Mirror movements can be defined as involuntary movements on one side of the body that occur as mirror reversals of intended movement on the other side of the body. These are common as normal phenomenon in young children. When mirror movements persist after first decade of life, they are abnormal. We studied a patient with congenital mirror movement by neurophysiological methods. Neurological examination revealed mirror movements in both upper extremities, but not in legs or face. Transcranial magnetic stimulation elicited bilateral motor evoked potentials of the first dorsal interossei muscle and ipsilateral responses showed shorter onset latencies and larger peak to peak amplitude than contralateral response, implying greater ipsilateral projection than contralateral projection. This observation indicates direct ipsilateral corticospinal projections. Our findings are consistent with aberrant organization of motor representation areas and corticospinal pathways with ipsilateral as well as contralateral control of voluntary movement. (J Korean Acad Rehab Med 2009; 33: 502-505)
