Gait Analysis in Uner Tan Syndrome Cases with Key Symptoms of Quadrupedal Locomotion, Mental Impairment, and Dysarthric or No Speech

Introduction: Uner Tan syndrome (UTS) consists of quadrupedal locomotion (QL), impaired intelligence and dysarthric or no speech. Previously, I described the walk of cases with UTS as diagonal sequence (DS) because of ipsilateral limb interference, mostly observed in nonhuman primates with DS QL. The only gait analysis performed for UTS were a few cases with lateral sequence (LS) QL. The current work presents a gait analysis of UTS in more families. Methods: Hip and knee angles during quadrupedal standing were measured in UTS cases, healthy controls with requested QL, and nonhuman primates. Limb phases were assessed from video footages, as the percent of the hind limb’s stride durations. Results: UTS cases and nonhuman primates exhibited quadrupedal standing with straight legs nearly perpendicular to the ground. Healthy individuals could not walk quadrupedally like UTS cases. They could perform QL only with flexed legs. UTS cases and healthy individuals with free (flexed-leg) QL used predominantly lateral sequence-diagonal couplet (LSDC) walks. Terrestrial primates preferred DS gaits. The healthy individuals with free QL were similar to arboreal primates in quadrupedal posture. Conclusions: Although these results do not seem to support the thesis of locomotor evolution in reverse, nobody knows with certainty who our ancestors were or how they walked, and so the possibility of UTS as an example for the ancestral reappearance of QL in human beings cannot be positively excluded. This locomotor evolution in reverse was supported by experimental evidence, which proved reverse evolution as a scientific fact.