Abstract
Mirror movements (MMs) are specifically defined as involuntary movements occurring on one side of homologous muscles when performing unilateral movements with the contralateral limb. MMs have been considered a kind of soft neurological signs, and the persistence or reappearance of MMs in adults is usually pathologic. In addition to some congenital syndrome, MMs have been also described in age-related neurological diseases including pyramidal system diseases (e.g., stroke, amyotrophic lateral sclerosis) and extrapyramidal disorders (e.g., Parkinson's disease, essential tremor). With the advances in instrumentation and detection means, subtle or subclinical MMs have been deeply studied. Furthermore, the underlying mechanism is also being further elucidated. In this mini-review, we firstly discuss the MM examination means, and then review the literature regarding MMs in individuals with acquired neurological disorders, in order to further understand the pathogenesis of MMs.
Highlights
Mirror movements (MMs) refer to involuntary movements that appear during voluntary activity in the contralateral homologous muscles
Clinicians can refer to the items on the motor subscale of the Movement Disorder Society-sponsored revision of Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) [17, 18]
Evaluation of mirroring severity often includes three aspects: amplitude, distribution, and proportion
Summary
Mirror movements (MMs) refer to involuntary movements that appear during voluntary activity in the contralateral homologous muscles. Alongside associated movement and contralateral motor irradiation, MMs are a form of motor overflow phenomena [1,2,3]. Compared with the other forms, MMs have received the most attention from researchers. Physiological MMs may present during infancy stage in healthy children and persist until around the age of 10 years. They can be elicited in healthy young and older adults under conditions of severe fatigue, intense physical activity, movements involving large force generation, and proximal muscle use [4, 5]. Persistence of involuntary synkinetic mirror movements of the opposite limb is considered pathological
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