Neurologic bases for comorbidity of balance disorders, anxiety disorders and migraine: neurotherapeutic implications

Perspective: Hippocampal theta rhythm as a potential vestibuloacoustic biomarker of anxiety

Anxiety disorders are the most common mental illnesses - afflicting 19% of Americans every year and 31% within their lifetimes - yet diagnoses remain based on symptom checklists because existing technologies have yet to produce biomarkers sufficiently robust for clinical use. Some techniques provide superior spatial resolution of deep brain regions implicated in anxiety but have poor time resolution; while others measure signals in real time but lack spatial resolution. Often, the goal of probing deep brain regions in humans for anxiety research is to measure a putative analogue of a mammalian brain rhythm linked to behaviour that is suggestive of anxiety. This 4-12 Hz, 1-2 mV, behaviourally modulated, nearly sinusoidal "hippocampal theta rhythm" (hTheta) is one of the largest normal extracellular synchronous signals in mammals and although it has been linked to anxiety processes, its function remains unclear. This paper reviews the literature on hTheta as it relates to anxiety and sensory, in particular vestibuloacoustic, signals, concludes that hTheta can modulate sensory signals during anxiety and posits that such modulation of vestibular signals may be an anxiety biomarker that could be detected non-invasively in humans.

The Unveiled Potential of Telehealth Practice in Vestibular Rehabilitation: A Comparative Randomized Study

Background and Objectives: Unilateral vestibular hypofunction (UVH) in cases of insufficient central nervous system compensation leads to chronic dizziness. A customized vestibular rehabilitation (VR) program is more beneficial than a generic set of exercises for patients with chronic UVH. The purpose of the present study is to compare a customized remotely supervised VR program with a customized unsupervised VR program in chronic UVH patients. Methods: Participants were randomly allocated into two groups (Group A and Group B) and received an individualized 6-week home-based VR program that included adaptation and habituation exercises, balance and gait training. All individuals' VR program implementation was evaluated weekly, allowing for exercise modifications. Moreover, Group A received additional remote supervision via phone communication (twice per week). The effectiveness of each VR program was evaluated using the scores of the Mini-BESTest, the Functional Gait Assessment (FGA), and the Dizziness Handicap Inventory (DHI). Results: At the 6-week assessment, participants in Group A had significantly better scores in objective and subjective evaluated parameters than those in Group B (p < 0.001). Group A also showed better compliance with the VR program. On the contrary, participants' conformity in their individualized exercises was not affected by gender, duration of symptoms, or BMI (p > 0.05). Conclusions: Our clinical study highlights the advantages of using telephone communication, with a structured design and implementation, to assist individuals in successfully following a VR protocol.

Trigeminal cervical complex: A neural network affecting the head and neck

OBJECTIVES

To introduce the trigeminal cervical complex (TCC) as a comprehensive framework for understanding the anatomical and functional scope of the afferences and efferences of the trigeminal nerve and explaining common otolaryngologic symptoms, including head and neck myofascial pain syndrome. Additionally, it explores how the bidirectional transmission of neurotransmitters contributes to the sensitization of the TCC and motor nuclei.

METHODS

The study was conducted as a narrative review. The authors performed a comprehensive search of multiple databases, including Medline/OVID, Embase, Scopus, and PubMed, covering publications from inception until August 2023. Both keywords and medical subject headings related to the TCC were utilized in the search. Information from 66 studies was extracted based on predetermined inclusion and exclusion criteria.

RESULTS

This review discusses the multiple afferent connections from cranial nerves, specifically VII, IX, X, and XI, to the TCC, and their respective efferent pathways. These connections may explain various clinical manifestations in the head and neck that cannot be attributed to other medical conditions. Additionally, the review highlights the dual sensory and motor nature of cranial nerves, emphasizing the bidirectional transmission of neurotransmitters in head and neck areas, which leads to the sensitization of both the TCC and motor nuclei innervating the cervicofacial muscles.

CONCLUSION

The authors hypothesize that the central and peripheral sensitization and the intricate connections of the TCC can elucidate the pathophysiology of conditions such as otalgia, tinnitus, hearing loss, vertigo, headache, cervicogenic dizziness, bruxism, and other symptoms affecting the head and neck.

Vestibular Neurostimulation for Parkinson's Disease: A Novel Device-Aided Non-Invasive Therapeutic Option

Dopaminergic replacement therapy remains the mainstay of symptomatic treatment for Parkinson's disease (PD), but many unmet needs and gaps remain. Device-based treatments or device-aided non-oral therapies are typically used in the advanced stages of PD, ranging from stereotactic deep brain stimulation to levodopa or apomorphine infusion therapies. But there are concerns associated with these late-stage therapies due to a number of procedural, hardware, or long-term treatment-related side effects of these treatments, and their limited nonmotor benefit in PD. Therefore, there is an urgent unmet need for low-risk adjuvants or standalone therapies which can address the range of burdensome motor and nonmotor symptoms that occur in PD. Recent studies suggest that non-invasive neurostimulation of the vestibular system may be able to address these gaps through the stimulation of the vestibular brainstem sensory network which extensively innervates brain regions, regulating both motor and a range of nonmotor functions. Therapeutic non-invasive vestibular stimulation is a relatively modern concept that may potentially improve a broad range of motor and nonmotor symptoms of PD, even at early stages of the disease. Here, we review previous studies supporting the therapeutic potential of vestibular stimulation for the treatment of PD and discuss ongoing clinical trials and potential areas for future investigations.

Excessive smartphone use increases self-reported auditory and vestibular symptoms

BACKGROUND

With widespread smartphone use, there is growing concern about their potential impact on human health.

OBJECTIVE

The effects of smartphone use on self-reported hearing ability, tinnitus, balance, falls, and anxiety level were investigated in this study.

METHODS

This study included 682 participants who were divided into 2 groups: a high smartphone use (HSU) group and a low smartphone use (LSU) group. Both groups were evaluated for hearing ability using the Amsterdam inventory for auditory disability and handicap; balance status using the vertigo, dizziness, imbalance symptom scale; anxiety status using the Beck anxiety index; and fall and tinnitus status using the visual analog scale.

RESULTS

The HSU group showed significantly worse hearing ability, tinnitus, balance, falling, and anxiety status results than the LSU group (p < 0.001). There was a positive correlation between smartphone addiction severity and auditory impairment, tinnitus, risk of falling, and anxiety, as well as a negative correlation with balance score (p < 0.001).

CONCLUSION

The findings suggest that individuals with excessive smartphone use are more likely to experience hearing, tinnitus, balance, falling, and anxiety problems than those who use smartphones less frequently. Excessive smartphone use may be considered a potential risk factor for these problems.

Post-earthquake dizziness and its psychiatric comorbidities among adolescents following the 2023 Kahramanmaraş earthquakes in Turkey

OBJECTIVE

Natural disasters, such as earthquakes, have detrimental effects on mental health. The occurrence of dizziness following earthquakes, termed post-earthquake dizziness syndrome (PEDS), has been noted in the epicenter and surrounding areas. The current study aimed to explore the prevalence of PEDS and its association with psychiatric disorders among adolescents.

METHODS

The sample consisted of 100 adolescents, aged 10-17 years, who had no history of vertigo or dizziness and were treated at a child and adolescent psychiatry outpatient clinic.

RESULTS

In the aftermath of the earthquake, 68.0% of the adolescents reported experiencing PEDS. A higher prevalence of PEDS was found among female adolescents compared to males. The most frequently reported symptom of PEDS was a sensation of ground shaking, typically experienced indoors within a week following the earthquake. Unpaired t-test analysis revealed that adolescents with PEDS had significantly higher scores on scales measuring panic disorder, generalized anxiety disorder, and post-traumatic stress disorder compared to those without PEDS.

CONCLUSIONS

In summary, the findings highlight the potential association between PEDS and psychiatric disorders in adolescents. However, the underlying mechanisms remain elusive, necessitating further research to elucidate the connections between PEDS and psychiatric conditions for more effective treatment strategies.

