The presenile psychoses have been the subject of intensive study in recent years. Both Alzheimer's and Pick's disease can now be regarded as well-defined clinico-pathological conditions. However, there occur cases with dementia developing in middle age or in early senium which do not fit into any of the established clinical types. A small group of cases characterized by dementia, extra-pyramidal symptoms and involvement of the spinal cord has been described by Jakob (1920) and Creutzfeldt (1920) independently. Similar cases have since been reported by Meyer (1929), Davison (1932), Jansen and Monrad-Krohn (1938), Davison and Rabiner (1940), and most recently by Jervis, Burdum and O'Neill (1942). McMenemy (1940), in a review of dementia in middle age, stated that the number of cases of that type reported in the literature did not exceed 14. Though all of them had the syndrome mentioned above in common, they varied considerably in respect of the leading symptoms. While in some the clinical picture was dominated by dementia associated with a variety of psychotic features, in others the extrapyramidal and in a few the spinal symptoms were predominant. Nothing definite is known about the etiology of that condition, though the hypothesis has been expressed that it may represent an atypical form of encephalitis. Josephy (1936) suggested that it might be a deficiency disease. No agreement has been reached on a suitable terminology. Jakob's original description of the condition as spastic pseudosclerosis has been found to be misleading. K. Wilson (1940) proposed to call it “cortico-striato-spinal degeneration.” Davison and Rabiner (1940) speak of “diffuse encephalomyelopathy.” Other authors advocated the provisional term Jakob-Creutzfeldt disease. In view of the scanty knowledge of the symptomatology and pathology of the disease, this term seems at present to be the most acceptable.