COVID-19 mortality is associated with low vitamin D levels in patients with risk factors and/or advanced age.

BACKGROUND & AIMS: Although conclusive evidence is yet lacking, it has been suggested that vitamin D deficiency (VD) may be associated with a more severe course of SARS-CoV-2 Infection (COVID-19). In this retrospective study we assessed the association of VD deficiency with mortality in a group of COVID-19 patients treated in a tertiary referral center. METHODS: Data of 257 Covid-19 patients hospitalized between 30th September 2020 and 2nd March 2021 have been collected retrospectively. The following parameters were collected: age, gender, serum level of 25-OH-Vitamin D3, outcome (survival/death), comorbidities (cancer, diabetes mellitus and chronic obstructive pulmonary disease). Serum VD measurement was done within 3 days of admission. RESULTS: VD levels were significantly lower in patients who did not survive, however, in this patients' group the average age was significantly higher than among those, who survived. After age-matching, in a subgroup of patients with risk factors and/or 60 years of age or older who survived had significantly higher VD level in their serum than those who deceased. Serum C-reactive protein, lactate-dehydrogenase and creatinin-kinase were significantly higher in the group in which the patients died, however these laboratory parameters did not correlate with the VD levels. CONCLUSION: We found that in COVID-19 infection, when old age as risk factor (60 years of age or older) was pooled with risk factors (cancer, diabetes and/or COPD), the VD levels were significantly lower in the patient group, in which the patients did not survive. We suggest further, prospective studies in similar subgroups to explore a possible causal relationship.

Prevalence of and Theoretical Explanation for Type 2 Benign Paroxysmal Positional Vertigo.

BACKGROUND AND PURPOSE: A variant of benign paroxysmal positional vertigo (BPPV) involves the subjective report of vertigo without the coinciding nystagmus. This presentation includes truncal retropulsion when sitting up from the ipsilesional provocative test (ie, Dix-Hallpike), which we term type 2 BPPV. The primary objective of this study is to prospectively determine the prevalence and describe the clinical course of type 2 BPPV. We offer a theoretical explanation for the absence of nystagmus. METHODS: Prospective, observational study carried out in 2 tertiary hospitals. One hundred eighty patients (134 women, 46 men) met the inclusion criteria and were included between January 10, 2018, and October 30, 2019. Efficacy of physical therapy maneuvers was determined at 1-week follow-up. Three-dimensional reconstructions of the planes of the semicircular canal cupula from histological preparations are offered as evidence for the theoretical explanation. RESULTS: One-third of the patients met the criteria for type 2 BPPV; the remainder had typical posterior or horizontal semicircular canal involvement. Symptoms from type 2 BPPV were longer in duration yet responded favorably to physical therapy maneuvers. Upon repeat testing, 19 patients treated for posterior canalithiasis developed a slight, persistent positional downbeat nystagmus in the Dix-Hallpike position that we propose as evidence the otoconia entered the short arm of the posterior semicircular canal. DISCUSSION AND CONCLUSIONS: Our data and 3-dimensional rendering suggest the report of vertigo, yet absent nystagmus in type 2 BPPV is from otoconia aligning with the gravitoinertial vector during provocative testing that precludes cupular stimulation. Type 2 BPPV appears to be a common and treatable form of vertigo.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A372).

Vergence increases the amplitude of lateral ocular vestibular evoked myogenic potentials.

The angular and linear vestibulo-ocular reflex responses are greater when viewing near targets to compensate for the relatively larger translation of the eyes with respect to the target. Our aim was to measure vestibular evoked myogenic potentials using a lateral ocular electrode montage (oVEMP) with a laterally applied stimulus using a mini-shaker during both far- and near-viewing (vergence) distances to determine whether vergence affects the oVEMP response as it does the semicircular canal vestibulo-ocular reflex response. Our results show that during vergence, the p1 and n1-p1 amplitude of the lateral oVEMP response increases significantly, whereas the latencies do not change significantly. We suggest that the physiological basis for this vergence-mediated amplitude increase in potentials may be the same as those already documented using transient linear head accelerations. Our data also suggest that irregular vestibular afferents are likely mediating the vergence-mediated gain increase during linear head accelerations because only irregular afferents are stimulated during short, transient 500 Hz stimuli.

Absence of a vergence-mediated vestibulo-ocular reflex gain increase does not preclude adaptation.

BACKGROUND: The gain (eye-velocity/head-velocity) of the angular vestibuloocular reflex (aVOR) during head impulses can be increased while viewing near-targets and when exposed to unilateral, incremental retinal image velocity error signals. It is not clear however, whether the tonic or phasic vestibular pathways mediate these gain increases. OBJECTIVE: Determine whether a shared pathway is responsible for gain enhancement between vergence and adaptation of aVOR gain in patients with unilateral vestibular hypofunction (UVH). MATERIAL AND METHODS: 20 patients with UVH were examined for change in aVOR gain during a vergence task and after 15-minutes of ipsilesional incremental VOR adaptation (uIVA) using StableEyes (a device that controls a laser target as a function of head velocity) during horizontal passive head impulses. A 5 % aVOR gain increase was defined as the threshold for significant change. RESULTS: 11/20 patients had >5% vergence-mediated gain increase during ipsi-lesional impulses. For uIVA, 10/20 patients had >5% ipsi-lesional gain increase. There was no correlation between the vergence-mediated gain increase and gain increase after uIVA training. CONCLUSION: Vergence-enhanced and uIVA training gain increases are mediated by separate mechanisms and/or vestibular pathways (tonic/phasic). The ability to increase the aVOR gain during vergence is not prognostic for successful adaptation training.

