Search

Objective: Saccadic Intrusions (SIs) are abnormal eye movements during gaze fixation. Studies have indicated the clinical relevance of SIs, especially of square wave jerks (SWJ) in ALS. We used a software-based platform to extract SIs as a part of an interventional drug trial. The objective was to examine SIs' change over time as a potential biomarker of ALS disease progression. Methods: 28 ALS patients (61.95 ± 8.6 years) were assessed with the revised ALS Functional Rating Scale (ALSFRS-R) and with an oculometric test. Changes of SIs over time and correlations with ALSFRS-R and its bulbar subscale were calculated. A power calculation was conducted to understand the practical implications of results. Results: A significant increase of SWJ over trial duration was observed, with an increase in frequency (mean rise of 0.14 ± 0.28, p < 0.01), amplitude (0.001 ± 0.0016 degrees, p < 0.005), overall duration of SWJ (0.13 ± 0.25, in %, p < 0.01), and in their relative part out of all intrusions (0.18 ± 0.32, in %, p < 0.005). Negative correlations were found with the bulbar subscale (R=-0.43, −0.41, −0.39 and −0.47, respectively, p < 0.001). The required sample size for observing a 40% reduction in bulbar aspects when using the oculometric test (α = 0.05 and β = 0.8), was found to be 150 patients per arm, compared with 200 patients using the bulbar subscale. Conclusions: Evaluation of saccadic intrusions during fixation was able to detect disease progression over time, correlated with ALSFRS-R bulbar subscale. Eye movements can potentially serve as an objective biomarker in ALS clinical trials and reduce the required sample size to show clinical effect of therapies. [ABSTRACT FROM AUTHOR]

Background: The presence of frequent macro-square-wave jerks (SWJs) has been recently included in the diagnostic criteria for progressive supranuclear palsy (PSP). The aim of the current video-oculographic study was to systematically assess the presence and features of SWJs during a brief fixation task in PSP, in comparison with Parkinson's disease (PD) patients and healthy controls (HC). Methods: Thirty-eight PSP patients, 55 PD patients and 40 HC were enrolled in the study. All patients underwent a video-oculographic (VOG) examination including a 5-s fixation task, and the number, duration and amplitude of SWJs were recorded. The diagnostic performance of several SWJs parameters were then compared in distinguishing PSP from PD patients and controls. Results: PSP patients showed a higher number and amplitude of SWJs compared to PD patients and controls. At least two SWJs within the 5-s fixation task were observed in 81.6% of PSP patients, 52.7% of PD patients and 25% of HC. The SWJs amplitude was the parameter showing the highest performances in distinguishing PSP from PD (AUC: 0.78) and HC (AUC: 0.88), outperforming the SWJ number and duration. The SWJ amplitude was larger in PSP-Richardson's syndrome than in PSP-Parkinsonism patients, while no difference was found between PSP patients with different degrees of vertical ocular motor dysfunction. Conclusions: This video-oculographic study provides robust evidence of larger SWJs number and amplitude in PSP than in PD patients, with some potential for differential diagnosis, supporting the inclusion of this ocular sign in PSP criteria. [ABSTRACT FROM AUTHOR]

