Suppression of spontaneous nystagmus during different visual fixation conditions

Effect of ocular fixation on positional nystagmus in BPPV patients

OBJECTIVE

The quantitative suppression rate of positional nystagmus (PN) by ocular fixation (OF) is unknown. This study aims to analyse the effect of OF on the slow phase velocity (SPV) of PN during diagnostic positional manoeuvres (DPMs) with videonystagmography in patients with benign paroxysmal positional vertigo (BPPV).

DESIGN

DPMs were performed on 58 patients with BPPV, 33 (56.9%) of whom were women. OF was initiated when PN was most evident, and recording was continued. The mean SPV of three consecutive nystagmus before (F0) and after (F1) OF initiation was calculated. The rate of suppression of PN by OF was found in percent with the formula (F0 - F1) x 100/F0.

STUDY SAMPLE

58 patients were included in this study.

RESULTS

The mean age was 56.1 ± 11.2 (range 27-76). F0 and F1 values were calculated as 5.742 ± 5.589 and 1.948 ± 3.424 degrees/second, respectively (p < 0.001). The rate of suppression of PN by OF was found to be 66.1%.

CONCLUSIONS

OF significantly suppresses PN during DPMs in BPPV patients. Elimination of OF during DPMs is important for accurate diagnosis.

The Role of the Smartphone in the Diagnosis of Vestibular Hypofunction: A Clinical Strategy for Teleconsultation during the COVID-19 Pandemic and Beyond

Introduction  Vestibular disorders (VDs) are highly prevalent in primary care. Although in general they comprise conditions that are not life-threatening, they are associated with significant functional and physical disability. However, the current coronavirus disease 2019 (COVID-19) pandemic has imposed limitations on the standard treatment of benign conditions, including VDs. In this context, other resources may aid in the diagnosis and management of patients with VDs. It is well known that teleconsultation and teletreatment are both safe and effective alternatives to manage a variety of conditions, and we maintain that VDs should be among these. Objective  To develop a preliminary model of clinical guidelines for the evaluation by teleconsultation of patients with suspected diagnosis of vestibular hypofunction during the COVID-19 pandemic and beyond. Methods  A bibliographic review of the diagnostic feasibility in VDs by teleconsultation was carried out in the LILACS, SciELO, MEDLINE, and PubMed databases; books and specialized websites were also consulted. The legal, regulatory, and technical issues involving digital consultations were reviewed. Results  We found 6 field studies published between 1990 and 2020 in which the efficiency of teleconsultations was observed in the contexts of epidemics and environmental disorders and disadvantageous geographical conditions. After reviewing them, we proposed a strategy to examine and address vestibular complaints related to vestibular hypofunction. Conclusion  The creation of a digital vestibular management algorithm for the identification, counseling, initial intervention, monitoring and targeting of people with possible vestibular hypofunction seems to be feasible, and it will provide a reasonable alternative to in-person evaluations during the COVID-19 pandemic and beyond.

Dizzy triathlete-evidence supporting vestibular etiology

Dizziness during or after the swimming leg is a common complaint among triathletes. We hypothesized that the dizziness is caused by asymmetrical cooling of the vestibular organ. This caloric response is characterized by involuntary eye movements called nystagmus. Altogether, 125 triathletes completed an electronic questionnaire. Fifteen triathletes who had frequently experienced dizziness during the swimming leg agreed to take part in a cold water swimming test. The test comprised two cold water swimming legs, first without earplugs and then with earplugs to prevent a potential caloric response. Eye movements and possible nystagmus were recorded immediately after the swimming legs. A majority (87%, 109/125) of athletes had experienced dizziness during triathlon races or training. Of these, almost all (97%, 106/109) experienced it during or after swimming. Dizziness affected the triathlon performance in half of the athletes with dizziness (50%, 51/102). Fifteen athletes participated in a cold water swimming test. During the first leg (without earplugs), 11/15 athletes (73%) experienced dizziness. Of these, six had nystagmus (55%), four had uncertain nystagmus (36%), and one did not have nystagmus (9%). Only one of these athletes experienced dizziness during the second leg with earplugs. The prevalence of dizziness among triathletes is notable. A large part of the dizziness is likely to be caused by caloric reaction of the vestibular organ. We recommend earplug usage for triathletes suffering from dizziness during the swimming leg.

