Gait Alterations Due to <scp> <i>DCC</i> </scp> Gene Variants in Individuals with Congenital Mirror Movements

BACKGROUND: Congenital Mirror Movement Syndrome (CMMS) involves involuntary movements on one side of the body while voluntary movements are performed on the other side. They disrupt left-right coordination and can be caused by a pathogenic variant in the DCC gene. CMMS have been extensively studied in the upper limb, but its impact on lower limb during gait in humans is unclear. OBJECTIVES: Determine the impact of CMMS on locomotor patterns in individuals with a DCC pathogenic variant. METHODS: The gait pattern of seven individuals with a DCC pathogenic variant and ten healthy controls was assessed using 3D motion capture (kinematics), electromyographic recordings (EMG) of the soleus (SOL) and tibialis anterior (TA) muscles and foot pressure distribution during comfortable walking, fast walking, and running. RESULTS: In comparison to controls, the DCC group exhibited prolonged soleus (SOL) EMG activity and overlapping left-right SOL activation at a comfortable walking speed. No change was noted in TA. Both groups demonstrated increased pressure at the toe during the push-off phase; however, individuals with the most severe CMMS also displayed an early stance-phase pressure peak, reflecting contralateral push-off. These features diminished at higher walking speeds. Kinematic analysis revealed delayed knee flexion and prolonged double-limb support in the DCC group. Group differences were more pronounced when comparing control participants to DCC individuals with observable CMMS (Wood and Tauber scale). CONCLUSIONS: DCC variants impair left-right coordination, particularly affecting distal extensor muscle timing during gait. These disruptions are most evident during slow walking and correlate with mirror movement severity.