ABSTRACT
Many different types of organisms including bacteria, viruses, fungi and others can infect the central nervous system and its coverings. Bacterial infections are dealt with in this chapter and viral, fungal and other infections are dealt with in the following chapter. There are certain features that are relevant to all infections. The brain and spinal cord are relatively well-protected by bone and by the dura from infective agents and consequently bloodborne (hematogenous) spread is more common than direct spread of infection. Direct spread of infection may occur following a skull fracture or as a result of spread of infection from a localized infection in the middle ear, air sinuses or the bone of the skull or spine. A few infective agents, particularly viruses, gain access to the central nervous system (CNS) by spread along peripheral nerves. Once infection becomes established in the CNS local defense mechanisms are relatively ineffective and if microorganisms gain access to the cerebrospinal fluid (CSF) they can disseminate rapidly throughout the subarachnoid space and the ventricles. Immunocompromised individuals are susceptible to overwhelming infection, often from organisms that are relatively non-pathogenic in the immunocompetent (i.e. opportunistic infections). Points to note in the autopsy of infection are listed in Table 6.1. Sites
of infection are given in Table 6.2, and cytological and biochemical findings in various infections are listed in Table 6.3.
