A group of diseases of the brain characterized by dementia have been discussed. The pathologic features of each were described and illustrated. It seems that, in summary, several points merit emphasis. First of all, as more people survive to the seventh, eighth, and ninth decades, the most common dementia, senile Alzheimer's disease, will become a more significant public health problem. Second, while at the present time there is no successful therapy available, there are some glimmerings of hope on the horizon. The discovery of the agent of Creutzfeldt-Jakob disease seems to have placed us on the fringe of a whole new series of advances. A novel type of disease agent awaits characterization and definition, and there are hints that similar agents could be responsible for the development of the degenerative diseases, perhaps in conjunction with environmental toxins and in the medium of a permissive genetic background. In the case of Huntington's chorea, it seems reasonable that a pharmacologic agent could be found to control the symptoms such as L-dopa therapy has done for patients with Parkinson's disease. It may develop, however, that such an agent will control the choreiform movements but will not influence the dementing condition.
