Sexual dimorphism in vestibular function and dysfunction

Novel cVEMP procedure reveals sexual dimorphism in peak to trough latency

Introduction

Sex difference in latency for cervical vestibular-evoked myogenic potential (VEMP) has been reported in Brown Norway rats. Human investigations of sex difference in VEMP latency have shown inconsistent results, although there are indicators of sexual dimorphism in vestibular function and a higher reporting rate for vestibular disorder in women than in men.

Methods

Sex effects in human VEMP were re-evaluated here using a procedure adapting clinical protocols for higher sensitivity. VEMP was compared between 24 women and 24 men using a novel procedure that (1) controlled neck tension with biofeedback and a padded head bar; (2) used body-conducted stimuli to eliminate sound exposure concerns and collect appreciably more data than is feasible with air-conducted stimuli; which in turn (3) increased statistical power because there were sufficient data for a linear mixed effects regression modelling analysis.

Results

Women had significantly shorter VEMP peak to trough latency than men. The sex difference of 2.4 ms (95% CI [-0.9, -3.9], p = 0.0020) was 21% of the mean 11.4 ms VEMP peak to trough latency measured across women and men. There was no significant sex difference in VEMP peak to trough amplitude. These findings are a reversal of several prior studies in humans, reviewed here with a simulation indicating the studies may have been underpowered.

Discussion

Findings are consistent with those in Brown Norway Rats, for which a study design featuring a custom rodent holder to control neck tension, extension of test sequences in comparison to those typically used in VEMP protocols for humans, and insertion of electrodes subcutaneously will have increased sensitivity compared to that achievable with clinical VEMP protocols for humans. Findings are interpreted as sex hormones affecting myelination or synaptic response; sexual dimorphism in neck/head size may also have contributed. The vestibular periphery and brainstem are highly conserved across vertebrates with similar findings in rat and human supporting use of VEMP as a reliable, non-invasive indicator of vestibular function. VEMP measures in humans may require higher sensitivity than is achievable using current clinical protocols in order to produce consistent results.

Sex differences in caloric nystagmus intensity: Should reference values be updated?

Bithermal caloric irrigation of the horizontal semicircular canals is a key method of neurotological diagnostics, allowing the detection of peripheral vestibular hypofunction in the low-frequency range. Current diagnostic criteria for unilateral vestibulopathy (UVP), bilateral vestibulopathy (BVP), and presbyvestibulopathy (PVP) rely on gender-neutral absolute or relative metrics. Here, we analyzed all bithermal water caloric examinations performed in the German Center for Vertigo and Balance Disorders (DSGZ) between 07/2018 and 01/2024 and calculated the total caloric reactivity (TR). Patient age and sex were collected as covariates. For UVP, BVP, and PVP diagnoses, international diagnostic criteria were applied. In total, 11,332 patients (6219 females, mean age 55.97±17.52 years) were included. Females displayed a higher TR (mean difference: 6.41°/s, p<0.001). The frequency of UVP, BVP, and PVP diagnoses based on absolute cut-off values showed a significant male predominance (UVP: n = 1144, 548 females, odd ratio [OR] -0.32, p<0.001; BVP: n = 305, 138 females, OR -0.40, p<0.001; PVP: n = 813, 378 females, OR -0.37, p<0.001). However, the rate of UVP based on relative asymmetries showed no sex differences (n = 2971, 1595 females, OR -0.08, p = 0.06). Diagnostic criteria for UVP, BVP, or PVP, which utilize absolute caloric excitability cut-offs, might need to be updated to address sex-specific differences of caloric excitability.

Sex differences in dizziness diagnoses across acute and chronic neurological settings

BACKGROUND & OBJECTIVE

Dizziness is commoner in females and therefore clinical diagnostic frameworks are perhaps biased towards this gender. This study specifically aimed to analyse the distribution of diagnoses in neuro-otology clinics based on sex, and across age.

METHODS

Retrospective cohort study based on a case note review of 474 adult patients (≥ 18 years) using electronic healthcare records from patients who were referred with a primary complaint of dizziness, vertigo, or unsteadiness in outpatient neurological clinics from January 2023 to September 2024 at University College London Hospitals, UK.

RESULTS

Among the 474 patients, the most common diagnosis for dizziness was persistent postural perceptual dizziness (PPPD) (24.3%), followed by vestibular migraine (VM) (22.4%). In women the most common diagnosis was VM (31.9%), while in men it was PPPD (21.7%). In the population under 65 years old the major cause was VM (28.9%), followed by PPPD (28.6%) and "other central causes" (12.19%), while in the population over 65 years old they were benign paroxysmal positional vertigo (BPPV) (18.4%) and "other central causes" (18.4%). PPPD (28.3%) and VM (21.4%) were the commonest causes of chronic vertigo, while in the acute phase the commonest causes were VM (26%), vascular (14%) and BPPV (14%).

DISCUSSION

Overall, PPPD is the most common cause of dizziness in males, and vascular vertigo was the most common cause of acute dizziness in males, regardless of age. The combination of age and sex may be helpful in constructing a priori diagnostic possibilities for Neurologists, Otorhinolaryngologists and other clinicians seeing dizzy patients.

