Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria

Nodosauridae is a group of thyreophoran dinosaurs characterized by a collar of prominent osteoderms. In comparison to its sister group, the often club-tailed ankylosaurids, a different lifestyle of nodosaurids could be assumed based on their neuroanatomy and weaponry, e.g., regarding applied defensive strategies. The holotype of the nodosaurid Struthiosaurus austriacus consists of a single partial braincase from the Late Cretaceous of Austria. Since neuroanatomy is considered to be associated with ecological tendencies, we created digital models of the braincase based on micro-CT data. The cranial endocast of S. austriacus generally resembles those of its relatives. A network of vascular canals surrounding the brain cavity further supports special thermoregulatory adaptations within Ankylosauria. The horizontal orientation of the lateral semicircular canal independently confirms previous appraisals of head posture for S. austriacus and, hence, strengthens the usage of the LSC as proxy for habitual head posture in fossil tetrapods. The short anterior and angular lateral semicircular canals, combined with the relatively shortest dinosaurian cochlear duct known so far and the lack of a floccular recess suggest a rather inert lifestyle without the necessity of sophisticated senses for equilibrium and hearing in S. austriacus. These observations agree with an animal that adapted to a comparatively inactive lifestyle with limited social interactions.

Evaluation of the effects of Covid-19 on cochleovestibular system with audiovestibular tests

Purpose The purpose of the present study was to investigate the effects of COVID-19 on audiovestibular system with Transiently Evoked Distortion Otoacoustic Emissions (TOAE), Distortion Product Otoacoustic Emissions (DPOAE), video head impulse test (vHIT) and caloric test. Methods Audiovestibular findings of 24 patients with moderate/severe COVID-19 and 24 healthy controls were compared using pure tone audiometry, tympanometry, TOAE, DPOAE, caloric test, and vHIT. Results On audiometry, the pure tone averages of the COVID-19 patients were higher than the controls ( P = .038). The TEOAE amplitudes at 4000 and 5000 Hz ( P = .006 and P < .01), and DPOAE amplitudes at 3000, 6000, and 8000 Hz ( P < .001, P = .003 and P < .001) were significantly lower in COVID-19 patients compared to the controls. On vestibular tests, there was no significant difference between the caloric test results of the patients and the controls ( P > .05). On vHIT testing, amplitudes of right semicircular canal was found to be significantly lower in COVID-19 group compared to the control group ( P = .008). Conclusion COVID-19 may affect inner ear functions causing a subtle damage in the outer hair cells and lateral semicircular canals. It must be kept in mind that COVID-19 may cause cochleovestibular problems.

Malformations of the sacculus and the semicircular canals in spider morph pythons

Spider morph ball pythons are a frequently bred design morph with striking alterations of the skin color pattern. We created high resolution µCT-image series through the otical region of the skulls, used 3D-reconstruction software for rendering anatomical models, and compare the anatomy of the semicircular ducts, sacculus and ampullae of wildtype Python regius (ball python) with spider morph snakes. All spider morph snakes showed the wobble condition. We describe the inner ear structures in wild-type and spider-morph snakes and report a deviant morphology of semicircular canals, ampullae and sacculus in spider morph snakes. We also report about associated differences in the desmal skull bones of spider morph snakes. The spider morph snakes were characterized by wider semicircular canals, anatomically poorly defined ampulla, a deformed crus communis and a small sacculus, with a highly deviant x-ray morphology as compared to wildtype individuals. We observed considerable intra- and interindividual variability of these features. This deviant morphology of spider morph snakes can easily be associated with an impairment of sense of equilibrium and the observed neurological wobble condition. Limitations in sample size prevent statistical analyses, but the anatomical evidence is strong enough to support an association between the wobble condition in design bread spider morph snakes and a malformation of the inner ear structures. A link between artificially selected alterations in pattern and specific color design with neural-crest associated developmental malformations of the statoacoustic organ as known from other vertebrates is discussed.

