The New Method to Determine the Causing Site of Horizontal Canal Benign Paroxysmal Positional Vertigo: “Bowing and Leaning Nystagmus”

Abstract

Background and Objectives: One of problems for the management of horizontal semicircular canal benign paroxysmal positional vertigo (HSC-BPPV) is the difficulty of determining the affected ear using Ewald’s second law. The purpose of this study is to develop the new “Bow and Lean Test (BLT)” to determine easily the affected ear of HSC-BPPV and evaluate its efficiency. Materials and Method: We compared the efficiency between the classical method and BLT in 26 patients with HSC-BPPV. The classical method is based on Ewald's second law comparing the intensity of nystagmus or symptoms in head roll test. BLT is based on the direction of both “bowing nystagmus” and “leaning nystagmus” at head’s bowing and leaning state on sitting position. The affected ear is the same direction of bowing nystagmus in canalolithiasis and the same direction of leaning nystagmus in cupulolithiasis. Results: In 26 patents (15 canalolithiasis, 11 cupulolithiasis), 3 (11.5%) patients did not show a prominent affected ear in the classical method, and 7 (26.9%) patients showed the different affected ear between two methods. All 10patients were successfully treated with just one trial of barbecue rotation based on the affected ear in BLT. Three patients did not show any bowing or leaning nystagmus. The side with canal paresis in all 4 patients, who showed significant canal paresis in bithermal caloric tests, was equal to the affected ear based on BLT. Conclusion: “Bow and Lean Test” (also called “Choung’s test”) is a new method which can easily determine the affected ear of HC-BPPV.