Impaired fixation suppression of horizontal vestibular nystagmus during smooth pursuit: pathophysiology and clinical implications

Background and purpose

A peripheral spontaneous nystagmus (SN) is typically enhanced or revealed by removing fixation. Conversely, failure of fixation suppression of SN is usually a sign of a central disorder. Based on Luebke and Robinson (Vision Res 1988, vol. 28 (8), pp. 941–946), who suggested that the normal fixation mechanism is disengaged during pursuit, it is hypothesized that vertical tracking in the light would bring out or enhance a horizontal SN.

Methods

Eighteen patients with acute vestibular neuritis were studied. Eye movements were recorded using video‐oculography at straight‐ahead gaze with and without visual fixation, and during smooth pursuit. The slow‐phase velocity and the fixation suppression indices of nystagmus (relative to SN in darkness) were compared in each condition.

Results

During vertical tracking, the slow‐phase velocity of horizontal SN with eyes near straight‐ahead gaze was significantly higher (median 2.7°/s) than under static visual fixation (median 1.2°/s). Likewise, the fixation index was significantly higher (worse suppression) during pursuit (median 48%) than during fixation (median 26%). A release of SN was also suggested during horizontal pursuit, if one assumes superposition of SN on a normal and symmetrical pursuit capability.

Stroke Prediction Based on the Spontaneous Nystagmus Suppression Test in Dizzy Patients: A Diagnostic Accuracy Study

OBJECTIVE

Failure of fixation suppression of spontaneous nystagmus is sometimes seen in patients with vestibular strokes involving the cerebellum or brainstem; however, the accuracy of this test for the discrimination between peripheral and central causes in patients with an acute vestibular syndrome (AVS) is unknown.

METHODS

Patients with AVS were screened and recruited (convenience sample) as part of a prospective cross-sectional study in the emergency department between 2015 and 2020. All patients received neuroimaging, which served as a reference standard. We recorded fixation suppression with video-oculography (VOG) for forward, right, and left gaze. The ocular fixation index (OFI) and the spontaneous nystagmus slow velocity reduction was calculated.

RESULTS

We screened 1,646 patients reporting dizziness in the emergency department and tested for spontaneous nystagmus in 148 patients with AVS. We analyzed 56 patients with a diagnosed acute unilateral vestibulopathy (vestibular neuritis) and 28 patients with a confirmed stroke. There was a complete nystagmus fixation suppression in 49.5% of patients with AVS, in 40% of patients with vestibular neuritis, and in 62.5% of patients with vestibular strokes. OFI scores had no predictive value for detecting strokes; however, a nystagmus reduction of less than 2 °/s showed a high accuracy of 76.9% (confidence interval 0.59-0.89) with a sensitivity of 62.2% and specificity of 84.8% in detecting strokes.

CONCLUSIONS

The presence of fixation suppression does not rule out a central lesion. The magnitude of suppression was lower compared to patients with vestibular neuritis. The nystagmus suppression test predicts vestibular strokes accurately provided that eye movements are recorded with VOG.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in patients with an AVS, decreased fixation suppression recorded with VOG occurred more often in stroke (76.9%) than in vestibular neuritis (37.8%).

Nystagmus goggles: how to use them, what you find and what it means

A fundamental characteristic of peripheral vestibular nystagmus, in particular horizontal nystagmus, is that it is suppressed by visual fixation. This means that a patient with a vertigo attack of peripheral vestibular origin might have no obvious spontaneous nystagmus on clinical examination. Goggles that reduce or remove visual fixation allow the cliniican to observe nystagmus in this situation. Nystagmus goggles are essential for any clinician dealing with dizzy patients. Here, we discuss why this is so and how easy it is to acquire and use them.

Clinical significance of spontaneous nystagmus in pediatric patients

OBJECTIVE

To analyze spontaneous nystagmus recorded in pediatric patients and determine its diagnostic value.

MATERIALS AND METHODS

Retrospective review of 86 patients (mean age = 13.9 ± 4.7 years) with definitive spontaneous nystagmus recorded by videonystagmography (VNG). Spontaneous nystagmus was categorized and analyzed based on its characteristics. Correlations between spontaneous nystagmus and established clinical diagnoses were explored.

RESULTS

Among the patients seen in a period of three years at our pediatric vestibular clinic, 15.4% (86 out of 560) were found to have spontaneous nystagmus and half of them had horizontal nystagmus with a fixed-direction. The majority of cases with spontaneous nystagmus (77%, 66/86) were present without fixation only, while the presence of spontaneous nystagmus with and without fixation was found in 16 patients (19%). Most patients with spontaneous nystagmus without fixation only (68%) were diagnosed with a peripheral vestibular disorder (e.g., vestibular neuritis) or vestibular migraine. In contrast, vertical nystagmus was found in 15 patients, most of whom had central vestibular disorders. Other rare forms of nystagmus or abnormal eye movements, such as pendular nystagmus, ocular oscillation or flutter were recorded in only four patients.

