Incidence and Clinical Significance of Positional Downbeat Nystagmus in Posterior Canal Benign Paroxysmal Positional Vertigo

Bow and Lean Test for Rare Variants of Vertical Semicircular Canal BPPV

OBJECTIVE

The objective of this study was to assess the clinical significance of the Bow and Lean Test (BLT) for the diagnosis of different variants of vertical canal Benign Paroxysmal Positional Vertigo (BPPV). BLT is commonly used for diagnoses of lateral semicircular canal (LSC) BPPV. However, vertical nystagmus in the BLT may indicate the presence of other variants such as PSC-BPPV.

METHODS

567 patients with vertical canal BPPV were recruited. Patients with anterior semicircular canal (ASC) or PSC-BPPV were weekly examined until the negativization of BPPV. Nystagmus characteristics during BLT were analyzed.

RESULTS

Of 567 patients with vertical canal BPPV, 1.4% had ASC-BPPV. BLT was positive in 155 patients, showing patterns like down-beating nystagmus in bowing and no nystagmus in leaning (15.52% of patients), and down-beating in bowing and up-beating in leaning (6.17%), which was predominantly present in PSC-canalolithiasis. Statistically significant differences were observed in the direction of nystagmus provoked by BLT in PSC-BPPV subtypes. No significant differences were found in nystagmus latency or duration during BLT positions. Among BPPV subtypes, there was a significant difference in nystagmus duration and latency, especially between cupulolithiasis and other variants. BLT's sensitivity was 0.93 in bowing and 1 in a leaning position, while specificity was 0.93 and 0.82 respectively.

CONCLUSION

Beyond the LSC, the BLT has expanded to other variants. However, study results differ likely due to variations in patient characteristics and test execution. Currently, no specific features for ASC have been found to differentiate it from PSC-BPPV limiting the test's use for this variant.

LEVEL OF EVIDENCE

3, according to Oxford Center for Evidence-Based Medicine Laryngoscope, 134:2405-2410, 2024.

Case Report: Keep your eyes open! Nystagmus guides atypical BPPV

The clinical diagnosis of benign paroxysmal positional vertigo (BPPV) is confirmed from observing the direction, intensity, and duration of nystagmus from unique head positions that advantage gravity to overcome the inertia of otoconia displaced inside the semicircular canals. This case series highlights BPPV with atypical nystagmus presentations relative to the head position. Clinicians should carefully observe symptoms and nystagmus presentations regardless of the testing position and utilize technology and rules of vestibular physiology to enhance their diagnostic acumen.

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.

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.

Update on benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo worldwide. This review considers recent advances in the diagnosis and management of BPPV including the use of web-based technology and artificial intelligence as well as the evidence supporting the use of vitamin D supplements for patients with BPPV and subnormal serum vitamin D.

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.

A new variant of posterior canal-benign paroxysmal positional vertigo-canalolithiasis

OBJECTIVE

The characteristics of typical posterior canal-benign paroxysmal positional vertigo-canalolithiasis (P-BPPV-Can) are well known. We found 10 patients with a new variant of P-BPPV-Can: Reverse (Rev)-P-BPPV-Can. The characteristics and pathophysiology of Rev-P-BPPV-Can are discussed.

METHODS

For 4 years and 9 months, 10 patients with Rev-P-BPPV-Can (9 women and 1 man; mean age: 73 years) visited our clinic. Within the same period, 268 patients with unilateral typical P-BPPV-Can were treated. During the Dix-Hallpike and Epley maneuvers, nystagmus was recorded using an infrared charge-coupled device camera mounted on a pair of spectacles.

RESULTS

The patients exhibited entirely opposite direction of nystagmus from typical P-BPPV-Can in both the Dix-Hallpike head position and upright sitting position. The patients had typical characteristics of nystagmus due to canalolithiasis, such as latency, duration of <1 min, linear-torsional nystagmus, and fatigability. Rev-P-BPPV-Can appeared after the Epley maneuver for typical P-BPPV-Can; in other patients, Rev-P-BPPV-Can changed to typical P-BPPV-Can. The affected sides of Rev-P-BPPV-Can were decided by those of typical P-BPPV-Can.

CONCLUSION

Canalolithiasis in the non-ampullary distal portion of the posterior semicircular canal may be a potential pathophysiology of Rev-P-BPPV-Can. The Epley maneuver has little effect for treating Rev-P-BPPV-Can, but spontaneous transition to typical P-BPPV-Can or spontaneous recovery is expected.

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.