In early disease stages, it can be difficult to differentiate clinically between Parkinson’s disease and the various forms of atypical parkinsonism, like multiple system atrophy or progressive supranuclear palsy. Balance impairment in the medio-lateral plane (i.e. sideways) is often seen in patients with a form of atypical parkinsonism, but not in patients with Parkinson’s disease.
This is reflected by the distance between the feet during gait, which is typically normal (or even narrow) in Parkinson’s disease, but widened in atypical parkinsonism. Estimating this stance width depends on subjective judgement, and is difficult to quantify in clinical practice.
