NYSTAGMUS

involuntary back and forth, up and down, or circular movement of the eyes. There are two types of nystagmus with respect to movement. In one type, called pendular nystagmus, the movements are even and rhythmical; in the other, called jerk nystagmus, the movements are jerky and quicker in one direction than in the other. Pendular nystagmus may result from loss of central vision early in life. A subtype of pendular nystagmus, called spasmus nutans, occurs in infants. It is associated with nodding of the head and with holding the neck in a twisted position. Affected infants usually recover in a few months. Jerk nystagmus, the more common type, may occur normally when one is dizzy from being rotated or when one is watching from the window of a moving vehicle: the slow phase of the nystagmus occurs while the gaze is fixed on a particular object; the quick phase, when the eyes return to their original position. Jerk nystagmus may also result from intoxication with barbiturate drugs or from disease of those portions of the inner ear the function of which is concerned with balance. Disease of the brainstem may also result in jerk nystagmus. Pulses of electric energy generated by the eye movements of nystagmus can be recorded by the electronystagmograph, thus giving a precise record of such movements.