Pharmacotherapy of vestibular and cerebellar disorders and downbeat nystagmus: translational and back-translational research

Significance of endolymphatic sac surgery with and/or without simultaneous cochlea implant surgery in respect of vertigo control and speech perception in patients with Menière's disease

PURPOSE

The focus on treating patients with Menière's Disease (MD) lies on the reduction of vertigo attacks and the preservation of sensory function. Endolympathic hydrops is considered as an epiphenomenon in MD, which can potentially be altered by endolymphatic sac surgery (ESS). Purpose of the study was to investigate the influences on vertigo control through manipulation of the perilymphatic system with or without ESS.

METHODS

Retrospective data analysis of 86 consecutive patients with MD according to current diagnostic criteria after endolymphatic sac surgery alone (ESSalone; n = 45), cochlear implantation (CI) alone (CIalone; n = 12), and ESS with CI (ESS + CI; n = 29), treated at a tertiary referral center.

MAIN OUTCOME MEASURES

vertigo control, speech perception pre- and postoperatively.

RESULTS

Gender, side, and preoperative treatment were similar in all groups. Age was younger in the ESSalone-group with 56.2 ± 13.0 years (CIalone = 64.2 ± 11.4 years; ESS + CI = 63.1 ± 9.7 years). Definitive MD was present in all the CIalone, in 79.3% of the ESS + CI and in 59.6% of the ESSalone-patients. Likewise, vertigo control rate was 100% in the CIalone, 89.7% in the ESS + CI and 66.0% in the ESSalone-group.

CONCLUSIONS

Vertigo control was improved in all three groups, however, superior in groups treated with CI, potentially contributed by the manipulation of both the endo- and perilymphatic systems. A more systematic characterization of the patients with larger case numbers and documentation of follow up data would be needed to evaluate a clinical effect more properly.

Rapid analysis of the chemical constituents in Qiangli Dingxuan tablets using ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry

Qiangli Dingxuan (QLDX) tablet is a widely recognized traditional Chinese medicine formula that has been extensively used in China for decades to treat vertigo, tinnitus, and dizziness owing to its outstanding therapeutic outcomes. However, the complexity of the chemical components in this tablet makes it challenging to separate and identify these components. This study presented an effective and sensitive strategy for the rapid separation and simultaneous structural identification of QLDX tablet components using ultra-performance liquid chromatography with quadrupole time-of-flight tandem mass spectrometry and the UNIFI platform. Based on retention times, accurate masses, fragment ions, related literature, and authentic standards, 119 compounds were identified or tentatively characterized; these included 9 iridoids, 12 lignans, 21 phenylpropanoids, 27 flavonoids, 7 phthalides, and 43 others. Among them, 36 were confirmed using reference standards. The representative compounds with various chemical structures were studied by analyzing their fragmentation patterns and characteristic ions. In conclusion, this study established a rapid approach for characterizing the chemical constituents in QLDX tablet. The proposed approach provides a basis for qualitative analysis and quality control in the manufacturing process and is beneficial for advancing investigations into the efficacy and mechanism of action of this tablet.

Comparison of the Efficacy of Vestibular Rehabilitation and Pharmacological Treatment in Benign Paroxysmal Positional Vertigo

