Peripheral Downbeat Positional Nystagmus: Apogeotropic Posterior Canal or Anterior Canal BPPV

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.

Less talked variants of benign paroxysmal positional vertigo

The diagnostic criteria were established for benign paroxysmal positional vertigo (BPPV), the most common vestibular disorder worldwide, by the Barany Society in 2015. This marked an important milestone in the diagnosis and treatment of BPPV. However, there still remain uncertainties and ambiguities regarding the clinical features and pathophysiology of BPPV, and its clinical variants. In this manuscript, we will discuss 1) the emerging and controversial syndromes of BPPV (i.e., canalolithiasis of the anterior canal, cupulolthiasis of the posterior canal, and lithiasis of multiple canals) with updates, 2) atypical nystagmus according to the canal involved (e.g., nystagmus induced by head position changes in the pitch plane in horizontal canal BPPV, and positional downbeat nystagmus in posterior canal BPPV), 3) persistent geotropic positional nystagmus. Consideration of these uncommon types and manifestations of BPPV would broaden our understanding of BPPV pathomechanisms and allow differentiation from central vertigo and nystagmus.

Prevalence of and Theoretical Explanation for Type 2 Benign Paroxysmal Positional Vertigo

BACKGROUND AND PURPOSE

A variant of benign paroxysmal positional vertigo (BPPV) involves the subjective report of vertigo without the coinciding nystagmus. This presentation includes truncal retropulsion when sitting up from the ipsilesional provocative test (ie, Dix-Hallpike), which we term type 2 BPPV. The primary objective of this study is to prospectively determine the prevalence and describe the clinical course of type 2 BPPV. We offer a theoretical explanation for the absence of nystagmus.

METHODS

Prospective, observational study carried out in 2 tertiary hospitals. One hundred eighty patients (134 women, 46 men) met the inclusion criteria and were included between January 10, 2018, and October 30, 2019. Efficacy of physical therapy maneuvers was determined at 1-week follow-up. Three-dimensional reconstructions of the planes of the semicircular canal cupula from histological preparations are offered as evidence for the theoretical explanation.

RESULTS

One-third of the patients met the criteria for type 2 BPPV; the remainder had typical posterior or horizontal semicircular canal involvement. Symptoms from type 2 BPPV were longer in duration yet responded favorably to physical therapy maneuvers. Upon repeat testing, 19 patients treated for posterior canalithiasis developed a slight, persistent positional downbeat nystagmus in the Dix-Hallpike position that we propose as evidence the otoconia entered the short arm of the posterior semicircular canal.

DISCUSSION AND CONCLUSIONS

Our data and 3-dimensional rendering suggest the report of vertigo, yet absent nystagmus in type 2 BPPV is from otoconia aligning with the gravitoinertial vector during provocative testing that precludes cupular stimulation. Type 2 BPPV appears to be a common and treatable form of vertigo.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A372).

Case Report: Bow Hunter Syndrome—One Reason to Add Non-gravity Dependent Positional Nystagmus Testing to Your Clinical Neuro-Otologic Exam

This case study describes transient downbeat nystagmus with vertigo due to a bilateral Bow Hunters Syndrome that was initially treated for 7 months as a peripheral benign paroxysmal positional vertigo. Normal static angiography and imaging studies (magnetic resonance, computed tomography) contributed to the mis-diagnosis. However, not until positional testing with the patient in upright (non-gravity dependent) was a transient downbeat nystagmus revealed with vertigo. The patient was referred for neurosurgical consult. Unfortunately, surgery was delayed due to suicidal ideation and hospitalization. Eventually, vertigo symptoms resolved following a C4-5 anterior cervical dissection and fusion. This case highlights the critical inclusion of non-gravity dependent position testing as an augment to the positional testing component of the clinical examination as well as the extreme duress that prolonged positional vertigo can cause.

The frequency and impact of undiagnosed benign paroxysmal positional vertigo in outpatients with high falls risk

BACKGROUND

The frequency and impact of undiagnosed benign paroxysmal positional vertigo (BPPV) in people identified with high falls risk has not been investigated.

OBJECTIVE

To determine the frequency and impact on key psychosocial measures of undiagnosed BPPV in adult community rehabilitation outpatients identified with a high falls risk.

DESIGN

A frequency study with cross-sectional design.

SETTING

A Community Rehabilitation Program in Melbourne, Australia.

SUBJECTS

Adult community rehabilitation outpatients with a Falls Risk for Older People in the Community Screen score of four or higher.