: Introduction and objective: Nystagmus is a rhythmic and involuntary oscillation of one or both eyes in which a fixation drift and a refixation movement occur. It affects 14-17 out of 10,000 children. There are multiple underlying causes. The objective is to know the different types of non-vestibular nystagmus and non-nystagmic saccadic intrusions, with their characteristics, differential diagnosis, etiologies, diagnosis, and treatment. Method: A narrative bibliographic review has been carried out through the PubMed, Scopus, Google Scholar, and Clinical Key databases. Articles on vestibular nystagmus and clinical cases were excluded. Results: Seventeen articles, book chapters and clinical guidelines of the American Society of Ophthalmology and the Spanish Society of Ophthalmology have been analyzed. Discussion: There are various types of non-vestibular nystagmus that can debut in the pediatric age: infantile nystagmus syndrome, classically called congenital nystagmus, the most frequent; nystagmus syndrome due to maldevelopment of fusion, classically known as latent nystagmus, the second most frequent and related to amblyopia; Spasmus nutans, a syndrome characterized by nystagmus, nodding, and torticollis, the third most frequent; monocular nystagmus such as the Heimann-Bielchowsky phenomenon or myokymia of the superior oblique muscle; alternating periodic nystagmus, which cyclically changes direction, amplitude, and frequency; downbeat nystagmus, most frequent central nystagmus; acquired pendular nystagmus, which may be related to masticatory or palatal disorders; and see-saw nystagmus, with “up and down” eye movement similar to a see-saw. There are also three main types of non-nystagmic saccadic intrusions, which correspond to the opsoclonus syndrome, consisting of disordered multiplanar saccades that can be associated with myoclonus and ataxia ocular bobbing, with vertical saccadic movements and ocular flutter, with horizontal saccadic movements. Conclusions: The characteristics of the different types of non-vestibular nystagmus and non-nystagmic saccadic intrusions and their possible etiologies should be known, since in a large percentage of cases the underlying cause is serious, frequently neurological. In the same way, we must know how to carry out the diagnosis and the therapeutic options that we have within our reach to improve the quality of life of patients. [ABSTRACT FROM AUTHOR]

Human eye fixation is steadily interrupted by small, physiological or abnormal, eye movements. Square-wave jerks (SWJ) are the most common saccadic intrusion which can be readily seen at the bedside and also quantified using oculographic techniques. Various neurological, neuropsychiatric and psychiatric disorders display abnormal fixational eye movement patterns characterized by frequent SWJ. For the clinician, SWJ are particularly important because they can be readily observed at the bedside. Here, we will discuss the pathological conditions that present with SWJ and explore the expanding body of literature suggesting that SWJ may serve as a potential indicator for various clinical conditions.

During the attempt to steadily fixate at a single spot, sequences of small involuntary fixation saccades (SIFSs, known also as microsaccades οr intrusions) occur which form spatio-temporal patterns such as square wave jerks (SWJs), a pattern characterised by alternating centrifugal and centripetal movements of similar magnitude. In many neurodegenerative disorders, SIFSs exhibit elevated amplitudes and frequencies. Elevated SIFS amplitudes have been shown to favour the occurrence of SWJs ("SWJ coupling"). We analysed SIFSs in different subject groups comprising both healthy controls (CTR) and patients with amyotrophic lateral sclerosis (ALS) and progressive supranuclear palsy (PSP), i.e. two neurodegenerative diseases with completely different neuropathological basis and different clinical phenotypes. We show that, across these groups, the relations between SIFS amplitude and the relative frequency of SWJ-like patterns and other SIFS characteristics follow a common law. As an explanation, we propose that physiological and technical noise comprises a small, amplitude-independent component that has little effect on large SIFSs, but causes considerable deviations from the intended amplitude and direction of small ones. Therefore, in contrast to large SIFSs, successive small SIFSs have a lower chance to meet the SWJ similarity criteria. In principle, every measurement of SIFSs is affected by an amplitude-independent noise background. Therefore, the dependence of SWJ coupling on SIFS amplitude will probably be encountered in almost any group of subjects. In addition, we find a positive correlation between SIFS amplitude and frequency in ALS, but none in PSP, suggesting that the elevated amplitudes might arise at different sites in the two disorders. [ABSTRACT FROM AUTHOR]

Purpose: To report a case of saccadic intrusions in a 9-month-old under the context of non-accidental trauma. Observations: A 9-month-old female presented with the eye finding of intermittent ocular flutter. Upon imaging for neuroblastoma, she was discovered to have bilateral supratentorial subdural hematomas with internal septations, moderate mass effect on adjacent cerebral parenchyma, pachymeningeal and tentorial enhancement, and cortical vein thrombosis. This constellation of findings was concerning for non-accidental trauma. Conclusions and importance: Although an extremely rare occurrence, ocular flutter may be a presenting sign in non-accidental trauma, and imaging should absolutely be considered under such circumstances.

