Density difference between perilymph and endolymph: A new hypothesis for light cupula phenomenon

Variants of posterior semicircular canal involvement in benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo is the most common cause of peripheral vertigo. It is characterized by short and recurrent episodes of vertigo, trigged by specific head movements that displace otoconia within the semicircular canals. The movement of dislodge otoconia from the utricle cause abnormal positional endolymphatic currents. Primary treatment involves reposition maneuvers aimed at moving the displaced otoconia out the affected canal, therefore correct identification of the affected canal is essential for the diagnosis. The posterior semicircular canal (PSC) is the most frequently affected due to its spatial orientation and the force of gravity. Recent technological advances have allowed for better assessment of positional nystagmus during diagnostic and therapeutic maneuvers, revealing various possible scenarios of PSC involvement. Regarding the PSC, otoconia may be found in different parts of the canal, and not just in the expected location, floating in the long arm of the canal. The understanding of these variants is crucial, as the prognosis and the disease progression differ in such cases. This review aims to describe the six possible variants of PSC involvement described so far.

Analysis of etiology and clinical features of spontaneous downbeat nystagmus: a retrospective study

Objective

To investigate the topical diagnosis, possible etiology and mechanism of spontaneous downbeat nystagmus (sDBN) patients with dizziness/vertigo.

Methods

The clinical features of dizziness/vertigo patients accompanied with DBN were retrospectively reviewed in the Vertigo Center of our hospital from January 2018 to March 2021. The clinical features of dizziness/vertigo patients accompanied with DBN were reviewed. Comprehensive VNG, bithermal caloric testing, video-head-impulse test (vHIT), vestibular-evoked myogenic potentials (VEMP), head magnetic resonance imaging (MRI), three-dimensional fluid-attenuated incersion recovery magnetic resonance imaging (3D-FLAIR MRI) in the inner ear, serum immunology and other examinations were to determine the lesion site, and analyze its possible etiology and mechanism.

Results

A total of 54 patients were included. Among them, 70.4% (n = 38) of DBN patients were diagnosed with episodic vestibular syndrome (EVS), 22.2% (n = 12) with chronic vestibular syndrome (CVS), and 7.4% (n = 4) with acute vestibular syndrome (AVS). Among all the patients, 51.9% of DBN patients had clear etiology, with central lesions of 29.6% and peripheral diseases of 22.2%. The most common diseases in DBN patients were cerebellar lesions (13.0%, n = 7) and vestibular migraine (13.0%, n = 7), followed by benign positional paroxysmal vertigo (7.4%, n = 4) and drug-related dizziness/vertigo (5.6%, n = 3). The other 48.1% of the patients had unknown etiology. 53.8% (14/26) of patients with idiopathic DBN had decreased semicircular canal function, with 42.9% (6/14) decreased posterior semicircular canal function. The posterior semicircular canal gain in DBN patients decreased compared to the anterior semicircular canal in the same conjugate plane. Patients with peripheral DBN were more prone to horizontal/torsional nystagmus during positional testing.

Conclusion

In our study, DBN patients have a relative decrease in posterior semicircular canal gain, which is possibly a particular result found in a subset of downbeat nystagmus patients. The changes in nystagmus during positional testing may be helpful in distinguishing between peripheral and central causes.

The Light Cupula Phenomenon: A Scoping Review

Direction-changing positional nystagmus (DCPN), which refers to the change in the direction of nystagmus with different head positions, is a well-known characteristic of horizontal semicircular canal BPPV. The supine head roll test is commonly used to diagnose horizontal canal BPPV. However, persistent geotropic DCPN observed during this test cannot be explained by the conventional explanations of canalolithiasis or cupulolithiasis. To account for this unique nystagmus, the concept of a "light cupula" has been recently introduced. In this review, we provide an overview of the historical background, clinical features and diagnostic methods, proposed mechanisms, and treatment strategies associated with the light cupula phenomenon based on the available literature to date.

Clinical Characteristics of persistent geotropic horizontal direction-changing positional nystagmus: Experience in 189 participants

BACKGROUND

The etiology and mechanism of persistent geotropic horizontal direction-changing positional nystagmus (DCPN) are still unclear. Whether this pattern of nystagmus is a subtype of benign paroxysmal positional vertigo (BPPV) remains controversial.

OBJECTIVE

The goal of this study was to observe the clinical characteristics of persistent geotropic horizontal DCPN involving the lateral semicircular canal.

METHODS

The analysis was performed to participants with episodic positional vertigo in our clinic from 2014 to 2021. Participants were included via positional test. We observed and summarized the distribution data, vertigo history, follow-up tests, and recurrence situations of 189 persistent geotropic horizontal DCPN participants.

