Mirror movements in movement disorders: a review

Area of Science:

• Neuroscience
• Movement Disorders
• Clinical Neurology

Background:

• Mirror movements (MM) are involuntary homologous muscle movements during contralateral voluntary actions.
• Subtle MM occur in healthy adults, but overt MM are prevalent in many movement disorders.
• Understanding MM aids in defining their clinical significance.

Purpose of the Study:

• To review research on the presence, clinical significance, and pathophysiology of MM.
• To examine MM in Parkinson's disease (PD), corticobasal syndrome (CBS), essential tremor (ET), focal hand dystonia, Creutzfeldt-Jakob's disease (CJD), and Huntington's disease.
• To compare MM in these disorders with healthy controls and congenital conditions.

Main Methods:

• Systematic review of English language research articles.
• Focused on MM presence, clinical significance, and pathophysiology.
• Comparative analysis with controls and congenital disorders.

Main Results:

• MM are common in asymmetric parkinsonian disorders (early PD, CBS).
• MM presentation varies by affected side, disease stage, and associated phenomena (e.g., alien hand).
• MM generation involves uncrossed corticospinal projections or abnormal ipsilateral motor cortex activation.

Conclusions:

• Mirror movements are common in acquired and congenital disorders, presenting distinct patterns.
• Further MM research can improve clinical diagnosis of movement disorders.
• Studies on MM contribute to understanding bimanual coordination physiology.