Aim: The aim of the study is to compare the effects of vestibular rehabilitation and pharmacological treatment in benign paroxysmal positional vertigo (BPPV). Materials and methods: Thirty patients (40.93 ± 8.66 years old) diagnosed with BPPV were recruited. Patients were equally divided into pharmacological control group and vestibular rehabilitation group. The pharmacological control group was further divided into Group A (n = 8, 2 doses/day, 24 mg betahistine) and Group B (n = 7, 1 dose/day, 50 mg dimenhydrinate in addition to betahistine). Patients in the rehabilitation group underwent repeated head and eye movements, and Epley or Barbecue Roll Maneuvers were applied for 4 weeks. Subjective assessment of vertigo was measured with the visual analog scale. Static balance parameters were measured with the tandem, one-legged stance, and Romberg tests. Dynamic visual acuity was measured with a Snellen chart, and vestibular dysfunction was measured with the Unterberger (Fukuda stepping) test. All parameters were evaluated before and after treatment. Results: Vestibular rehabilitation resulted in greater improvement in severity of vertigo, balance parameters except Romberg test, and vestibular dysfunction than pharmacological therapy (p < 0,001). There was no significant difference in dynamic visual acuity between groups (p = 0,24). The effects of medication with the active ingredients betahistine and dimenhydrinate were similar (p > 0,05). Conclusion: The vestibular rehabilitation method can positively change the severity of vertigo, balance ability, and vestibular dysfunction compared to pharmacological therapy. Dimenhydrinate administered in combination with betahistine was not superior to betahistine alone but can be recommended for its antiemetic effect.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03598-4.

Vestibular and audiometric results after endolymphatic mastoid shunt surgery in patients with Menière's disease

PURPOSE

Treatment of Menière's Disease (MD) comprises an array of both non-destructive and destructive treatment options. In patients who are therapy-refractory to non-destructive medical treatment, endolymphatic mastoid shunt surgery (EMSS) is both recommended and debated controversially. The aim of this study was to investigate safety in terms of hearing, vestibular function, complication rate, and efficacy with regards to vertigo control of EMSS in patients with MD according to the current diagnostic criteria of 2015.

METHODS

Retrospective analysis of 47 consecutive patients with definite or probable MD with description of demographic parameters, pre- and postoperative MD treatment, pre- and postoperative audiometric (pure tone audiometry) and vestibular (caloric testing) results. The parameters were compared between patients with and without postoperative vertigo control.

RESULTS

31/47 patients (66.0%) had improved vertigo control postoperatively. Postoperative hearing and vestibular preservation were predominantly stable. No significant differences between patients with improved vertigo control and patients with no change or worse vertigo episodes were found. In the treatment refractory group, 4 patients required a revision EMSS and 6 a destructive MD treatment (5 gentamicin intratympanically, 1 labyrinthectomy). No peri- or postsurgical complications were reported.

CONCLUSIONS

EMSS was found to be beneficial in two thirds of the patients with definite or probable Morbus Menière and a safe procedure regarding hearing and vestibular preservation with no postoperative complications. Therefore, EMSS should be considered before inducing destructive treatment options, such as intratympanic gentamicin application or labyrinthectomy.

[Vertical nystagmus]

The review article provides a definition and classification of different nystagmus types, a comparative description of the central and peripheral vestibular nystagmus. The pathogenetic patterns of up-beating and down-beating nystagmus are accurately described. The features of nystagmus formation in various diseases are discussed, such as Wernicke encephalopathy, Arnold-Chiari anomaly, spinocerebellar ataxia and vestibular migraine. The authors provide their own data on oculomotor disorders in 100 patients with vestibular migraine and migraine with a brain stem aura. This article considers approaches to treatment: surgical and conservative. In conclusion, was noted the possibility of differentiating the central and peripheral vestibular nystagmus by means of clinical study. As well, the differences between vertical nystagmus associated with organic lesions of the brain stem or cerebellum and transient nystagmus with vestibular migraine are highlighted. The authors note the need for in-depth studies of nystagmus in vestibular migraine patients and methods of dealing with it.