Optimizing spatial normalization of multisubject inner ear MRI: comparison of different geometry-preserving co-registration approaches

Spatial normalization of multisubject inner ear imaging data is challenging, due to both substantial intraindividual differences and the small size of the organ compared to other intracranial structures. Automatic whole brain co-registration to standard space can only roughly co-align the peripheral vestibular endorgan, and complemental manual registration is highly time-consuming. Here, we compared the accuracy of four geometry-maintaining co-registration methods (one semi-manual method and three automatic methods). High-resolution structural T2-MRI of 153 inner ears from patients and healthy participants were co-registered to an inner-ear atlas. The semi-manual method used a three-point landmark-based approach (3P), two automatic methods were based on unassisted standard algorithms (Advanced Normalization Tools (ANTs), Elastix (EL)), while the fourth automatic method utilized a volumetrically dilated, atlas-based mask (thick inner ear, TIE) for probabilistic inner ear masking. Registration accuracy was evaluated by neurotologists blinded to the respective registration paradigm, and the resulting median volumes were quantified using colocalization analyses. The mask-aided automatic approach showed the best ratings, followed by the semi-manual three-point landmark-based registration (mean ratings (lower: better) TIE 2.21 ± 1.15; 3P 2.58 ± 0.61; EL 3.42 ± 1.06; ANTs 3.49 ± 1.26). The semi-manual method had the lowest rate of insufficient registrations, followed by TIE (3P: 3.70%; TIE: 8.28%; EL: 22.66%; ANTs: 27.02%). TIE showed the highest colocalization metrics with the atlas. Only TIE and 3P allowed for sufficient semicircular canal visualization in method-wise average volumes. Overall, geometry-preserving spatial normalization of multisubject inner ear imaging data is possible and could allow groupwise examinations of the bony labyrinth or temporal bone morphology in the future.

The impact of gravity on perceived object height

Altering posture relative to the direction of gravity, or exposure to microgravity has been shown to affect many aspects of perception, including size perception. Our aims in this study were to investigate whether changes in posture and long-term exposure to microgravity bias the visual perception of object height and to test whether any such biases are accompanied by changes in precision. We also explored the possibility of sex/gender differences. Two cohorts of participants (12 astronauts and 20 controls, 50% women) varied the size of a virtual square in a simulated corridor until it was perceived to match a reference stick held in their hands. Astronauts performed the task before, twice during, and twice after an extended stay onboard the International Space Station. On Earth, they performed the task of sitting upright and lying supine. Earth-bound controls also completed the task five times with test sessions spaced similarly to the astronauts; to simulate the microgravity sessions on the ISS they lay supine. In contrast to earlier studies, we found no immediate effect of microgravity exposure on perceived object height. However, astronauts robustly underestimated the height of the square relative to the haptic reference and these estimates were significantly smaller 60 days or more after their return to Earth. No differences were found in the precision of the astronauts' judgments. Controls underestimated the height of the square when supine relative to sitting in their first test session (simulating Pre-Flight) but not in later sessions. While these results are largely inconsistent with previous results in the literature, a posture-dependent effect of simulated eye height might provide a unifying explanation. We were unable to make any firm statements related to sex/gender differences. We conclude that no countermeasures are required to mitigate the acute effects of microgravity exposure on object height perception. However, space travelers should be warned about late-emerging and potentially long-lasting changes in this perceptual skill.

Scopolamine for patients with motion sickness: a systematic review and meta-analysis with trial sequential analysis

BACKGROUND

Scopolamine has been demonstrated to relieve motion sickness. However, repeated significance testing may increase false-positive results.

OBJECTIVES

Review the efficacy and safety of scopolamine in the prevention of motion sickness by performing a meta-analysis with Trial Sequential Analysis (TSA).

MATERIAL AND METHODS

Randomized controlled trials (RCTs) compared scopolamine with other medications or placebo were included. Primary outcomes were nausea reported and head movement time.

RESULTS

Twenty studies with 753 participants were included. Scopolamine had a greater reported reduction in nausea than placebo (relative risk [RR] 0.35; 95% confidence interval [CI] 0.24 to 0.52; p<0.00001; I2 = 45%), while TSA showed the included sample size exceeded the required information size (RIS). There is no difference in head movement time between scopolamine and placebo (mean difference [MD] 2.02; 95% CI -1.2 to 5.25; p = 0.6; I2 = 0%), while the included sample size did not reach RIS.

CONCLUSION

Scopolamine is effective for motion sickness nausea compared to placebo. The TSA recommends conducting more head movement trials to validate the objective efficacy of scopolamine.

SIGNIFICANCE

Clarifying the efficacy of scopolamine for motion sickness, the TSA highlights the need for more prospective studies using head movement as an outcome.

Analysis of characteristics of and risk factors for otological symptoms after COVID-19 infection

The purpose of this study was to explore the characteristics of and risk factors for otological symptoms after contracting COVID-19. We invited 468 participants who had been infected with COVID-19 to participate in a survey. 310 (66.2%) were women and 158 (33.8%) were men. The mean age is 38.73 (12.21) years. The questionnaire included their basic information, symptoms and symptom duration after SARS-CoV-2 infection, number of vaccine doses received, and details regarding otological symptoms. In total, 106/468 (22.6%) participants experienced tinnitus, 66/468 (14.1%) hearing loss, 103/468 (22.0%) aural fullness, and 71/468 (15.2%) dizziness. Women were more prone to experience tinnitus (P = 0.022) and dizziness (P = 0.001) than men. The group with hearing loss were older (P = 0.025), and their initial COVID-19 symptoms lasted longer (P = 0.028) than those of patients without. Patients with aural fullness were more likely to experience fatigue than patients without (P = 0.002). Patients experiencing dizziness were more likely to experience pharyngalgia (P = 0.040) and fatigue (P = 0.005) than those without. The number of vaccine doses was positively associated with the resolution of otological symptoms (P = 0.035). Multiple logistic regression analysis revealed that sex was an independent risk factor for tinnitus (odds ratio [OR], 1.802; 95% confidence interval [CI], 1.099-2.953; P = 0.020), the duration of initial COVID-19 symptoms for hearing loss (OR, 1.055; 95% CI, 1.008-1.105; P = 0.023), and sex for dizziness (OR, 2.870; 95% CI, 1.489-5.535; P = 0.002). Sex, age, COVID-19-related fatigue, and the duration of initial COVID-19 symptoms may affect the occurrence of otological symptoms, and vaccines may aid their resolution.