Combination of UPLC-Q-TOF/MS and network pharmacology to reveal the mechanism of Chaihu-jia-Longgu-Muli decoction for treating vertigo with anxiety disorder

Chaihu-jia-Longgu-Muli decoction (CLMD) has been proven clinically effective in treating vertigo with anxiety disorder. However, the mechanism is not clear. This study aimed to explore the mechanism of CLMD in treating vertigo with anxiety disorder based on ultra-performance liquid chromatography-quadrupole time-of-flight/mass spectrometry (UPLC-Q-TOF/MS) and network pharmacology. UPLC-Q-TOF/MS was performed to identify the compounds in blood and the targets of compounds of CLMD in vertigo and anxiety were searched using databases. A protein-protein interaction network was built to screen the core targets. The core targets were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. In addition, the vertigo with anxiety rat model was used to verify the results. A total of 22 compounds were absorbed into the blood. Eighty-one potential targets associated with CLMD for vertigo with anxiety disorder were identified through network pharmacological analysis. Subsequently, GO and KEGG analysis showed that CLMD treatment for vertigo with anxiety disorder is associated with neurotransmitter levels and other pertinent physiological processes. The results of the animal experiments showed that CLMD decreased the levels of serotonin, norepinephrine and dopamine, alleviating the symptoms of vertigo and anxiety disorder in model rats. The study revealed CLMD could alleviate vertigo and anxiety symptoms through reducing the levels of neurotransmitters.

Impact and experiences of vestibular disorders and psychological distress: Qualitative findings from patients, family members and healthcare professionals

INTRODUCTION

People with vestibular disorders frequently experience reduced quality of life and challenges with activities of daily living. Anxiety, depression and cognitive problems often co-present with vestibular disorders and can aggravate symptoms and prolong clinical recovery. We aimed to gain in-depth insights into the impact of vestibular disorders and the contribution of psychological factors by exploring multistakeholder perspectives.

METHODS

Semistructured interviews were conducted between October 2021 and March 2022 with 47 participants in the United Kingdom including: 20 patients (age M = 50.45 ± 13.75; 15 females), nine family members (age M = 61.0 ± 14.10; four females), and 18 healthcare professionals. Data were analysed using framework analysis.

RESULTS

Vestibular disorders impact diverse aspects of patients' lives including work, household chores, socialising, and relationships with family and friends. Being unable to engage in valued activities or fulfil social roles contributes to feelings of grief and frustration, affecting identity, confidence, and autonomy. Anxiety and low mood contribute to negative thought processes, avoidance, and social withdrawal, which can impede clinical recovery through reduced activity levels, and end engagement with treatment. Coping strategies were thought to help empower patients to self-manage their symptoms and regain a sense of control, but these require oversight from healthcare providers.

CONCLUSIONS

Daily activity limitations, social participation restrictions, and psychological distress can interact to impact quality of life, sense of self, and clinical recovery amongst people with vestibular disorders. Information and resources could aid societal awareness of the impact of vestibular disorders and help patients and families feel understood. An individualised and comprehensive approach that concurrently addresses mental, physical, social, and occupational needs is likely to be beneficial.

PATIENT OR PUBLIC CONTRIBUTION

Two group meetings were held at the beginning and end of the study with a patient and public involvement network formed of people with vestibular disorders and family members. These individuals commented on the study aims, interview schedule, participant recruitment practices, and interpretation of the themes identified. Two core patient members were involved at all stages of the research. These individuals contributed to the formulation of the interview schedule, development and application of the coding scheme, development and interpretation of themes, and preparation of the final manuscript.

Association of Benign Paroxysmal Positional Vertigo with Depression and Anxiety-A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the extent to which Benign Paroxysmal Positional Vertigo (BPPV) is associated with a higher prevalence of depression and anxiety in patients.

DATA SOURCES

Three databases including PubMed, Embase, and The Cochrane Library were searched by two independent authors from inception to June 12, 2022 for observational studies and randomized controlled trials investigating the association between BPPV and depression and anxiety. We included studies published as full-length articles in peer-reviewed journals with an adult population aged at least 18 years who have BPPV, detected through validated clinical methods like clinical diagnosis, interview and Dix-Hallpike test.

RESULTS

A total of 23 articles met the final inclusion criteria and 19 articles were included in the meta-analysis. BPPV was associated with a 3.19 increased risk of anxiety compared to controls, and 27% (17%-39%) of BPPV patients suffered from anxiety. Furthermore, the weighted average Beck's Anxiety Inventory score was 18.38 (12.57; 24.18), while the weighted average State-Trait Anxiety Index score was 43.08 (37.57; 48.60).

CONCLUSION

There appears to be some association between BPPV and anxiety, but further studies are required to confirm these associations. Laryngoscope, 134:526-534, 2024.

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.

Measuring anxiety disorder in bipolar disorder using EVestG: broad impact of medication groups

Objectives

Anxiety disorder is present in approximately half of all bipolar disorder (BD) patients. There are neurologic bases for the comorbidity of balance (vestibular) disorders and anxiety. Our objective is to use electrovestibulography (EVestG), which is predominantly a measure of vestibular neural activity to not only quantitatively detect and measure comorbid anxiety disorder but also to quantitatively measure the impacts of anti-depressant, anti-psychotic, and mood stabilizer medication groups on anxiety measures in BD patients.

Methods

In a population of 50 (24 with anxiety disorder) depressive phase BD patients, EVestG signals were measured. Participants were labeled depression-wise as anxious or non-anxious using standard questionnaires. Analyses were conducted on the whole dataset as well as on matched (age/gender/MADRS) and "modeled medication-free" subsets. Modulations of the low-frequency EVestG firing pattern data were measured.

Findings

For BD, the main anxious minus non-anxious difference was the presence of an increase in spectral power proximal to 8-9 Hz, which was best attenuated by mood stabilizers.

Novelty

This is the first study to use an oto-acoustic physiological measure to quantify anxiety disorder in BD wherein it appears to manifest as a peak proximal to 8-9 Hz which we hypothesize as likely linked to hippocampal theta.

Characterization of Vestibular Perception in Patients with Persistent Postural-Perceptual Dizziness

OBJECTIVE

To assess vestibular (i.e., passive self-motion) perception in patients diagnosed with persistent postural-perceptual dizziness (PPPD).

STUDY DESIGN

Case-controlled, cross-sectional, observational investigation.

SETTING

Single-center laboratory-based study.

PATIENTS

Thirteen patients with PPPD, 13 age-matched healthy control volunteers. Of those with PPPD, eight had co-occurring vestibular migraine (VM).

INTERVENTIONS

All participants completed a vestibular threshold test battery reflecting perception with predominant inputs from ( a ) the otoliths (1-Hz interaural y -axis translation, 1-Hz superior-inferior z -axis translation), ( b ) the semicircular canals (2-Hz yaw rotation, 2-Hz tilts in the planes of the vertical canal pairs), and ( c ) and canal-otolith integration (0.5-Hz roll tilt).

MAIN OUTCOME MEASURES

Direction-recognition thresholds for each vestibular threshold test condition.

RESULTS

Across all patients with PPPD, higher thresholds for superior-inferior z -translations thresholds in comparison to age-matched healthy control participants were identified ( p < 0.001). Those patients with co-occurring VM and PPPD (PPPD/+VM) displayed significantly higher z -translation thresholds ( p = 0.006), whereas patients with PPPD without VM (PPPD/-VM) displayed significantly higher roll tilt thresholds ( p = 0.029).

CONCLUSIONS

Patients with PPPD did not display a global worsening of passive self-motion perception as quantified by vestibular perceptual thresholds. Instead, patients with PPPD displayed elevated thresholds for only roll tilt and z -translation thresholds, with the relative change in each threshold impacted by the co-occurrence of VM. Because both z -translation and roll tilt motions are reliant on accurate gravity perception, our data suggest that patients with PPPD may exhibit impaired processing of graviceptive cues.