[Betahistine in vestibular disorders: current concepts and perspectives]

The goal of this paper is to review the pharmacological profile of betahistine and evidence for using it in the treatment of common vestibular disorders. Betahistine is a weak agonist for histamine H1 receptors and strong antagonist for histamine H3 receptors. It demonstrates the maximum benefit in different types of peripheral vertigo, especially in Meniere's disease. The best results in decreasing intensity of vertigo, frequency of attacks and stimulation of vestibular compensation were obtained in daily dose 48 mg during 3 months. In benign paroxysmal positional vertigo betahistine is used to treat residual dizziness after successful treatment of otolithiasis and to reduce the severity of vertigo during repositioning maneuvers. In vestibular neuritis betahistine stimulates central compensation during vestibular rehabilitation. A new once-daily drug formulation of modified-release betahistine is non-inferior to traditional and has a comparable safety profile, and could improve patient adherence. The implication of betahistine in the treatment of central vestibular disorders is under-researched. The efficacy of betahistine in increasing of vestibular compensation in post-stroke central vestibular disorders, persistent postural-perceptual dizziness and its role in vestibular migraine need further investigation.

Neurotology: definitions and evidence-based therapies - Results of the I Brazilian Forum of Neurotology

Introduction

Neurotology is a rapidly expanding field of knowledge. The study of the vestibular system has advanced so much that even basic definitions, such as the meaning of vestibular symptoms, have only recently been standardized.

Objective

To present a review of the main subjects of neurotology, including concepts, diagnosis and treatment of Neurotology, defining current scientific evidence to facilitate decision-making and to point out the most evidence-lacking areas to stimulate further new research.

Methods

This text is the result of the I Brazilian Forum of Neurotology, which brought together the foremost Brazilian researchers in this area for a literature review. In all, there will be three review papers to be published. This first review will address definitions and therapies, the second one will address diagnostic tools, and the third will define the main diseases diagnoses. Each author performed a bibliographic search in the LILACS, SciELO, PubMed and MEDLINE databases on a given subject. The text was then submitted to the other Forum participants for a period of 30 days for analysis. A special chapter, on the definition of vestibular symptoms, was translated by an official translation service, and equally submitted to the other stages of the process. There was then a in-person meeting in which all the texts were orally presented, and there was a discussion among the participants to define a consensual text for each chapter. The consensual texts were then submitted to a final review by four professors of neurotology disciplines from three Brazilian universities and finally concluded. Based on the full text, available on the website of the Brazilian Association of Otorhinolaryngology and Cervical-Facial Surgery, this summary version was written as a review article.

Result

The text presents the official translation into Portuguese of the definition of vestibular symptoms proposed by the Bárány Society and brings together the main scientific evidence for each of the main existing therapies for neurotological diseases.

Conclusion

This text rationally grouped the main topics of knowledge regarding the definitions and therapies of Neurotology, allowing the reader a broad view of the approach of neurotological patients based on scientific evidence and national experience, which should assist them in clinical decision-making, and show the most evidence-lacking topics to stimulate further study.

Economic burden of vertigo: a systematic review

BACKGROUND

Vertigo, a highly prevalent disease, imposes a rising burden on the health care system, exacerbated by the ageing of the population; and further, contributes to a wide span of indirect burden due to reduced capacity to work or need of assistance in activities of daily living. The aim of this review was to summarise the evidence on the economic burden of vertigo.

METHODS

All original studies published between 2008 and 2018 about the economic evaluation of peripheral or central vestibular vertigo in developed countries were considered eligible, unrestricted to setting, health care provider, or study type.

RESULTS

The electronic search in three databases identified 154 studies from which 16 qualified for inclusion. All studies presented partial economic evaluation referring to a variety of vestibular vertigo including unspecified vertigo. Nine studies presented monetised cost results and seven studies reported health care utilization. Direct costs derived mainly from repeated and not well-targeted consultations at all levels of health care, excessive use of diagnostic imaging, and/or of emergency care. Considerable societal burden was caused by decreased productivity, mainly due to work absenteeism.

CONCLUSION

To the best of our knowledge, this is the first systematic review of the existing evidence of the economic burden of vertigo. The lack of conclusive evidence revealed apparent targets of future research. First, studies of diagnostics and therapies for vestibular disease should include cost-effectiveness considerations. Population-based studies of health services utilization should include simple vestibular assessments to get more reliable estimates of the burden of disease and associated costs on the level of the general population. Further, clinical and population-based registries that include patients with vestibular disease, should consider collecting long-term data of societal burden. Primary data collection should increasingly include assessment of health care utilization e.g. by linking their diagnoses and outcomes to routine data from health insurances.