Cognition in vestibular disorders: state of the field, challenges, and priorities for the future

Vestibular disorders are prevalent and debilitating conditions of the inner ear and brain which affect balance, coordination, and the integration of multisensory inputs. A growing body of research has linked vestibular disorders to cognitive problems, most notably attention, visuospatial perception, spatial memory, and executive function. However, the mechanistic bases of these cognitive sequelae remain poorly defined, and there is a gap between our theoretical understanding of vestibular cognitive dysfunction, and how best to identify and manage this within clinical practice. This article takes stock of these shortcomings and provides recommendations and priorities for healthcare professionals who assess and treat vestibular disorders, and for researchers developing cognitive models and rehabilitation interventions. We highlight the importance of multidisciplinary collaboration for developing and evaluating clinically relevant theoretical models of vestibular cognition, to advance research and treatment.

Appropriate Vestibular Stimulation in Children and Adolescents-A Prerequisite for Normal Cognitive, Motor Development and Bodily Homeostasis-A Review

The structural development of the vestibular part of the inner ear is completed by birth but its central connections continue to develop until adolescence. Their development is dependent on vestibular stimulation-vestibular experience. Studies have shown that vestibular function, modulated by experience and epigenetic factors, is not solely an instrument for body position regulation, navigation, and stabilization of the head and images but also influences cognition, emotion, the autonomous nervous system and hormones. To emphasize the importance of appropriate vestibular stimulation, we present a literature review of its effect on bodily homeostasis, cognition and emotion.

Delayed Diagnoses in Patients With Dizziness in the US Commonwealth of Virginia and the Tidewater Region

Objective

In a region of approximately 1.7 million people (Tidewater, coastal Virginia), identify secondary diagnoses in persons with dizziness.

Methods

This cross-sectional study utilizing TriNetX included individuals in the region of interest diagnosed with dizziness between 2010 and 2020. Subsequent diagnoses of vestibular disease or medical conditions possibly associated with dizziness in the same subjects were catalogued.

Results

During the study period, 31,670 subjects were identified with diagnoses of dizziness as a symptom; 18,390 subjects were subsequently given a dizziness-related nonvestibular diagnosis, and 930 were given a subsequent vestibular disease diagnosis. The proportion of subjects diagnosed with vestibular disease (3%) after the dizziness diagnosis is far below expected norms (25%-34%) in the general population. There were greater proportions of delayed diagnoses of labyrinth dysfunction (odds ratio [OR], 4.8; P < 0.0001), superior semicircular canal dehiscence (OR, 3.1; P = 0.0023), otolith disease (OR, 3.1; P = 0.0023), among others, and a decreased proportion of delayed diagnosis of benign paroxysmal positional vertigo (OR, 0.56; P < 0.0001).

Conclusions

The discrepancy between expected and observed prevalence in our region indicates that vestibular disease is likely underdiagnosed.

The burden of vestibular disorders among military health system (MHS) beneficiaries, fiscal years 2018-2019

INTRODUCTION

Vestibular disorders affect an estimated 33 million adults and 3.5 million children and adolescents in the United States. Previous research relying on self-reported symptoms versus actual diagnosis has limited the ability to provide prevalence estimates for specific vestibular disorders at the population level. This study seeks to describe the burden of vestibular disorders among children and working-age adult beneficiaries in the Military Health System (MHS).

MATERIALS AND METHODS

Using the MHS Data Repository (MDR), we conducted a cross-sectional study of all TRICARE Prime and Plus MHS beneficiaries aged 0 to 64 years from fiscal years (FY) 2018 to 2019. Study analyses included descriptive statistics of patient demographics and assessing the prevalence of vestibular disorders in pediatric and working-age adult beneficiaries.

RESULTS

Of the 5,541,932 TRICARE Prime/Prime Plus MHS beneficiaries, 52,878 (0.95%) had a diagnosis of vestibular disorder during fiscal years 2018 to 2019, of which 1,359 were pediatric and adolescents (aged 0 to 17 years) and 51,519 were working-age adults (18 to 64 years). Vertigo was the most common diagnosis in both age-group populations (11.46 per 1,000 working-age adults; 0.52 per 1,000 children and adolescents), with benign vertigo being the most prevalent of the three diagnoses and occurring at a seven times higher rate in adults versus pediatric and adolescents.

CONCLUSIONS

This study demonstrates the effectiveness of using medical claims data to estimate prevalence compared to self-reported survey data and supports prevalence estimates of vestibular disease in <1% of children overall, but indicate much higher prevalence for adolescents.

Interpreting the meaning of changes in hippocampal volume associated with vestibular loss

Many studies have documented cognitive deficits, especially spatial cognitive deficits, in patients with some form of vestibular loss. Almost 20 years ago, hippocampal (HPC) atrophy was reported to be correlated with spatial memory deficits in such patients and the idea has gradually emerged that HPC atrophy may be causally responsible for the cognitive deficits. However, the results of studies of HPC volume following vestibular loss have not always been consistent, and a number of studies have reported no evidence of HPC atrophy. This paper argues that HPC atrophy, if it does occur following vestibular loss, may not be directly, causally responsible for the cognitive deficits, and that it is more likely that rapid functional changes in the HPC are responsible, due to the interruption of the transmission of vestibular information to the HPC. The argument presented here rests on 3 tranches of evidence: (1) Cognitive deficits have been observed in humans even in the absence of HPC atrophy; (2) HPC atrophy has not been reported in animal studies following vestibular loss, despite cognitive deficits; and (3) Animal studies have shown that the interruption of the transmission of vestibular information to the HPC has immediate consequences for HPC place cells, far too quickly to be explained by HPC atrophy. It is possible that HPC atrophy, when it does occur, is related to the longer-term consquences of living with vestibular loss, which are likely to increase circulating cortisol.