Sense of direction in vestibular disorders

BACKGROUND

Our sense of direction (SOD) ability relies on the sensory integration of both visual information and self-motion cues from the proprioceptive and vestibular systems. Here, we assess how dysfunction of the vestibular system impacts perceived SOD in varying vestibular disorders, and secondly, we explore the effects of dizziness, migraine and psychological symptoms on SOD ability in patient and control groups.

METHODS

87 patients with vestibular disorder and 69 control subjects were assessed with validated symptom and SOD questionnaires (Santa Barbara Sense of Direction scale and the Object Perspective test).

RESULTS

While patients with vestibular disorders performed significantly worse than controls at the group level, only central and functional disorders (vestibular migraine and persistent postural perceptual dizziness), not peripheral disorders (benign-paroxysmal positional vertigo, bilateral vestibular failure and Meniere's disease) showed significant differences compared to controls on the level of individual vestibular groups. Additionally, orientational abilities associated strongly with spatial anxiety and showed clear separation from general dizziness and psychological factors in both patient and control groups.

CONCLUSIONS

SOD appears to be less affected by peripheral vestibular dysfunction than by functional and/or central diagnoses, indicating that higher level disruptions to central vestibular processing networks may impact SOD more than reductions in sensory peripheral inputs. Additionally, spatial anxiety is highly associated with orientational abilities in both patients and control subjects.

Evaluating the Diagnostic Value of Electrovestibulography (EVestG) in Alzheimer's Patients with Mixed Pathology: A Pilot Study

Background and Objectives: Diagnosis of dementia subtypes caused by different brain pathophysiologies, particularly Alzheimer's disease (AD) from AD mixed with levels of cerebrovascular disease (CVD) symptomology (AD-CVD), is challenging due to overlapping symptoms. In this pilot study, the potential of Electrovestibulography (EVestG) for identifying AD, AD-CVD, and healthy control populations was investigated. Materials and Methods: A novel hierarchical multiclass diagnostic algorithm based on the outcomes of its lower levels of binary classifications was developed using data of 16 patients with AD, 13 with AD-CVD, and 24 healthy age-matched controls, and then evaluated on a blind testing dataset made up of a new population of 12 patients diagnosed with AD, 9 with AD-CVD, and 8 healthy controls. Multivariate analysis was run to test the between population differences while controlling for sex and age covariates. Results: The accuracies of the multiclass diagnostic algorithm were found to be 85.7% and 79.6% for the training and blind testing datasets, respectively. While a statistically significant difference was found between the populations after accounting for sex and age, no significant effect was found for sex or age covariates. The best characteristic EVestG features were extracted from the upright sitting and supine up/down stimulus responses. Conclusions: Two EVestG movements (stimuli) and their most informative features that are best selective of the above-populations' separations were identified, and a hierarchy diagnostic algorithm was developed for three-way classification. Given that the two stimuli predominantly stimulate the otholithic organs, physiological and experimental evidence supportive of the results are presented. Disruptions of inhibition associated with GABAergic activity might be responsible for the changes in the EVestG features.

Multidomain concussion symptoms in adolescents: A network analysis

Concussion is a heterogeneous injury involving symptoms and impairment that represent multiple domains (e.g., anxiety, cognitive, vestibular). Network analysis, a modeling technique that estimates relationships among symptoms, provides a statistically sound and clinically practical method for evaluating these interrelationships. The purpose of this study was to examine, using network analysis, relationships among clinical assessments and multidomain symptom report within a sample of adolescent patients following a concussion. Participants included 326 patients (49.7% female) aged 10-21 years presenting to a concussion specialty clinic within 28 days of a diagnosed concussion. Participants completed the Post-Concussion Symptom Scale (PCSS) and Vestibular-Ocular Motor Screening (VOMS) tool at initial visit. Network models were applied to PCSS symptoms initially, and then applied to VOMS and PCSS symptom data together. Dizziness (Expected influence (EI) = 1.10) and sadness (EI = 1.91) were most central (i.e., highest cumulative partial correlations) to the symptom network. Numerous interdomain relationships were supported, including irritability with mental fogginess (edgeweight = 0.12), dizziness with headache (edgeweight = 0.16), and dizziness with vision problems (edgeweight = 0.13). Community analyses resulted in VOMS groupings by domain (e.g., vestibular) and symptom (e.g., dizziness). The findings suggest a more direct focus on symptom interrelationships, such as how dizziness contributes to emotional symptoms, may help guide and better target treatments. Also, results suggest grouping VOMS assessment by symptom (e.g., dizziness) and item (e.g., vestibular-ocular reflex) may better reflect underlying impairments reflected by these symptom-item combinations.

Emotional state as a modulator of autonomic and somatic nervous system activity in postural control: a review

Advances in our understanding of postural control have highlighted the need to examine the influence of higher brain centers in the modulation of this complex function. There is strong evidence of a link between emotional state, autonomic nervous system (ANS) activity and somatic nervous system (somatic NS) activity in postural control. For example, relationships have been demonstrated between postural threat, anxiety, fear of falling, balance confidence, and physiological arousal. Behaviorally, increased arousal has been associated with changes in velocity and amplitude of postural sway during quiet standing. The potential links between ANS and somatic NS, observed in control of posture, are associated with shared neuroanatomical connections within the central nervous system (CNS). The influence of emotional state on postural control likely reflects the important influence the limbic system has on these ANS/somatic NS control networks. This narrative review will highlight several examples of behaviors which routinely require coordination between the ANS and somatic NS, highlighting the importance of the neurofunctional link between these systems. Furthermore, we will extend beyond the more historical focus on threat models and examine how disordered/altered emotional state and ANS processing may influence postural control and assessment. Finally, this paper will discuss studies that have been important in uncovering the modulatory effect of emotional state on postural control including links that may inform our understanding of disordered control, such as that observed in individuals living with Parkinson's disease and discuss methodological tools that have the potential to advance understanding of this complex relationship.

Manual cervical therapy and vestibular migraine: A case series

Background

Vestibular migraine (VM) is a relatively new diagnostic entity with incomplete knowledge regarding pathophysiological mechanisms and therapeutic guidelines. By reporting the effect of manual cervical therapy (MCT) on people with VM, we suggest a possible role for upper cervical afferents in VM treatment and/or pathogenesis. The objective was to describe the change in clinical presentation and self-reported symptoms of VM corresponding to MCT and followed up to six months.

Methods

A nonrandomised *ABA design was utilised to consecutively and prospectively evaluate selected patients with diagnosed VM. Symptom characteristics (frequency and intensity) were recorded along with standardised patient-reported outcomes (PROs) to document the response to MCT.

Results

Three patients were recruited who met the diagnostic criteria for VM. All three patients demonstrated improvement in both migraine attack and interictal symptom frequency. These improvements mirrored changes in PROs and were sustained over a six-month follow-up period.

Conclusions

The improvement that coincided with the intervention including MCT was rapid, observable and sustained. This suggests that the upper cervical spine could be a therapeutic target in VM and may have implications for future research into the pathogenesis of VM.

Microbiota-ear-brain interaction is associated with generalized anxiety disorder through activation of inflammatory cytokine responses

Introduction

Generalized anxiety disorder (GAD) is one of the most enduring anxiety disorders, being associated with increased systemic inflammation. However, the trigger and mechanisms underlying the activation of inflammatory cytokine responses in GAD remain poorly understood.

Materials and methods

We characterized the ear canal microbiome in GAD patients through 16S rRNA gene sequencing and metagenomic sequencing and identified the serum inflammatory markers in GAD patients. Spearman correlations were applied to test the relationship between the microbiota changes and systemic inflammation.

