytic processes on the surface of the brain. (Figure 5.1) Consequently, most bacterial infections spread to the brain by the bloodstream. Bacteria can penetrate into the brain from the environment if there is a break in the continuity of these protective layers. Such a discontinuity may be due to congenital defects (encephalocele, meningomyelocele) or may be caused by trauma or a shunt. Bacteria can also spread to the brain from infected adjacent air sinuses, the middle ear and the mastoids.They can reach the brain either directly through the bone, especially in areas where the bone plate is thin, or through veins (diploic veins, dural venous sinuses, intracerebral veins). The various protective layers may also help contain infections within certain spaces or planes. EPIDURAL ABSCESS An epidural space filled with adipose tissue exists normally around the spinal cord. A spinal epidural abscess arises when organisms from osteomyelitis and tuberculosis of the vertebral column spread to this space. There is no epidural space normally in the cranium. However, a cranial epidural abscess may develop when bacteria colonize a traumatic epidural hematoma, or when infection from air sinuses extends in the plane between the dura and bone. | |
|
