Fig. 2.

Schematic illustrations of Parkinson’s disease gait. (A) Parkinson’s disease gait is characterized by step length reduction, swing phase shortening, narrowing of the base of support and reduced foot clearance (shuffling gait); bradykinesia also contributes to ‘sequence effect’, defined as the progressive shortening of step length (bottom row). The asymmetry of these gait features tends to persist during disease progression. (B) The pharmacokinetics of levodopa provides a useful framework to understand how axial motor problems can respond to dopaminergic treatment, be caused by or be resistant to levodopa.