Results

Our findings showed the higher microbial diversity, accompanied with the significantly increased abundance of Proteobacteria, and decreased abundance of Firmicutes in the ear canal of GAD participants compared to that of the age- and sex-matched healthy controls (HC). Metagenomic sequencing showed that Pseudomonas aeruginosa were significantly increased at species-level in GAD patients. Furthermore, we observed the relative abundance of Pseudomonas aeruginosa was positively associated with elevated systemic inflammatory markers and the severity of disease, suggesting that these ear canal microbiota alterations might be correlated with GAD by activating the inflammatory response.

Conclusions

These findings indicate that microbiota-ear-brain interaction via upregulating inflammatory reaction involve in the development of GAD, as well as suggest that ear canal bacterial communities may be a target for therapeutic intervention.

Dizziness, psychological disorders and cognitive decline

INTRODUCTION

Dizziness is a common disorder, particularly among the elderly population. Aim of this paper was to revise the current concepts surrounding the relationship between dizziness, psychological disorders and cognitive decline.

EVIDENCE ACQUISITION

This is a PRISMA-compliant systematic review, including observational studies in people with dizziness. Database inception, Medline/Cochrane/Embase/Web of Science/Scopus/NHS evidence were searched until October 30, 2019.

EVIDENCE SYNTHESIS

Overall 22 studies, and 65,730 participants were included. Eleven studies were cross-sectional, 7 cross-sectional controlled, 2 prospective case-control, 1 retrospective case series, and 1 cohort study. The persistence of vestibular impairment (for 6 months or more) was correlated to the presence of psychological disorders affecting patient's Quality of Life and causing social anxiety, particularly in some conditions such as Ménière's disease. Interestingly, vestibular loss has been also correlated to cognitive impairment, with certain vestibular dysfunctions reported to be more prevalent in cognitive impaired individuals.

CONCLUSIONS

The current literature suggests that there is an association between vestibular function, psychological disorders and cognitive functions. The findings from this review could be useful in informing on the need for a multidimensional diagnostic and rehabilitative programs for patients with dizziness. More studies could explore the role of counseling or behavioral therapy with an aim to reduce the perceived dizziness-related disability.

Can vigilance predict the status of safe functional gait and risk of falls in patients with peripheral vestibular disorders? A cross-sectional study

OBJECTIVES

Peripheral vestibular disorders except from reflexes dysfunction correspond also to cognitive decline. The objectives of this cross-sectional study were to a) identify correlations among variables of functional gait, cognitive function, and perceived dizziness and b) explore variables that could be used as prognostic factors of functional gait in people with peripheral vestibular deficits.

METHODS

We recruited 154 people with peripheral vestibular deficits. The participants presented with moderate disability in terms of the Dizziness Handicap Inventory questionnaire (mean: 48.00, 95% confidence interval: 45.24-50.75), deficits in the Functional Gait Assessment test (mean: 22.75, 95% confidence interval: 22.13-23.40) and indication of mild cognitive impairment based on Montreal Cognitive Assessment tool (mean: 25.18, 95% confidence interval: 24.75-25.60).

RESULTS

Statistically significant correlations found among functional gait and gender, age, educational level, perceived level of disability and the total score of the Montreal Cognitive Assessment tool. Several components of the cognitive screening test (executive function, vigilance, language skills, verbal fluency) also correlated statistically significant with functional gait. Linear regression models revealed that age, perceived level of disability and vigilance significantly predicted functional gait variability (R² = 0.350; p < 0.001) as well as high risk of falling, as indicated by a score on Functional Gait Assessment test <22/30 (R² = 0.380).

CONCLUSIONS

Cognitive impairments affect functional gait in people with peripheral vestibular disorders. Thus, the integration of cognitive functional assessment must be considered as a prerequisite for functional assessment and designing rehabilitation programs that will include dual task training.

The brain-body disconnect: A somatic sensory basis for trauma-related disorders

Although the manifestation of trauma in the body is a phenomenon well-endorsed by clinicians and traumatized individuals, the neurobiological underpinnings of this manifestation remain unclear. The notion of somatic sensory processing, which encompasses vestibular and somatosensory processing and relates to the sensory systems concerned with how the physical body exists in and relates to physical space, is introduced as a major contributor to overall regulatory, social-emotional, and self-referential functioning. From a phylogenetically and ontogenetically informed perspective, trauma-related symptomology is conceptualized to be grounded in brainstem-level somatic sensory processing dysfunction and its cascading influences on physiological arousal modulation, affect regulation, and higher-order capacities. Lastly, we introduce a novel hierarchical model bridging somatic sensory processes with limbic and neocortical mechanisms regulating an individual's emotional experience and sense of a relational, agentive self. This model provides a working framework for the neurobiologically informed assessment and treatment of trauma-related conditions from a somatic sensory processing perspective.

Persistent Postural Perceptual Dizziness in Episodic Vestibular Disorders

Benign Paroxysmal Positional Vertigo (BPPV), Vestibular Migraine (VM), and Meniere Disease (MD) are among the most common episodic vestibulopathies. Persistent Postural Perceptual Dizziness (PPPD) is a chronic functional vestibular disorder that can arise in patients suffering from one or more of these conditions. We analyzed the role of these vestibular disorders as single or multiple associated comorbidities and as a precipitating condition for PPPD. A total of 376 patients suffering from dizziness with a known history of single or multiple vestibular disorders were preliminarily evaluated. We conducted a careful anamnesis to determine whether the reported dizziness could meet the diagnostic criteria for PPPD. PPPD was diagnosed in 24 cases; its incidence in patients with history of a single comorbidity or multiple vestibular comorbidities was 3.9% and 22.4%, respectively. BPPV, VM, and MD were identified as a precipitating condition in 2.34%, 16.45%, and 3.92%, respectively. BPPV constituted a precipitating condition mainly at the first episode. We observed that the presence of multiple vestibular comorbidities (BPPV, VM, and MD) in patients' clinical history increased the risk of PPPD. VM plays a significant role in representing a precipitating condition for PPPD, both when present individually or in association with the other vestibular disorders.

Involvement of the cerebellum in migraine

Migraine is a disabling neurological disease characterized by moderate or severe headaches and accompanied by sensory abnormalities, e.g., photophobia, allodynia, and vertigo. It affects approximately 15% of people worldwide. Despite advancements in current migraine therapeutics, mechanisms underlying migraine remain elusive. Within the central nervous system, studies have hinted that the cerebellum may play an important sensory integrative role in migraine. More specifically, the cerebellum has been proposed to modulate pain processing, and imaging studies have revealed cerebellar alterations in migraine patients. This review aims to summarize the clinical and preclinical studies that link the cerebellum to migraine. We will first discuss cerebellar roles in pain modulation, including cerebellar neuronal connections with pain-related brain regions. Next, we will review cerebellar symptoms and cerebellar imaging data in migraine patients. Lastly, we will highlight the possible roles of the neuropeptide calcitonin gene-related peptide (CGRP) in migraine symptoms, including preclinical cerebellar studies in animal models of migraine.

The Role of the Cerebellar and Vestibular Networks in Anxiety Disorders and Depression: the Internal Model Hypothesis

Clinical data and animal studies confirmed that the cerebellum and the vestibular system are involved in emotions. Nowadays, no real consensus has really emerged to explain the clinical symptoms in humans and behavioral deficits in the animal models. We envisage here that the cerebellum and the vestibular system play complementary roles in emotional reactivity. The cerebellum integrates a large variety of exteroceptive and proprioceptive information necessary to elaborate and to update the internal model: in emotion, as in motor processes, it helps our body and self to adapt to the environment, and to anticipate any changes in such environment in order to produce a time-adapted response. The vestibular system provides relevant environmental stimuli (i.e., gravity, self-position, and movement) and is involved in self-perception. Consequently, cerebellar or vestibular disorders could generate « internal fake news» (due to lack or false sensory information and/or integration) that could, in turn, generate potential internal model deficiencies. In this case, the alterations provoke false anticipation of motor command and external sensory feedback, associated with unsuited behaviors. As a result, the individual becomes progressively unable to cope with the environmental solicitation. We postulate that chronically unsuited, and potentially inefficient, behavioral and visceral responses to environmental solicitations lead to stressful situations. Furthermore, this inability to adapt to the context of the situation generates chronic anxiety which could precede depressive states.