METHODS

BPPV was assessed in 34 consecutive high falls risk rehabilitation outpatients using the Dix-Hallpike test and supine roll test. Participants were assessed for anxiety, depression, fear of falls, social isolation and loneliness using the Hospital Anxiety and Depression Scale, Falls Efficacy Scale-International and De Jong Gierveld 6-Item Loneliness Scale.

RESULTS

A total of 18 (53%; 95% confidence interval: 36, 70) participants tested positive for BPPV. There was no significant difference between those who tested positive for BPPV and those who did not for Falls Risk for Older People in the Community Screen scores (P = 0.555), Hospital Anxiety and Depression Scale (Anxiety) scores (P = 0.627), Hospital Anxiety and Depression Scale (Depression) scores (P = 0.368) or Falls Efficacy Scale-International scores (P = 0.481). Higher scores for the De Jong Gierveld 6-Item Loneliness Scale in participants with BPPV did not reach significance (P = 0.056).

CONCLUSIONS

Undiagnosed BPPV is very common and associated with a trend towards increased loneliness in adult rehabilitation outpatients identified as having a high falls risk.

Analysis of Dix-Hallpike maneuver induced nystagmus based on virtual simulation

BACKGROUND

How to interpret the various forms of nystagmus induced by the Dix-Hallpike maneuver has been the hotspot and difficulty of research.

OBJECTIVES

Analysis of the types of nystagmus induced by Dix-Hallpike maneuver, and establish a diagnosis strategy based on dynamic nystagmus observation.

MATERIALS AND METHODS

We observed the otolithic movements at different locations during the Dix-Hallpike maneuver through physical virtual simulation experiments and inferred the nystagmus performance, so as to establish the nystagmus interpretation rules for the repeated Dix-Hallpike maneuver.

RESULTS

There are six types of nystagmus induced by the Dix-Hallpike maneuver. Nystagmus induced by the unilateral Dix-Hallpike maneuver does not accurately locate the otolith. The typical nystagmus that is consistent before and after the repetition of the Dix-Hallpike maneuver is the outward and upbeat nystagmus, considering the ipsilateral posterior semicircular canal BPPV.

CONCLUSION

The atypical nystagmus often turns negative when the Dix-Hallpike maneuver is repeated. If the repeat test is positive and consistent with the results of the first diagnostic test, the otolith can be accurately located.

Complex nystagmus in traumatic benign paroxysmal positional vertigo: A case study on the critical value of knowing semicircular canal excitation and inhibition patterns

A 73-year-old female presented to the emergency department with chief complaint of dizziness after sustaining a fall one month prior to dizziness onset. Although careful examination of eye movement patterns during positional testing was attempted at varying stages of her inpatient admission, her complex nystagmus patterns as a result of traumatic benign paroxysmal vertigo were difficult to manage. In particular, the nystagmus pattern from this case suggests the BPPV was variable and affecting either 1) left posterior semicircular canal (pSCC) exclusively 2) left pSCC and right anterior semicircular canal, 3) left and right pSCC canal. This case illustrates the importance of two critical details; positional testing should include observing nystagmus with fixation removed and an experienced clinician should be involved as early as possible.

Feasibility of Using the Video-Head Impulse Test to Detect the Involved Canal in Benign Paroxysmal Positional Vertigo Presenting With Positional Downbeat Nystagmus

Positional downbeat nystagmus (pDBN) represents a relatively frequent finding. Its possible peripheral origin has been widely ascertained. Nevertheless, distinguishing features of peripheral positional nystagmus, including latency, paroxysm and torsional components, may be missing, resulting in challenging differential diagnosis with central pDBN. Moreover, in case of benign paroxysmal positional vertigo (BPPV), detection of the affected canal may be challenging as involvement of the non-ampullary arm of posterior semicircular canal (PSC) results in the same oculomotor responses generated by contralateral anterior canal (ASC)-canalolithiasis. Recent acquisitions suggest that patients with persistent pDBN due to vertical canal-BPPV may exhibit impaired vestibulo-ocular reflex (VOR) for the involved canal on video-head impulse test (vHIT). Since canal hypofunction normalizes following proper canalith repositioning procedures (CRP), an incomplete canalith jam acting as a "low-pass filter" for the affected ampullary receptor has been hypothesized. This study aims to determine the sensitivity of vHIT in detecting canal involvement in patients presenting with pDBN due to vertical canal-BPPV. We retrospectively reviewed the clinical records of 59 consecutive subjects presenting with peripheral pDBN. All patients were tested with video-Frenzel examination and vHIT at presentation and after resolution of symptoms or transformation in typical BPPV-variant. BPPV involving non-ampullary tract of PSC was diagnosed in 78%, ASC-BPPV in 11.9% whereas in 6 cases the involved canal remained unidentified. Presenting VOR-gain values for the affected canal were greatly impaired in cases with persistent pDBN compared to subjects with paroxysmal/transitory nystagmus (p < 0.001). Each patient received CRP for BPPV involving the hypoactive canal or, in case of normal VOR-gain, the assumed affected canal. Each subject exhibiting VOR-gain reduction for the involved canal developed normalization of vHIT data after proper repositioning (p < 0.001), proving a close relationship with otoliths altering high-frequency cupular responses. According to our results, overall vHIT sensitivity in detecting the affected SC was 72.9%, increasing up to 88.6% when considering only cases with persistent pDBN where an incomplete canal plug is more likely to occur. vHIT should be routinely used in patients with pDBN as it may enable to localize otoconia within the labyrinth, providing further insights to the pathophysiology of peripheral pDBN.