Impacts of Rotation Axis and Frequency on Vestibular Perceptual Thresholds

In an effort to characterize the factors influencing the perception of self-motion rotational cues, vestibular self-motion perceptual thresholds were measured in 14 subjects for rotations in the roll and pitch planes, as well as in the planes aligned with the anatomic orientation of the vertical semicircular canals (i.e., left anterior, right posterior; LARP, and right anterior, left posterior; RALP). To determine the multisensory influence of concurrent otolith cues, within each plane of motion, thresholds were measured at four discrete frequencies for rotations about earth-horizontal (i.e., tilts; EH) and earth-vertical axes (i.e., head positioned in the plane of the rotation; EV). We found that the perception of rotations, stimulating primarily the vertical canals, was consistent with the behavior of a high-pass filter for all planes of motion, with velocity thresholds increasing at lower frequencies of rotation. In contrast, tilt (i.e, EH rotation) velocity thresholds, stimulating both the canals and otoliths (i.e., multisensory integration), decreased at lower frequencies and were significantly lower than earth-vertical rotation thresholds at each frequency below 2 Hz. These data suggest that multisensory integration of otolithic gravity cues with semicircular canal rotation cues enhances perceptual precision for tilt motions at frequencies below 2 Hz. We also showed that rotation thresholds, at least partially, were dependent on the orientation of the rotation plane relative to the anatomical alignment of the vertical canals. Collectively these data provide the first comprehensive report of how frequency and axis of rotation influence perception of rotational self-motion cues stimulating the vertical canals.

A New Coordinate System for Magnetic Resonance Imaging of the Vestibular System

Objectives: To develop and evaluate a new coordinate system for MRI of the vestibular system.Methods: In this study, 53 internal auditory canal MRI and 78 temporal bone CT datasets were analyzed. Mimics Medical software version 21.0 was used to visualize and three-dimensionally reconstruct the image data. We established a new coordinate system, named W–X, based on the center of the bilateral eyeballs and vertex of the bilateral superior semicircular canals. Using the W–X coordinate system and Reid's coordinate system, we measured the orientations of the planes of the anterior semicircular canal (ASCC), the lateral semicircular canal (LSCC), and the posterior semicircular canal (PSCC).Results: No significant differences between the angles measured using CT and MRI were found for any of the semicircular canal planes (p &gt; 0.05). No statistical differences were found between the angles measured using Reid's coordinate system (CT) and the W–X coordinate system (MRI). The mean values of ∠ASCC &amp; LSCC, ∠ASCC &amp; PSCC, and ∠LSCC &amp; PSCC were 84.67 ± 5.76, 94.21 ± 3.81, and 91.79 ± 5.22 degrees, respectively. The angle between the LSCC plane and the horizontal imaging plane was 15.64 ± 3.92 degrees, and the angle between the PSCC plane and the sagittal imaging plane was 48.79 ± 4.46 degrees.Conclusion: A new W–X coordinate system was developed for MRI studies of the vestibular system and can be used to measure the orientations of the semicircular canals.

Comparison of verticality perception and postural sway induced by double temple-mastoidal and bipolar binaural 20 Hz sinusoidal galvanic vestibular stimulation

