Hypomimia in Parkinson's disease: an axial sign responsive to levodopa

Background and purpose Hypomimia is a prominent clinical feature in people with Parkinson's disease (PD), but it remains under-investigated. We aimed to examine the clinical correlates of hypomimia in PD and to determine whether this is a levodopa-responsive sign. Methods We included 89 people with PD. Hypomimia was assessed from digital video recordings by movement disorder specialists. Clinical evaluation included use of the Unified Parkinson's Disease Rating Scale part III (UPDRS-III), and assessment of motor and non-motor symptoms using standardized clinical scales. The relationships between hypomimia and other clinical data were analysed using Mann-WhitneyU-tests and regression analysis. Results Hypomimia occurred in up to 70% of patients with PD. Patients with hypomimia had worse UPDRS-III 'off-medication' scores, mainly driven by bradykinesia and rigidity subscores. Patients with hypomimia also had worse apathy than patients without hypomimia. Finally, we found that hypomimia was levodopa-responsive and its improvement mirrored the change by levodopa in axial motor symptoms. Conclusion Our study provides novel information regarding the clinical correlates of hypomimia in people with PD. A better understanding of hypomimia may be relevant for improving treatment and quality of life in PD.