Benign Paroxysmal Positional Vertigo of the Horizontal Semicircular Canal

Kim, Young Ki; Yoon, Yong Joo; Kim, In

Abstract

BACKGROUND AND OBJECTIVES: Benign paroxysmal positional vertigo (BPPV) is the most common disease of the peripheral vestibular disorders. Canalithiasis theory of the posterior semicircular canal is widely accepted as the pathophysiologic mechanism of BPPV. Recently, some authors reported that geotropic direction-changing horizontal nystagmus is attributed to the BPPV of the horizontal semicircular canal. The purpose of this study is to aid in the understanding and diagnosis of this disease through the analysis of the clinical features and electronystagmographic (ENG) results.
MATERIALS AND METHODS
Nine patients who showed geotropic direction-changing horizontal nystagmus were included in this study. Supine head turning test was performed to induce positional nystagmus. Various findings of the nystagmus were recorded with ENG. Other ENG tests (visual tracking tests and bithermal caloric test) and MRI (4 cases) were checked to exclude the possibility of the central origin.
RESULTS
All patients showed geotropic direction-changing horizontal nystagmus in supine head turning test. The nystagmus had a short latency, no fatigabilily and long duration (>1 min). The nystagmus was more intense in diseased ear of down position and changed its direction spontaneously (secondary nystagmus) in 7 cases.
CONCLUSION
All patients complaining of paroxysmal positional vertigo should undergo two positional tests: Dix-Hallpike test and supine head turning test. Characteristics of nystagmus can be explained by canalithiasis theory of the horizontal semicircular canal.