Motor Evoked Potential Study of Mirror Movements in a Patient with Klippel-Feil Syndrome

ABSTRACT

Mirror movements(MMs) are involuntary movements executed on one side of the body during voluntary movements of the contralateral homologous body parts. Motor evoked potentials(MEP) to focal transcranial magnetic stimulation(TMS) have postulated that abnormal ipsilateral corticospinal tract is active in the patient with congenital MMs. MEP and post-MEP SP following to focal TMS were investigated in a patient with the Klippel-Feil syndrome(KFS) showing MMs and in five normal volunteers. In the patient unilateral transcranial stimulation evoked bilateral motor responses of normal latencies and SP was observed bilaterally, which tended to be shortened in duration. In the condition of KFS, the mechanism of MMs has been attributed to the presence of abnormally activated ipsilateral corticospinal tract, but it does not suffice for explaining the shortened SP. We propose that concurrent activation of both motor cortices be responsible for the mechanism of MMs in this case of KFS, in addition to the abnormality of the corticospinal tracts.