Eye movements serve vision in orienting gaze toward an object of interest in order to place its image simultaneously on both foveas and in stabilizing gaze relative to the environment in order to maintain fixation on the object of interest, even in the case of body displacement. Disorders of eye movements can interfere with ocular alignment and/or monocular motility, and result in diplopia, which is the most common symptom. Eye movement disorders can also interfere with binocular motility without ocular misalignment and result in gaze palsy. Finally, disorders of eye movement can interfere with ocular stability during fixation or body displacement and result in oscillopsia, which is an illusion of an unstable visual world. A systematic examination of eye movements should be part of the neurological exam in order to detect asymptomatic manifestations that can help for the diagnosis of multiple neurological pathologies. In the case of eye movement disorders, the goals of the examination are to precisely characterize the disorder of motility, alignment, or stability, in order to finally localize anatomically the lesion among the peripheral ocular motor system or the more complex central eye movement neural network and suggest mechanisms and etiologies. In this review, we are describing the standard methods of ocular motor examination, including a "general" approach to any ocular motor assessment, and also the specific approaches to evaluating ocular misalignment, difficulty moving both eyes, and finally unstable gaze. This article will include practical tips on how to perform the tests most effectively or how to interpret the clinical signs elicited. [ABSTRACT FROM AUTHOR]

Saccadic intrusions such as opsoclonus and ocular flutter are often due to a paraneoplastic or a parainfectious condition. Toxins/drugs may rarely cause them. Herein, we report a rare case of ocular flutter/opsoclonus due to phencyclidine (PCP) toxicity. Our patient is a 21-year-old male who presented with a 3-day history of headache, generalized ill health, and aggressive behavior. He was admitted with reduced level of consciousness following generalized seizures. He had features of sympathetic overactivity with ocular flutter and opsoclonus. Urine toxicology was positive for PCP. Despite supportive care, he succumbed to complications of rhabdomyolysis. Several drugs including cocaine, phenytoin, lithium, and amitriptyline are known to cause ocular flutter/opsoclonus rarely. It is poorly described with PCP. This case highlights PCP as a rare cause of toxin-induced saccadic intrusions and attempts to postulate its pathogenesis. Moreover, our report is the first case of PCP intoxication in Sri Lanka and one of the few documented reports in the South Asian region. Therefore, it represents a significant worrisome alarm about the spread of this substance in this region.

The attempt to steadily fixate at a small visual object is continuously interrupted by a variety of fixational eye movements comprising, among others, a continuum of saccadic intrusions (SI) which ranges in size from microsaccades with amplitudes ≤0.25° to larger refixation saccades of up to about 2°. The size and frequency of SI varies considerably among individuals and is known to increase in neurodegenerative diseases such as neurodegenerative parkinsonism and amyotrophic lateral sclerosis (ALS). However, studies of ALS disagree whether also the frequency of SI increases. We undertook an analysis of SI in 119 ALS patients and 47 age-matched healthy controls whose eye movements during fixation and tests of executive functions (e.g antisaccades) had been recorded by video-oculography according to standardised procedures. SI were categorised according to their spatio-temporal patterns as stair case, back-and-forth and square wave jerks (a subcategory of back-and-forth). The SI of patients and controls were qualitatively similar (same direction preferences, similar differences between patterns), but were enlarged in ALS. Notably however, no increase of SI frequency could be demonstrated. Yet, there were clear correlations with parameters such as eye blink rate or errors in a delayed saccade task that suggest an impairment of inhibitory mechanisms, in keeping with the notion of a frontal dysfunction in ALS. However, it remains unclear how the impairment of inhibitory mechanisms in ALS could selectively increase the amplitude of intrusions without changing their frequency of occurrence.

Human eye fixation is steadily interrupted by small, physiological or abnormal, eye movements. Square-wave jerks (SWJ) are the most common saccadic intrusion which can be readily seen at the bedside and also quantified using oculographic techniques. Various neurological, neuropsychiatric and psychiatric disorders display abnormal fixational eye movement patterns characterized by frequent SWJ. For the clinician, SWJ are particularly important because they can be readily observed at the bedside. Here, we will discuss the pathological conditions that present with SWJ and explore the expanding body of literature suggesting that SWJ may serve as a potential indicator for various clinical conditions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zachou, Armenis, Stamelos, Stratigakou-Polychronaki, Athanasopoulos and Anagnostou.)

