RESUMEN
BACKGROUND AND OBJECTIVES: Benign paroxysmal positional vertigo (BPPV) is one of the most common peripheral vestibular disorders. There have been some reports suggesting that directional changing positional nystagmus occurs due to canalolithiasis and cupulolithiasis of the horizontal semicircular canal (HC). The canalolithiasis theory of HC-BPPV is presented with a transient geotropic direction changing horizontal nystagmus as the pathophysiologic mechanism of BPPV. The HC-BPPV cupulolithiasis is characterized by a positional nystagmus that does not fatigue, but persists as long as the position is held, and changes direction in different head positions. There is still a controversy relating to differentiating the lesion side and the otolith adherent sites on the cupula differentiation. The purpose of this study was to differentiate the lesion side and the otolith adherent site on the cupula, and propose a treatment through analyses of clinical features, electronystagmographic (ENG) results, treatment maneuvers and its effectiveness. SUBJECTS AND METHOD: Fifteen patients who showed ageotropic 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 magnetic resonance imaging were checked to exclude the possibility of any central lesion. Cupulolith repositioning maneuver (CuRM) was applied on the all patients and these patients were instructed to keep the healthy side at the lateral decubitus position while sleeping. RESULTS: All patients showed significant differences between the intensity of each side nystagmus, and all of them showed stronger ageotropic direction changing horizontal nystagmus when the head was rotated to the unaffected side in a supine head turning test. The nystagmus had a short latency, no fatigability, and persistency in character. Typical nystagmus and spinning sensation in the supine head turning test had completely subsided after physical therapy. CONCLUSION: In the cupulolithiasis of horizontal semicircular canal, ageotropic nystagmus was stronger when the pathological ear was at the uppermost position, and this excitatory nystagmus beats to the lesion side. The proposed CuRM and post-treatment lateral decubitus position kept during the night (while sleeping on the day of treatment) were effective in differentiating the otolith adherent site on the cupula and treating the cupulolithiasis of the horizontal semicircular canal.