XCV Nystagmus as a Sign of Central Nervous System Involvement

The individual, sitting or standing erect, is constantly shifting slightly the position of his head and body. Impulses are passing then continually over the vestibular arcs, with the balance in favor of first one vestibular area and then the other. Consequently there are almost constant, very fine to-and-fro, or up-and-down, movements of the eyes, except when they are fixed definitely upon an object. These movements are usually so slight as to pass unnoticed. Nevertheless, they have been studied carefully by Marx and Trendelenburg (Kestenbauml"), They represent a vestibular reflex and depend upon the secondary vestibular connections within the central nervous system. When they are exaggerated due to an increase in the imbalance between the vestibular areas of the two sides, they become a vestibular nystagmus. Strangely enough, although their presence in the normal individual is usually unnoticed, their absence gives a continuously fixed, staring quality to the gaze which is startling.