The attempt to quietly fixate at a small visual object is continuously interrupted by a variety of fixational eye movements comprising, among others, a continuum of saccadic intrusions (SI) which range in size from microsaccades with amplitudes ≤0.25° to larger refixation saccades of up to about 2°. The size and frequency of SI varies considerably among individuals and is known to increase in neurodegenerative diseases such as progressive supranuclear palsy (PSP), and amyotrophic lateral sclerosis (ALS). However, studies of ALS disagree whether also the frequency of SI increases. We undertook an analysis of SI in 119 ALS patients and 47 age-matched healthy controls whose eye movements during fixation and tests of executive functions (e.g antisaccades) had been recorded by video-oculography according to standardised procedures. SI were categorised according to their spatio-temporal patterns as stair case, back-and-forth and square wave jerks (a subcategory of back-and-forth). The SI of patients and controls were qualitatively similar (same direction preferences, similar differences between patterns), but were enlarged in ALS. Notably however, no increase of SI frequency could be demonstrated. Yet, there were clear correlations with parameters such as eye blink rate or errors in a delayed saccade task that suggest an impairment of inhibitory mechanisms, in keeping with the notion of a frontal dysfunction in ALS. However, it remains unclear how the impairment of inhibitory mechanisms in ALS could selectively increase the amplitude of intrusions without changing their frequency of occurrence. [ABSTRACT FROM AUTHOR]

Saccadic intrusions are small involuntary saccadic movements that disrupt visual fixation. Among saccadic intrusions without intersaccadic intervals, ocular flutter and opsoclonus are prominent. The saccade amplitude can occasionally be very small, which is referred to as ocular microflutter. The authors present a patient with acute-onset oscillopsia following a non-specific viral condition. An ocular microflutter was subsequently detected using video-oculography. After extensive investigation, a diagnosis of isolated idiopathic or post-viral ocular microflutter was made. The evolution of the condition was favourable, and the progressive improvement of oscillopsia occurred during the following months; however, complete resolution was not achieved. Ocular microflutter is a saccadic intrusion that is rarely described in the literature and is likely go clinically unnoticed because of its small amplitude and the rare use of video-oculography in daily practice. In patients in whom this condition is suspected, the use of video-oculography is essential for a correct diagnosis. [ABSTRACT FROM PUBLISHER]

Saccadic intrusions such as opsoclonus and ocular flutter are often due to a paraneoplastic or a parainfectious condition. Toxins/drugs may rarely cause them. Herein, we report a rare case of ocular flutter/opsoclonus due to phencyclidine (PCP) toxicity. Our patient is a 21-year-old male who presented with a 3-day history of headache, generalized ill health, and aggressive behavior. He was admitted with reduced level of consciousness following generalized seizures. He had features of sympathetic overactivity with ocular flutter and opsoclonus. Urine toxicology was positive for PCP. Despite supportive care, he succumbed to complications of rhabdomyolysis. Several drugs including cocaine, phenytoin, lithium, and amitriptyline are known to cause ocular flutter/opsoclonus rarely. It is poorly described with PCP. This case highlights PCP as a rare cause of toxin-induced saccadic intrusions and attempts to postulate its pathogenesis. Moreover, our report is the first case of PCP intoxication in Sri Lanka and one of the few documented reports in the South Asian region. Therefore, it represents a significant worrisome alarm about the spread of this substance in this region. [ABSTRACT FROM AUTHOR]

A large amount of classic and contemporary vision studies require subjects to fixate a target. Target fixation serves as a normalizing factor across studies, promoting the field’s ability to compare and contrast experiments. Yet, fixation target parameters, including luminance, contrast, size, shape and color, vary across studies, potentially affecting the interpretation of results. Previous research on the effects of fixation target size and luminance on the control of fixation position rendered conflicting results, and no study has examined the effects of fixation target characteristics on square-wave jerks, the most common type of saccadic intrusion. Here we set out to determine the effects of fixation target size and luminance on the characteristics of microsaccades and square-wave jerks, over a large range of stimulus parameters. Human subjects fixated a circular target with varying luminance and size while we recorded their eye movements with an infrared video tracker (EyeLink 1000, SR Research). We detected microsaccades and SWJs automatically with objective algorithms developed previously. Microsaccade rates decreased linearly and microsaccade magnitudes increased linearly with target size. The percent of microsaccades forming part of SWJs decreased, and the time from the end of the initial SWJ saccade to the beginning of the second SWJ saccade (SWJ inter-saccadic interval; ISI) increased with target size. The microsaccadic preference for horizontal direction also decreased moderately with target size . Target luminance did not affect significantly microsaccades or SWJs, however. In the absence of a fixation target, microsaccades became scarcer and larger, while SWJ prevalence decreased and SWJ ISIs increased. Thus, the choice of fixation target can affect experimental outcomes, especially in human factors and in visual and oculomotor studies. These results have implications for previous and future research conducted under fixation conditions, and should encourage forthcoming studies to report the size of fixation targets to aid the interpretation and replication of their results.

