Secondary Nystagmus Research Articles

Study of secondary postrotary nystagmus in adolescents

When studying the vestibular apparatus of healthy adolescents by the method of electronistagmography after a rotational test, 23 of 36 adolescents revealed secondary nystagmus. Secondary nystagmus was often observed and was more pronounced to the left. Its duration exceeded the duration of primary nystagmus, but the intensity in terms of frequency, amplitude and speed of the slow phase was much less. Secondary nystagmus was closely associated with latent spontaneous nystagmus. The latter has always been accompanied by prolonged secondary nystagmus in the same direction. Detection of prolonged unilateral secondary nystagmus should obviously have the same significance for issues of professional suitability as the detection of latent spontaneous nystagmus.

The Effects of Ketamine on Cognitive Function in Elderly Patients Undergoing Ophthalmic Surgery

Acute postoperative cognitive dysfunction is characterized by neurocognitive dysfunction and confusion. In this study, we compared the cognitive status of a geriatric population undergoing ophthalmic surgery, as assessed by the Short Portable Mental Status Questionnaire (SPMSQ) before and after ketamine administration. Eighty patients were enrolled and randomly assigned in a double-blind study to receive either ketamine (0.3 mg/kg dose) or physiologic solution (control group). Sixty-five (control, n = 32; ketamine, n = 33) patients completed the trial. Cognitive performance was assessed with an abbreviated version of the SPMSQ. Measurements of analgesia, sedation, intraocular pressure, and hemodynamic variables were recorded. With respect to cognitive performance, the baseline evaluation was similar for the control and ketamine groups. Postoperative evaluation showed an improvement only in the ketamine group. No increase in intraocular pressure or a secondary nystagmus was observed. The average dose of midazolam was higher in the control group, but the difference was not clinically significant. After surgery, analgesic behavior was better in the ketamine group than in the control group. There were no differences between groups in the sedation scale or in hemodynamic variables. The administration of 0.3 mg/kg ketamine during ophthalmic surgery in geriatric patients changed their cognitive status as assessed by the SPMSQ, decreased the required dose of anesthetics, and produced no increase in intraocular pressure or in hemodynamic variables. However, because the evaluation only analyzed the immediate effects of the administered drug, further research will be required to examine the impact of ketamine on the postoperative cognitive performance of geriatric patients before the drug can be formally recommended for this purpose.

Isolated foveal hypoplasia with secondary nystagmus and low vision is associated with a homozygous SLC38A8 mutation

Foveal hypoplasia, always accompanied by nystagmus, is found as part of the clinical spectrum of various eye disorders such as aniridia, albinism and achromatopsia. However, the molecular basis of isolated autosomal recessive foveal hypoplasia is yet unknown. Individuals of apparently unrelated non consanguineous Israeli families of Jewish Indian (Mumbai) ancestry presented with isolated foveal hypoplasia associated with congenital nystagmus and reduced visual acuity. Genome-wide homozygosity mapping followed by fine mapping defined a 830 Kb disease-associated locus (LOD score 3.5). Whole-exome sequencing identified a single missense mutation in the homozygosity region: c.95T>G, p.(Ile32Ser), in a conserved amino acid within the first predicted transmembrane domain of SLC38A8. The mutation fully segregated with the disease-associated phenotype, demonstrating an ∼10% carrier rate in Mumbai Jews. SLC38A8 encodes a putative sodium-dependent amino-acid/proton antiporter, which we showed to be expressed solely in the eye. Thus, a homozygous SLC38A8 mutation likely underlies isolated foveal hypoplasia.

Positional nystagmus reversing from geotropic to apogeotropic: a new central vestibular syndrome