Cognitive functions in episodic vestibular disorders: Meniere's disease and vestibular migraine

BACKGROUND

Cognitive deficits have been defined in patients with bilateral and unilateral vestibular loss.

OBJECTIVE

To investigate cognitive functions in patients with episodic vestibular disorders.

METHODS

Nineteen patients with Meniere's disease (MD), 19 patients with vestibular migraine (VM) and 21 age and education matched healthy controls were studied. Mini Mental State Examination assessing global mental status, Reading Span Test and the Stroop Test evaluating working memory, cognitive processing, reading comprehension and attention, Trail Making Test and Benton's Judgment of Line Orientation Test investigating visual processing, visuospatial skills, processing speed were used. Beck depression and anxiety inventories were given to evaluate the emotional status.

RESULTS

Cognitive test results of the MD and VM patients were not significantly different from the healthy controls (p > 0.05) as well as Beck depression scores (p = 0.14). Beck anxiety scores showed significant difference (p = 0.003). VM patients had significantly higher scores than the healthy controls (p = 0.002) on pairwise comparisons. The scores of the MD patients did not reach statistical significance (p = 0.15).

CONCLUSION

Episodic vestibular disorders like MD and VM without inter-ictal vestibular deficits do not seem to be associated with cognitive impairment. Patients with VM have significantly higher anxiety scores than the healthy controls and MD patients.

The Walls Are Closing In: Postural Responses to a Virtual Reality Claustrophobic Simulation

Background: Changes in the visual environment and thereby, the spatial orientation, can induce postural instability leading to falls. Virtual reality (VR) has been used to expose individuals to virtual environments (VE) that increase postural threats. Claustrophobia is an anxiety disorder categorized under situational phobias and can induce such postural threats in a VE. Purpose: The purpose of the study was to investigate if VR-generated claustrophobic simulation has any impact on postural threats that might lead to postural instability. Methods: Thirty healthy men and women (age: 20.7 ± 1.2 years; height: 166.5 ± 7.3 cm; mass: 71.7 ± 16.2 kg) were tested for postural stability while standing on a force platform, upon exposure to five different testing trials, including a normal stance (NoVR), in stationary VE (VR), and three consecutive, randomly initiated, unexpected claustrophobia trials (VR CP1, VR CP2, VR CP3). The claustrophobia trials involved all four walls closing in towards the center of the room. Center of pressure (COP)-derived postural sway variables were analyzed with a one-way repeated measures analysis of variance at an alpha level of 0.05. Results: Significant main effect differences existed in all but one dependent COP-derived postural sway variables, at p < 0.05. Post-hoc pairwise comparisons with a Bonferroni correction revealed that, predominantly, postural sway excursions were significantly lower in claustrophobia trials compared to NoVR and VR, but only accomplished with significantly increased sway velocity. Conclusion: The VR CP trials induced lower postural sway magnitude, but with increased velocity, suggesting a bracing and co-contraction strategy when exposed to virtual claustrophobic postural threats. Additionally, postural sway decreased with subsequent claustrophobia trials, suggesting potential motor learning effects. Findings from the study offer insights to postural control behavior under virtual claustrophobic simulations and can aid in VR exposure therapy for claustrophobia.

Gut Microbiome and Metabolome Changes in Mice With Acute Vestibular Deficit

Vestibular deficit is a very common disorder in clinical practice and is characterized by vertigo, spontaneous nystagmus, and autonomic nervous symptoms, including nausea, vomiting, and sweating. In addition, the comorbidity of vestibular deficit and anxiety has long been an integral component of the medical literature. Previous studies have suggested that the mechanisms underlying this comorbidity involved overlap of vestibular and cerebellar networks. Emerging evidence has shown that the microbiota–gut–brain axis plays a key role in the regulation of affective disorders. Thus, we hypothesized that the gut microbiota may be involved in the comorbidity of vestibular deficit and anxiety. To verify this, we constructed a unilateral labyrinthectomy mouse model to simulate vestibular deficit. Then, 16S rRNA gene sequencing and liquid chromatography–mass spectrometry (LC-MS) were used to analyze the microbiome and metabolome of the cecal samples collected from mice in the unilateral labyrinthectomy, sham surgery, and control groups. Notably, unilateral labyrinthectomy shaped the composition of the mouse gut microbiome, resulting in increased abundance of Lachnospiraceae NK4A136 group, Odoribacter and Roseburia and decreased abundance of Prevotella and Parasutterella at the genus level. Tax4Fun functional prediction indicated a decrease in tryptophan metabolism in mice in the unilateral labyrinthectomy group. Moreover, functional correlation of changes in gut microbes and metabolites between different groups showed that the oleamide level was negatively correlated with Odoribacter abundance (r = -0.89, p = 0.0002). The butyric acid level was positively correlated with Parasutterella abundance (r = 0.85, p = 0.0010). The propanoate level was negatively correlated with Prevotella abundance (r = -0.81, p = 0.0020). The 20-HETE level was positively correlated with Parasutterella abundance (r = 0.84, p = 0.0013). The altered microbes and metabolites were closely related to the pathogenesis of affective disorders. Our results not only offer novel insights into the vestibular deficit comorbid with anxiety but also build an important basis for future research on this etiology.

Influence of sex hormones on vestibular disorders

PURPOSE OF REVIEW

Vestibular disorders are gender distributed with a higher prevalence in women. Although research has increased in this field, the mechanisms underlying this unbalance is unclear. This review summarises recent advances in this research sphere, and briefly discusses sex hormone effects on various vestibular conditions and highlights some recent theories.

RECENT FINDINGS

Recent work has identified a direct link between aberrant gonadal hormone levels and vestibular dysfunction. Benign paroxysmal positional vertigo research suggests that the disorder may be linked to the rapid decrease in oestrogen, observed in menopausal women, which disrupts otoconial metabolism within the inner ear. A successful hormonal therapeutic intervention study has advanced our knowledge of hormonal influences in the inner ear in Ménière's disease. Also, several studies have focused on potential mechanisms involved in the interaction between Vestibular Migraine, Mal de Debarquement Syndrome, and gonadal hormones.

SUMMARY

In females, gonadal hormones and sex-specific synaptic plasticity may play a significant role in the underlying pathophysiology of peripheral and central vestibular disorders. Overall, this review concludes that clinical assessment of female vestibular patients requires a multifaceted approach which includes auditory and vestibular medicine physicians, gynaecologists and/or endocrinologists, in conjunction with hormonal profile evaluations.

Migraine phenotype differentially modulates the attentional network: A cross sectional observation study

Background:

Signs of distinct brain dysfunction in patients where migraine intersects with vertigo (i.e. vestibular migraine (VM)), remain elusive. As migraine and vertigo can both independently modulate attentional processes, here we seek the utility of the attentional network to functionally differentiate patients.

Methods:

We used the Attentional Network Task (ANT) to elucidate three separate functional networks: Alerting, orienting and resolving conflict. 120 participants had to attend to the direction of a target visual stimulus, while other parameters were simultaneously manipulated. Reaction times across the networks were assessed in, (i) 30 healthy controls, (ii) 30 VM patients, (iii) 30 patients with migraine without vertigo, and (iv) 30 patients with benign paroxysmal positional vertigo (BPPV) but no migraine.

Results:

Patients with VM (mean = 737.1 ms, SEM = 28), migraine (mean = 735.3 ms, SEM = 36.4), and BPPV (mean = 720.3 ms SEM = 24.3) all exhibited significantly delayed ANT reaction times compared to healthy controls (mean = 661.3 ms, SEM = 23.4). Specific attentional network deficits were observed for resolving conflict in VM, alerting in migraine and orienting in BPPV.