During visual fixation, the eyes are never completely still, but produce small involuntary movements, called 'fixational eye movements,' including microsaccades, drift, and tremor. In certain neurological disorders, attempted fixation results in abnormal fixational eye movements with distinctive characteristics. Thus, determining how normal fixation differs from pathological fixation has the potential to aid early and differential noninvasive diagnosis of neurological disease as well as the quantification of its progression and response to treatment. Here, we recorded the eye movements produced by patients with Alzheimer's disease, patients with mild cognitive impairment, and healthy age-matched individuals during attempted fixation. We found that microsaccade magnitudes, velocities, durations, and intersaccadic intervals were comparable in the three subject groups, but microsaccade direction differed in patients versus healthy subjects. Our results indicate that microsaccades are more prevalently oblique in patients with Alzheimer's disease or mild cognitive impairment than in healthy subjects. These findings extended to those microsaccades paired in square-wave jerks, supporting the hypothesis that microsaccades and square-wave jerks form a continuum, both in healthy subjects and in neurological patients. [ABSTRACT FROM AUTHOR]

Chiari type II malformation is a congenital deformity of the hindbrain. Square wave jerks are horizontal involuntary saccades that interrupt fixation. Cerebellar disorders may be associated with frequent square wave jerks or saccadic oscillations such as ocular flutter. The effects of Chiari type II malformation on visual fixation are unknown. We recorded eye movements using an eye tracker in 21 participants with Chiari type II malformation, aged 8 to 19 years while they fixated a target for 1 minute. Thirty-eight age-matched healthy participants served as controls. Square wave jerks' parameters were similar in the 2 groups. Saccadic oscillations were not seen. Chiari type II malformation is not associated with pathological square wave jerks or abnormal saccadic oscillations. The congenital nature of this deformity may permit compensation that preserves stable visual fixation. Alternatively, the deformity of Chiari type II malformation may spare parts of the cerebellum that usually cause fixation instability when damaged. [ABSTRACT FROM AUTHOR]

Albinism effects a surprising manipulation of the visual pathway in which some of the normally uncrossed axons of the temporal retina instead cross at the chiasm. An expected consequence of this misrouting is that subjects with albinism will have difficulty in specifying the targets of saccades. Usually albinos have nystagmus so the stability of their saccadic eye movements is not readily accessible, but some albinos do not have nystagmus. In these subjects it was found that they had frequent saccadic intrusions, the sizes of which were correlated with velocities of steady drifts in fixations ( r = 0.802, P < 0.05). An explanation for the correlation between the amplitudes of the intrusions and the velocities of the drifts is that it is due to a common failure in the development of a saccadic system which is responsible for converting a given retinal displacement into a matching eye movement, with the extent of the failure reflecting the severity of the misrouting. [ABSTRACT FROM AUTHOR]

Abstract: Eye movements during fixation were recorded in 55 normal subjects with ages ranging from 21 to 81 years. We analysed ocular fixation recordings using measurements of saccadic intrusion amplitudes and frequencies along with fixation periods and mean fixation displacement. Viewing conditions included monocular, binocular and presence or absence of a visual fixation target. Visual feedback reduced the saccadic intrusion amplitudes but had no effect on fixation periods or mean fixation displacements. Binocular viewing had no effect on saccadic intrusion amplitudes, fixation periods or mean fixation displacements. A decrease in fixation periods and an increase in the number of saccadic intrusions with age was observed. This approach could be a clinically useful tool to quantify ocular fixation in neurological disease. [Copyright &y& Elsevier]

