Myoclonus in Alzheimer disease. A confusing sign.

Myoclonus in association with dementia of later adult life has been considered almost pathognomonic of Creutzfeldt-Jakob disease. However, myoclonus may also be seen with Alzheimer disease, and when the myoclonus occurs as an early manifestation of Alzheimer disease, distinction from Creutzfeldt-Jakob disease may prove difficult.