CONCLUSIONS

Spontaneous nystagmus in children and young adults with possible vestibular impairments may vary in clinical presentation. Identification of its characteristics may help to make an accurate clinical diagnosis. While spontaneous nystagmus associated with peripheral vestibular disorders can be readily recognized, spontaneous nystagmus in pediatric patients with vestibular migraine appears to be more complex and variable in form.

Failure of Fixation Suppression of Spontaneous Nystagmus in Cerebellar Infarction: Frequency, Pattern, and a Possible Structure

To investigate the frequency and pattern of failure of the fixation suppression (FFS) of spontaneous nystagmus (SN) in unilateral cerebellar infarction, and to identify the structure responsible for FFS, 29 patients with acute, mainly unilateral, isolated cerebellar infarction who had SN with a predominantly horizontal component were enrolled in this study. The ocular fixation index (OFI) was defined as the mean slow phase velocity (SPV) of the horizontal component of SN with fixation divided by the mean SPV of the horizontal component of SN without fixation. The OFI from age- and sex-matched patients with vestibular neuritis was calculated and used as the control data. The FFS of SN was only found in less than half (41 %, 12/29) of the patients. Approximately 65 % (n = 7) of the patients with isolated anterior inferior cerebellar artery territory cerebellar infarction showed FFS, whereas only a quarter (n = 3) of the patients with isolated posterior inferior cerebellar artery (PICA) territory cerebellar infarction showed FFS. The proportion of gaze-evoked nystagmus (6/12 [50 %] vs. 2/17 [12 %], p = 0.04) and deficient gain of ipsilesional pursuit (10/12 [83 %] vs. 6/17 [35 %], p = 0.05) was more frequent in the FFS group than in the group without FFS. Lesion subtraction analysis in isolated PICA territory cerebellar infarction revealed that the nodulus was commonly damaged in patients with FFS, compared to that of patients without FFS. Our study shows that FFS of SN due to acute cerebellar infarction is less common than previously thought and the nodulus may be an important structure for the suppression of SN in humans.

Prevalence and Characteristics of Positional Nystagmus in Normal Subjects

OBJECTIVE

In clinical practice, patients are often referred due to a finding of positional nystagmus that does not always appear to correlate with clinical symptoms of benign paroxysmal positional vertigo. To know when to consider nystagmus to be of clinical relevance, it is necessary to know the prevalence and characteristics of positional nystagmus in a healthy population.

STUDY DESIGN

Case series of 75 healthy subjects.

SETTING

Two tertiary referral centers in Norway.

SUBJECTS AND METHODS

Seventy-five adult subjects aged 40 ± 13 years (mean ± SD; range, 21-87) without a history of vertigo or balance disorder were included from 2013 to 2015. The subjects underwent 6 different standardized positional tests in a repositioning chair. Videonystagmography was used to record eye movements. Of 1350 recordings, 1329 were included and analyzed.

RESULTS

Positional nystagmus was detected in 88% of the subjects. The most common finding was nystagmus in the Dix-Hallpike position, which occurred in 55% of the subjects. The 95th percentile of the maximum slow-phase velocity for each subject was found to be 5.06° per second (n = 54) in the horizontal plane and 6.48° per second (n = 48) in the vertical plane.

CONCLUSION

Positional nystagmus is a common finding in normal subjects and occurred in 88% of the healthy subjects in the present study. Horizontal direction-changing apogeotropic or geotropic nystagmus may occur in asymptomatic subjects. However, nystagmus that is of the paroxysmal type or has a slow-phase velocity greater than approximately 5° per second in the horizontal plane or 6.5° per second in the vertical plane should be considered outside the 95th percentile.

Recent onset disequilibrium mimicking acute vestibulopathy in early multiple sclerosis

The differential diagnosis of patients with acute unilateral vestibulopathy rests in the proper clinical assessment and use of selected tests of vestibular function. In case of a central nervous system lesion as in Multiple Sclerosis, the case shown here, it is of particular importance to observe congruency between severity of symptoms and signs and, of topographic diagnosis. We report a case of a 37-year-old woman with recent onset disequilibrium that after careful analysis of the different test results several incongruences were found; this prompted a radiological study that provided the clue to diagnosis. After treatment the patient recovered completely not only clinically but also in vestibular deficit.