A protective effect of 5-HT3 antagonist against vestibular deficit? Metoclopramide versus ondansetron at the early stage of vestibular neuritis: A pilot study

Pharmacological Treatment of Acute Unilateral Vestibulopathy: A Review

There have been few investigations on the epidemiology, etiology, and medical management of acute unilateral vestibulopathy (AUV). Short-term pharmaceutical resolutions include vestibular symptomatic suppressants, anti-emetics, and some cause-based therapies. Anticholinergics, phenothiazines, antihistamines, antidopaminergics, benzodiazepines, and calcium channel antagonists are examples of vestibular suppressants. Some of these medications may show their effects through multiple mechanisms. In contrast, N-acetyl-L-leucine, Ginkgo biloba, and betahistine improve central vestibular compensation. Currently, AUV pathophysiology is poorly understood. Diverse hypotheses have previously been identified which have brought about some causal treatments presently used. According to some publications, acute administration of anti-inflammatory medications may have a deleterious impact on both post-lesional functional recovery and endogenous adaptive plasticity processes. Thus, some authors do not recommend the use of corticosteroids in AUV. Antivirals are even more contentious in the context of AUV treatment. Although vascular theories have been presented, no verified investigations employing anti-clotting or vasodilator medications have been conducted. There are no standardized treatment protocols for AUV to date, and the pharmacological treatment of AUV is still questionable. This review addresses the most current developments and controversies in AUV medical treatment.

5-HT3 Receptor Antagonists in Neurologic and Neuropsychiatric Disorders: The Iceberg Still Lies beneath the Surface

5-HT₃ receptor antagonists, first introduced to the market in the mid-1980s, are proven efficient agents to counteract chemotherapy-induced emesis. Nonetheless, recent investigations have shed light on unappreciated dimensions of this class of compounds in conditions with an immunoinflammatory component as well as in neurologic and psychiatric disorders. The promising findings from multiple studies have unveiled several beneficial effects of these compounds in multiple sclerosis, stroke, Alzheimer disease, and Parkinson disease. Reports continue to uncover important roles for 5-HT₃ receptors in the physiopathology of neuropsychiatric disorders, including depression, anxiety, drug abuse, and schizophrenia. This review addresses the potential of 5-HT₃ receptor antagonists in neurology- and neuropsychiatry-related disorders. The broad therapeutic window and high compliance observed with these agents position them as suitable prototypes for the development of novel pharmacotherapeutics with higher efficacy and fewer adverse effects.

From Pathogenesis to Novel Therapeutics for Spinocerebellar Ataxia Type 3: Evading Potholes on the Way to Translation

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is a neurodegenerative disorder caused by a polyglutamine expansion in the ATXN3 gene. In spite of the identification of a clear monogenic cause 25 years ago, the pathological process still puzzles researchers, impairing prospects for an effective therapy. Here, we propose the disruption of protein homeostasis as the hub of SCA3 pathogenesis, being the molecular mechanisms and cellular pathways that are deregulated in SCA3 downstream consequences of the misfolding and aggregation of ATXN3. Moreover, we attempt to provide a realistic perspective on how the translational/clinical research in SCA3 should evolve. This was based on molecular findings, clinical and epidemiological characteristics, studies of proposed treatments in other conditions, and how that information is essential for their (re-)application in SCA3. This review thus aims i) to critically evaluate the current state of research on SCA3, from fundamental to translational and clinical perspectives; ii) to bring up the current key questions that remain unanswered in this disorder; and iii) to provide a frame on how those answers should be pursued.

New mouse model for inducing and evaluating unilateral vestibular deafferentation syndrome

BACKGROUND

Unilateral vestibular deafferentation syndrome (uVDS) holds a particular place in the vestibular pathology domain. Due to its suddenness, the violence of its symptoms that often result in emergency hospitalization, and its associated original neurophysiological properties, this syndrome is a major source of questioning for the otoneurology community. Also, its putative pathogenic causes remain to be determined. There is currently a strong medical need for the development of targeted and effective countermeasures to improve the therapeutic management of uVDS.

NEW METHODS

The present study reports the development of a new mouse model for inducing and evaluating uVDS. Both the method for generating controlled excitotoxic-type peripheral vestibular damages, through transtympanic administration of the glutamate receptors agonist kainate (TTK), and the procedure for evaluating the ensuing clinical signs are detailed.

COMPARISON WITH EXISTING METHODS

Through extensive analysis of the clinical symptoms characteristics, this new animal model provides the opportunity to better follow the temporal evolution of various uVDS specific symptoms, while better appreciating the different phases that composed this syndrome.

RESULTS

The uVDS evoked in the TTK mouse model displays two main phases distinguishable by their kinetics and amplitudes. Several parameters of the altered vestibular behaviour mimic those observed in the human syndrome.

CONCLUSION

This new murine model brings concrete information about how uVDS develops and how it affects global behaviour. In addition, it opens new opportunity to decipher the etiopathological substrate of this pathology by authorizing the use of genetically modified mouse models.

