[Disorders of walking in elderly subjects: towards new concepts]

While gait disorders directly related to a muscular, skeletal neurological defect are easily recognized, others, which we address here, appear to result from some unknown and mysterious mechanism. Gait disorders in elderly patients cannot be conceived as a simple impairment in muscle, tendon or joint effectors but must be assessed in relation to defective central programmation or dysfunctioning synergy. Posture is the result of a series of successive reflex reactions, and locomotion itself is the result of a series of sequential stimulations and inhibitions originating in the spinal generator controlled by supraspinal centres. Obviously, in man, cortical and subcortical activation is essential as is the activity of the limbic system and the associative zones, together with the basal gangia and the cerebellum. Peripheral proprioception accelerates consciousness of information originating in the muscles, tendons and joints; vestibular and visual input adds further, though redundant, information. Advanced methods of quantifying posture and walking offer a new approach to the analysis of gait disorders. The Bessou locometer analyzes physiological senescence leading to an inconscient strategy which decreases the speed and length of each step. This mechanism might be explained by the aging process leading to non-necrotic cell failure without any specific lesion, vascular for example. Another method is the ELITE system (Elaboratore de Immagini Televisive). This system evaluates the way the subject modelizes and reconstructs his environment. Interesting results have been obtained with postural imbalance induced by visual stimulations.