Comparison of optokinetic nystagmus elicited by full versus partial visual field stimulation: Diagnostic implications
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Abstract:
Optokinetic nystagmus (OKN) testing is one method to determine central vestibular dysfunction. OKN may be elicited by partial visual field stimulation with a light bar (OKN‐ENG) or by full visual field stimulation with rotating stripes in a rotational chair test booth (OKN‐RVT). OKN‐ENG and OKN‐RVT were elicited in 36 healthy subjects and 48 patients with known peripheral or central vestibular disorders. Abnormal test results suggested central pathology in 29 of 36 healthy subjects with OKN‐ENG versus 1 of 36 with OKN‐RVT. Twenty‐eight of 33 patients with peripheral pathology demonstrated abnormal OKN‐ENG findings, whereas 4 of 33 had abnormal OKN‐RVT results. Thirteen of 15 patients with central vestibular disorders had abnormal OKN‐ENG, whereas 7 of 15 had abnormal OKN‐RVT. Sensitivity and specificity of OKN‐ENG were 86.7% and 17.4% versus 46.7% and 92.7%, respectively, for OKN‐RVT. These findings were statistically significant ( P < 0.00001). OKN elicited by full visual field stimulation (OKN‐RVT) is a more accurate indicator of central disease than OKN elicited by partial visual field stimulation (OKN‐ENG). The use of OKN‐ENG to identify central vestibular dysfunction is questionable.Keywords:
Optokinetic reflex
Since Blohmke and Toda described it, the fact has been known that the horizontal nystagmus of the eyes can be induced by electrical stimulation of the meso-diencephalon in rabbits. According to the method described by Lachmann et al, who did a great deal of research in this field, “the nystagmogenic area” was electrically stimulated in 26 rabbits. In addition to the electrical stimulation, they were given optokinetic and labyrinthine stimulations (1°/sec2 in 90see), simultaneously or independently.It was evaluated how the central nystagmus, which was induced by electrical stimulation to this area, interacted with the optokinetic and labyrinthine nystagmus and, furthermore, how the nystagmogenic area related to the physiological cooperation of the visual organ and the vestibular organ i.e. the so-called “optic-vestibular coordination”, in development of nystagmus. Following conclusions were obtained.1. Central nystagmus is always facillitated by optokinetic stimulation irrespective of the direction of the optokinetic stimulation.2. Central nystagmus is sometimes facillitated and sometimes inhibited by the labyrinthine stimulation depending on the direction of the stimulus. The effect is observed even if the subliminal rotation, which does not provoke nystagmus by itself, is applied.3. Central nystagmus is markedly facillitated by simultaneous aprication of the optokinetic and labyrinthine stimulations.4. The nystagmogenic area relates closely to the neural pathway of the optokinetic nystagmus. and plays an important role in the optic-vestibular coordination in development of nystagmus.
Optokinetic reflex
Stimulus (psychology)
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The second phase of nystagmus in human appeared in 100 per cent with rotatory, in 72 per cent with caloric and in 80 per cent with optokinetic stimuli. In rabbits it appeared in 30 per cent with rotatory, in 78 per cent with caloric and in 100 per cent with optokinetic.Secondary phase is one of fundamental patterns common to all retatory, caloric and optokinetic nystagmus. However, it can not be observed in the presence of such inhibitory factors as vision, noise and etc.The value of minimal stimuli which is necessary to induce secondary nystagmus (secondary nystagmus threshold) varies under different conditions even in the same subjects. There is, however, a certain correlation between the threshold of rotatory and caloric secondary nystagmus. If one increases the other also increases, and vice versa.In animal-experiments, secondary nystagmus is apt to be recorded on the side of directional preponderance.It is thought that the secondary nystagmus is constituted by the primival tracts in the brain stem which are constantly influenced or controlled by the higher regulating vestibular nystagmus. tracts such as the cerebrum and the cerebellum.
Optokinetic reflex
Caloric theory
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Afternystagmus, the concept of which has not yet been clearly defined, may be interpreted as a phenomenon which fits in phase II, or the reversal phase, of experimentally-induced nystagmus such as rotational or postrotational nystagmus or caloric nystagmus, in addition to optokinetic afternystagmus and its reversal phase and headshaking (after-) nystagmus including the reversal phase. A feature common to these phases of nystagmus may be the appearance of a temporary nystagmic reaction following, either immediately or after a definite interval of time (“latent period”), the elimination of an optokinetic stimulus or a physical vestibular stimulus that induces deviation of the cupula and then following the subsequent disappearance of excitement of the peripheral sensory organs, i.e., optic organ and vestibular labyrinth, that respond to these stimuli. Afternystagmus in this sense has never been generalized and the phenomenon may not actually be so simple. A panel discussion of this phenomenon and the neural mechanisms involved was held at the 51st Annual Meeting of the Japan Society for Equilibrium Research, which opened in Maebashi, Gunma prefecture on November 7, 1992
Optokinetic reflex
Stimulus (psychology)
Phenomenon
Caloric theory
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Congenital nystagmus has been relatively easily diagnosed by using optokinetic nystagmus test because of its characteristic reactions, such as lack of optokinetic nystagmus, so-called “inversive reactions (bilateral, unilateral, and partial)”, or ataxic reaction. These characteristic reactions have long been believed to be seen only in patients with congenital nystagmus. However, recently we experienced an ataxic pattern of optokinetic nystagmus in acquired diseases which is quite similar to the ataxic pattern of optokinetic nystagmus in congenital nystagmus.This fact has brought confusion in diagnosing congenital nystagmus, but at the same time, this might be a clue to elucidate the unknown pathophysiological mechanism of congenital nystagmus. In this paper we report 8 cases of acquired diseases which manifested ataxic reaction in optokinetic nystagmus test.