European Position Statement on Diagnosis, and Treatment of Meniere's Disease

Meniere Disease keeps challenges in its diagnosis and treatment since was defined by Prosper Meniere at the beginning of 19th Century. Several classifications and definition were made until now and speculations still exist on its etiology. As the etiology remains speculative the treatment models remain in discussion also. The European Academy of Otology and Neurotology Vertigo Guidelines Study Group intended to work on the diagnosis and treatment of Meniere's disease and created the European Positional Statement Document also by resuming the consensus studies on it. The new techniques on diagnosis are emphasized as well as the treatment models for each stage of the disease are clarified by disregarding the dilemmas on its treatment. The conservative, noninvasive and invasive therapeutic models are highlighted.

Effect of the novel histamine H4 receptor antagonist SENS-111 on spontaneous nystagmus in a rat model of acute unilateral vestibular loss

BACKGROUND AND PURPOSE

Histamine H₄ receptors are expressed in the peripheral vestibular system, and their selective inhibition improves vertigo symptoms in rats with unilateral vestibular lesions. The effects of SENS-111, a selective oral H₄ receptor antagonist with high affinity to both animal and human receptors, on vertigo symptoms was evaluated in a translational in vivo model of unilateral vestibular loss.

EXPERIMENTAL APPROACH

Pharmacokinetics of SENS-111 in rats was determined to aid dose selection for efficacy testing. Vestibular lesions were induced in rats by unilateral transtympanic injection of kainic acid. The effect of SENS-111 (10 or 20 mg·kg^-1 ) on spontaneous nystagmus was evaluated compared with placebo vehicle using video-nystagmography, and the effective dose was compared with those of similar drugs used clinically, as single agents or combined with SENS-111.

KEY RESULTS

Doses were selected for plasma exposure were consistent with published phase 1 results from healthy volunteers. SENS-111 of 10 mg·kg^-1 gave a 21-22% reduction in nystagmus at 1 hr post-administration, whereas a loss of efficacy was seen with 20 mg·kg^-1 . Compared with SENS-111, meclizine and methylprednisolone had minimal effects on nystagmus as single agents, and meclizine abolished the effect of SENS-111 when combined with SENS-111. All evaluated drugs were well tolerated.

CONCLUSIONS AND IMPLICATIONS

The exposure-efficacy relationship for improved spontaneous nystagmus seen with SENS-111 in this in vivo model is consistent with phase 1 clinical results and provides preclinical support for pharmacokinetic/pharmacodynamic modelling and selection of effective clinical drug concentrations.

LINKED ARTICLES

This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc.

Advances in pharmacotherapy of vestibular and ocular motor disorders

INTRODUCTION

Vertigo and dizziness are common chief complaints of vestibular and ocular motor disorders (lifetime prevalence 30%). Treatment relies on physical, pharmacological, psychological and rarely surgical approaches. Eight groups of drugs are currently used in vestibular and ocular motor disorders, namely anti-vertiginous, anti-inflammatory, anti-menière's, anti-migrainous medications, anti-depressants, anti-convulsants, aminopyridines and agents that enhance vestibular plasticity.

AREAS COVERED

The purpose of this review is to summarize the pharmacological characteristics and clinical applications of medications that are used for peripheral, central and functional vestibular and ocular motor disorders. The level of evidence for the respective drugs is described alongside the pathophysiological premises supporting their use. The authors place particular focus on translation and back-translation in vestibular pharmacological research and the repurposing of known drugs for new indications and rare disorders.

