Coexistence of Mirror Movements and Polymicrogyria

Mirror movements are defined as involuntary movements of the contralateral homologous extremities during voluntary movements of one side. They are usually observed in the distal parts of the upper extremities and are not considered a pathological finding within the first decade. Congenital malformations are mostly responsible for mirror movements. Polymicrogyria is a cortical organization defect. It is defined as thickening of gray matter, loss of gyral pattern and flattened border of gray and white matter. Clinical findings of polymicrogyria vary according to the location and width of the lesion. We present a 21-year-old male patient with left-sided hemiparesis who also had mirror movements. Polymicrogyria and hypoplasia of the corpus callosum were observed in cerebral magnetic resonance imaging. Coexistence of polymicrogyria and mirror movements is seen only rarely. According to the electrophysiological studies, we suggest that polymicrogyria may lead to a decrease in transcallosal inhibition on the affected side and increased activity of the ipsilateral corticospinal pathway in the opposite hemisphere, causing the mirror movements.