Central positional paroxysmal vertigo (CPPV) is rarely encountered in clinical practice. It must be distinguished from the more frequent benign positional paroxysmal vertigo (BPPV) [1, 2] and only an accurate clinical evaluation can identify it. Mostly, CPPV is due to cerebellar disease from various aetiologies, including neoplasm, as in the case reported here [3–5]. In this patient, clinical examination with video-oculography revealed right beating horizontal nystagmus in the right lateral head position (geotropic nystagmus) that reversed direction (to apogeotropic nystagmus) while the head position was maintained. In the left lateral position, the patient had again geotropic nystagmus reversing to apogeotropic nystagmus. Brain imaging revealed the presence of a right hemisphere cerebellar neoplasm causing compression of the IV ventricle and hence the vestibular disturbance. A 50-year-old female patient was referred to our neurootology service because of imbalance and vertigo subacutely developed a fortnight earlier. She had a history of breast cancer treated with surgery in May 1997, followed by adjuvant chemotherapy and hormone therapy. Neurological examination revealed a retropulsion in Romberg position and a backward displacement on the Fukuda stepping test. Coordination was only mildly impaired, with limb dysmetria on right finger-to-nose test. Cranial nerves were intact. Tendon reflexes were symmetrical with flexor plantar responses. Video-oculography showed no spontaneous nystagmus in primary position and no gaze-evoked nystagmus was revealed. Head-shaking test was normal. A slight delay was observed on the horizontal head impulse test toward the right side. Upon slowly positioning the patient in the right lateral head position, first-phase nystagmus manifested itself as right beating paroxysmal nystagmus (geotropic) without any latency. It gradually diminished, only to reverse its direction after about 10 s with the development of left beating (apogeotropic) second-phase nystagmus, as shown in the video (Online resource 1). On the left side, a similar, although less intense, geotropic nystagmus was observed. It reversed its direction in about 20 s, changing to apogeotropic nystagmus, as shown in the video (Online resource 2). Recording of the nystagmus activity revealed a maximal slow-phase velocity (SPV) of 19.6 /s for right geotropic nystagmus, while on the left side it showed an SPV of 8.6 /s. First-phase nystagmus was more intense both on the right and left sides, although it didn’t last as long as secondary apogeotropic nystagmus (Fig. 1). When tested in the straight head-hanging position, no nystagmus was detected. Electronic supplementary material The online version of this article (doi:10.1007/s00415-010-5701-6) contains supplementary material, which is available to authorized users.

Visual dysfunctions and ocular disorders in children with developmental delay. I. prevalence, diagnoses and aetiology of visual impairment

To describe the prevalence, diagnoses and aetiologies of visual impairment in children with developmental delay (DD) in a Danish county with a population of 618 000 citizens. We carried out a cross-sectional study in Copenhagen County of children aged 4-15 years with profound to borderline DD (IQ <or= 80). Children were located through school psychologists or paediatric clinics. The number of children with DD was estimated using the capture-recapture method. A total of 1126 children fulfilled the inclusion criteria, corresponding to 97.7% of the estimated number of children with DD in the county. Ophthalmological examinations were performed in 923 children. The prevalence of visual impairment was 10.5% in the study group and 22.4% in those with an IQ <or= 50. The diagnoses were predominantly cerebral visual impairment, optic atrophy, retinal dystrophies and congenital nystagmus. The aetiology of visual impairment was prenatal in 54 children, perinatal in 29 children and postnatal in seven children. Visual impairment is highly increased in children with DD and is correlated to low IQ.

Habituation of Horizontal Nystagmus of the Eyes in Pigeons in Conditions of Alternating Central and Eccentric Rotations

Intact pigeons (n=19) were rotated in the dark in the horizontal plane in different orientations relative to the axis of rotation. In central (evoking habituation) rotations, the animal's head was located on the axis of rotation; in eccentric rotations, the animal's head was 0.6 m from the axis of rotation. Pigeons were subjected to series of alternating central and eccentric rotations; rotation directions were also alternated. Series consisted of 2-5 rotation using a trapezoidal program. Each stimulus evoking habituation was used no more than 14 times during the experiment. Eccentric rotations were found not to prevent the gradual decrease in the peak rates of the slow components of primary nystagmus occurring on the transition from one series of central rotations to another in 17 individuals (group 1); these were increased in two individuals (group 2). Group 1 showed direct relationships between changes in this measure of primary nystagmus, changes in the duration of nystagmus, and changes in the peak rates of secondary nystagmus. Modifications of nystagmus within series varied. When two identical stimuli did not follow immediately one after the other, the second stimulus induced the same changes in nystagmus as observed in the individual in the first and next series of central rotations. If two identical stimuli followed one immediately after the other, the second stimulus in the pair often induced increases in the peak rates of primary and secondary nystagmus, along with increases in the time taken to reach the peak rate of primary nystagmus. These changes were non-random at a probability of >95%.

Three hundred sixty-degree rotation of the posterior semicircular canal for treatment of benign positional vertigo: a placebo-controlled trial.