Conclusion:

VM patients displayed deficits in executive function characterized by an inability to focus attentional resources and suppress peripheral distractors, whereas migraineurs without vertigo exhibited changes in the alerting network that reflects hypervigilance.

The role of basolateral amygdala orexin 1 receptors on the modulation of pain and psychosocial deficits in nitroglycerin-induced migraine model in adult male rats

Background

Migraine headaches have been associated with sensory hyperactivity and anomalies in social/emotional responses. The main objective of this study was to evaluate the potential involvement of orexin 1 receptors (Orx1R) within the basolateral amygdala (BLA) in the modulation of pain and psychosocial dysfunction in a nitroglycerin (NTG)-induced rat model of migraine.

Methods

Adult male Wistar rats were injected with NTG (5 mg/kg, intraperitoneal) every second day over nine days to induce migraine. The experiments were done in the following six groups (6 rats per group) untreated control, NTG, NTG plus vehicle, and NTG groups that were post-treated with intra-BLA microinjection of Orx1R antagonist SB-334867 (10, 20, and 40 nM). Thermal hyperalgesia was assessed using the hot plate and tail-flick tests. Moreover, the elevated plus maze (EPM) and open field (OF) tests were used to assess anxiety-like behaviors. The animals’ sociability was evaluated using the three-chamber social task. The NTG-induced photophobia was assessed using a light-dark box.

Results

We observed no change in NTG-induced thermal hyperalgesia following administration of SB-334867 (10, 20, and 40 nM). However, SB-334867 (20 and 40 nM) aggravated the NTG-induced anxiogenic responses in both the EPM and OF tasks. The NTG-induced social impairment was overpowered by SB-334867 at all doses. Time spent in the dark chamber of light-dark box was significantly increased in rats treated with SB-334867 (20 and 40 nM/rat).

Conclusions

The findings suggest a role for Orx1R within the BLA in control comorbid affective complaints with migraine in rats.

Danger and distress: Parabrachial-extended amygdala circuits

Our understanding of the role of the parabrachial nucleus (PBN) has evolved as technology has advanced, in part due to cell-specific studies and complex behavioral assays. This is reflected in the heterogeneous neuronal populations within the PBN to the extended amygdala (EA) circuits which encompass the bed nucleus of the stria terminalis (BNST) and central amygdala (CeA) circuitry, as they differentially modulate aspects of behavior in response to diverse threat-like contexts necessary for survival. Here we review how the PBN→CeA and PBN→BNST pathways differentially modulate fear-like behavior, innate and conditioned, through unique changes in neurotransmission in response to stress-inducing contexts. Furthermore, we hypothesize how in specific instances the PBN→CeA and PBN→BNST circuits are redundant and in part intertwined with their respective reciprocal projections. By deconstructing the interoceptive and exteroceptive components of affect- and stress related behavioral paradigms, evidence suggests that the PBN→CeA circuit modulates innate response to physical stimuli and fear conditioning. Conversely, the PBN→BNST circuit modulates distress-like stress in unpredictable contexts. Thereby, the PBN provides a pathway for alarming interoceptive and exteroceptive stimuli to be processed and relayed to the EA to induce stress-relevant affect. Additionally, we provide a framework for future studies to detail the cell-type specific intricacies of PBN→EA circuits in mediating behavioral responses to threats, and the relevance of the PBN in drug-use as it relates to threat and negative reinforcement. This article is part of the special Issue on 'Neurocircuitry Modulating Drug and Alcohol Abuse'.

Reduced vestibular perception thresholds in persistent postural-perceptual dizziness- a cross-sectional study

Background

Persistent postural-perceptual dizziness (PPPD) is the most common functional vestibular disorder. A multisensory mismatch altered by psychological influences is considered to be an important pathophysiological mechanism. Increased cortical and subcortical excitability may play a role in the pathophysiology of PPPD. We hypothesized that decreased motion perception thresholds reflect one mechanism of the abnormal vestibular responsiveness in this disorder. We investigated the vestibular perception thresholds and the vestibular ocular reflex with a rotatory chair experiment to gain insights in the processing and adaption to vestibular provocation.

Methods

In this cross-sectional study 26 female PPPD patients and 33 healthy female age matched controls (HC) were investigated sitting in a motorized rotary chair shielded regarding visual and acoustic stimuli. The chair was rotated for 20 minutes with slowly increasing velocity to a maximum of 72°/s. We functionally tested motion perception thresholds and vegetative responses to rotation as well as vestibular-ocular reflex thresholds. We additionally investigated several psychological comorbidities (i.e. depression, anxiety, somatosensory amplification) using validated scores. Conventional dizziness scores were obtained to quantify the experienced dizziness and impact on daily life.

Results

PPPD patients showed a significant reduced vestibulo-perceptual threshold (PPPD: 10.9°/s vs. HC: 29.5°/s; p<0.001) with increased motion sensitivity and concomitant vegetative response during and after the chair rotation compared to healthy controls. The extent of increased vestibular sensitivity was in correlation with the duration of the disease (p=0.043). No significant difference was measured regarding nystagmus parameters between both groups.

Conclusion

PPPD patients showed increased vegetative response as well as decreased vestibulo-perceptual thresholds which are related to disease duration. This is of interest as PPPD might be sustained by increased vestibular excitability leading to motion intolerance and induction of dizziness when exposed to movement.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02417-z.

The Role of the Functional Head Impulse Test with and without Optokinetic Stimuli in Vestibular Migraine and Acute Unilateral Vestibulopathy: Discovering a Dynamic Visual Dependence

(1) Background: Visually induced vertigo (i.e., vertigo provoked by moving visual scenes) can be considered a noticeable feature of vestibular migraines (VM) and can be present in patients suffering from acute unilateral vestibulopathy (AUV). Hypersensitivity to moving or conflicting visual stimulation is named visual dependence. (2) Methods: Visuo-vestibular interactions were analyzed via the functional Head Impulse Test (fHIT) with and without optokinetic stimulation (o-fHIT) in 25 patients with VM, in 20 subjects affected by AUV, and in 20 healthy subjects. We calculated the percentage of correct answers (%CA) without and with the addition of the optokinetic background (OB). (3) In VM groups, the %CA on the fHIT was 92.07% without OB and 73.66% with OB. A significant difference was found between %CA on the deficit side and that on the normal side in AUV, both without OB and with OB. (4) Conclusions: The fHIT results in terms of %CA with and without OB could be useful to identify the presence of a dynamic visual dependence, especially in patients suffering from VM. The difference in %CA with and without OB could provide instrumental support to help correctly identify subjects suffering from VM. We propose the use of the fHIT in clinical practice whenever there is a need to highlight a condition of dynamic visual dependence.

Persistent postural perceptual dizziness following paroxysmal positional vertigo in migraine

Objective

This prospective study aimed to investigate the role of migraine in favouring the onset of persistent postural perceptual dizziness (PPPD) following paroxysmal positional vertigo (PPV).

Methods

A group of patients who came to our attention suffering of PPV with or without migraine and/or vestibular migraine (VM) was examined. Three months after the resolution, an anamnestic research was conducted aimed at establishing whether any patient-related dizziness could meet the diagnostic criteria for PPPD.

Results

12 of the 240 patients recruited met the diagnostic criteria for PPPD for an overall incidence of 5%, with 3 (1.85%) belonging to the non-migraine group and 9 (11.5%) to the migraine group. In the latter, 6 (28.6%) patients with VM and 3 (5.26%) without VM were affected.

Conclusions

The study shows a significant increase of PPPD diagnosis in migraine compared to patients without migraine (p = 0.003). Within migraine there was a significant increase in those with VM compared to patients without VM (p = 0.0016). No difference emerged between patients without migraine and migraine patients without VM (p > 0.05). The presence of VM in patient’s history, but not migraine without VM, appears to significantly increase the incidence of PPPD in patients with PPV.

