Approach to the Examination and Classification of Nystagmus.

BACKGROUND AND PURPOSE: Physical therapists caring for patients with neurologic or vestibular disorders must routinely examine and characterize nystagmus and other oscillatory eye movements. Often, the diagnosis hinges on proper interpretation of the nystagmus pattern. This requires understanding the terminology surrounding the numerous attributes and influencing factors of nystagmus, a systematic approach to the examination, and a classification structure that guides practitioners to the specific nystagmus type and subsequent evaluation and management. SUMMARY OF KEY POINTS: Nystagmus is an involuntary, rapid, rhythmic, oscillatory eye movement with at least 1 slow phase. Jerk nystagmus has a slow phase and a fast phase. Pendular nystagmus has only slow phases. Nystagmus is distinguished from other types of oscillatory eye movements, such as saccadic intrusions or oscillations. Characterizing nystagmus requires clearly describing its trajectory. This includes choosing a reference frame to describe the axes or planes and direction of eye movements. Several attributes are used to describe nystagmus: binocularity, conjugacy, velocity, waveform, frequency, amplitude, intensity, temporal profile, and age at first appearance. Several factors may influence nystagmus, including gaze position, visual fixation, vergence, and a variety of provocative maneuvers. Classification of nystagmus may be organized by physiologic or pathologic nystagmus versus other nystagmus-like movements. Pathologic nystagmus may be spontaneous, gaze-evoked, or triggered by provocative maneuvers. The combination of attributes allows differentiation between the many peripheral and central forms. RECOMMENDATIONS FOR CLINICAL PRACTICE: Therapists should carefully examine and characterize the trajectory and other attributes and influencing factors of nystagmus to accurately classify it and arrive at the correct diagnosis.

Treatment of Nystagmus.

Acquired and congenital forms of nystagmus are commonly encountered in the course of clinical practice. Although some patients are asymptomatic, many others describe disabling oscillopsia that impairs visual function, social function, and quality of life. Such patients may present to the neurologist to request treatment. Numerous treatment approaches for nystagmus have been proposed, including medical, surgical, and optical treatments. Some of the treatments aim to reduce nystagmus slow-phase speed, whereas others aim to negate the visual consequences of the nystagmus. The approach must be tailored depending on the type of nystagmus, its characteristics, and in some cases, its cause. In this review, the treatment approach for acquired and congenital forms of nystagmus is summarized with an emphasis on treatments that have been evaluated in well-designed clinical trials. Novel approaches that have not yet been evaluated in clinical trials are also discussed.

Don't Miss This! Red Flags in the Pediatric Eye Examination: Acquired Nystagmus.

When a new patient presents with a chief complaint of nystagmus, the clinician must know what further action is necessary in order to identify vision or life-threatening diseases. Some types of acquired nystagmus include upbeat nystagmus, downbeat nystagmus, see-saw nystagmus, and period alternating nystagmus. By identifying the characteristics and causes, acquired nystagmus can be recognized as a "red flag." In contrast, children diagnosed with infantile or physiological nystagmus generally will not need neurological testing. As crucial as it is to recognize acquired nystagmus, it is equally important to differentiate among the specific subtypes and to be familiar with the key features of infantile nystagmus.

Uphill/downhill nystagmus.

Differential diagnosis between peripheral and central spontaneous nystagmus can be difficult to classify (as peripheral or central) even on the basis of criteria recommended in the recent literature. The aim of this paper is to use the combination of spontaneous nystagmus and ocular tilt reaction to determine the site of origin of the disease that causes nystagmus. We propose to classify the nystagmus in: 1) "Uphill" nystagmus in which the nystagmus takes on an inclined plane and the direction of the fast phase is towards the hypertropic eye (this type of nystagmus is likely peripheral); 2) "Downhill" nystagmus when the nystagmus beats toward the hypotropic eye (this type of nystagmus is likely central); 3) "Flat" nystagmus when the plane on which nystagmus beats is perfectly horizontal: in this case, we cannot say anything about the site of lesion (it was only detected in 15% of cases). The spatial position of nystagmus vector has to be considered as an intrinsic characteristic of the nystagmus itself (as direction, frequency, angular velocity etc.) and must be reported in the description, possibly giving an indication of the site of damage (peripheral or central). In particular, similar results are obtained by comparing the inclination of the nystagmus with the head impulse test (HIT, considered the best bedside test now available). It seems that this sign may confirm HIT for safer diagnosis or replace it in case of doubt. In contrast, in case of "Flat" nystagmus (probably attributable to the fact that the utricular maculae are spared), HIT can replace observation of the plane of the nystagmus. Thus, the two signs confirm and integrate each other. The test does not require additional time and is not tedious for the patient. It is proposed that it be included in the evaluation of spontaneous nystagmus in everyday clinical practice.

