Prevalence and Clinical Characteristics of Mirror Movements in a Chinese Cohort of Parkinson's Disease Patients

Abstract

Background: Mirror movements (MMs) are involuntary movements made by the contralateral homologous muscles during voluntary activity. MMs have been observed in age-related neurological movement disorders, including Parkinson’s disease (PD), but are not widely known. This study describes the prevalence and clinical features of MMs in PD patients from a tertiary care center in Eastern China.

Methods: In total, 140 PD patients were evaluated using a standardized videotaping protocol. A clinical scale was used to compare the amplitude, distribution, and proportion of mirroring between the suspended and supported positions. Classic motor and non-motor symptoms, including rapid eye movement sleep behavior disorder(RBD), constipation, and hyposmia were compared between patients with and without MMs. The relationship between MMs and the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) motor score was also explored.

Results: MMs were more obvious when the less affected limb was suspended. In total, 82 of the 140 (58.6%) PD patients exhibited MMs. There were no significant differences in age, disease duration, disease onset age, gender, the Hoehn and Yahr score, the prevalence rates of RBD, constipation, and hyposmia, or the MDS-UPDRS tremor, rigidity, and bradykinesia scores between PD patients with and without MMs. The unilateral MM score was positively and negatively correlated with the contralateral and ipsilateral limb MDS-UPDRS motor scores, respectively.

Conclusions: MMs are common in PD; we advise suspending the limb to detect MMs. Further studies are needed to investigate changes in MMs with disease progression and the association with nonmotor symptoms.

Note:
Funding declaration: This work is financially supported by the National Natural Science Foundation of China (grant no. 82101251), the Ministry of Science and Technology of the People's Republic of China (grant no. 2022YFC3602604) and the Medical and Health Science and Technology Program of Zhejiang Provincial Health Commission (grant no. 2019KY378).

Conflict of Interests: None.

Ethical Approval: The study was approved by the ethics committee of the First Affiliated Hospital of Zhejiang University School of Medicine.

Keywords: Parkinson's disease, mirror movements, asymmetry parkinsonism, non-motor symptoms