Characteristics and Correlates of Mirror Movements in Parkinson's Disease

This study aimed to assess the frequency, characteristics, and clinical associations of mirror movements in individuals with Parkinson's disease, considering factors such as age, side of symptom onset, disease severity, and motor asymmetry.

This cross-sectional observational study included 87 individuals with Parkinson's disease, diagnosed according to Movement Disorder Society criteria. Exclusion criteria included atypical Parkinsonism, dementia, and refusal to consent. Mirror movements were assessed using video-recorded standardized tasks and scored with the Woods Teuber scale. Clinical parameters, including the Unified Parkinson's Disease Rating Scale (UPDRS-III), Hoehn and Yahr scale (H and Y staging), and lateralized motor severity, were analyzed. Statistical correlations were performed using SPSS version 26.

Mirror movements were observed in 65.5% of participants, predominantly affecting the upper limbs (98% in fingers). The frequency of mirror movements increased with age (84.6% in those aged 70-90 years, P = 0.04) and was significantly higher in individuals with left-sided symptom onset (74.1% vs. 51.5%, P = 0.03). The severity of mirroring correlated with the side of disease onset and greater lateral differences in UPDRS motor scores (>30, P = 0.015). A rare subtype of discordant mirror movements (non-homologous movements) was identified in 8.2% of individuals.

Mirror movements are a frequent and underrecognized feature in individuals with Parkinson's disease. Their clinical associations indicate a greater frequency in older individuals, those with left-sided onset, and those with more asymmetric motor involvement. These findings highlight the potential utility of mirror movements as a clinical biomarker for disease lateralization and progression. Further research, including functional imaging studies, is warranted to elucidate the underlying mechanisms.