Mirror movements in Parkinson's disease: An under-appreciated clinical sign.

INTRODUCTION: Mirror movements (MM) have been previously reported in patients with Parkinson's disease (PD). Despite being potentially relevant in PD, MM as a neurological sign have remained less recognized. In this study we critically evaluated the characteristic features of MM and their attributes among a cohort of PD patients from a tertiary care center of eastern part of India.

METHODS: In this analytical cross-sectional study, 70 patients with PD were evaluated using Unified Parkinson's Disease Rating Scale (UPDRS) and a previously used scale to score MM in the OFF and ON phases of l-Dopa therapy. MM was video-recorded for 4 motor tasks (finger- tapping, hand-movement, pronation-supination, rapid ankle-flexion-extension) and scored for the MM attributes i.e. amplitude, distribution and proportion.

RESULTS: A vast majority of PD patients (95.7%) exhibited MM and there was a trend of higher MM score with lesser severity of disease affection. Marked differences in amplitude, distribution and proportion of MM in the upper and lower limbs were evident in response to l-Dopa therapy in certain motor tasks. In addition, less involved limbs exhibited higher MM and the MM scores were higher for lower limb tasks in the ON phase.

CONCLUSIONS: The high prevalence of MM in PD patients and its correlation to disease severity echoed previous studies across the globe. In addition, this study provides evidence for a differential response of MM attributes to l-Dopa. To our knowledge, this is the first study that characterized MM in a cohort of PD patients from India. Our findings suggest the significance of MM as a clinical neurological sign in PD.