EXPERT OPINION

The use of drugs in vestibular and ocular motor disorders is often based on open-label, non-controlled studies and expert opinion. In the future, strong evidence derived from RCTs is needed to support the effectiveness and tolerability of these therapies in well-defined vestibular and ocular motor disorders. Vestibular pharmacological research must be guided by a better understanding of the molecular targets relevant in the pathophysiology of vestibular and ocular motor disorders.

Histamine H1 Receptor Contributes to Vestibular Compensation

Vestibular compensation is responsible for the spontaneous recovery of postural, locomotor, and oculomotor dysfunctions in patients with peripheral vestibular lesion or posterior circulation stroke. Mechanism investigation of vestibular compensation is of great importance in both facilitating recovery of vestibular function and understanding the postlesion functional plasticity in the adult CNS. Here, we report that postsynaptic histamine H1 receptor contributes greatly to facilitating vestibular compensation. The expression of H1 receptor is restrictedly increased in the ipsilesional rather than contralesional GABAergic projection neurons in the medial vestibular nucleus (MVN), one of the most important centers for vestibular compensation, in unilateral labyrinthectomized male rats. Furthermore, H1 receptor mediates an asymmetric excitation of the commissural GABAergic but not glutamatergic neurons in the ipsilesional MVN, which may help to rebalance bilateral vestibular systems and promote vestibular compensation. Selective blockage of H1 receptor in the MVN significantly retards the recovery of both static and dynamic vestibular symptoms following unilateral labyrinthectomy, and remarkably attenuates the facilitation of betahistine, whose effect has traditionally been attributed to its antagonistic action on the presynaptic H3 receptor, on vestibular compensation. These results reveal a previously unknown role for histamine H1 receptor in vestibular compensation and amelioration of vestibular motor deficits, as well as an involvement of H1 receptor in potential therapeutic effects of betahistine. The findings provide not only a new insight into the postlesion neuronal circuit plasticity and functional recovery in the CNS, but also a novel potential therapeutic target for vestibular disorders.SIGNIFICANCE STATEMENT Vestibular disorders manifest postural imbalance, nystagmus, and vertigo. Vestibular compensation is critical for facilitating recovery from vestibular disorders, and of great importance in understanding the postlesion functional plasticity in the adult CNS. Here, we show that postsynaptic H1 receptor in the medial vestibular nucleus (MVN) contributes greatly to the recovery of both static and dynamic symptoms following unilateral vestibular lesion. H1 receptor selectively mediates the asymmetric activation of commissural inhibitory system in the ipsilesional MVN and actively promotes vestibular compensation. The findings provide not only a new insight into the postlesion neuronal circuit plasticity and functional recovery of CNS, but also a novel potential therapeutic target for promoting vestibular compensation and ameliorating vestibular disorders.

Dexamethasone protects against arsanilic acid‑induced rat vestibular dysfunction through the BDNF and JNK 1/2 signaling pathways

The brain‑derived neurotrophic factor (BDNF) and c‑Jun NH 2‑terminal kinase (JNK) signaling pathways are therapeutic targets to prevent degeneration in the central nervous system. Dexamethasone (DXMS), a glucocorticoid, protects against vestibular brain injury, however, the molecular mechanisms have yet to be fully elucidated. To investigate whether the BDNF and JNK signaling pathways are involved in the protective effects of DXMS in rats with vestibular dysfunction, a rat model of severe vestibular deficits was established by middle ear injection of arsanilic acid (AA; 100 mg/ml; 0.05 ml). After 3 days, rat symptoms and behavior scores with vestibular disorders were detected. In brain tissues, histopathological alterations, cell apoptosis, expression levels and patterns of BDNF signaling pathway‑associated BDNF, tyrosine receptor kinase B (TrKB) and K+/Cl‑ cotransporter isoform 2 (KCC2), and the expression of apoptosis‑related cleaved‑caspase 3 and the JNK signaling pathway were detected. It was identified that DXMS relieved AA‑induced vestibular dysfunction, leading to improvement in rat behavior scores to normal levels, minimizing brain damage at the histopatholojnnkngical level, reducing cell apoptosis, enhancing the expression of BDNF, TrKB and KCC2, and downregulating cleaved‑caspase 3 and phosphorylated‑JNK1/2 in brain tissues. Together, these findings indicated the protective effect of DXMS on AA‑induced rat vestibular dysfunction, and that activating BDNF and inhibiting JNK singling pathways were the underlying mechanisms. In addition, with additional treatment of mifepristone (RU486), a specific glucocorticoid agonist, all the events elicited by DXMS mentioned above in the AA‑treated rat rats were reversed. In conclusion, DXMS was identified as a therapeutic agent targeting the BDNF and JNK singling pathways for AA‑induced rat vestibular dysfunction.