RESULTS

The mean age at the first time showing of persistent geotropic horizontal DCPN was 56±14.7 and more women than men were affected by persistent geotropic horizontal DCPN (female-to-male ratio 2.4 : 1). Overall, 58.7% (57/94) of participants who came for the first-week follow-up test were asymptomatic. Thirty-three participants experienced recurrence (female-to-male ratio: 4.5 : 1). Fifty-three (28.0%) participants experienced the conversion of the patterns of DCPN in the history, the follow-up tests and the recurrence compared to the first showing of persistent geotropic horizontal DCPN. 24(12.1%) participants still experienced persistent geotropic horizontal DCPN attack in the follow-up tests and the recurrences without benign paroxysmal positional vertigo history.

CONCLUSION

Persistent geotropic horizontal DCPN affected more women than men. The persistent geotropic horizontal DCPN that with conversion to transient geotropic horizontal DCPN or to persistent apogeotropic horizontal DCPN might be a subtype of BPPV or in a stage of BPPV process. However, the persistent geotropic horizontal DCPN without conversion might be an independent disease that is not related to BPPV.

Light cupula phenomenon: a systematic review

Geotropic direction-changing positional nystagmus (DCPN) is transient in lateral semicircular canal (LSSK) canalolithiasis; it usually cuts off within a minute and fatigues. However, a “light cupula” mechanism has been described for patients with positional vertigo who exhibit a persistent geotropic DCPN without delay or fatigue. When the cupula becomes lighter than the surrounding endolymph, deflection may occur in the cupula under the influence of gravity. The person experiences dizziness and persistent positional nystagmus can be observed while remaining in that position.

In this review, studies investigating the “light cupula phenomenon,” which is a newly defined phenomenon in the literature, were compiled. A systematic literature search was conducted on the light cupula phenomenon in PubMed and Google Scholar databases to illuminate the clinical side of this new phenomenon and reveal its distinctive features. Turkish and English articles published between 2010 and 2021 were scanned; the thesis, reviews, and books were excluded from the study. Forty-eight articles were included in the study.

Mechanisms underlying light cupula has been explained as the “heavier endolymph hypothesis” with increased endolymph specific gravity due to an acute attack such as labyrinth hemorrhage, insufficient inner ear perfusion, or inflammation in the inner ear; “lighter cupula hypothesis” based on alcohol acting on the cupula earlier and making it lighter than the endolymph; “light particle hypothesis” due to the buoyancy of light debris, which are degenerative, swollen, and inflammatory cells in the endolymph adhering to the cupula and the “altered endolymph/perilymph density ratio hypothesis” that the difference in density between perilymph and endolymph causes light cupula. The pathophysiology of the light cupula phenomenon is still unclear, but it can be thought that all the different hypotheses may be effective in this phenomenon. Therefore, nystagmus characteristics and clinical course should be considered in patients for a more effective diagnosis and treatment process. In addition, the results of the studies show that light cupula may not be an uncommon disease and that some patients with geotropic DCPN can often be misdiagnosed as canalolithiasis LSCC-BPPV.

Analysis of the nystagmus characteristics of cupula diseases: A case report

INTRODUCTION

Clinically, there is a kind of patients with positional vertigo or dizziness, which occurs when they turn left or right, look down or up, lie down or sit up. With a long duration and varying frequency, it is not consistent with the manifestations of benign paroxysmal positional vertigo (BPPV). In addition, the persistent geotropic direction-changing positional nystagmus (PG-DCPN) was observed in a supine head-roll test.

PATIENT CONCERNS

With no apparent trigger for visual rotation and a sense of self instability, an 81-year-old female patient had suffered from vertigo for 3 days. The vertigo occurred every day, lasting several minutes each time, and associated with head movements and changes in body position. In a supine head-roll test, it appeared persistent geotropic direction-changing positional nystagmus for a long time, without latency, fatigability and in the presence of 3 zero planes.

DIAGNOSIS

Light cupula.

INTERVENTIONS

Difenidol hydrochloride 25 mg orally 3 times/day for 2 weeks and betahistine hydrochloride 12 mg orally 3 times/day for 1 month were administered.

OUTCOMES

After 1 month of treatment, the patient's vertigo symptoms disappeared. And in the supine head-roll test, the persistent geotropic direction-changing positional nystagmus disappeared.

CONCLUSION

We report the characteristics of nystagmus produced in a typical patient with light cupula during the supine head-roll test. After reviewing the relevant literatures, we believe that a simpler method can be used to identify canalolithiasis and cupula disease, to distinguish light and heavy cupula, and to determine the pathological semicircular canal to which the lesion belongs.

Less common forms of posterior canal benign paroxysmal positional vertigo

The most common form of posterior canal benign paroxysmal positional vertigo (BPPV) is characterised by positional, paroxysmal, upbeat nystagmus, with a torsional component beating towards the downward ear. Rarer variants have been reported, putatively due to either the position of otoconia in the canal or anatomic variations of the semicircular canals. The most frequent less common form is apogeotropic posterior canal BPPV, in which the positional nystagmus is downbeat and torsional apogeotropic. In this form, the main problems are differential diagnosis with central mimics of BPPV and identification of the affected canal and its side. The authors propose a new subtype of apogeotropic posterior canal BPPV hypothesising the localization of otoconia in the ampullary tract of the affected canal, which might explain the modality of the conversion in typical posterior canal BPPV which they observed in some of these cases. If nystagmus of the less common forms of posterior canal BPPV is explicable through purely peripheral mechanisms, these forms should no longer be defined as “atypical” but, in a less demanding way, as “less common” variants, which must be recognised by any expert otoneurologist.