Incidence and Types of Pediatric Nystagmus.

PURPOSE: To report the incidence, prevalent subtypes, and clinical characteristics of pediatric nystagmus diagnosed over a 30-year period. DESIGN: Retrospective, population-based study. METHODS: Using the Rochester Epidemiology Project, we reviewed the medical records of all children (<19 years) diagnosed as residents in Olmsted County, Minnesota, with any form of nystagmus from January 1, 1976, through December 31, 2005. RESULTS: Seventy-one children were diagnosed during the 30-year period, yielding an annual incidence of 6.72 per 100,000 younger than 19 years (95% confidence interval [CI], 5.15-8.28) Infantile nystagmus, onset by 6 months, comprised 62 (87.3%) of the study patients, corresponding to a birth prevalence of 1 in 821. The median age at diagnosis for the cohort was 12.7 months (range, 0 days to 18.6 years) and 42 subjects (59.2%) were male. The main types of nystagmus, in declining order, were nystagmus associated with retinal/optic nerve disease in 23 (32.4%), idiopathic or congenital motor nystagmus in 22 (31.0%), manifest latent nystagmus or latent nystagmus in 17 (24.0%), and 2 (2.8%) each associated with Chiari malformation, medication use, tumor of the central nervous system, and no diagnosis. Developmental delay was diagnosed in 31 (43.6%), strabismus in 25 (35.2%), and amblyopia in 10 (14.1%). Eighty percent had 20/40 (or equivalent) or better vision at presentation in at least 1 eye. CONCLUSIONS: This study provides population-based data on incidence and clinical characteristics of childhood nystagmus in North America. Idiopathic and nystagmus associated with retinal/optic nerve disease were the most common presentations, with most patients having good vision. Developmental delay, strabismus, and amblyopia were common in this cohort.

Classification of infantile nystagmus waveforms.

Classification of infantile nystagmus waveforms is an important problem because the characteristic waveforms can be used to distinguish between infantile and acquired nystagmus. A clear description of the nystagmus is also a necessary first stage in understanding its origin. Currently infantile nystagmus waveforms are classified into at least 12 different types. In this study we analyse a database of nystagmus recordings in order to investigate if this classification can be simplified. Application of principal components analysis revealed that 96.9% of the variance of the waveforms is described by a linear sum of two component waveforms. The components consist of sawtooth and pseudocycloid waveforms that account for 78.7% and 18.2% of the variance respectively for the most common single cycle waveforms. This simplified description of infantile nystagmus highlights the importance of identifying the origin of the jerk component and its synchronisation with the pseudocycloid component for the characterisation and treatment of the nystagmus.

[Nystagmus. Clinical characteristics and therapeutic options]. / Nystagmus. Klinische Charakteristika, therapeutische Optionen.

This article presents an overview of the pathophysiology of nystagmus and the differential diagnostics of congenital and acquired nystagmus. In addition, the principles of conservative, surgical and pharmacotherapy treatment options are described. The pathophysiological basis of nystagmus deepens the understanding of the etiology of the individual forms of nystagmus. The therapeutic approach to calming of nystagmus aims at an extension of the foveation time, which has the most significant impact on visual acuity. In congenital nystagmus this can be carried out by optimization of the retinal image, prisms or by bilateral surgical muscle repositioning to use the phenomenon of a null or neutral zone. In acquired nystagmus the off-label use of centrally acting medications can sometimes be helpful to calm the nystagmus and the associated oscillopsia.

End-point nystagmus.

Infrared oculography was performed during sustained lateral gaze in 12 normal subjects to investigate end-point nystagmus while fixating a target light. Five failed to develop nystagmus despite deviation up to 40 degrees from 4 to 5 min. Six subjects developed nystagmus immediately or shortly after reaching the deviated position. In one, the nystagmus (0.5 degrees to 1 degree and 1.0 Hz) began with only a 20 degree deviation. In another subject, "fatigue" nystagmus developed after 1 min at 30 degrees, and at 35 degrees nystagmus began within 2 sec. One subject developed only fatigue nystagmus, which began after more than 4 min of sustained deviation. In all instances the slow phase had primarily a linear, rather than exponential, waveform.

Latent/manifest latent nystagmus reversal using an ocular prosthesis. Implications for vision and ocular dominance.