Clinical and electrophysiological results of eye muscle surgery in 17 patients with downbeat nystagmus

Purpose

To test the hypothesis that eye muscle surgery in treatment of patients with acquired downbeat nystagmus results in improvement measures of visual and ocular motor function.

Methods

This is a prospective, interventional case series analysis of clinical and electrophyisological data before and after eye muscle surgery in 17 patients with acquired downbeat nystagmus who did not respond to medical treatments. Outcome measures included: 1) routine demography and clinical characteristics, 2) subjective oscillopsia (SO), 3) binocular best-corrected visual acuity in the null position (BVA), 3) primary position strabismic deviation (SD), 5) anomalous head posture (AHP), 6) contrast sensitivity function (CS), and 7) nystagmus slow phase velocity (SPV). All patients were followed at least 12 months. Parametric and non-parametric statistical analysis of outcome measure data above pre- and post-treatment were perfomed using standard software on grouped data using computerized software.

Results

Patients' age ranged from 5 to 85 years (average 27 years). About 59% were male. Follow up ranged from 1-10 years (average 2.0 years). Around 70% had an associated central nervous systemic diagnosis, 100% had an AHP, oscillopsia and decreased CS, 53% had other eye disease, and 59% had strabismus. There were no complications from surgery. There were signficant post-treatment improvements in mean/median group BVA, SO, SD, AHP, CS, and SPV.

Conclusion

This study supports the hypothesis that eye muscle surgery as treatments for patients with acquired downbeat nystagmus can result in improvements in multiple aspects of ocular motor and visual functions.

International consensus (ICON) on treatment of Ménière's disease

OBJECTIVE

To present the international consensus for recommendations for Ménière's disease (MD) treatment.

METHODS

Based on a literature review and report of 4 experts from 4 continents, the recommendations have been presented during the 21st IFOS congress in Paris, in June 2017 and are presented in this work.

RESULTS

The recommendation is to change the lifestyle, to use the vestibular rehabilitation in the intercritic period and to propose psychotherapy. As a conservative medical treatment of first line, the authors recommend to use diuretics and Betahistine or local pressure therapy. When medical treatment fails, the recommendation is to use a second line treatment, which consists in the intratympanic injection of steroids. Then as a third line treatment, depending on the hearing function, could be either the endolymphatic sac surgery (when hearing is worth being preserved) or the intratympanic injection of gentamicin (with higher risks of hearing loss). The very last option is the destructive surgical treatment labyrinthectomy, associated or not to cochlear implantation or vestibular nerve section (when hearing is worth being preserved), which is the most frequent option.

A Randomized, Double-Blind, Placebo-Controlled Pilot Study of Betahistine to Counteract Olanzapine-Associated Weight Gain

