Acute and chronic bacterial infections and sarcoidosis.

Pathogen-induced inflammatory diseases mostly involving, but sometimes exclusively affecting, the central nervous system (CNS) manifest with a plethora of signs and symptoms. The different diseases are still difficult to cure despite modern diagnostic, preventive, and therapeutic advances, and this is mainly due to the host inflammatory response, leading to irreversible tissue damage. Knowledge about underlying pathomechanisms is constantly growing, and numerous studies on humans, human material, and animal models as well as in vitro systems have considerably increased our understanding of molecular mechanisms; however, there are still enormous uncertainties with respect to host-pathogen interaction and treatment. There are important regional variations as to prevalence and susceptibility of diseases, reflecting the importance of environmental factors, and immunogenetic peculiarities of different ethnicities. In addition, the opportunistic infections of the CNS are becoming very relevant, not only in the context of human immunodeficiency virus (HIV), but also in the context of modern, highly specific immunosuppressive or immunomodulatory treatments, evoking new and unmet diagnostic and therapeutic challenges. This chapter summarizes up-to-date knowledge about bacterial CNS infections, as well as cerebral sarcoidosis, focussing on morphologic aspects.