Vestibular Disorders and Hormonal Dysregulations: State of the Art and Clinical Perspectives

The interaction between endocrine and vestibular systems remains poorly documented so far, despite numerous observations in humans and animals revealing direct links between the two systems. For example, dizziness or vestibular instabilities often accompany the menstrual cycle and are highly associated with the pre-menopause period, while sex hormones, together with their specific receptors, are expressed at key places of the vestibular sensory network. Similarly, other hormones may be associated with vestibular disorders either as causal/inductive factors or as correlates of the pathology. This review was carried out according to the PRISMA method, covering the last two decades and using the MEDLINE and COCHRANE databases in order to identify studies associating the terms vestibular system and/or vestibular pathologies and hormones. Our literature search identified 646 articles, 67 of which referred directly to vestibular dysfunction associated with hormonal variations. While we noted specific hormonal profiles depending on the pathology considered, very few clinical studies attempted to establish a direct link between the expression of the vestibular syndrome and the level of circulating hormones. This review also proposes different approaches to shed new light on the link between hormones and vestibular disorders, and to improve both the diagnosis and the therapeutic management of dizzy patients.

Vestibular contribution to path integration deficits in 'at-genetic-risk' for Alzheimer's disease

Path integration changes may precede a clinical presentation of Alzheimer's disease by several years. Studies to date have focused on how spatial cell changes affect path integration in preclinical AD. However, vestibular input is also critical for intact path integration. Here, we developed the vestibular rotation task that requires individuals to manually point an iPad device in the direction of their starting point following rotational movement, without any visual cues. Vestibular features were derived from the sensor data using feature selection. Machine learning models illustrate that the vestibular features accurately classified Apolipoprotein E ε3ε4 carriers and ε3ε3 carrier controls (mean age 62.7 years), with 65% to 79% accuracy depending on task trial. All machine learning models produced a similar classification accuracy. Our results demonstrate the cross-sectional role of the vestibular system in Alzheimer's disease risk carriers. Future investigations should examine if vestibular functions explain individual phenotypic heterogeneity in path integration among Alzheimer's disease risk carriers.

Comparative Study of Audiovestibular Symptoms between Early and Late Variants of COVID-19

Audiovestibular symptoms during the acute phase of the corona virus disease 2019 (COVID-19), have been reported for earlier waves of the pandemic, while no studies investigated nor compared audiovestibular manifestations during subsequent waves of COVID-19. In the current study, we aimed to compare the occurrence of audiovestibular symptoms associated with COVID-19 between the alpha/beta, delta, and omicron variants. An online questionnaire was distributed to individuals with confirmed test results for COVID-19. We asked participants to report whether they experienced audiovestibular symptoms during the acute phase of the disease. The study included 939 participants; 120 un-infected controls and infected participants during alpha/beta (n = 301), delta (n = 102), and omicron (n = 416) predominance periods. Self-reported audiovestibular symptoms were found to be statistically significantly different between un-infected controls and COVID-19 infected individuals in all analyzed variants. Furthermore, our results showed no significant differences in audiovestibular symptoms among individuals infected during alpha/beta, delta, and omicron waves. Although individuals infected during the delta variant predominance period reported higher percentages of audiovestibular symptoms (ranging from 11.8% to 26.5% for auditory symptoms and from 12.7% to 34.3% for vestibular symptoms) than for the alpha/beta (ranging from 6.3% to 18.9% for auditory symptoms and 8.3% to 29.9% for vestibular symptoms) and omicron (ranging from 9.6% to 21.2% for auditory and 12.5 to 29.1% for vestibular symptoms) variants, this did not achieve statistical significance. With regards to auditory symptoms, the most commonly reported symptoms were aural fullness followed by hearing loss and tinnitus. With regards to vestibular symptoms, dizziness was the most commonly reported symptom followed by vertigo and unsteadiness. Logistic regression revealed that experiencing auditory symptoms were associated with other neurological symptoms, back and joint pain, and chest pain as COVID-19 symptoms. Vestibular symptoms were associated with anemia, gender, fatigue, headache, and breathing difficulties. In conclusion, our study shows that audiovestibular symptoms are common during the acute phase of early and late COVID-19 variants with no significant differences between them.

Age-related High-frequency Hearing Loss Is Not Associated With Horizontal Semicircular Canal Function

OBJECTIVE

Investigate the association between age-related hearing loss and reduced peripheral vestibular function using paired assessments of high-frequency hearing and horizontal semicircular canal (HSC) function. We hypothesized that age-related high-frequency hearing loss would be correlated with reduced HSC function and, therefore, useful to predict age-related vestibular hypofunction.

DESIGN

We conducted a single center, retrospective cross-sectional study in a tertiary/academic referral hospital. This study included 185 patients who were diagnosed with a cerebellopontine angle (CPA) tumor and referred to the academic hospital to evaluate treatment options. Data collected included pure-tone audiometry, caloric reflex test, video head-impulse test (vHIT), and medical history. High-frequency hearing loss was quantified by the high Fletcher index (hFI), and horizontal semicircular canal (HSC) function were quantified by the caloric reflex test and vHIT.

RESULTS

We observed a significant association between age and high-frequency hearing loss that was significantly worse in men compared with women. In contrast, we observed no significant association between age and HSC function assessed by either the caloric reflex test or vHIT. We observed associations between HSC function and sex, with male sex predicting reduced HSC function by caloric reflex testing but enhanced HSC function by vHIT. High-frequency hearing loss did not predict HSC hypofunction.