Patients with schizophrenia experience higher rates of obesity and related morbidity and mortality than the general population does. Given preclinical studies revealing the role of histamine H1 receptor in human eating behavior, and the potential of olanzapine to block with this system, we hypothesized that histamine H1 receptor agonists may be beneficial in reducing antipsychotic-associated weight gain. In the present study, 36 patients with a diagnosis of schizophrenia or schizoaffective disorder and treated with olanzapine were randomized to betahistine (48 mg/d) or matching placebo for 16 weeks. Study outcomes were change in body weight from baseline and effect on antipsychotic efficacy of olanzapine. The patients in the betahistine group had less weight gain (-1.95 kg) compared with placebo group (5.6 + 5.5 kg vs 6.9 + 5.6 kg, respectively). Positive and Negative Syndrome Scale Questionnaire showed improvement within each group and that subjects treated with betahistine enjoyed an improvement (reduction) by a mean of 35.7 points, higher when compared with placebo subjects who had a reduction of 26.6 points (P = 0.233). An almost equal amount of subjects in both groups experienced adverse effects during the course of this study (87.5% of betahistine vs 85.0% of placebo-treated subjects). Overall, there were no clinically marked differences in safety signals between both groups. A larger study addressing the weaknesses of this pilot study is warranted.

Meniere's disease

Meniere's disease (MD) is a disorder of the inner ear that causes vertigo attacks, fluctuating hearing loss, tinnitus and aural fullness. The aetiology of MD is multifactorial. A characteristic sign of MD is endolymphatic hydrops (EH), a disorder in which excessive endolymph accumulates in the inner ear and causes damage to the ganglion cells. In most patients, the clinical symptoms of MD present after considerable accumulation of endolymph has occurred. However, some patients develop symptoms in the early stages of EH. The reason for the variability in the symptomatology is unknown and the relationship between EH and the clinical symptoms of MD requires further study. The diagnosis of MD is based on clinical symptoms but can be complemented with functional inner ear tests, including audiometry, vestibular-evoked myogenic potential testing, caloric testing, electrocochleography or head impulse tests. MRI has been optimized to directly visualize EH in the cochlea, vestibule and semicircular canals, and its use is shifting from the research setting to the clinic. The management of MD is mainly aimed at the relief of acute attacks of vertigo and the prevention of recurrent attacks. Therapeutic options are based on empirical evidence and include the management of risk factors and a conservative approach as the first line of treatment. When medical treatment is unable to suppress vertigo attacks, intratympanic gentamicin therapy or endolymphatic sac decompression surgery is usually considered. This Primer covers the pathophysiology, symptomatology, diagnosis, management, quality of life and prevention of MD.

Therapeutic Approaches to Genetic Ion Channelopathies and Perspectives in Drug Discovery

In the human genome more than 400 genes encode ion channels, which are transmembrane proteins mediating ion fluxes across membranes. Being expressed in all cell types, they are involved in almost all physiological processes, including sense perception, neurotransmission, muscle contraction, secretion, immune response, cell proliferation, and differentiation. Due to the widespread tissue distribution of ion channels and their physiological functions, mutations in genes encoding ion channel subunits, or their interacting proteins, are responsible for inherited ion channelopathies. These diseases can range from common to very rare disorders and their severity can be mild, disabling, or life-threatening. In spite of this, ion channels are the primary target of only about 5% of the marketed drugs suggesting their potential in drug discovery. The current review summarizes the therapeutic management of the principal ion channelopathies of central and peripheral nervous system, heart, kidney, bone, skeletal muscle and pancreas, resulting from mutations in calcium, sodium, potassium, and chloride ion channels. For most channelopathies the therapy is mainly empirical and symptomatic, often limited by lack of efficacy and tolerability for a significant number of patients. Other channelopathies can exploit ion channel targeted drugs, such as marketed sodium channel blockers. Developing new and more specific therapeutic approaches is therefore required. To this aim, a major advancement in the pharmacotherapy of channelopathies has been the discovery that ion channel mutations lead to change in biophysics that can in turn specifically modify the sensitivity to drugs: this opens the way to a pharmacogenetics strategy, allowing the development of a personalized therapy with increased efficacy and reduced side effects. In addition, the identification of disease modifiers in ion channelopathies appears an alternative strategy to discover novel druggable targets.

