Postural Control during Gait Initiation in children with Cerebellar Ataxia

Cerebellar Ataxia (CA) is a heterogeneous group of rare neurological diseases with often a genetic aetiology. The cerebellum plays a crucial role in both balance and locomotion, where the feed-forward control of dynamic phenomena prior to stepping is essential for walking effectively. Aim of this work was to evaluate how CA affects the postural control during gait initiation. Eight pathological and nine age-matched healthy children were asked to stand on a dynamometric platform for 30 seconds and then start walking spontaneously, self-selecting the stepping limb. Body kinematics were also recorded, by a 6-TVC optoelectronic system. During stance, the Centre of Pressure (CoP) covered a larger area (95% confidence ellipse) in CA patients than in healthy children, especially in the medial-lateral direction (p<0.05). With regard to the unloading and imbalance phases of the first step, only the anterior-posterior CoP displacement during imbalance was significantly larger in CA patients than in healthy children (p<0.01), while all other parameters (duration, length of CoP trajectory, medial-lateral CoP displacement & mean velocity) were comparable for both phases. However, the length and speed of the first step were lower in CA patients (p<0.05). The significant changes in CoP area during stance confirm in children that CA is associated to an impaired control of balance, underlining their difficulty in maintaining the upright posture. The fact that the imbalance and unloading phases were in most part comparable between the two groups indicates that CA patients are still able to output an operative motor program, like healthy individuals, but the slower and smaller first step may actually be considered a compensatory strategy for an impaired control of dynamic posture.