The canalithiasis hypothesis proposes that benign positional vertigo (BPV) is caused by dislodged otoconia that settle in the posterior semicircular canal (PSC). When head position is changed these particles move within the canal and induce abnormal endolymph flow. To clear the PSC from debris we developed a procedure that consists of a full circle of backward head rotation in the exact plane of the canal. Patients were seated in a three-dimensional motion device that rotated in steps of 110 degrees every 30 seconds. The first part of the study was conducted as an open trial; the second part followed a single-blinded, placebo-controlled design: Forward rotation (placebo) was applied first and backward rotation was applied 1 week later if BPV persisted. All patients were assessed with a symptom diary and, in the controlled trial, also with the Dix-Hallpike maneuver. In the open study 10 of 15 patients became asymptomatic after one treatment session. In the controlled trial all 15 patients remained symptomatic after forward rotation while 10 of 14 undergoing backward rotation were relieved from positional vertigo immediately (p = 0.004). The presence of secondary nystagmus during the procedure indicated a favorable outcome. Our findings provide evidence for the efficacy of canal-clearing procedures that validate the canalithiasis hypothesis of BPV.

頭位変換でのＢＰＰＶ治療における眼振の変化と予後について

Several benign paroxysmal positional vertigo (BPPV) treatments, including Particle Repositioning Maneuver (PRM) and Liberatory Maneuver (LM), are based on the theory, and the usefulness of these treatments has been confirmed. We examined whether the accuracy of prognosis can be improved by checking the direction of nystagmus during treatment (secondary nystagmus). When secondary nystagmus occurred in the same direction as the provoked initial position, the efficacy of treatment was 90.9%. When secondary nystagmus was reversed, the efficacy was 30.8%. When there was no nystagmus appearing after the initial position, all cases improved. These results support the canalolithiasis theory and the spontaneous improvement rate seems to be about 30%. It is thus important to check secondary nystagmus to predict the prognosis of the BPPV after positioning treatment.

Characteristics of Nystagmus Evoked by Electrical Stimulation of The Uvular/Nodular Lobules of the Cerebellum in Monkey

Electrical stimulation in the monkey vestibulocerebellum has previously been shown to produce ocular nystagmus, but large stimulating current values were used. Using long duration (< or = 10-second) stimulus pulse trains and low current values (< 50 microA), we studied the nystagmus evoked by microstimulation in the uvular/nodular regions of the cerebellum. In doing this, we found quantitative differences in the nystagmus evoked from these two regions. Stimulation of the nodulus typically produced a vigorous nystagmus with a contralateral slow phase and a prolonged afternystagmus in the same direction. In contrast, stimulation of the uvula typically produced a regular ipsilateral nystagmus pattern with a very short, if any, afternystagmus in the same direction. In addition, at some stimulation sites in the uvula we observed an adaptation in the slow phase eye velocity during the time that the stimulation remained on. This effect could result in a secondary nystagmus, with a slow phase velocity direction opposite to that first evoked by the stimulation, followed by a prolonged afternystagmus in the direction of the secondary nystagmus at stimulus offset. The nystagmus evoked by these cerebellar stimulations differs from both natural nystagmus produced by large field visual motion and from the nystagmus produced by electrical stimulation of the nucleus of the optic tract. The nystagmus produced by uvular and nodular stimulation shows a shorter latency and a more rapid slow phase eye velocity buildup. The uvula stimulations also showed a much shorter afternystagmus. Also, the same nystagmus was evoked whether the animal was in a lighted or dark surround. These characteristics and recent single-unit recording studies in the uvula seem to suggest that the uvula acts not as a direct input to the velocity storage mechanism, but instead perhaps as part of an internal regulator for balance between the bilateral vestibular nuclei which are normally part of the nystagmus response. On the other hand, the nodulus, with its prolonged afternystagmus in the same direction as the evoked nystagmus, may be involved as a part of the velocity storage mechanism.

The membrane rupture theory of meniere's disease — is it valid?

The Membrane Rupture Theory states that the acute attack of Menière's disease occurs when endolymph, with its high potassium ion concentration, escapes into the perilymph and surrounds the first-order neuron. Initially, this causes partial depolarization of the nerve and an increased resting discharge, followed by complete depolarization. Clinically, one would expect an initial irritative nystagmus (toward the affected side) followed by a paralytic nystagmus (toward the unaffected side). To confirm this, the guinea pig perilymphatic space was perfused with an artificial endolymph solution. The results confirmed an irritative/paralytic sequence of nystagmus that differs from the pattern of spontaneous nystagmus observed with ENG monitoring during the acute attack of Menière's disease. Early in the attack, one observes a paralytic nystagmus followed by a secondary nystagmus beating toward the affected side (similar to an irritative nystagmus) as the patient recovers. This raises questions about the validity of the Membrane Rupture Theory.

Caloric vestibular test in the weightless phase of parabolic flight.

