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

Abstract

ObjectiveThe 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.Methods567 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.ResultsOf 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.ConclusionBeyond 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 EvidenceLevel 3, according to Oxford Center for Evidence‐Based Medicine Laryngoscope, 2023

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

“…This was most notable on the second day of testing when the patient initially displayed right beating apogeotropic nystagmus before transiently changing to upbeat and left torsional nystagmus while in the left SRT. The bow and lean test helped lateralize the affected horizontal semicircular canal but was also beneficial in clearly revealing a concomitant left posterior canal BPPV ( 18 ).…”

Editorial: Benign paroxysmal positional vertigo

“…However, it has undergone a gradual implementation by experienced vertigo clinicians as an additional examination for any BPPV subtype. In addition, a 45° tilt of the head has been proposed to explore the presence of BPPV affecting posterior and anterior canals to increase the sensitivity of the bow and lean test in the diagnosis of vertical canal BPPV ( 5 ). The 60° roll test and prone roll test are supplementary tests that have also been proposed to aid in determining the position of otoliths within the affected canals and in distinguishing between canalolithiasis and cupulolithiasis ( 6 ).…”