CONCLUSIONS

We found no evidence indicating age-related decline in HSC function or an association between age-related high-frequency hearing loss and age-related decline in HSC function. We did observe sex-specific differences in HSC function. Our study highlights the need for sex-specific normative values for identifying age-related reduced peripheral vestibular function and for future work linking comprehensive assessments of inner ear function with tests of balance and stability to understand the complex interactions underlying hearing loss and imbalance, especially in the elderly.

Age-related changes in the organization of spontaneously occurring behaviors

Age-related changes in spatial and temporal processing have been documented across a range of species. Rodent studies typically investigate differences in performance between adult and senescent animals; however, progressive loss of neurons in the hippocampus and cortex has been observed to occur as early as after adolescence. Therefore, the current study evaluated the effects of age in three- and ten-month-old female rats on the organization of movement in open field and food protection behaviors, two tasks that have previously dissociated hippocampal and cortical pathology. Age-related differences were observed in general measures of locomotion, spatial orientation, and attentional processing. The results of the current study are consistent with age-related changes in the processing of spatial information and motivation that occur earlier in life than previously anticipated. These observations establish a foundation for future studies evaluating interventions that influence these age-related differences in performance.

Vestibular Sensory Conflict During Postural Control, Freezing of Gait, and Falls in Parkinson's Disease

BACKGROUND

The vestibular system has been implicated in the pathophysiology of episodic motor impairments in Parkinson's disease (PD), but specific evidence remains lacking.

OBJECTIVE

We investigated the relationship between the presence of freezing of gait and falls and postural failure during the performance on Romberg test condition 4 in patients with PD.

METHODS

Modified Romberg sensory conflict test, fall, and freezing-of-gait assessments were performed in 92 patients with PD (70 males/22 females; mean age, 67.6 ± 7.4 years; Hoehn and Yahr stage, 2.4 ± 0.6; mean Montreal Cognitive Assessment, 26.4 ± 2.8).

RESULTS

Failure during Romberg condition 4 was present in 33 patients (35.9%). Patients who failed the Romberg condition 4 were older and had more severe motor and cognitive impairments than those without. About 84.6% of all patients with freezing of gait had failure during Romberg condition 4, whereas 13.4% of patients with freezing of gait had normal performance (χ²  = 15.6; P < 0.0001). Multiple logistic regression analysis showed that the regressor effect of Romberg condition 4 test failure for the presence of freezing of gait (Wald χ²  = 5.0; P = 0.026) remained significant after accounting for the degree of severity of parkinsonian motor ratings (Wald χ²  = 6.2; P = 0.013), age (Wald χ²  = 0.3; P = 0.59), and cognition (Wald χ²  = 0.3; P = 0.75; total model: Wald χ²  = 16.1; P < 0.0001). Patients with PD who failed the Romberg condition 4 (45.5%) did not have a statistically significant difference in frequency of patients with falls compared with patients with PD without abnormal performance (30.5%; χ²  = 2.1; P = 0.15).

CONCLUSIONS

The presence of deficient vestibular processing may have specific pathophysiological relevance for freezing of gait, but not falls, in PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Express: Cognition in Zero Gravity: Effects of Non-Terrestrial Gravity on Human Behaviour

As humanity prepares for deep space exploration, understanding the impact of spaceflight on bodily physiology is critical. While the effects of non-terrestrial gravity on the body are well established, little is known about its impact on human behaviour and cognition. Astronauts often describe dramatic alterations in sensorimotor functioning, including orientation, postural control and balance. Changes in cognitive functioning as well as in socio-affective processing have also been observed. Here we have reviewed the key literature and explored the impact of non-terrestrial gravity across three key functional domains: sensorimotor, cognition, and socio-affective processing. We have proposed a neuroanatomical model to account for the effects of non-terrestrial gravity in these domains. Understanding the impact of non-terrestrial gravity on human behaviour has never been more timely and it will help mitigate against risks in both commercial and non-commercial spaceflight.

Reduced Gain and Shortened Time Constant of Vestibular Velocity Storage as a Source of Balance and Movement Sensitivities in Gravitational Insecurity

Gravitational insecurity (GrI) involves lifetime movement and balance concerns whose pathophysiological origins are unclear. We tested whether balance symptoms in mild GrI might involve anomalies in vestibular velocity storage (VVS), a brainstem/cerebellar circuit that amplifies gain and prolongs the persistence of weak vestibular signals from small/slow head movements. A Provisional Gravitational Insecurity Index (PGrI) was developed, evaluated for psychometrics/demographics, and used to identify otherwise healthy adults with life-long balance challenges as well as sex, age, and ethnicity-matched comparison adults without such challenges. Balance confidence, sensory hypersensitivities, spatial orientation, anxiety, and hearing loss were self-reported. Standing balance under visual/proprioceptive restrictions and perrotary vestibulo-ocular nystagmus were evaluated. The PGrI showed approximated test-retest reliability and convergent and discriminant validity. When only vestibular input was available, mild GrI participants on a tilting platform used effortful hip strategies for balance significantly more than did comparison participants. Rotation testing revealed that mild GrI participants had significantly less low frequency gain and shortened VVS persistence. Combined, these two parameters correlated significantly with PGrI. The PGrI also correlated with problematic spatial orientation, but surprisingly, not to anxiety. Balance/movement issues in GrI are likely due to VVS deficiencies. Additional mechanisms may account for other GrI symptoms. Better understanding of GrI’s pathophysiological basis will be useful in informing the larger health-provider community about this condition.

