Physicians suspect a diagnosis of CJD on the basis of the typical signs and symptoms and progression of the disease. In most CJD patients, the presence of 14-3-3 protein in the cerebrospinal fluid and/or a typical electroencephalogram (EEG) pattern, both of which are believed to be diagnostic for CJD, have been reported. However, a confirmatory diagnosis of CJD requires neuropathologic and/or immunodiagnostic testing of brain tissue obtained either at biopsy or autopsy.