Canal switch in benign paroxysmal positional vertigo: Clinical characteristics and possible mechanisms

Rapid axial roll test outperforms alternative positional tests in identifying the affected ear in HSC-BPPV: an observational cohort study

Purpose

To evaluate the utility of supine roll test (SRT) and alternative positional tests, such as head-shaking test (HST), seated supine positioning test (SSPT), bow and lean test (BLT), and rapid axial roll test (RART) in determining the affected semicircular canal of horizontal semicircular canal benign paroxysmal positional vertigo (HSC-BPPV).

Methods

In an observational cohort study, 553 patients diagnosed with HSC-BPPV were divided into five groups in terms of different positional tests received: SRT group (n = 110), HST+ SRT (n = 112), BLT + SRT (n = 114), SSPT+SRT (n = 108) and RART+SRT (n = 109). The same method was used for the last four groups: The patients were first subjected to different alternative positional tests and then to SRT, and the nystagmus was observed separately to determine the affected side. The primary outcomes compared included the accuracy and sensitivity of these tests in the determination of the affected semicircular canal in HSC-BPPV.

Results

Patients with nystagmus elicited by positional tests accounted for 84.99% (470/553). The elicitation rate of nystagmus of SRT was lowest, being 77.27% (85/110). The elicitation rate of nystagmus were higher in the test groups than in the control group, and RART+SRT group yielded the highest elicitation rate of nystagmus (95.41%, 104/109). Among the alternative positional tests, RART attained the highest elicitation rate of nystagmus (101/109, 92.66%). Comparison between alternative positional tests and SRT, RART and SRT showed obviously better agreement in determining the affected semicircular canal (85.45%, 96/109) and eliciting nystagmus (95.41%, Kappa = 0.642), but no difference was found in curative effect when the affected side was accurately determined (χ2 = 1.618, p = 0.655).

Conclusion

All alternative positional tests are helpful for eliciting nystagmus in patients with HSC-BPPV, and the significant advantages of RART include high-sensitivity in eliciting nystagmus and high accuracy in determining the affected semicircular canal, which provided objective support for the correct diagnosis of HSC-BPPV and the successful reduction of otolith.

No genetic causality between obesity and benign paroxysmal vertigo: A two-sample Mendelian randomization study

Objective

We applied Mendelian randomization to explore the causal relationship between obesity and benign paroxysmal vertigo (BPV).

Methods

We chose two types of obesity diseases. Obesity due to excessive calories and other or unspecified obesity from the FinnGen database. We used genomic significance (p < 5 × 10-8) to obtain independent single nucleotide polymorphisms (SNPs) as instrumental variables. Similarly, genome-wide association study data for the disease BPV were selected from the FinnGen database. R was then used to test the data for multiplicity and heterogeneity, as well as to detect the effect of individual SNPs on the results. Random effects inverse variance weighting was used as the main statistical analysis.

Results

First, by analyzing, we found an outlier in obesity due to excessive calories (rs12956821). Outliers were then removed, and the statistical results were analyzed without heterogeneity (p > 0.05) and horizontal pleiotropy (p > 0.05), as well as individual SNPs having no effect on the results. Meanwhile, random-effects IVW results showed obesity due to excessive calories (p = 0.481; OR = 0.941), and other or unspecified obesity (p = 0.640; OR = 0.964).

Conclusions

The present study did not find a causal relationship between the above two obesity types and BPV at the genetic level.

Mechanical rotational chair-assisted multiple canalith repositioning procedures for benign paroxysmal positional vertigo: enhanced vertigo relief, comparable adverse effects, and decreased incidence of residual dizziness

Objectives

This retrospective study aimed to assess the effectiveness and adverse effects of mechanical rotational chair-assisted multiple canalith repositioning procedures (CRPs) to treat benign paroxysmal positional vertigo (BPPV).