Twenty-four caloric vestibular tests were conducted in 20 test subjects during parabolic flight, in which weightless periods of about 10 seconds were elicited. The caloric nystagmus disappeared completely in all experiments in weightlessness, whereas in the higher G-periods the speed of the nystagmus increased. With regard to the modes of response during the periods with increased G-values prior to and following the weightlessness, four different types could be distinguished. In mode I the speed of the slow nystagmus phase increased in the higher G-periods, the nystagmus showed a prolonged duration, while in weightlessness it faded out completely. A reversed nystagmus appeared when the primary caloric nystagmus had disappeared. In modes II, III and IV the direction of the nystagmus reversed during weightlessness. In modes II and III this reversed nystagmus appeared even when the primary caloric nystagmus had disappeared. In mode III the nystagmus resembled the type of mode II, with the difference that it faded away much earlier than could be expected. In mode IV the primary nystagmus lasted rather briefly, while the reversed nystagmus during weightlessness was also much shorter. The experiments produced two remarkable facts: the appearance of a nystagmus reversal, a 'secondary nystagmus', in all experiments in weightlessness, and furthermore great differences in findings between the individuals as well as between experiments in the same person. The only explanation for the inconsistency in the findings is the assumption that effects on other canals, otoliths and vestibular nuclei are continuously changing and therefore interfere with the only endproduct measured, the horizontal nystagmus.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of postrotatory nystagmus time constants.

Models of the slow phase portion of postrotatory nystagmus in the adult include time constants which describe primary and secondary nystagmus. The cupular time constant (T1) is believed to reflect the activity of the cupula of the semicircular canal, while the adaptation time constant (Ta) defines the rate of change of the baseline firing rate. Values for T1 and Ta have been published for the adult. In this study 37 normal infants under one year of age and 12 children, 3 to 13 years of age were examined for postrotatory nystagmus, and values for the two time constants were determined. The cupular time constant does not change with age and is concluded to be at an adult level at birth. This is correlated with the relative maturity of ear morphology at birth. The adaptation time constant increases from 79.5 sec at one month of age to 260.7 sec at 12-13 years of age, implying that maturation of adaption is a relatively slow process.

Post-caloric secondary phase nystagmus.

Spontaneous direction reversal of a peripherally induced nystagmus, known as secondary phase nystagmus, can be found following a thermal stimulus. In 120 patients with various vestibular symptoms, post-caloric secondary phase nystagmus has been examined and its diagnostic value is discussed. Although the mechanism responsible for the post-caloric secondary phase nystagmus is not clear, there seem to be three factors that play a role in its occurrence: a the intensity of the stimulus; b the sensitivity of the vestibular and optokinetic systems; c the anatomical features of the external and middle ear. Because of these multiple factors, it is difficult to define the diagnostic value of the secondary phase nystagmus. However, we assume that secondary phase nystagmus is due to the adaptation of the organism to the peripheral vestibular stimulus, and factors mentioned above may induce or suppress its occurrence.

Mechanisms underlying modulations of thermal nystagmic responses in parabolic flight.

In six subjects nystagmography was used to compare the responses to cold calorization of one horizontal semicircular canal under ground-based and parabolic flight conditions. On the ground the expected individual differences in primary nystagmic responses were observed; only one subject manifested a brief weak secondary nystagmus. Aloft, the irrigation was carried out in straight-and-level flight prior to a pushover (half-parabola) that initiated a series of four to nine typical parabolas in a modified KC-135 aircraft. Thereafter, the free-fall phases of the parabolas furnished a zero baseline for measuring weight differences in endolymph due to changes in gravitoinertial force. In all subjects a secondary nystagmus was generated in addition to the primary nystagmus during the course of the parabolic maneuvers. The slow phase of the secondary nystagmus rarely exceeded 10 mm per sec. Evidence is presented that secondary nystagmus arises as a direction-specific adaptation effect countering the primary nystagmic response. Three stages were recognizable: first, when primary and secondary nystagmus alternated in step with the high and low force phases of the parabolas; second, after disappearance of primary nystagmus when secondary nystagmus appeared alone and was modulated by the changes in force; and third, when the secondary nystagmus present became independent of the highest gravitoinertial forces generated. Great individual differences were observed, suggesting that with large departures of the cupula from its functional rest position there are large individual variations in rate of restoration.