Latent/manifest latent nystagmus (LMLN) is a jerk nystagmus with a decreasing-velocity or linear slow phase whose fast phase is in the direction of the fixating eye. Change of the fixating eye by alternating tropias or cover will cause reversal of the LMLN to preserve this relationship. In the dark, where no fixation is possible, the fast phases of LMLN are in the direction of the intended fixating eye; actual visual input will override this effect of intention. A patient with persistent hyperplastic primary vitreous of the right eye, which was enucleated at age 9 due to glaucoma, had LMLN with fast phases to the left. His congenitally blind right eye was replaced with an ocular prosthesis whose movements were conjugate with his seeing eye. In the dark, we found that his LMLN spontaneously reversed as the normally fixating left eye became esotropic. Furthermore, as is the case with LMLN patients who have sight in both eyes, he was able to willfully reverse his LMLN in the dark by alternating his "fixating" eye. We conclude from these observations that the direction of LMLN is determined at a cortical level, is intimately related to the intended fixating eye and that eye "dominance" is predetermined and not altered by visual abnormalities, including blindness.

Compensatory mechanisms in congenital nystagmus.

Congenital nystagmus may occur in a manifest or latent form. Since most patients with latent nystagmus also have nystagmus with both eyes open (manifest latent nystagmus), differentiation between these two entities frequently requires electronystagmographic wave form analysis. Such analysis shows distinctive characteristics for manifest and latent or manifest latent congenital nystagmus, suggesting different origins. Several compensation mechanisms exist by which congenital nystagmus is decreased and visual acuity improved. For manifest nystagmus, these mechanisms include version or convergence innervation or a rest point between primary position and maximal lateroversion. In latent or manifest latent nystagmus, the nystagmus decreases when the fixating eye is adducted. Patients with manifest congenital nystagmus may use several of these compensation strategies. Because of the difficulties involved in distinguishing between manifest and manifest latent nystagmus without electronystagmography, confusion has arisen regarding the etiologic relationship between congenital nystagmus and infantile esotropia. Such relationship clearly exists in some patients with manifest nystagmus and convergence dampening. However, in most patients with infantile esotropia and congenital nystagmus, the nystagmus is latent or manifest latent and there is no evidence of a causal relationship between these two entities.

Is spontaneous nystagmus a pathological sign?

This study was undertaken to determine the incidence of spontaneous nystagmus (SN) in normals and evaluate its significance in patients. There were 60 normal subjects and SN was recorded in 8 (13%). Between January 1979 and November 1981, SN without past pointing was the only detectable abnormality in 41 patients undergoing a vestibular evaluation. An intracranial lesion could be confirmed in 34 patients (83%). There results from both normal subjects and patients are compared with earlier reports in the literature. Because of differences in nomenclature and classification of SN and differences in technique of searching and recording SN, no true comparisons are possible. Our conclusion is that SN in normals should be regarded as an oculomotor abnormality for which there is no detectable cause. In patients SN is a valuable diagnostic sign and should be considered significant regardless of its slow phase velocity.

Parametric classification of segments in ocular nystagmus.

A new method for nystagmus classification, using system identification techniques, is presented. We formulate a system whose input is head position and whose output is eye position. We approximate this system with an autoregressive with exogenous input (ARX) model which relates the input and output (transfer function) regardless of the temporal profile for the sensory stimulation. The system is then identified using a least squares criteria and three indicators are produced. From these a flag is produced that marks slow and fast phases as well as blinks and bad data segments. Tests with simulated and real data are presented and indicate that the segment classification is remarkably insensitive to recording noise and that it is more robust than previous techniques. Operator intervention is minimal. We expect the method to be applicable for all types of ocular nystagmus. Here, however, we illustrate our results only in the context of the vestibuloocular reflex (VOR). A discussion explains how this method can also be applied for optokinetic (OKN) or pursuit nystagmus.

Neurodevelopmental criteria in the classification of congenital motor nystagmus.

Congenital motor nystagmus (CMN) can be familial or non-familial. The expressivity of CMN is so variable that in one affected member of the family the oscillations are obvious, while in the others the nystagmus could be overlooked even by the patients themselves. In spontaneous cases the proof of heredity might be discovered by an ophthalmological examination or eye movement recordings of other family members. Our multidisciplinary studies of 27 children with CMN suggests that a neurodevelopmental assessment can also be valuable in establishing a diagnosis of heredity. Our studies suggest that the hereditary form of CMN is free from neurodevelopmental problems, while the non-familial form is not. Therefore, children with spontaneous CMN could be referred for neurodevelopmental evaluation in order to establish a more accurate diagnosis.