Expression of circadian clock genes in leukocytes of patients with Meniere's disease

Objectives

The underlying etiology of Meniere's disease (MD) is not completely clear, but the precipitated triggers may alter the circadian clock in patients with MD. This study aims to survey the expression of circadian clock genes in peripheral blood (PB) leukocytes of MD patients.

Methods

We investigated the expression of nine circadian clock genes in the PB leukocytes of patients with MD and normal controls using real‐time quantitative reverse transcriptase‐polymerase chain reaction (qRT‐PCR).

Results

We observed significantly lower expression of PER1 gene and higher expression of CLOCK gene in MD patients than those in normal controls (p < 0.05). PER1 did not associate with the degree of dizziness handicap in the patients with MD, but a lower expression of PER1 was significantly correlated with higher pure tone average (PTA) and speech reception threshold of the affected ear (p < 0.05). Patients with PTA > 30 dB had significantly lower PER1 expression than those with PTA ≤30 dB in the affected ear (p < 0.05). Our qRT‐PCR result was validated by fewer positively stained leukocytes for PER1 protein in the MD patients using the immunocytochemical study.

Conclusion

Our study implies the alteration of the circadian clock in patients with MD. In particular, the downregulation of PER1 correlated with the degree of hearing loss in the affected ear. PER1 in PB leukocytes may be a potential marker for the progression of hearing loss in MD.

Estimating the minimal clinically important difference for balance and gait outcome measures in individuals with vestibular disorders

BACKGROUND

Vestibular Rehabilitation Therapists (VRT) utilize outcome measures to quantify gait and balance abilities in individuals with vestibular disorders (IVD). The minimal clinically important difference (MCID) in gait and balance outcome measures for IVD is unknown.

OBJECTIVE

The purpose of this study is to estimate the MCID of the Activities-specific Balance Confidence Scale (ABC), Functional Gait Assessment (FGA), and Gait Speed (GS) using distribution and anchor-based methods relative to the Dizziness Handicap Inventory (DHI) in IVD.

METHODS

Data were collected using a retrospective chart review from two outpatient Vestibular Rehabilitation (VR) clinics. Data included demographic characteristics, diagnosis, VR course, and pre and post outcome measures including DHI, ABC, FGA, and GS. The DHI was used to classify subjects as "responders" or "non-responders" in order to calculate MCID values.

RESULTS

The total number of subjects analyzed for each outcome measure was 222 for the ABC, 220 for FGA, and 237 for GS. Subjects made statistically significant improvements in ABC, DHI, FGA, and GS (p <  0.001) from pre to post VR. The MCID calculated for ABC, FGA, and GS using the anchor-based approach was 18.1%, 4 points, and 0.09 m/s respectively. The MCIDs calculated using distribution-based approach for the ABC ranged between 7.5-23.5%, FGA ranged between 1.31-4.15 points, and GS ranged between 0.07 m/s-0.22 m/s.

CONCLUSIONS

The anchor-based calculations of the MCID of 18.1%, 4 points, and 0.09 m/s for ABC, FGA, and GS respectively for IVD should be used over distribution-based calculations. This is due to strength of DHI as the anchor and statistical analysis. VRT and researches can use these values to indicate meaningful changes in gait and balance function in IVD.

Differential organization of open field behavior in mice following acute or chronic simulated GCR exposure

Astronauts undertaking deep space travel will receive chronic exposure to the mixed spectrum of particles that comprise Galactic Cosmic Radiation (GCR). Exposure to the different charged particles of varied fluence and energy that characterize GCR may impact neural systems that support performance on mission critical tasks. Indeed, growing evidence derived from years of terrestrial-based simulations of the space radiation environment using rodents has indicated that a variety of exposure scenarios can result in significant and long-lasting decrements to CNS functionality. Many of the behavioral tasks used to quantify radiation effects on the CNS depend on neural systems that support maintaining spatial orientation and organization of rodent open field behavior. The current study examined the effects of acute or chronic exposure to simulated GCR on the organization of open field behavior under conditions with varied access to environmental cues in male and female C57BL/6 J mice. In general, groups exhibited similar organization of open field behavior under dark and light conditions. Two exceptions were noted: the acute exposure group exhibited significantly slower and more circuitous homeward progressions relative to the chronic group under light conditions. These results demonstrate the potential of open field behavior organization to discriminate between the effects of select GCR exposure paradigms.

Unilateral mimicking bilateral BPPV- a forgotten entity? Characteristics of a large cohort of patients, comparison with posterior canal BPPV and clinical implications

Objective

Unilateral mimicking bilateral benign paroxysmal positional vertigo (umb-BPPV) was attributed to inappropriate head positioning during testing of the posterior canal. Despite its inclusion in the Diagnostic criteria for the classification of vestibular disorders of the Bárány Society, the clinical characteristics and treatment responsiveness of this BPPV subtype have not been intensively studied.

Methods

Records of patients with BPPV seen at a single outpatient dizziness clinic during the years 2000–2020 were reviewed. Eighty seven patients with umb-BPPV and 86 random patients with posterior canal BPPV (p-BPPV) were retrieved. Their demographics and BPPV characteristics were analyzed.

Results

Patients' and BPPV characteristics were similar in umb- and p-BPPV except for the prevalence of males in the umb-BPPV group. No differences were found between treatment responsiveness and recurrences in both groups. The recurrence rate of umb-BPPV was not influenced by age, gender, BPPV side, duration of symptoms or treatment responsiveness during the first attack.

Conclusions

In accordance with our hypothesis about mixed canalo- and cupulolithiasis as the underlying mechanism of umb-BPPV, patients did not differ in characteristics and treatment responsiveness from p-BPPV patients. Recognition of umb-BPPV is important since inappropriate treatment can cause an unnecessary delay in therapy success.