Principles of vestibular pharmacotherapy

Ideally, vestibular pharmacotherapy is intended, through specific and targeted molecular actions, to significantly alleviate vertigo symptoms, to protect or repair the vestibular sensory network under pathologic conditions, and to promote vestibular compensation, with the eventual aim of improving the patient's quality of life. In fact, in order to achieve this aim, considerable progress still needs to be made. The lack of information on the etiology of vestibular disorders and the pharmacologic targets to modulate, as well as the technical challenge of targeting a drug to its effective site are some of the main issues yet to be overcome. In this review, my intention is to provide an account of the therapeutic principles that have shaped current vestibular pharmacotherapy and to further explore crucial questions that must be taken into consideration in order to develop targeted and specific pharmacologic therapies for each type and stage of vestibular disorders.

The Effect of Intravenous Dexamethasone on the Nausea Accompanying Vestibular Neuritis: A Preliminary Study

PURPOSE

We undertook a preliminary assessment of the efficacy of administering intravenous dexamethasone (DEX) for relieving the nausea and dizziness accompanying vestibular neuritis (VN).

METHODS

Between November 2013 and October 2014, 26 patients with VN were prospectively enrolled in this study. The patients were randomly assigned to treatment with a combination of 20 mg/d of intravenous metoclopramide, 100 mg of oral dimenhydrinate, and 5 mg/d of intravenous DEX or 20 mg/d of intravenous metoclopramide, 100 mg of oral dimenhydrinate, and intravenous normal saline as a placebo therapy. Patients' subjective assessments of the severity of their nausea and dizziness were recorded using a visual analog scale on the day of admission and 2 days, 3 days, 1 month, and 3 months thereafter. Bedside examinations consisted of spontaneous nystagmus (SPN) assessment, the head shaking nystagmus test, and the head impulse test, which were performed at every follow-up visit.

FINDINGS

The severity of nausea and dizziness was significantly reduced over time (both P < 0.05). However, there was no significant effect of DEX injection on the severity of nausea or dizziness (P > 0.05). The presence of SPN was solely associated with nausea (hazard ratio = 3.34; 95% CI, 1.85-6.02).

IMPLICATIONS

The administration of intravenous DEX did not relieve nausea or dizziness any better than a placebo treatment. However, further research is required to confirm whether there is a dose-dependent effect of DEX on the control of nausea or dizziness in VN.

Betahistine dihydrochloride with and without early vestibular rehabilitation for the management of patients with balance disorders following head trauma: a preliminary randomized clinical trial

OBJECTIVE

The purpose of this study was to compare the effect of betahistine dihydrochloride alone and in combination with vestibular rehabilitation for the management of patients with balance disorders following head trauma.

METHODS

In this preliminary clinical trial, a group of patients with head trauma was referred to our university-based tertiary care balance unit over a 1-year period. The study included 60 patients with balance disorder following head trauma. Patients were randomly divided into 3 groups with 20 patients each. The first group was treated by betahistine dihydrochloride tablets 48 mg/d alone. The second group was treated with a standard vestibular rehabilitation program. The third group was given betahistine dihydrochloride tablets (48 mg/d) in addition to the early standard vestibular rehabilitation program. Videonystagmography was used in the diagnosis, characterization, and monitoring of all patients with balance disorders, with improvement of the pretreatment objective results taken as a marker for treatment progress.

RESULTS

Recovery time was within the first 3 months following head trauma in 57 (95%) of the patients. Recovery was faster after mild head trauma than after moderate and severe traumas. Patients who underwent vestibular rehabilitation immediately after the onset of head trauma (with or without addition of betahistine dihydrochloride) recovered earlier than those treated with betahistine dihydrochloride alone.

CONCLUSION

Based on these preliminary findings in a small group of patients, early vestibular rehabilitation with the concomitant use of betahistine dihydrochloride showed better results than the other 2 treatments alone in patients with balance disorders following head trauma. Early vestibular rehabilitation seemed to improve recovery that was enhanced by the use of betahistine dihydrochloride, and may have depressed the associated adverse effects such as nausea and vomiting.

5-HT(3) receptor expression in the mouse vestibular ganglion

The 5-hydroxytryptamine type 3 (5-HT3) receptor is a ligand-gated ion channel and a member of the Cys-loop family of receptors. Previous studies have shown 5-HT3 receptor expression in various neural cells of the central and peripheral nervous systems. Although the function and distribution of the 5-HT3 receptor has been well established, its role in the inner ear is still poorly understood. Moreover, no study has yet determined its localization and function in the peripheral vestibular nervous system. In the present study, we reveal mRNA expression of both 5-HT3A and 5-HT3B receptor subunits in the mouse vestibular ganglion (VG) by RT-PCR and in situ hybridization (ISH). We also show by ISH that 5-HT3 receptor mRNA is only expressed in the VG (superior and inferior division) in the peripheral vestibular nervous system. Moreover, we performed Ca(2+) imaging to determine whether functional 5-HT3 receptors are present in the mouse VG, using a selective 5-HT3 receptor agonist, SR57227A. In wild mice, 32% of VG neurons responded to the agonist, whereas there was no response in 5-HT3A receptor knockout mice. These results indicate that VG cells express functional 5-HT3 receptor channels and might play a modulatory role in the peripheral vestibular nervous system.