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Abstract of the Week

June Topic of the month: Visual Dependence

No 477: June 26, 2019

Roberts RE, Da Silva Melo M, Siddiqui AA, Arshad Q, Patel M. Vestibular and oculomotor influences on visual dependency.  J Neurophysiol. 2016 Sep 1;116(3):1480-7. doi: 10.1152/jn.00895.2015. Epub 2016 Jun 29.

Abstract

The degree to which a person relies on visual stimuli for spatial orientation is termed visual dependency (VD). VD is considered a perceptual trait or cognitive style influenced by psychological factors and mediated by central reweighting of the sensory inputs involved in spatial orientation. VD is often measured with the rod-and-disk test, in which participants align a central rod to the subjective visual vertical (SVV) in the presence of a background that is either stationary or rotating around the line of sight-dynamic SVV. Although this task has been employed to assess VD in health and vestibular disease, what effect torsional nystagmic eye movements may have on individual performance is unknown. Using caloric ear irrigation, 3D video-oculography, and the rod-and-disk test, we show that caloric torsional nystagmus modulates measures of VD and demonstrate that increases in tilt after irrigation are positively correlated with changes in ocular torsional eye movements. When the direction of the slow phase of the torsional eye movement induced by the caloric is congruent with that induced by the rotating visual stimulus, there is a significant increase in tilt. When these two torsional components are in opposition, there is a decrease. These findings show that measures of VD can be influenced by oculomotor responses induced by caloric stimulation. The findings are of significance for clinical studies, as they indicate that VD, which often increases in vestibular disorders, is modulated not only by changes in cognitive style but also by eye movements, in particular nystagmus.

PMID: 27358321

Link to free article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5040385/

No 476: June 19, 2019

Maire R, Mallinson A, Ceyte H, Caudron S, Van Nechel C, Bisdorff A, Magnusson M, Petersen H, Kingma H, Perrin P.  Discussion about Visual Dependence in Balance Control: European Society for Clinical Evaluation of Balance Disorders. J Int Adv Otol. 2017 Dec;13(3):404-406. doi: 10.5152/iao.2017.4344.

Abstract

The executive committee of the European Society for the clinical evaluation of balance disorders meets annually to address equilibrium problems that are not well understood. This is a review paper on discussions in the latest meeting we held.

MATERIALS AND METHODS: Seeing patients with vestibular disorders who end up depending on visual information as part of their compensation process is a common clinical occurrence. However, this "visual dependence" can generate symptoms, which include nausea, sensations of imbalance, and anxiety. It is unclear how this develops, as symptoms can be widely variable from patient to patient. There are several triggering factors to this symptom set, and quantifying it in a given patient is extremely difficult Results: The committee agreed that the presence of this symptom set can be suggestive of vestibular pathology, but the pathology does not have to be present. As a result, there is no correlation between symptom severity and test results.

CONCLUSION: Visual dependence can often be present in a patient, although little, if any, measurable pathology is present. It is important to emphasize that although we cannot accurately measure this with either standardized testing or pertinent questionnaires, "hypersensitive" patients have a genuine disease and their symptoms are not of psychiatric origin.

PMID: 29360093

No 475: June 12, 2019

Bronstein AM, Dieterich M. Long-term clinical outcome in vestibular neuritis. Curr Opin Neurol. 2019 Feb;32(1):174-180. doi: 10.1097/WCO.0000000000000652.

Abstract

PURPOSE OF REVIEW: To review recent work on clinical and imaging aspects of vestibular neuritis (or acute vestibular syndrome), in particular with a view to identifying factors predicting long-term clinical outcome.

RECENT FINDINGS: Evidence for a role of inflammation in the vestibular nerve, and the presence of Gadolinium enhancement acutely in vestibular neuritis, is accruing. Visual dependence, anxiety and somatization traits predict the development of chronic dizziness after acute vestibular neuritis. Adaptation to asymmetric rotation is impaired in vestibular neuritis and this may indicate insufficient central compensation in chronic dizzy patients. Corticosteroids appear ineffective at improving long-term clinical outcome. Functional imaging changes during the central compensation period lead to structural brain changes; both processes correlate with clinical recovery.

SUMMARY: Vestibular neuritis appears to be the result of postviral neuroinflammation of the vestibular nerve. However, long-term prognosis is not dependent on the magnitude of the peripheral residual damage (as measured with caloric and video head-impulse test). Instead, a combination of visuovestibular psychophysical factors (visual dependence), psychological traits and dysfunctional vestibular perception are relevant. Several functional and structural neuroimaging changes develop after vestibular neuritis, which reflect and underlie the aforementioned psychophysiological and psychological features.

PMID: 30566414

No 474: June 7, 2019

Smyth N, Flynn M, Rajcani J, F Hucklebridge M, Thorn L, Wood C, Golding J, Evans P, Clow A.  Attenuated cortisol reactivity to psychosocial stress is associated with greater visual dependency in postural control.  Psychoneuroendocrinology. 2019 Jun;104:185-190. doi: 10.1016/j.psyneuen.2019.02.028. Epub 2019 Mar 2.

Abstract

Despite known anatomical links between the hypothalamic-pituitary-adrenal (HPA) axis and the vestibular system, there are no studies on the relationship between postural control and HPA axis function. Visual dependence in postural control, often measured by increased postural sway on exposure to visual motion, is an indication of altered visual-vestibular integration with greater weighting towards visual cues for balance. Visual dependence is more common in older age and a range of vestibular and non-vestibular health conditions. The relationship between visual dependence in postural control was investigated in relation to cortisol reactivity to psychosocial stress (using the Trier Social Stress Test for groups: TSST-G), as an index of HPA axis function, in healthy young females. In those who exhibited a cortisol response (>2 nmol/l), a negative relationship between stress-induced cortisol reactivity and visual dependence in postural control was observed, since those with the largest cortisol response showed less visual motion induced postural sway (measured by force platform). This finding in healthy females indicates that subtle non-clinical differences in vestibular function are associated with dysregulated HPA axis activity as indicated by lower cortisol reactivity to psychosocial stress. It adds to the growing body of evidence linking blunted cortisol reactivity to stress to poor homeostatic regulation and potential negative health and behavioural outcomes.

PMID: 30856424

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