Vertical Nystagmus in the Bow and Lean Test may Indicate Hidden Posterior Semicircular Canal Benign Paroxysmal Positional Vertigo: Hypothesis of the Location of Otoconia

The ‘Bow and Lean Test’ (BLT) was developed for proper diagnosis of horizontal semicircular canal benign paroxysmal positional vertigo (HSC-BPPV). Occasionally, down- and/or up-beating vertical nystagmus is observed during the BLT. This study analyzed patients who exhibited vertical nystagmus in the BLT to comprehend the clinical significance of this sign. Of 2872 patients with vertigo between 2010 and 2015, 225 patients who showed vertical nystagmus in the BLT were enrolled. All patterns of vertical nystagmus were described based on their types of BPPV. After performing therapeutic maneuvers for BPPV, remnant symptoms in the BLT findings were investigated. Of the 225 patients with vertical nystagmus, 163 were posterior semicircular canal BPPV (PSC-BPPV). Down-beating in the bowing position and no nystagmus in the leaning position (‘Down/–’) was the most common type (190 of 225 patients). In addition, the nystagmus occurred in the form of ‘–/Up’, ‘Down/Up’, and ‘–/Down’. The pattern of vertical nystagmus may be related to the position of otoconia in the canals. The location of the otoconia enables the diagnosis of hidden PSC-BPPV. Even after treatment for BPPV, patients with vertical nystagmus in the BLT tended to complain remnant vertigo symptoms (44.8% vs. 23.9%, P = 0.022, in PSC-BPPV; 70.0% vs. 24.0%, P = 0.020, in HSC-BPPV). We thought that they actually had hidden PSC-BPPV and the otoconial debris may still in the PSC; this untreated PSC-BPPV might cause the remnant symptoms. In conclusion, vertical nystagmus in the BLT may indicate the presence of PSC-BPPV. Moreover, vertical nystagmus during the BLT may occur in patients with hidden PSC-BPPV who complain of remnant vertigo symptoms. Vertical nystagmus shown in the BLT may not include the possibility of central vertigo.

Benign Positional Paroxysmal Vertigo Treatment: a Practical Update

PURPOSE OF THE REVIEW

To define the best up-to-date practical approach to treat benign paroxysmal positional vertigo (BPPV).

RECENT FINDINGS

Both posterior and horizontal canal BPPV canalith repositioning maneuvers (Semont, Epley, and Gufoni's maneuvers) are level 1 evidence treatment for evidence-based medicine. The choice of maneuver (since their efficacy is comparable) is up to the clinician's preferences, failure of the previous maneuver, or movement restrictions of the patient. Maneuvers for controversial variants, such as anterior canal and apogeotropic posterior canal BPPV, have weaker evidence of efficacy. Despite this, these variants are increasingly diagnosed and treated. Maneuvers also play a role in the differential diagnosis with central vestibular disorders. Chair-assisted treatment may be of help if available while surgical canal plugging should be indicated in selected same-canal, same-side intractable severe BPPV. The primary evidence-based treatment strategy for BPPV should be physical therapy through maneuvers. Despite the high success rate of liberatory maneuvers, there is a low percentage of subjects who have unsatisfactory outcomes. These patients need to be investigated to identify recurrences, multiple canal involvement, associated comorbidities (migraine, persistent postural perceptual dizziness), or risk factors for recurrences (low vitamin D serum level). Future research should also identify the optimum maneuvers for variants whose diagnosis and treatment are still a matter of some debate.