Optokinetic reflex
Confusion
Electronystagmography
Dysmetria
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Optokinetic reflex
Vestibulo–ocular reflex
Caloric theory
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The authors evaluated the interaction of follow-up eye movements, of the optokinetic nystagmus with the nystagmus of labyrinthine origin. In 15 subjects without data on an impaired vestibular system they observed during a calorically induced nystagmus follow-up eye movements and the optokinetic nystagmus. They confirmed changes of these curves which were closely associated with the direction of the nystagmus. The above changes can be used as one of the criteria for the differentiation of a spontaneous nystagmus of peripheral origin from central nystagmus.
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For the investigation of the effect of the otolith system on optokinetic nystagmus, the crab was examined using an optical cylinder. The results obtained were as follows: (1) Optokinetic nystagmus always occurred with the stimulation of the optical cylinder. (2) In crabs of which statocysts were removed, the nystagmus was depressed. (3) The nystagmus was not depressed by forward position but depressed by backward position. (4) The nystagmus directed to the right side was depressed by right lateral position but not depressed by left lateral position. Similar findings were observed in cases of nystagmus directed to the left side. Analyzation of the results indicated that the otolith system has a certain effect on optokinetic nystagmus.
Optokinetic reflex
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When a man looks around while on a revolving object, nystagmus is elicited. This type of nystagmus consists of two components, i.e. optokinetic nystagmus and labyrinthine nystagmus. Labyrinthine nystagmus is caused by the movement of endolymph in the semicircular canals and can be elicited by rotating the body in the dark room with the eyes opened (perrotatory nystagmus). Optokinetic nystagmus can be elicited by applying visual stimuli with the eyes opened.Optokinetic nystagmus may or may not be affected by additionally induced rotation nystagmus. It is also known that labyrinthine nystagmus is inhibited by gaze. In the present study electronystagmographic study was performed on the effect of concomitant perrotatory nystagmus (as induced by pendular rotation of the body) on the pattern of optokinetic nystagmus and the inhibitory effect of gaze on perrotatory nystagmus.The subjects were 20 healthy adults. In all subjects an inhibitory effect of gaze on perrotatory nystagmus was noted. The effect, however, was complete (total suppression of perrotatory nystagmus) in 39% of the cases and incomplete (the nystagmus still appeared though diminished in frequency and amplitude) in the other 61%.Optokinetic nystragmus was demonstrated in all cases. When a stimulus of pendular rotatory movements was applied to the subjects while optokinetic nystagmus was being elicited, no appreciable changes were observed in 39% of cases. In the remaining 61% of the cases, clearly noticeable changes in the slow component of the optokinetic nystagmus were observed.In the group whose perrotatory nystagmus was inhibited incompletely, the changes of the optokinetic nystagmus by the rotation was more clealy observed than in the group whose perrotatory nystagmus was inhibited completely.This finding suggests that the inhibition of labyrinthine nystagmus by gase should be taken into account when interaction between optokinetic nystagmus and labyrinthine nystagmus is studied.
Optokinetic reflex
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The aim of our work was the presence of the second phase nystagmus after rotatory, caloric and optokinetic irritation; estimation of this nystagmus magnitude and the clinical application of the second phase nystagmus. The investigation was performed in 30 healthy subjects and 65 cases of the peripheral and central vestibular pathology. Our results show that the second phase nystagmus appears more often after strong vestibular or visual irritation; the largeness of this reaction is bigger than the first reaction nystagmus. Only the asymmetry of the second phase nystagmus has the clinical apply. Labyrinthine disorders has the influence on the formation of the post-optokinetic reaction.
Optokinetic reflex
Eye irritation
Electronystagmography
Caloric theory
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Horizontal optokinetic nystagmus (OKN), caloric nystagmus, and positional alcohol nystagmus (PAN) of the rhesus monkey (Macaca mulatto) were surveyed using electrooculography. OKN of the monkey appears to be similar in most respects to that of man although optokinetic after-nystagmus is more prominent in the monkey. of the parameters of OKN which were measured, slow phase velocity was most closely related to the optokinetic stimulus. Caloric nystagmus is easily induced in the monkey and parameters of caloric nystagmus declined exponentially on repeated testing. The first phase of positional alcohol nystagmus was present in all animals tested and the secondary phase in some. The data indicate that oculomotor findings in the monkey can probably be applied to man with few reservations.
Optokinetic reflex
Electrooculography
Stimulus (psychology)
Caloric theory
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