Nystagmus and other abnormal ocular movements in children.

This article at first reviews the normal maturation of the ocular system in infants and then progresses to a discussion of the ways that this system can vary and produce nystagmus and nystagmus-like disorders.

Nystagmus.

Patients who present with nystagmus may have visual loss, a benign peripheral vestibular abnormality, or an important central nervous system disorder. The clinical history, features of nystagmus on examination, and accompanying symptoms and findings often help to localize the lesion. These features also determine the appropriate evaluation and treatment of the underlying disorder. Additionally, if there is oscillopsia or blurred vision, treatment of the nystagmus itself may be warranted. Possible treatments include medication, optical manipulations, and surgery.

Effects of otitis media with effusion on the vestibular system in children.

Middle ear effusion has been considered the most common cause of vestibular disturbance in children. However, there have been only a few studies on vestibular disturbance in children with otitis media with effusion. We studied the vestibular systems of 30 children with otitis media with effusion aged 8 to 13 years and compared the results with 15 age- and sex-matched controls. A questionnaire relating to vestibular disturbance was given to patients and their parents. Spontaneous nystagmus and positional nystagmus were recorded by electronystagmography as diagnostic tests of the vestibular system. Romberg's and past-pointing tests were performed on children with otitis media with effusion and controls. After vestibular tests were completed, myringotomy was performed, and a ventilation tube was inserted. The questionnaire and the vestibular tests were repeated after the operation and during the first month after surgery. Our study showed that there was a history of vestibular disturbance in 33% of children with otitis media with effusion. Electronystagmography and Romberg's test findings demonstrated that 33% of the children had vestibular dysfunction (p < 0.05). After myringotomy with ventilation tube insertion, vestibular test results returned to normal, and symptoms related to vestibular disturbance improved. These findings confirm the assumption that middle ear effusion may affect the vestibular system, which can be resolved after myringotomy with ventilation tube insertion.

Making sense of nystagmus--can it be done?

In recent years elegant recording techniques have been used to study the amplitudes, waveforms, velocities, and other characteristics of nystagmus and ocular oscillatory movement disorders. Mathematical modeling based on inferred neurophysiologic control systems and integrators have added some insight into the pathology of these conditions. From this data has developed a rather structured and complex classification system. Most specific, recognizable, localizing types of nystagmus can be diagnosed by a thorough office examination. Other types of nystagmus will be reviewed as well as those ocular movements that are oscillatory but not rhythmic and are referred to as nystagmoid movements.

Subclassification of vestibular disorders by means of statistical analysis in caloric labyrinth testing.

OBJECTIVE: In the past, various attempts were made to perform a quantitative analysis of nystagmographic findings but their diagnostic value was limited. Therefore, the authors present a multivariate analysis of nystagmus findings with the aim of increasing the precision of diagnostic differentiation in cases of vestibular dysfunction. MATERIAL AND METHODS: A group of 387 patients and 40 healthy volunteers were examined over a 14-month period using electronystagmography after stimulation by bithermal, bilateral irrigation of the labyrinth. Amplitude, slow-phase velocity, frequency and directional preponderance were evaluated. RESULTS: No defined normal values for caloric nystagmus parameters could be obtained. However, by using the Mann Whitney U-test and logistic regression analysis a differentiation between pathological and healthy findings as well as between central and peripheral vestibular disorders and even between distinct vestibular disease entities is possible. Using these methods, the nystagmus amplitude was found to be the strongest discriminating parameter. Therefore, sole assessment of nystagmographic findings by selective calculation of the nystagmus slow-phase velocity falls short of the potential offered by electronystagmographic registration. CONCLUSION: For daily clinical routine, counting nystagmus beats leads to the same diagnostic precision as the analysis of slow-phase velocities. In contrast, multivariate analysis of several nystagmus parameters can distinguish between distinct diseases with fairly high precision. This stepwise analysis of nystagmographic data could create the basis for an expert-system tool in the near future.

Electronystagmographic findings in a case of Lermoyez's syndrome.

A 40-year-old female patient with Lermoyez's syndrome is presented. Prior to the vertiginous attack, right low-tone hearing loss and tinnitus were noted. During the vertiginous attack, spontaneous nystagmus was directed to the right (lesioned) side, with improvement of cochlear symptoms. After the vertiginous attack, nystagmus was positional rather than spontaneous, and was directed to the left (opposite) side, with the subsidence of cochlear symptoms. One week later, follow-up audiometry revealed bilateral normal hearing.