The Maturation of Vestibular Nystagmus in Infancy and Childhood

The displacements, durations, and velocities of the slow and fast components of both the primary and secondary nystagmus induced by constant angular acceleration were measured in 46 normal children 1 month to 11 years old. There were significant changes in nystagmus parameters in respect to maturation. The young infant had larger amplitude, higher velocity beats than the older child during both the primary and the secondary nystagmus. Parameters describing both the primary and the secondary nystagmus reached their peak values and terminated earlier in the infant than in the older child. Although the slow component velocity during secondary nystagmus was much slower than during the primary nystagmus at all ages, the secondary nystagmus/primary nystagmus ratio was significantly greater in early infancy. Thus, in infancy, as compared with later childhood, the vigor of the secondary nystagmus was disproportionately greater than the primary nystagmus. These results were discussed in relation to the maturation both of vestibular responsiveness and of vestibular adaptation.

Air caloric stimulation with tympanic membrane perforation.

Warm air caloric stimulation in an ear with tympanic membrane perforation or mastoidectomy cavity often causes contralateral nystagmus. Secondary nystagmus is common. Our evidence with squirrel monkeys and patients indicates that the primary "inversion" results from endolymph cooling due to evaporative cooling due to evaporative cooling of the mucus lining the middle ear cavity, by the dry air stimulus. Disconjugate horizontal nystagmus was found in a patient with large eardrum perforation, after cold air caloric stimulation. The effect probably resulted from stimulation of the anterior or posterior vertical semicircular canal. Inverted or disconjugate caloric nystagmus after air stimulation is much more frequently due to tympanic membrane perforation, or moisture in the external ear, than to central nervous system disease.

Mathematical modelling. A contribution to clinical vestibular analysis.

A model of the vestibulo-ocular system used by the authors to explain mathematically some peculiarities of the nystagmus patterns and general phenomena such as vestibular Actaptation and secondary nystagmus is illustrated after a brief revue of the current status of vestibular modelling. The model has been implemented on a digital computer, and several rotational tests have been simulated. By comparing the experimental data obtained from young healthy subjects with the model predictions, it has been possible to define the model parameters quantitatively. The results of these investigations are reported in this paper. Finally, a method for an automatic analysis of the vestibular function from E.N.G. data recorded during post-rotational tests is discussed in the concluding section.

Effect of vestibular stimulation on pupillary size

The action of utricular stimulation on ocular reflexes has been examined with particular attention to the effects upon autonomic outflow and intraocular muscle activity. Brisk, conjugate deviations of the eyes in response to single air puff stimulation, in both cats and monkeys, were accompanied by pupillary reactions, constriction during the fast phase of eye movement, and dilatation during the slow phase. During the nystagmus obtained in monkeys and evoked by an air jet directed at the utricle, the pupils showed initially a strong dilatation with superimposed, rapid, minor constrictions of a random frequency. After the end of stimulation and at the occurrence of a secondary nystagmus, there was a dilatation during the fast phase and constriction during the slow. As the nystagmus gradually diminished, the pupils concomitantly returned to control size and ceased to fluctuate. Prolonged stimulation gave rise to an increased stream of efferent impulses in sympathetic fibers to the eye in synchrony with pupillary dilatation while the activity of ciliary nerves showed a simultaneous decrease. However, anatomical integrity of the sympathetic connections is not a prerequisite for the presence of these pupillary reactions to vestibular stimulation since their sectioning did not change the effect. Thus, the results of these experiments substantiate the conclusion previously reached that reflex pupillary dilatation can be accomplished by pure inhibition of parasympathetic tone.

A quantitative study of vestibular adaptation in humans.

A mathematical model for short-term adaptation to vestibular stimuli is presented. A transfer function is derived relating slow phase angular velocity of resulting nystagmus to the angular velocity of head rotation. The resulting model has been tested by comparing its responses to controlled step and ramp angular velocity stimuli with those of 8 human subjects, and in all cases a close match was obtained. The mean time constant of the adaptive term was 82 sec (S.E.±6.5) and the mean cupular restoration time constant (Tc) was 21 sec (S.E.±1.5). It is suggested that previous values quoted for Tc represent underestimates of the true value owing to superposition of the adaptive term here described. The adaptive term accounts well for the phenomenon of secondary nystagmus, especially during either strong stimuli or prolonged rotations. Some implications of the findings in relation to clinical and aviation medicine are discussed.

Nystagmus evoked by utricular stimulation

The effects of selective utricular stimulation upon eye movements, as recorded by the corneoretinal potential method, have been studied in experiments on cats and monkeys. Single air puff stimulation of the gravioceptors of the isolated utricle evoked brisk, conjugate eye deviations, demonstrating the existence of strong maculoocular connections. The principal aim, investigating the relationship of nystagmus to the otoliths, has been achieved, and it can be firmly stated that long-lasting mechanical stimulation of constant intensity of the utricle can evoke strong, primary nystagmus, followed by a secondary nystagmus at the cessation of stimulation.