Light Cupula: To Be Or Not to Be?

Benign paroxysmal positional vertigo (BPPV) represents the most common form of positional vertigo. It is caused by dislodged otoconia that freely float in the semicircular canals (canalolithiasis) or attach to the cupula (cupulolithiasis). A cupulolithiasis-type (or a heavy cupula-type) of BPPV implicating the lateral semicircular canal (LSCC) exhibits persistent ageotropic direction-changing positional nystagmus (DCPN) in a head-roll test. However, in some cases, unlike any type of BPPV, persistent geotropic DCPN cannot be explained by any mechanisms of BPPV, and don't fit the current classifications. Recently, the notion of light cupula has been introduced to refer to the persistent geotropic DCPN. In this study, we looked at the clinical features of light cuplula and discussed the possible mechanisms and therapeutic strategies of the condition. The notion of light cupula is a helpful addition to the theory of peripheral positional vertigo and nystagmus.

Benign Paroxysmal Positional Vertigo in the Elderly: A Single-center Experience

OBJECTIVES

Dizziness and balance problems are common in the elderly, and benign paroxysmal positional vertigo (BPPV) is one of the most common causes of dizziness. The aim of this study is to investigate the subtype distribution of geriatric BPPV in a single tertiary referral center, and compare the treatment efficacy according to the subtype of BPPV.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral academic center.

PATIENTS

The consecutive 316 elderly patients diagnosed with BPPV between March 2013 and March 2019 were included.

MAIN OUTCOME MEASURES

Using a head-roll and Dix-Hallpike tests, subtype of BPPV was determined. Once the diagnosis of BPPV was made, patients were treated by its corresponding canalith repositioning maneuver (CRM).

RESULTS

Among 316 elderly patients with BPPV, 143 patients (45%) were diagnosed with posterior semicircular canal BPPV, 46 patients (15%) were diagnosed with lateral semicircular canal (LSCC) canalolithiasis, 126 patients (40%) were diagnosed with LSCC cupulolithiasis, and 1 patient (0%) was diagnosed with anterior semicircular canal BPPV. While 66 and 63% of the patients with posterior semicircular canal BPPV and LSCC canalolithiasis recovered after one session of CRM, only 32% of the patients with LSCC cupulolithiasis recovered after one session of CRM.

CONCLUSION

The proportion of LSCC cupulolithiasis was higher in the elderly, and treatment efficacy by CRM is lower in LSCC cupulolithiasis than other subtypes of BPPV. High prevalence of LSCC cupulolithiasis may be explained by a delay between onset of BPPV and patient's presentation to the tertiary referral hospital or pathophysiology of ageotropic positional nystagmus other than otoconial attachment on the LSCC cupula in the elderly.

Positional alcohol nystagmus and serum osmolality: New insights into dizziness associated with acute alcohol intoxication

Positional alcohol nystagmus (PAN) is characterized by positional direction-changing nystagmus. Although the buoyancy cupulopathy, which implies that the cupula becomes lighter or heavier than the endolymph due to different diffusion rates of alcohol, has been accepted as possible mechanism of PAN, the evidence supporting this hypothesis is weak. The aim of present study is to investigate the possibility of serum osmolality change following alcohol intake as a cause of PAN. Nine healthy adults were recruited voluntarily. Positional nystagmus was examined before and every 1 hr after alcohol intake until 7 hr. Serum osmolality was measured before and 1 and 7 hr after alcohol intake. Before ingesting alcohol, no subject showed positional nystagmus, and mean serum osmolality was 285.9 ± 4.4 mOsm/kg. At 1 hr after drinking, mean serum osmolality increased to 302.9 ± 8.9 mOsm/kg, and all subjects exhibited geotropic positional nystagmus. At 7 hr after drinking, mean serum osmolality decreased to 289.1 ± 9.4 mOsm/kg, and all subjects showed ageotropic positional nystagmus. Change in serum osmolality following alcohol ingestion and subsequent change in specific gravity in the perilymph and endolymph may be a cause of PAN.

Dialysis disequilibrium syndrome revisited: Feeling "Disequilibrated" due to inner ear dyshomeostasis?

Dizziness is one of the most common hemodialysis-associated symptoms, and has been thought to be caused by cerebral edema or intravascular hypovolemia. However, the possibility of a peripheral vestibular disturbance due to hemodialysis has not been addressed as a cause of hemodialysis-associated dizziness. In the present study, we propose a new hypothesis accounting for hemodialysis-associated dizziness, i.e., the decrease in serum osmolality due to rapid removal of urea during dialysis causes inner ear fluid dyshomeostasis, leading to density difference between perilymph and endolymph.