Sex Differences in the Triad of Acquired Sensorineural Hearing Loss

The triad of noise-generated, drug-induced, and age-related hearing loss is the major cause of acquired sensorineural hearing loss (ASNHL) in modern society. Although these three forms of hearing loss display similar underlying mechanisms, detailed studies have revealed the presence of sex differences in the auditory system both in human and animal models of ASNHL. However, the sexual dimorphism of hearing varies among noise-induced hearing loss (NIHL), ototoxicity, and age-related hearing loss (ARHL). Importantly, estrogen may play an essential role in modulating the pathophysiological mechanisms in the cochlea and several reports have shown that the effects of hormone replacement therapy on hearing loss are complex. This review will summarize the clinical features of sex differences in ASNHL, compare the animal investigations of cochlear sexual dimorphism in response to the three insults, and address how estrogen affects the auditory organ at molecular levels.

Organization of exploratory behavior under dark conditions in female and male rats

Sexually dimorphic performance has been observed across humans and rodents in many spatial tasks. In general, these spatial tasks do not dissociate the use of environmental and self-movement cues. Previous work has demonstrated a role for self-movement cue processing in organizing open field behavior; however, these studies have not directly compared female and male movement characteristics. The current study examined the organization of open field behavior under dark conditions in female and male rats. Significant differences between female and male rats were observed in the location of stopping behavior relative to a cue and the topography exhibited during lateral movements. In contrast, no sex differences were observed on measures used to detect self-movement cue processing deficits. These results provide evidence that female and male rats are similar in their use of self-movement cues to organize open field behavior; however, other factors may be contributing to differences in performance.

Clinical significance of serum sex hormones in postmenopausal women with vestibular migraine: potential role of estradiol

OBJECTIVE

This study aimed to investigate the role of sex hormones in postmenopausal women with vestibular migraine.

METHODS

This observational study included 242 female patients with vestibular migraine who were postmenopausal during April 2017 to December 2019. Serum levels of sex hormones, including estradiol, progesterone, testosterone, follicle-stimulating hormone, luteinizing hormone, and prolactin, were determined by radioimmunoassay. The duration and frequency (every month) of onset of vestibular migraine were recorded. The degree of vestibular migraine was measured by the visual analogue scale.

RESULTS

Serum levels of estradiol, progesterone, and testosterone were significantly lower, while serum prolactin levels were significantly higher in postmenopausal patients with vestibular migraine compared with healthy controls. Serum estradiol levels were negatively correlated with the duration, frequency, and severity of onset of vestibular migraine. Patients with higher serum estradiol levels showed a longer disease-free survival time.

CONCLUSION

Sex hormones are correlated with vestibular migraine in postmenopausal women. Additionally, estradiol levels are correlated with the duration, frequency, and severity of onset of vestibular migraine, as well as the disease-free survival time.

Turning Toward Monitoring of Gaze Stability Exercises: The Utility of Wearable Sensors

BACKGROUND AND PURPOSE

Few tools are currently available to quantify gaze stability retraining exercises. This project examined the utility of a head-worn inertial measurement unit (IMU) to quantify head movement frequency, velocity, and amplitude during gaze stability exercises.

METHODS

Twenty-eight individuals with multiple sclerosis and complaints of dizziness or a history of falls were randomly assigned to either a strength and aerobic exercise (SAE) or gaze and postural stability (GPS) group. During a 6-week intervention, participants wore a head-mounted IMU 3 times (early, middle, and late). For aim 1, the frequency, mean peak velocity, and mean peak amplitude of head turns during equivalent duration components of group-specific exercises were compared using general linear models. For aim 2, the progression of treatment in the GPS group was examined using general linear regression models for each outcome.

RESULTS

Aim 1 revealed the GPS group demonstrated significantly greater velocity and amplitude head turns during treatment than the SAE group. The frequency of head turns did not significantly differ between the 2 groups. The aim 2 analyses demonstrated that the yaw and pitch frequency of head turns significantly increased during gaze stability exercises over the 6-week intervention. Velocity and amplitude of head turns during yaw and pitch gaze stability exercises did not significantly change.

DISCUSSION AND CONCLUSIONS

A head-worn IMU during rehabilitation distinguished between groups. Furthermore, within the GPS group, the IMU quantified the progression of the frequency of head movements during gaze stability exercises over time.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A320).

Repeated video head impulse testing in patients is a stable measure of the passive vestibulo-ocular reflex

Objectives

The video head impulse test (vHIT) is used as a measure of compensation yet it's stability in patients with vestibular pathology is unknown.

Methods

144 patients (n = 72 female, mean 54.46 ± 15.8 years) were grouped into one of three primary diagnoses (Peripheral, Central, or Mixed). Subjects were further categorized based on sex (male versus female), ear (left versus right; ipsilesional versus contralesional), age (six groups ranging from 19 to 84 years), and duration between visits (five groups, mean 191.46 ± SE 29.42 days, median 55.5 days). The gain of the VOR during passive head rotation was measured for each semicircular canal (horizontal, anterior, posterior).

Results

There was no difference in the VOR gain within any semicircular canal between the two visits (horizontal: p = 0.179; anterior: p = 0.628; posterior: p = 0.613). However, the VOR gain from the horizontal canals was higher than the vertical canals for each visit (p < 0.001). Patients diagnosed with peripheral vestibular pathology had significantly lower (p ≤ 0.001) horizontal semicircular canal gains at each visit. There was no difference in VOR gain between sex (p = 0.215) or age groupings (p = 0.331). Test-retest reliability of vHIT in patient subjects is good (ICC = 0.801) and the VOR gain values across two separate visits were significant and positively correlated (r = 0.67) regardless of sex, ear, age, or duration between visits.