Materials and methods

A retrospective analysis of 1,273 BPPV patients was conducted, with 241 patients included in the final study. The participants diagnosed with BPPV, unresolved by a single previous CRP, were categorized into either the single or multiple CRP groups. In both groups, on days 1, 4, and 7 after the initial treatment, the participants were re-evaluated after a single CRP; if positional vertigo was resolved, the treatment was regarded as successful. The remission rate, adverse effects (such as canal switch (CS), falls, and vomiting), residual dizziness (RD) rate, and RD duration were compared between the two groups.

Results

The resolution rates for the single and multiple CRP groups were significantly different on days 1 and 4 (55.7% vs. 85.1%, 75.5% vs. 91.9%; P < 0.05) but not on day 7 (93.3% vs. 94.8%; P > 0.05). There were no significant differences between the single and multiple CRP groups in terms of CS and falls (3.8% vs. 5.2%, 10.3% vs. 8.9%; P > 0.05). However, there was a significant difference in the incidence of vomiting (6.6% vs. 14.8%; P < 0.05). RD such as head heaviness, imbalance, and non-specific dizziness is more common in the single CRP group than in the multiple CRP group (34.9% vs. 20.7%, 42.5% vs. 26.7%, 47.2% vs. 32.6%; P < 0.05). The incidence and duration of RD were notably diminished in the group undergoing multiple CRPs compared to the single CRP group, with incidence rates of 41.5% and 57.5%, respectively (P < 0.05).

Conclusion

For patients with BPPV, multiple CRPs offer greater benefits than a single CRP.

Characteristics and Possible Mechanisms of Direction-Reversing Nystagmus During Positional Testing in Patients With Benign Paroxysmal Positional Vertigo

OBJECTIVES

The occurrence of direction-reversing nystagmus during positional testing in patients with benign paroxysmal positional vertigo (BPPV) is not uncommon. Further in-depth analysis of the characteristics and possible mechanisms of direction-reversing nystagmus will help us to diagnose and treat BPPV more precisely. The study aimed to analyze the incidence and characteristics of direction-reversing nystagmus during positional testing in BPPV patients, evaluate the outcomes of canalith repositioning procedure for these patients, and further explore the possible mechanism of reversal nystagmus in BPPV patients.

STUDY DESIGN

Retrospective study.

SETTING

Single-center study.

PATIENTS

A total of 575 patients with BPPV who visited the Vertigo Clinic of our hospital between April 2017 and June 2021 were enrolled.

MAIN OUTCOME MEASURES

Dix-Hallpike and supine roll tests were performed. The nystagmus was recorded using videonystagmography. The characteristics of direction-reversing nystagmus and the possible underlying mechanism were analyzed.

RESULTS

Patients with BPPV who showed reversal nystagmus accounted for 9.39% (54 of 575) of all BPPV patients visiting our hospital during the same period, of which 5.57% (32 of 575) had horizontal semicircular canal BPPV (HC-BPPV), and 3.83% (22 of 575) had posterior semicircular canal BPPV (PC-BPPV). The maximum slow-phase velocities (mSPVs) of the first-phase nystagmus were greater in HC-BPPV and PC-BPPV patients with reversal nystagmus than those without (p = 0.04 and p = 0.01, respectively). In all HC-BPPV and PC-BPPV patients with reversal nystagmus, the mSPV of the first-phase nystagmus was greater than that of the second-phase nystagmus (p < 0.01). The duration of the second-phase nystagmus was longer than 60 seconds in 93.75% (30 of 32) of the HC-BPPV patients and 77.27% (17 of 22) of the PC-BPPV patients (p = 0.107, Fisher exact test). HC-BPPV and PC-BPPV patients with reversal nystagmus both required more than one canalith repositioning procedure compared with those without (HC-BPPV: 75 versus 28.13%, p < 0.001; PC-BPPV: 59.09 versus 13.64%, p = 0.002).

CONCLUSIONS

The cause of second-phase nystagmus in BPPV patients with direction-reversing nystagmus may be related to the involvement of central adaptation mechanisms secondary to the overpowering mSPV of the first-phase nystagmus.