Prion diseases, such as Creutzfeldt-Jakob Disease (CJD), are fast-moving, fatal dementia syndromes associated with the formation of aggregates of the prion protein, PrP. How these aggregates form within and kill brain cells has never been fully understood, but a new study from scientists at Scripps Research suggests that the aggregates kill neurons by damaging their axons, the narrow nerve fibers through which they send signals to other neurons.