Jerk nystagmus is found in 70% (1000,1157), including gaze-evoked, rebound, and upbeat forms. In some the nystagmus is monocular (999,1000,1154-1156).Īssociated signs are frequent. The nystagmus often varies between the two eyes in size and even trajectory, but not in frequency (999,1000) (Figure “acquired pendular nystagmus”, Video “acquired pendular nystagmus”, Video “acquired pendular nystagmus, PSP “) (28). In half the nystagmus alters with convergence, either diminishing or increasing (1000). Poor vision is due at least partly to image degradation by constant eye motion, but many cases also have associated optic neuropathy, particularly those with multiple sclerosis (1000).Īcquired pendular nystagmus is often present in primary position and seldom varies with direction of gaze (1154). However, patients with severely reduced visual acuity may not note oscillopsia (999,1000). Most patients complain of a constant oscillopsia that interferes with vision. Some variants have specific trajectories, including congenital pendular nystagmus, seesaw nystagmus and oculopalatal myoclonus. It can occur in any plane: torsional, horizontal, vertical, or a combination of these, resulting in circular or elliptical trajectories. Nystagmus in primary position is classified according to trajectory: downbeat, upbeat, torsional, and horizontal. Jerk nystagmus is divided into those seen when the eyes are in primary position, and those evident only with some maneuver, such as peripheral gaze or head position. In most cases this slow drift results from a tonic imbalance in vestibular or pursuit systems, or a deficiency in gaze-holding, and the fast phases restore the eye to its desired position. This is divided into a number of subtypes, based on associated conditions and special idiosyncratic trajectories.ī) Jerk nystagmus has a slow drift of the eyes in one direction alternating rhythmically with a fast movement in the other. Nystagmus can be sorted into two groups by appearance.Ī) Pendular nystagmus has a sinusoidal oscillation without fast phases. Nystagmus is a rhythmic regular oscillation of the eyes with low velocities in at least one direction. Superior oblique myokymia, or microtremor
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