Human prion diseases, such as Jakob-Creutzfeldt disease (CJD) are devastating neurodegenerative diseases that currently are untreatable. As treatment trials are underway and planned, we need to have improved methods for predicting the course of progression of an individual with CJD. Our CJD and rapidly progressive dementia (RPD) clinical research program is a major referral center for prion diseases in the United States with about 750 RPD/CJD referrals over the past four years. Through our past R01, "Early diagnosis of human prion disease," we acquired data that led to improved diagnosis of CJD. We had several important clinical findings regarding CJD, including: 1) the most widely used biomarker for sCJD diagnosis, CSF 14-3-3 protein, has relatively low sensitivity and specificity, despite being in several diagnostic criteria; 2) DWI brain MRI, showing restricted diffusion in gray matter, is the single best diagnostic test for sCJD, although CSF biomarkers, such as total tau and neuron-specific enolase, sometimes are useful; 3) Diffusion does not continually become increasingly restricted in gray matter during the disease course, but eventually becomes less restricted; thus, diffusion is linearly downward in the earlier part of disease, but then moving upward (less restricted) in later stages, thus giving a U or even J shaped curve: this makes following restricted diffusion as an outcome marker problematic in treatment trials; 4) Certain areas of gray matter appear to be preferentially involved on MRI in sCJD, and they overlap with various functional connectivity networks identified by fMRI. It is not clear if prion disease spreads in the brain via functional and structural networks or through transmission to adjacent brain regions; 5) Although not previously reported, we found diffuse restricted diffusion in the white matter in sCJD and 6) the presence of certain clinical signs/symptoms in patients, such as cerebellar or visual symptoms, predict shorter survival. Most of these findings were based on cross-sectional assessment. For this current project, we will be following approximately 120 patients with CJD longitudinally, studying patients for at serial visits, between about 1-4 months after their initial visit. At each serial visit we will conduct a detailed assessment (neurological exam, neuropsychological testing, functional scores, various brain MRI metrics (discussed above), and CSF biomarkers). Through this prospectively acquired data of longitudinal assessment of CJD, we will develop an algorithm for disease staging (predicting the survival) and predicting progression of individual patients. This information will not only be helpful for prognosticating for patients and families, but also for development of treatment trials