Central Nervous System Diseases Due to Slow Viruses and Prions

Several central nervous system diseases whose common elements include a long incubation period and a progressive clinical course were once called slow virus infections, because most of them are in fact caused by viruses. However, one group of these CNS diseases is now believed to be caused by abnormally configured proteins known as prions; rather than an etiologic designation, therefore, on the whole these diseases are better characterized by their chronicity, their transmissibility, and at this point, their inexorably deteriorating natural history. This chapter reviews the more common of these: HIV-associated dementia (HAD or HIVD), human T cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy, Creutzfeldt-Jakob disease (CJD), progressive multifocal leukoencephalopathy (PML), and subacute sclerosing encephalitis (SSPE), which is associated with a variant of measles virus. Figures illustrate the pathogenesis and the pathology of HIV dementia, propagation of scrapie prion protein (PrP) in brain neurons, and spongiform brain changes of CJD. Tables list the stages of HAD and the clinical and pathologic characteristics distinguishing classic CJD and varient CJD. This module contains ­5 highly rendered figures, 2 tables, 57 references, and 5 MCQs.