The Hoehn and Yahr scale is used to describe the symptom progression of Parkinson disease.[1, 2, 3] The scale originally was described in 1967 and included stages 1 through 5.[4] It has since been modified with the addition of stages 1.5 and 2.5 to account for the intermediate course of Parkinson disease. It was designed to be a descriptive staging scale to evaluate both disability and impairment related to clinical disease progression.
The modified Hoehn and Yahr scale is as follows[5] :