Guest: Ray D. Kent, PhD. - Diadochokinesis (DDK) has been in our field for almost a century and has applications in many specialties. A scoping review found 360 DDK articles and has been associated with diverse etiologies: motoric, structural, sensory, and cognitive. Its popularity notwithstanding, it is not unquestioned as an assessment tool. However, it has been used across a spectrum of disorders and as a proposed biomarker.