We present hypothesized ocular motor mechanisms of unique “staircase-like” sequences of saccadic intrusions in one direction that we have named, “staircase saccadic intrusions (SSI),” square-wave jerks/oscillations (SWJ/SWO), and transient failures of yoking and neural integrators in a patient with severe hypotonia, ataxic speech, motor and language developmental delays, and torticollis (Joubert syndrome). Brain magnetic resonance imaging showed hypoplasia of the cerebellar vermis and inferior cerebellar peduncles, abnormal superior cerebellar peduncles with deepening of the interpeduncular fossa, and enlargement of the fourth ventricle. During far and near fixation and smooth pursuit (rightward markedly better than leftward), the subject exhibited conjugate SSI (rightward more than leftward, with intersaccadic intervals equivalent to the normal 250 msec visual latency), SWJ, SWO, and uniocular, convergent and divergent saccades (including double saccades). Simulations using a behavioral ocular motor system model identified hypothetical mechanisms for SWJ, SWO, and SSI and ruled out the loss of efference copy as the cause. SSI may result from simultaneous dysfunctions: 1) a transient loss of accurate retinal-error information and/or sampled, reconstructed error; plus 2) a constant sampled, reconstructed retinal error that drives saccades. [ABSTRACT FROM AUTHOR]

Primary gaze fixation is never perfectly stable but can be interrupted by involuntary, conjugate saccadic intrusions (SI). SI have a high prevalence in the normal population and are characterised by a horizontal fast eye movement away from the desired eye position, followed, after a variable duration, by a return saccade or drift. Amplitudes are usually below 1° and they often exhibit a directional bias. The aim of the present study was to investigate the aetiology of SI in relation to saccadic behaviour. It was hypothesised that if SI resulted from deficits in the saccadic system (i.e. reduced inhibitory mechanisms), changes in voluntary saccade behaviour may be apparent and related to SI frequency. To examine this, synchrony (no gap), gap, overlap and antisaccade tasks were conducted on ten normal subjects. No significant correlations were found between SI frequency and voluntary saccade latencies, the percentage of express saccades, or the percentage of antisaccade errors. In addition, no significant correlations were found between SI directional biases and saccade latency directional biases, express saccade biases or antisaccade error biases. These results suggest that an underlying alteration to saccadic behaviour is unlikely to be involved in SI production, and that the SI command signal may arise from the influence of attention on an intact saccadic system. Specifically, descending corticofugal signals relating to attention level and orientation may alter the balance between fixation and saccade generation, so determining SI characteristics. [ABSTRACT FROM AUTHOR]

Primary fixation is never perfectly stable, but is frequently interrupted by slow drifts, microsaccades and saccadic intrusions (SI). SI are involuntary, conjugate movements which take the form of an initial fast movement away from the desired eye position and followed after a short duration, by either a return secondary saccade or a drift. The purpose of this study was to examine the prevalence and metrics of SI in a population of 50 healthy subjects. Using both one and two dimensional recordings we find that all 50 members of the subject group exhibited SI. The SI were bilateral, conjugate and horizontal. No purely vertical SI were detected when examined in three subjects. SI amplitude mean and range was 0.6°±0.5°, 0.1°–4.1°; SI frequency mean and range was 18.0±14.3 per min, 1.0–54.8 per min; SI duration mean and range was 225±150, 20–870 ms. The mean SI amplitude and frequency when SI<0.5° were removed was 0.97°±0.56° and 7.0±11.4 per min respectively. Age was positively correlated with SI amplitude (p<0.01), but there was no correlation between age and SI frequency. Three of four types of SI monophasic square wave intrusions (MSWI), biphasic square wave intrusions (BSWI) and double saccadic pulses (DSP) were found to be exclusively saccadic, whilst the fourth type, the single saccadic pulses (SSP), were confirmed to exhibit a slow secondary component. MSWI were the most frequently observed SI occurring in 47 out of 50 (94%) of the subjects with a mean amplitude, frequency and duration of 0.7°±0.5°, 11.5±11.6 per min, and 255±147 ms respectively. Mean amplitudes and frequencies for BSWI (n=20), SSP (n=11) and DSP (n=34) were found to be 0.50°±0.2°, 1.2±2.5 per min; 0.40°±0.20°, 0.4±1.0 per min and 0.3°±0.4°, 5.0±8.7 per min respectively. No differences in MSWI characteristics were found between binocular and monocular viewing. Possible explanations for SI occurrence include experimental viewing conditions, subject fatigue and covert shifts in attention. [Copyright &y& Elsevier]

