Jakob's disease: Better known as Creutzfeldt-Jakob disease (CJD), a dementing disease of the brain. It is believed due to an unconventional, transmissible agent (a prion). Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome, Jakob-Creutzfeldt disease, and spastic pseudoparalysis.