Biasing the semicircular canal cupula in excitatory direction decreases the gain of the vestibuloocular reflex for head impulses.

BACKGROUND: It has been shown that cold caloric irrigation decreases the vestibulo-ocular reflex (VOR) gain in the vertically positioned lateral canal as measured by head impulse testing. This effect is most probably caused by a sustained deflection of the cupula in the inhibitory direction. OBJECTIVE: The aim of the present experiment was to answer the question if a sustained excitatory deflection increases the gain of the reflex in healthy volunteers. METHODS: In order to deflect the cupula, cold caloric irrigation was applied in prone (forward head hanging) position. In this position cold thermal irrigation elicited an excitatory caloric nystagmus with an ipsilateral fast phase. RESULTS: When head impulses were applied immediately after cold caloric irrigation, the gain of the VOR decreased in comparison to the values measured before irrigation. CONCLUSIONS: Together with the previous results cited above, these data show that biasing the cupula in either direction decreases its sensitivity with respect to high acceleration stimuli. This might occur because the deviation elicits a partial mechanical and electrophysiological saturation of the cupula.

Endre Hogyes (1847-1906), Forgotten Father of the Vestibulo-Ocular Reflex.

OBJECTIVE: Throughout the history of vestibular research, the discovery of the vestibulo-ocular reflex in 1881 by Endre Hogyes (1847-1906) is rarely mentioned. The aim of this study is to review Hogyes' vestibular research articles, all originally written in Hungarian and emphasize their epoch-making content. MAIN DATA SOURCES: Hogyes' vestibular publications, originally written in Hungarian, which describe various eye movements of the rabbit in response to vestibular stimulation by rotation about three axes. RESULTS: Hogyes was the first to use a three-axis turntable on an experimental animal, in this case a rabbit. He found that depending on the plane of rotation, different types of binocular eye movements were produced. He then demonstrated by destructive and excitatory experiments, the anatomical pathways and the physiological function producing this phenomenon. Ultimately, he explained the exact connections between the inner ear labyrinth and certain muscle contractions during eye movements. He identified this pathway as the "associating center of the ocular movements," later defined as the vestibulo-ocular reflex. Hogyes' discovery was only superficially noted during his lifetime and ignored after his death. CONCLUSION: Hogyes was the first to demonstrate the vestibulo-ocular reflex. He was forgotten during the ensuing 140 years probably because his articles were appeared only in Hungarian and because a short time later, Róbert Bárány's award of the Nobel Prize overshadowed many of Bárány's predecessors and contemporaries, including Hogyes and relegated them to the background.

Vergence increases the gain of the human angular vestibulo-ocular reflex during peripheral hyposensitivity elicited by cold thermal irrigation.

BACKGROUND: When viewing a far target, the gain of the horizontal vestibulo-ocular reflex (VOR) is around 1.0, but when viewing a near target there is an increased response. It has been shown that while this convergence-mediated modulation is unaffected by canal plugging and clinically practical transmastoid galvanic stimulation, it is eliminated by a partial peripheral gentamicin lesion. OBJECTIVE: The aim of this study was to determine if convergence increases the gain during peripheral hyposensitivity elicited by cold thermal irrigation. METHODS: The high frequency VOR gain was measured using video head impulse testing immediately after the cold caloric stimulus in 9 healthy human subjects with the lateral semicircular canals oriented approximately earth-vertical. RESULTS: Before caloric irrigation, near viewing (15 cm) increased the average VOR gain by 28% (from 1 to 1.28). Cold (24°C) water irrigation of the right ear decreased the gain to 0.66 (far viewing) and 0.82 (near viewing) (22% difference). Although vergence also increased the gain for impulses to the left to the same degree before caloric stimulus, the caloric irrigation itself (applied to the right ear) did not influence the gain for contralateral impulses. CONCLUSION: In our experiments vergence increased the gain of the human angular VOR during peripheral hyposensitivity elicited by cold thermal irrigation. These results suggest that cold irrigation does not abolish the function of the nonlinear/phasic vestibular afferent pathway.

Cold Thermal Irrigation Decreases the Ipsilateral Gain of the Vestibulo-Ocular Reflex.

OBJECTIVES: During head rotations, neuronal firing rates increase in ipsilateral and decrease in contralateral vestibular afferents. At low accelerations, this "push-pull mechanism" is linear. At high accelerations, however, the change of firing rates is nonlinear in that the ipsilateral increase of firing rate is larger than the contralateral decrease. This mechanism of stronger ipsilateral excitation than contralateral inhibition during high-acceleration head rotation, known as Ewald's second law, is implemented within the nonlinear pathways. The authors asked whether caloric stimulation could provide an acceleration signal high enough to influence the contribution of the nonlinear pathway to the rotational vestibulo-ocular reflex gain (rVOR gain) during head impulses. DESIGN: Caloric warm (44°C) and cold (24, 27, and 30°C) water irrigations of the left ear were performed in 7 healthy human subjects with the lateral semicircular canals oriented approximately earth-vertical (head inclined 30° from supine) and earth-horizontal (head inclined 30° from upright). RESULTS: With the lateral semicircular canal oriented earth-vertical, the strongest cold caloric stimulus (24°C) significantly decreased the rVOR gain during ipsilateral head impulses, while all other irrigations, irrespective of head position, had no significant effect on rVOR gains during head impulses to either side. CONCLUSIONS: Strong caloric irrigation, which can only be achieved with cold water, reduces the rVOR gain during ipsilateral head impulses and thus demonstrates Ewald's second law in healthy subjects. This unilateral gain reduction suggests that cold-water caloric irritation shifts the set point of the nonlinear relation between head acceleration and the vestibular firing rate toward a less acceleration-sensitive zone.