Three-dimensional gait analysis as a biomarker for GTP cyclohydrolase 1-deficient dopa-responsive dystonia

Background GTP-cyclohydrolase 1-deficient dopa-responsive dystonia (GTPCH1-deficient DRD) typically presents in childhood with dystonic posture of the lower extremities, gait impairment, and a significant response to levodopa. We performed three-dimensional gait analysis (3DGA) to quantitatively assess the gait characteristics and changes associated with levodopa treatment in patients with GTPCH1-deficient DRD. Methods Three levodopa-treated patients with GTPCH1-deficient DRD underwent 3DGA twice, longitudinally. Changes were evaluated for cadence; gait speed; step length; gait deviation index; kinematic data of the pelvis, hip, knee, and ankle joints; and foot progression angle. Results Levodopa treatment increased the cadence and gait speed in one of three patients, and increased the gait deviation index in two of three patients. The kinematic data for each joint exhibited different characteristics, with some improvement observed in each of the three cases. There was consistent marked improvement in the abnormal foot progression angle; one patient had excessive external rotation of one foot, another had excessive bilateral internal rotation, and the other had excessive internal rotation of one foot and excessive external rotation of the opposite foot, all of which improved. Conclusion The 3DGA findings demonstrate that the gait pathology and recovery process in GTPCH1-deficient DRD vary from case to case. Changes in the foot progression angle and gait deviation index can enable the effects of treatment to be more easily evaluated.