Ataxy, Locomotor, a disease in which the co-ordination of movements is impaired, producing among other characteristic symptoms a staggering or "ataxic" gait, and a difficulty in maintaining the equilibrium of the body. The affection was first described and named in 1858 by Duchenne. The morbid process affects mainly the spinal cord, and was at one time confused with paralysis. The affected limbs, however, possess plenty of muscular power, but it is not so harmonised and directed by the nervous system as to produce natural movements. Locomotor ataxy is of insidious onset, and when once typically developed usually lasts till death, though it does not in itself as a rule tend to shorten life. Besides the impairment of movement, there are frequently present the so-called "lightning pains," certain ocular phenomena, and an absence of the knee-jerk (q.v.). Locomotor ataxy rarely commences before thirty years of age, though a disease of a somewhat similar though not identical character is sometimes met with in children, and from its occurring in families is known as hereditary ataxia.