Conclusion

The vHIT is a stable measure of VOR gain over two different times across a variety of vestibular patients with no influence of age or sex.

Perceiving jittering self-motion in a field of lollipops from ages 4 to 95

An internal model of self-motion provides a fundamental basis for action in our daily lives, yet little is known about its development. The ability to control self-motion develops in youth and often deteriorates with advanced age. Self-motion generates relative motion between the viewer and the environment. Thus, the smoothness of the visual motion created will vary as control improves. Here, we study the influence of the smoothness of visually simulated self-motion on an observer's ability to judge how far they have travelled over a wide range of ages. Previous studies were typically highly controlled and concentrated on university students. But are such populations representative of the general public? And are there developmental and sex effects? Here, estimates of distance travelled (visual odometry) during visually induced self-motion were obtained from 466 participants drawn from visitors to a public science museum. Participants were presented with visual motion that simulated forward linear self-motion through a field of lollipops using a head-mounted virtual reality display. They judged the distance of their simulated motion by indicating when they had reached the position of a previously presented target. The simulated visual motion was presented with or without horizontal or vertical sinusoidal jitter. Participants' responses indicated that they felt they travelled further in the presence of vertical jitter. The effectiveness of the display increased with age over all jitter conditions. The estimated time for participants to feel that they had started to move also increased slightly with age. There were no differences between the sexes. These results suggest that age should be taken into account when generating motion in a virtual reality environment. Citizen science studies like this can provide a unique and valuable insight into perceptual processes in a truly representative sample of people.

Benign Paroxysmal Positional Vertigo Risk Factors Unique to Perimenopausal Women

Many investigations have found common occurrences of benign paroxysmal positional vertigo (BPPV) in women, and clinical experience has shown that BPPV can develop due to increased hormonal fluctuations, especially during menopause. Therefore, knowledge about neurochemicals and their involvement with BPPV is imperative for the management of neurological issues in women. This review will discuss appropriate gender-based considerations of BPPV based on experimental and clinical evidence. The studies describe 2 lines of evidence regarding the association of perimenopause in women and the development of BPPV: (1) experimental evidence: the existence of estrogen receptors in the inner ear, otoconial malformations in osteopenic/osteoporotic rats, changes in otoconin 90 caused by hormone replacement therapy, and impaired calcium absorption following estrogen deprivation corrected by estrogen replacement therapy and (2) clinical evidence: epidemiological aspects, osteoporosis and estrogen deficiency. Future studies are necessary to validate the effects of hormonal replacement therapy and phytoestrogen in women with recurrent BPPV.

Gender-Specific Risk Factors and Comorbidities of Bothersome Tinnitus

Objective

This study aims to identify gender-specific risk factors associated with the presence of bothersome tinnitus (compared with non-bothersome tinnitus), including sociodemographic and lifestyle factors, tinnitus-associated phenomena (hearing loss, traumatic experiences, sleep disturbances), and physical as well as mental comorbidities.

Methods

We conducted a cross-sectional study using survey data from the Swedish LifeGene cohort containing information on self-reported tinnitus (N = 7615). We (1) analyzed risk factor and comorbidity frequencies, (2) computed multivariate logistic regression models to identify predictors of bothersome tinnitus within both genders, and (3) moderated logistic regression models to compare effects between genders.

Results

(1) The majority of factors that differed in frequencies between bothersome and non-bothersome tinnitus were equal for both genders. Women with bothersome tinnitus specifically reported higher rates of cardiovascular disease, thyroid disease, epilepsy, fibromyalgia, and burnout, and men with bothersome tinnitus reported higher rates of alcohol consumption, Ménière's disease, anxiety syndrome, and panic (compared with non-bothersome tinnitus, respectively). (2) Across both genders, multivariate logistic regression analyses revealed significant associations between bothersome tinnitus and age, reduced hearing ability, hearing-related difficulties in social situations, and reduced sleep quality. In women, bothersome tinnitus was specifically associated with cardiovascular disease and epilepsy; in men, with lower education levels and anxiety syndrome. (3) Moderated logistic regression analyses revealed that the effects of low education and anxiety syndrome were present in men, but not in women, whereas the effects of age, reduced hearing ability and related difficulties, cardiovascular disease, epilepsy, and burnout were not gender specific.

Conclusion

Irrespective of gender, bothersome tinnitus is associated with higher age, reduced hearing ability, hearing-related difficulties, cardiovascular disease, epilepsy, and burnout. Gender-specific effects comprise low levels of education and the presence of anxiety syndrome for men. These findings need to be interpreted with caution, yet they suggest the presence of gender-specific biopsychosocial influences in the emergence or maintenance of bothersome tinnitus. Future studies ought to investigate the underlying mechanisms of the observed relationships.

De Novo Synthesized Estradiol: A Role in Modulating the Cerebellar Function

The estrogen estradiol is a potent neuroactive steroid that may regulate brain structure and function. Although the effects of estradiol have been historically associated with gonadal secretion, the discovery that this steroid may be synthesized within the brain has expanded this traditional concept. Indeed, it is accepted that de novo synthesized estradiol in the nervous system (nE2) may modulate several aspects of neuronal physiology, including synaptic transmission and plasticity, thereby influencing a variety of behaviors. These modulations may be on a time scale of minutes via non-classical and often membrane-initiated mechanisms or hours and days by classical actions on gene transcription. Besides the high level, recent investigations in the cerebellum indicate that even a low aromatase expression can be related to the fast nE2 effect on brain functioning. These pieces of evidence point to the importance of an on-demand and localized nE2 synthesis to rapidly contribute to regulating the synaptic transmission. This review is geared at exploring a new scenario for the impact of estradiol on brain processes as it emerges from the nE2 action on cerebellar neurotransmission and cerebellum-dependent learning.