MAPT and cerebellar ataxia: Interestingly, several of the diseases with high plasma tau, such as Creutzfeldt-Jakob disease, amyotrophic lateral sclerosis, and spinocerebellar ataxia, do not accumulate fibrillar tau in the central nervous system (CNS), suggesting another dissociation between the accumulation of fibrillar aggregates in the brain and a change in soluble tau biology in the CNS that is associated with neuronal distress.