Nystamus in the infant is an important sign of a problem in the sensory/motor loop that controls eye position stability. Nystagmus, a repetitive oscillation of the eyes, must be differentiated clinically from saccadic intrusions. In infantile nystagmus, the time of onset and the history of ocular/visual symptoms and neurological symptoms help in directing our diagnosis. The ocular examination usually helps define ocular causes, with little serious visual loss. The ERG is essential to rule out retinal causes when the eye exam seems normal. Late onset nystagmus, even though it has the clinical characteristics of an ocular type of nystagmus, should raise the possibility of brain tumor. Strabismus-associated nystagmus forms include Binocular Deficiency Nystagmus Syndrome (BDNS) and Ciancia Syndrome. Neurological types of nystagmus often have anatomically localizing value for the pathology. Some knowledge of nystagmus helps the orthoptist understand sensory consequences and the clinical perspective for analysis of eye movement disorders. [ABSTRACT FROM AUTHOR]

An electro-oculogram based eye tracking system (the Cardiff System for the Generation and Analysis of Saccades) was used to quantify smooth pursuit eye movements (SPEM) and saccadic intrusions in 20 chronic schizophrenic patients and 16 normal, healthy controls. Statistically significant differences were found between the two groups at all four target frequencies tested (0·2, 0·25, 0·33 and 0·5 Hz) in three measures of SPEM dysfunction (position error, velocity error and saccadic intrusions). Of the patients' position errors, 50–70 per cent were greater than the 95th percentile for controls. Velocity errors gave a similar range of SPEM dysfunction (50–65 per cent) but the frequency of saccadic intrusion abnormality was more variable (20–60 per cent). Position error and saccadic intrusions, at the fastest target speed, correlated with total BPRS scores. Extrapyramidal symptoms (Simpson and Angus) and abnormal involuntary movements also correlated with saccadic intrusions at 0·5 Hz. There were no significant correlations between SPEM dysfunction and age, duration of illness, negative symptoms (total SANS score) or current dose of antipsychotic drug treatment. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Neurology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A 6.5-year-old male neutered Trailhound was admitted for hyperacute, nonprogressive, left-sided hemiparesis. Physical and neurologic examination revealed nonpainful, left-sided poorly ambulatory hemiparesis, decreased left-sided postural reactions and thoracic limbs hyporeflexia. Neuroanatomic localisation was consistent with a left-sided C6-T2 myelopathy. Haematology and biochemistry revealed nonspecific abnormalities. Magnetic resonance imaging of the neck revealed a focal intramedullary lesion at the level of C6-C7 vertebrae compatible with acute hydrated noncompressive nucleus pulposus extrusion or ischemic myelopathy. During the second day of hospitalization, the dog developed convergence-retraction nystagmus, up-gaze palsy and eyelid retraction (Collier's sign) compatible with dorsal midbrain syndrome. Magnetic resonance imaging of the brain revealed a focal lesion compatible with dorsal midbrain ischemic infarct. Further clinicopathologic testing, thoracic and abdominal imaging were unremarkable. Ischemic encephalopathy of unknown etiology was additionally diagnosed. Physiotherapy was performed therapeutically. At 1-year follow-up the dog was normal. This is an unusual report of a dog with myelopathy followed by ischemic encephalopathy with manifestation of convergence-retraction nystagmus in the absence of vestibular signs. This saccadic intrusion is a characteristic clinical manifestation of a dorsal midbrain syndrome localization. The importance of a complete differential diagnoses list formation in a dog with ischemic encephalopathy which leads to a thorough diagnostic investigation plan is highlighted. Moreover, this report contributes to the enrichment of the clinical reasoning veterinary literature on convergence-retraction nystagmus. To the authors' knowledge, this is the second case report (fourth dog) to describe convergence-retraction nystagmus in dogs as a manifestation of dorsal midbrain syndrome. [ABSTRACT FROM AUTHOR]