Vestibular paroxysmia: a treatable neurovascular cross-compression syndrome

The leading symptoms of vestibular paroxysmia (VP) are recurrent, spontaneous, short attacks of spinning or non-spinning vertigo that generally last less than one minute and occur in a series of up to 30 or more per day. VP may manifest when arteries in the cerebellar pontine angle cause a segmental, pressure-induced dysfunction of the eighth nerve. The symptoms are usually triggered by direct pulsatile compression with ephaptic discharges, less often by conduction blocks. MR imaging reveals the neurovascular compression of the eighth nerve (3D constructive interference in steady state and 3D time-of-flight sequences) in more than 95 % of cases. A loop of the anterior inferior cerebellar artery seems to be most often involved, less so the posterior inferior cerebellar artery, the vertebral artery, or a vein. The frequent attacks of vertigo respond to carbamazepine or oxcarbazepine, even in low dosages (200–600 mg/d or 300–900 mg/d, respectively), which have been shown to also be effective in children. Alternative drugs to try are lamotrigine, phenytoin, gabapentin, topiramate or baclofen or other non-antiepileptic drugs used in trigeminal neuralgia. The results of ongoing randomized placebo-controlled treatment studies, however, are not yet available. Surgical microvascular decompression of the eighth nerve is the “ultima ratio” for medically intractable cases or in exceptional cases of non-vascular compression of the eighth nerve by a tumor or cyst. The International Barany Society for Neuro-Otology is currently working on a consensus document on the clinical criteria for establishing a diagnosis of VP as a clinical entity.

[Peripheral, central and functional vertigo syndromes]

Depending on the temporal course, three forms of vertigo syndrome can be differentiated: 1) vertigo attacks, e.g. benign paroxysmal positional vertigo (BPPV), Menière's disease and vestibular migraine, 2) acute spontaneous vertigo lasting for days, e.g. acute unilateral vestibulopathy, brainstem or cerebellar infarction and 3) symptoms lasting for months or years, e.g. bilateral vestibulopathy and functional vertigo. The specific therapy of the various syndromes is based on three principles: 1) physical treatment with liberatory maneuvers for BPPV and balance training for vestibular deficits, 2) pharmacotherapy, e.g. for acute unilateral vestibulopathy (corticosteroids) and Menière's disease (transtympanic administration of gentamicin or steroids and high-dose betahistine therapy); placebo-controlled pharmacotherapy studies are currently being carried out for acute unilateral vestibulopathy, vestibular paroxysmia, prophylaxis of BPPV, vestibular migraine, episodic ataxia type 2 and cerebellar ataxia; 3) psychotherapy for functional dizziness.

Use of betahistine in the treatment of peripheral vertigo

CONCLUSION

Clinical studies and meta-analyses demonstrated that betahistine is effective and safe in the treatment of Ménière's disease, BPPV (benign paroxysmal positional vertigo), vestibular neuronitis, and other types of peripheral vertigo.

OBJECTIVES

The goal of this paper is to review the pharmacological profile of betahistine and the evidence for its effectiveness and safety in the treatment of peripheral vertigo.

METHODS

Selection criteria for the publications on betahistine included randomized clinical trials that evaluated the effectiveness and safety of betahistine vs placebo or active control in the treatment of peripheral vertigo. Recent meta-analyses were also included. Databases searched included PubMed, the Cochrane Ear, Nose and Throat Disorders Group Trials Register, and ICTRP. The review also presents an update on the mechanisms of action, pharmacodynamics, and pharmacokinetics of betahistine.

RESULTS

Efficacy and safety of betahistine has been demonstrated in numerous clinical trials. The precise mechanism of action of betahistine is still not completely understood, but the clinical experience demonstrated the benefit of betahistine in different types of peripheral vertigo. In more than 40 years of clinical use, betahistine has shown an excellent safety profile with the usual dose range from 8-48 mg daily. According to clinical studies, betahistine 48 mg daily during 3 months is an effective and safe option for the treatment of peripheral vertigo.