Physiological separation of Alzheimer's disease and Alzheimer's disease with significant levels of cerebrovascular symptomology and healthy controls

Most dementia patients with a mixed dementia (MxD) diagnosis have a mix of Alzheimer's disease (AD) and vascular dementia. Electrovestibulography (EVestG) records vestibuloacoustic afferent activity. We hypothesize EVestG recordings of AD and MxD patients are different. All patients were assessed with the Montreal cognitive assessment (MoCA) and Hachinski ischemic scale (HIS) (> 4 HIS score < 7 is representative of MxD cerebrovascular symptomology). EVestG recordings were made from 26 AD, 21 MxD and 44 healthy (control) participants. Features were derived from the EVestG recordings of the average field potential and field potential interval histogram to classify the AD, MxD and control groups. Multivariate analysis was used to test the features' significance. Using a leave-one-out cross-validated linear discriminant analysis with 3 EVestG features yielded accuracies > 80% for separating pairs of AD/MxD/control. Using the MoCA assessment and 2 EVestG features, a best accuracy of 81 to 91% depending on the classifier was obtained for the 3-way identification of AD, MxD and controls. EVestG measures provide a physiological basis for identifying AD from MxD. EVestG measures are hypothesized to be partly related to channelopathies and changes in the descending input to the vestibular periphery. Four of the five AD or MxD versus control features used had significant correlations with the MoCA. This supports assertions that the pathologic changes associated with AD impact the vestibular system and further are suggestive that the postulated physiological changes behind these features have an association with cognitive decline severity.

Caloric and galvanic vestibular stimulation for the treatment of Parkinson's disease: rationale and prospects

Introduction: Deeply embedded within the inner ear, the sensory organs of the vestibular system are exquisitely sensitive to the orientation and movement of the head. This information constrains aspects of autonomic reflex control as well as higher-level processes involved in cognition and affect. The anatomical pathways that underline these functional interactions project to many cortical and sub-cortical brain areas, and the question arises as to whether they can be therapeutically harnessed.Areas covered: The body of work reviewed here indicates that the controlled application of galvanic or thermal current to the vestibular end-organs can modulate activity throughout the ascending vestibular network and, under appropriate conditions, reduce motor and non-motor symptoms associated with Parkinson's disease, a disease of growing prevalence and continued unmet clinical need.Expert opinion: The appeal of vestibular stimulation in Parkinson's disease is underpinned by its noninvasive nature, favorable safety profile, and capacity for home-based administration. Clinical adoption now rests on the demonstration of cost-effectiveness and on the commercial availability of suitable devices, many of which are only permitted for research use or lack functionality. Dose optimization and mechanisms-of-action studies are also needed, along with a broader awareness amongst physicians of its therapeutic potential.

Vestibular Rehabilitation after Vestibulopathy Focusing on the Application of Virtual Reality

Human postural control is regulated by the vestibular, somatosensory, and visual systems. These types of sensory information are integrated in the central nervous system to ascertain the body’s position in space. Proper functioning of the vestibular, somatosensory, and visual senses is necessary for the body to maintain equilibrium. Bilateral vestibulopathy (BVP) is a condition in which bilateral peripheral vestibular function is reduced. Its treatment includes vestibular rehabilitation (VeR), balance training, counseling, treating the underlying cause, and avoiding further damage to the vestibular system. As VeR is often tedious for patients, patient motivation is required or patients may drop out of the program. To solve this problem, in recent years, there have been increasing reports of VeR using virtual reality, which increases vestibulo-ocular reflex gain and decreased dizziness by inducing adaptation. In this review, we discuss VeR, particularly for BVP, and VeR using virtual reality.

[Anxiety and depression state among patients with different type of vertigo and dizziness]

Objective:To assess the status of anxiety and depression among patients with different type of vertigo and dizziness, and to figure out the possible reason. Methods:The data of the patients with vertigo from November 2017 to June 2020 were reviewed, and their status of anxiety and depression were assessed using self-rating anxiety scale（SAS） and self-rating depression scale（SDS）. Results:A total of 559 patients with vertigo were enrolled, including 94 cases for vestibular migraine （VM）, 86 cases for Meniere disease （MD）, 78 cases for benign paroxysmal positional vertigo （BPPV）, 77 cases for sudden hearing loss（SHL） with vertigo, 74 cases for no definite diagnosis, 58 cases for vestibular neuritis （VN）, 57 cases for benign recurrent vertigo （BRV） and 35 cases for persistent postural-perceptual dizziness （PPPD）.The incidence of anxiety is 43.11%（no definite diagnosis=64.86%, VM=63.83%, MD=55.81%, PPPD=48.57%, BRV=47.37%）, and the incidence of depression is 11.27% （no definite diagnosis=25.68%, PPPD=17.14%, VM=14.89%, BRV=14.04%, MD=12.79%）. Kruskal-Wallis test was used to analyze SAS and SDS scores of patients with vertigo. The results showed that there were significant differences in each group. All patients were divided into 3 groups according to the duration of vertigo. The anxiety incidence of >2 years group was highest（58.56%）, and the second one was 2 months to 2 years group（54.75%）. There was no statistically significant difference between 2 groups by χ²test（P>0.05）. But both of them were significantly higher than the <2 months group（17.30%）. The depression incidence of >2 years group was highest（32.43%）, the second one was 2 months to 2 years group（10.27%）, and the lowest one was <2 months group（0%）. χ² test（P<0.01） showed statistically significant differences among these three groups. Conclusion:Anxiety is more common among patients with vertigo than depression, and the patients who suffer from VM，MD，PPPD or BRV have significantly higher rates of psychiatric comorbidity.

Impact of caloric test asymmetry on response to treatment in vestibular migraine

OBJECTIVE

This study aimed to examine the association between caloric asymmetry and response to treatment in patients with vestibular migraine.

METHOD

Dizziness Handicap Inventory scores were compared between patients with less than and more than 25 per cent asymmetry (using Cohen effect size) in a cohort of definite vestibular migraine patients who underwent caloric testing between August 2016 and March 2019.

RESULTS

A total of 31 patients (mean age: 48.7 ± 20.0 years; mean follow up: 9.1 ± 8.1 months) were included. Mean caloric asymmetry was 15.1 ± 15.6 per cent, with 6 (19.4 per cent) patients having asymmetry more than 25 per cent. Overall, patients experienced significant improvement in Dizziness Handicap Inventory total (d = 0.623 (95 per cent confidence interval, 0.007, 1.216)), emotional domain (d = 0.635 (95 per cent confidence interval, 0.019, 1.229)) and functional domain (d = 0.769 (95 per cent confidence interval, 0.143, 1.367)) but not physical domain (d = 0.227 (95 per cent confidence interval, -0.370, 0.815)) scores. Patients with more than 25 per cent asymmetry had no significant improvement in Dizziness Handicap Inventory scores, whereas those with less than 25 per cent asymmetry had significant improvement in Dizziness Handicap Inventory functional domain scores only (d = 0.636 (95 per cent confidence interval, 0.004, 1.244)).

CONCLUSION

Vestibular migraine patients with peripheral vestibular weakness on caloric testing may be less likely to improve after treatment compared with those without.

'Excess anxiety' and 'less anxiety': both depend on vestibular function

PURPOSE OF REVIEW

To present evidence of a functional interrelation between the vestibular and the anxiety systems based on a complex reciprocally organized network. The review focuses on the differential effects of various vestibular disorders, on psychiatric comorbidity, and on anxiety related to vertigo.

