Mirror movements in parkinsonism

Mirror movements in the less affected side are often a feature of mild asymmetric parkinsonism and may be useful in staging patients with early disease.In a Canadian study that videotaped 27 patients with early parkinsonism, 24 patients were found to exhibit mirror movements in the less affected side. The investigators report that patients with the most obvious mirror movements were those with the greater the degree of asymmetry of motor deficits. In contrast, patients with more symmetry showed little or no mirroring. Patients with more severe motor impairments were less likely to exhibit mirroring, which agrees with the findings of a previous study, suggesting an inverse relationship between motor UPDRS and the severity of mirroring. However the authors believe mirror movements are more likely a reflection of the degree of asymmetry than the degree of impairment. They say, "...our data suggest instead that it is the differential severity of motor impairment between sides, as demonstrated by the strong effect of the absolute and relative UPDRS lateralised scores, that best predicts mirroring on the less affected side." Mirroring occurred only in the hand in 10 patients, only in the foot in two patients, and in both hand and foot in 12 patients. The authors explain, "Mirroring in the resting limb could be conspicuous during one task (for example, finger tapping) but absent during another (for example, pronation-supination of the forearm)." No mirror movements were found in the most affected limb when the patient performed activities in the less affected limb.The underlying pathophysiology of mirror movements in parkinsonism is unknown, but the authors suggest it is almost certainly distinct from mirror movements related to pyramidal abnormalities in other conditions. The potential prognostic value of mirror movements in early parkinsonism is also an unknown and requires further research.Reference...