BACKGROUND: Galvanic vestibular stimulation (GVS) is believed to be one of the most valuable tools for studying the vestibular system. In our opinion, its combined effect on posture and perception needs to be examined more. OBJECTIVE: The present study was conducted to investigate the effect of a 20 Hz sinusoidal Galvanic Vestibular Stimulation (sGVS) on the body sway and subjective visual vertical (SVV) deviation through two sets of electrode montages (bipolar binaural and double temple-mastoidal stimulation) during a three-stage experiment (baseline, threshold, and supra-threshold levels). METHODS: While the individuals (32 normal individuals, 10 males, the mean age of 25.37±3.00 years) were standing on a posturography device and SVV goggles were put on, the parameters of the body sway and SVV deviation were measured simultaneously. Following the baseline stage (measuring without stimulation), the parameters were investigated during the threshold and supra-threshold stages (1 mA above the threshold) for 20 seconds. This was done separately for each electrode montage. Then, the results were compared between the three experimental stages and the two electrode montages. RESULTS: In both electrode montages, “the maximum amplitude” of the mediolateral (ML) and anteroposterior (AP) body sway decreased and increased in the threshold and supra-threshold stages, respectively, compared to the baseline stage. Comparison of the amount of “amplitude change” caused by each electrode montages showed that the double temple-mastoidal stimulation induced a significantly greater amplitude change in body sway during both threshold and supra-threshold stages (relative to the baseline stage). The absolute mean values of the SVV deviation were significantly different between the baseline and supra-threshold levels in both electrode montages. The SVV deviation in double temple-mastoidal stimulation was a bit greater than that in the bipolar binaural stimulation. CONCLUSION: Double temple-mastoidal stimulation has induced greater amount of change in the body sway and SVV deviation. This may be due to the more effective stimulation of the otoliths than semicircular canals.

Current Response in CaV1.3–/– Mouse Vestibular and Cochlear Hair Cells

Signal transmission by sensory auditory and vestibular hair cells relies upon Ca2+-dependent exocytosis of glutamate. The Ca2+ current in mammalian inner ear hair cells is predominantly carried through CaV1.3 voltage-gated Ca2+ channels. Despite this, CaV1.3 deficient mice (CaV1.3–/–) are deaf but do not show any obvious vestibular phenotype. Here, we compared the Ca2+ current (ICa) in auditory and vestibular hair cells from wild-type and CaV1.3–/– mice, to assess whether differences in the size of the residual ICa could explain, at least in part, the two phenotypes. Using 5 mM extracellular Ca2+ and near-body temperature conditions, we investigated the cochlear primary sensory receptors inner hair cells (IHCs) and both type I and type II hair cells of the semicircular canals. We found that the residual ICa in both auditory and vestibular hair cells from CaV1.3–/– mice was less than 20% (12–19%, depending on the hair cell type and age investigated) compared to controls, indicating a comparable expression of CaV1.3 Ca2+ channels in both sensory organs. We also showed that, different from IHCs, type I and type II hair cells from CaV1.3–/– mice were able to acquire the adult-like K+ current profile in their basolateral membrane. Intercellular K+ accumulation was still present in CaV1.3–/– mice during IK,L activation, suggesting that the K+-based, non-exocytotic, afferent transmission is still functional in these mice. This non-vesicular mechanism might contribute to the apparent normal vestibular functions in CaV1.3–/– mice.

Incomplete Partition type I: Radiological Evaluation of the Temporal Bone

Objective: Incomplete partition type I is an uncommon congenital anomaly of the inner ear, characterized by typical cystic cochleovestibular appearance. Incomplete partition type I was firstly defined as cystic cochlea and vestibule without large vestibular aqueduct; however, large vestibular aqueduct and/or enlarged endolymphatic duct could rarely be seen in incomplete partition type I anomaly. Correct diagnosis of the type of cochlear malformation and differentiation of incomplete partition type I is necessary for patient management and surgical approach. Our aim was to document the temporal bone imaging findings in a series of patients with incomplete partition type I. Materials and Methods: CT (n=85) and/or MRI (n=80) examinations of 99 ears in 59 incomplete partition type I patients were retrospectively evaluated. All structures of the otic capsule were retrospectively assessed. The appearances of cochlea and vestibule, vestibular aqueduct/endolymphatic duct, semicircular canals were qualitatively evaluated by an experienced neuroradiologist. The vertical dimension of vestibular aqueduct and/or endolymphatic duct (from the point where the duct arises from the vestibule) was measured on CT/MRI. Anterior-posterior diameter of the internal acoustic canal and the diameter of cochlear aperture were measured on CT. The cochleovestibular nerves were evaluated on sagittal-oblique high T2-weighted imaging. Results: All 99 ears had defective partition with unpartitioned cochlear basal turn and absent interscalar septae, separated but cystic cochlea. The vestibule was enlarged in all ears except one. Semicircular canals were usually dysplastic (92.9%). A total of 35 incomplete partition type I ears (35.3%) had large vestibular aqueduct and/or enlarged endolymphatic duct. Internal acoustic canal was wide in 21% of ears. Cochlear aperture was wide in 5.9% of ears. Cochlear nerve was either hypoplastic or aplastic in about a quarter of incomplete partition type I ears. Conclusion: In up to one-third of incomplete partition type I patients, an associated large vestibular aqueduct /endolymphatic duct could be seen accompanying typical inner ear findings. Although the cochlear nerves are normal in the majority of cases, auditory brainstem implantation may be necessary in certain cases of incomplete partition type I anomaly.