RECENT FINDINGS

Episodic vertigo syndromes such as vestibular migraine, vestibular paroxysmia, and Menière's disease are associated with a significant increase of psychiatric comorbidity, in particular anxiety/phobic disorders and depression. Chronic unilateral and bilateral vestibulopathy (BVP) do not exhibit a higher than normal psychiatric comorbidity. Anxiety related to the vertigo symptoms is also increased in episodic structural vestibular disorders but not in patients with chronic unilateral or bilateral loss of vestibular function. The lack of vertigo-related anxiety in BVP is a novel finding. Several studies have revealed special features related to anxiety in patients suffering from BVP: despite objectively impaired postural balance with frequent falls, they usually do not complain about fear of falling; they do not report an increased susceptibility to fear of heights; they do not have an increased psychiatric comorbidity; and they do not report increased anxiety related to the perceived vertigo. Subtle or moderate vestibular stimulation (by galvanic currents or use of a swing) may have beneficial effects on stress or mood state in healthy adults, and promote sleep in humans and rodents. The intimate structural and functional linkage of the vestibular and anxiety systems includes numerous nuclei, provincial and connector hubs, the thalamocortical network, and the cerebellum with many neural transmitter systems.

SUMMARY

The different involvement of emotional processes and anxiety - to the extent of 'excess anxiety' or 'less anxiety' - in structural vestibular disorders may be due to the specific dysfunction and whether the system activity is excited or diminished. Both psychiatric comorbidity and vertigo-related anxiety are maximal with excitation and minimal with loss of peripheral vestibular function.

The Migraine-Anxiety Comorbidity Among Migraineurs: A Systematic Review

Background: Migraine is recognized as a neurological condition that is often associated with comorbid psychiatric symptoms such as anxiety, depression, bipolar disorder and/or panic disorder. Though some studies have demonstrated the link between migraine and anxiety disorders, there are no systematic reviews that have been published in this area to summarize the evidence. The aim of the present study is to systematically review the literature associated with comorbidity of migraine and anxiety disorders among migraineurs compared to non-migraineurs.

Methods: The present systematic review included population-based, cohort and cross-sectional studies if they were reporting the frequency of migraine with either anxiety or depression as diagnosed by a medical practitioner according to the International Classification of Headache Disorders (ICHD-2/3).

Results: Eight eligible studies from 2060 relevant citations were included in the review. All participants were migraine patients from both primary care and outpatient settings, as well as tertiary headache and anxiety centers, and were compared to non-migraineurs. The results of the systematic review showed that there is a strong and consistent relationship between migraine and anxiety. The co-morbidity of co-occurrence for migraine and anxiety has an average OR of 2.33 (2.20–2.47) among the prevalence and cross sectional studies and an average RR of 1.63 (1.37–1.93) for two cohort studies; The major limitations of included studies were small sample sizes and a lack of adjusting of confounding factors.

Conclusion: The results highlight the need for inclusion of an anxiety screening tool during initial assessments of migraine patients by medical practitioners and/or physicians and may explain why some anxiolytic medications work better than others for migraine mitigation.

Severity and Its Contributing Factors in Patients With Vestibular Migraine: A Cohort Study

Objective: As a recently defined disease entity, vestibular migraine (VM) is a variant of migraine with broad spectrum of manifestations. We evaluated a prospective cohort of patients with VM in two centers to assess severity of VM attacks and investigate its contributing factors in patients with VM. Methods: Adult participants with the diagnosis of VM or probable VM were enrolled according to the 2012 International Headache Society-Bárány Society Criteria. Every outpatient was followed up for 6 months to record the occurrence of VM attacks. Clinical data such as age, sex, number of VM attacks, severity on the visual analog scale, and lipid intake were collected and analyzed. Generalized Anxiety Disorder-7, Patient Health Questionnaire-9, Horne and Ostberg Morningness-Eveningness Questionnaires, and Pittsburgh Sleep Quality Index were also administered to find contributing factors. Results: During a 6-month clinical follow-up, 313 VM attack were reported. According to the Visual Analog Scale, the patients were divided into two groups. Then univariate and multivariable analyses were conducted. Among the risk factors, duration of illness (adjusted OR, 1.041; 95% CI, 1.010-1.073; P = 0.009), time of onset: 00:00:00-12:00:00 (adjusted OR, 3.961; 95% CI, 1.966-7.979; P < 0.001) and PSQI scores (adjusted OR, 1.086; 95% CI, 1.002-1.178; P = 0.046) were significantly associated with the severity of VM attack assessed by VAS. Conclusion: The data suggest that patients tended to experienced more severe VM attacks in early hours of a day, especially for those sufferers with longer duration of illness or poor sleep quality. Targeted management of such factors is required to reduce the severity of attacks.

Mal de Debarquement Syndrome: A Matter of Loops?

Introduction: Mal de Debarquement Syndrome (MdDS) is a poorly understood neurological disorder affecting mostly perimenopausal women. MdDS has been hypothesized to be a maladaptation of the vestibulo-ocular reflex, a neuroplasticity disorder, and a consequence of neurochemical imbalances and hormonal changes. Our hypothesis considers elements from these theories, but presents a novel approach based on the analysis of functional loops, according to Systems and Control Theory.

Hypothesis: MdDS is characterized by a persistent sensation of self-motion, usually occurring after sea travels. We assume the existence of a neuronal mechanism acting as an oscillator, i.e., an adaptive internal model, that may be able to cancel a sinusoidal disturbance of posture experienced aboard, due to wave motion. Thereafter, we identify this mechanism as a multi-loop neural network that spans between vestibular nuclei and the flocculonodular lobe of the cerebellum. We demonstrate that this loop system has a tendency to oscillate, which increases with increasing strength of neuronal connections. Therefore, we hypothesize that synaptic plasticity, specifically long-term potentiation, may play a role in making these oscillations poorly damped. Finally, we assume that the neuromodulator Calcitonin Gene-Related Peptide, which is modulated in perimenopausal women, exacerbates this process thus rendering the transition irreversible and consequently leading to MdDS.

Conclusion and Validation: The concept of an oscillator that becomes noxiously permanent can be used as a model for MdDS, given a high correlation between patients with MdDS and sea travels involving undulating passive motion, and an alleviation of symptoms when patients are re-exposed to similar passive motion. The mechanism could be further investigated utilizing posturography tests to evaluate if subjective perception of motion matches with objective postural instability. Neurochemical imbalances that would render individuals more susceptible to developing MdDS could be investigated through hormonal profile screening. Alterations in the connections between vestibular nuclei and cerebellum, notably GABAergic fibers, could be explored by neuroimaging techniques as well as transcranial magnetic stimulation. If our hypothesis were tested and verified, optimal targets for MdDS treatment could be found within both the neural networks and biochemical factors that are deemed to play a fundamental role in loop functioning and synaptic plasticity.

Symptom Presentation After Concussion and Pre-existing Anxiety Among Youth Athletes

Our purpose was to evaluate the effect of self-reported pre-injury anxiety diagnosis on persistent symptom development, vestibular symptom severity, and balance control among youth who sustained a concussion. We performed a retrospective study of patients seen at a specialty pediatric concussion clinic. Patients were 18 years of age or younger, examined within 10 days of concussion, and received care until full recovery. A questionnaire was used to assess pre-existing medical and psychiatric conditions, including anxiety. Our main outcomes were prolonged symptom recovery defined as persistent symptoms for > 28 days after concussion) and severity of vestibular symptoms. Patients who reported pre-injury anxiety (n=43; median age=14.9 years; 37% female) were more likely to experience symptoms>28 days post-injury (76 vs. 54%; p=0.04) than those without pre-existing anxiety (n=241; median age=14.9 years; 53% female). After adjusting for sex, history of migraine, depression and ADHD, however, there was no independent association between pre-existing anxiety and prolonged symptom duration (adjusted odds ratio=2.34; 95% CI=0.083–6.63; p=0.11). Pre-existing anxiety was independently associated with self-reported nausea/vomiting severity (β coefficient=0.59, 95% CI=0.07–1.11). A pre-existing anxiety diagnosis does not appear to be associated with persistent symptoms after concussion, although it may be associated with post-injury nausea.