A case series shows independent vestibular labyrinthine function after major surgical trauma to the human cochlea

Background The receptors for hearing and balance are housed together in the labyrinth of the inner ear and share the same fluids. Surgical damage to either receptor system was widely believed to cause certain permanent loss of the receptor function of the other. That principle, however, has been called into question because there have been anecdotal reports in individual patients of at least partial preservation of cochlear function after major surgical damage to the vestibular division and vice versa. Methods We performed specific objective vestibular function tests before and after surgical trauma (partial or subtotal cochlear removal) for treatment of intracochlear tumors in 27 consecutive patients in a tertiary referral center. Vestibular function was assessed by calorics (low-frequency response of the lateral semicircular canal), vestibulo-ocular reflex by video head impulse test (vHIT) of the three semicircular canals, cervical and ocular vestibular evoked myogenic potentials (cVEMP, saccule and oVEMP, utricle). Preoperative and postoperative distributions were compared with paired t-tests. Results Here we show that there was no significant difference between pre- and post-operative measures for all tests of the five vestibular organs, and that after major surgical cochlear trauma, the vestibular receptors continue to function independently. Conclusions These surprising observations have important implications for our understanding of the function and the surgery of the peripheral auditory and vestibular system in general and open up new possibilities for the development, construction and evaluation of neural interfaces for electrical or optical stimulation of the peripheral auditory and vestibular nervous system.

Objective vestibular function changes in children following cochlear implantation

BACKGROUND: To date, systematically objective evaluations of vestibular function in children with cochlear implantation (CI) have been conducted sparsely, especiallyin children with large vestibular aqueduct syndrome (LVAS). OBJECTIVE: Our goal was to investigate the function of all five vestibular end-organs pre- and post-cochlear implantation in children with LVAS and normal CT. METHODS: In this retrospective cohort study, 34 children (age 4–17 years) with bilateral profound sensorineural hearing loss (SNHL) undergoing unilateral CI were included. Participants included 18 (52.9%) children with LVAS. Objective modalities to evaluate vestibular function included the caloric test, cervical vestibular-evoked myogenic potentials (cVEMP), ocular vestibular-evoked myogenic potentials (oVEMP), and video head impulse test (vHIT). All measurements were performed before surgery and 9 months after surgery. RESULTS: Mean age at CI was 8.1±3.7 years. Caloric testing showed hypofunction in 38.2%of cases before implantation and in 50%after (p > 0.05). We found a significant increase of overall abnormality rate in cVEMP and oVEMP from pre- to post-CI (p < 0.05). In all three semicircular canals tested by vHIT, there were no statistically significant mean gain changes (p > 0.05). Higher deterioration rates in cVEMP (53.3%) and oVEMP (52.0%) after surgery were observed (p < 0.05). In children with LVAS, cVEMP revealed a higher deterioration rate than superior semicircular canal (SSC) and posterior semicircular canal (PSC) (p < 0.05). In children with normal CT, the deterioration rates in VEMPs were both higher than those in vHIT (p < 0.05). CONCLUSIONS: In general, the otolith organs were the most affected peripheral vestibular sensors in children after cochlear implantation. The variations in otolith function influenced by CI were different between children with LVAS and normal CT. We recommend the use of this vestibular function test battery for children with cochlear implantation.