The clinical study of benign paroxysmal positional vertigo of horizontal semicircular canal origin

ABSTRACT

BACKGROUND & OBJECTIVES: It was well known that benign paroxysmal positional vertigo(BPPV) was caused by the involvement of the posterior semicircular canal, but there were a few reports about horizontal canal variant of BPPV. We studied the clinical features electronystagmographic (ENG) findings and the possible mechanism of BPPV of the horizontal canal(HBPPV). METHODS: We examined 10 cases of HBPPV with episodic vertigo and intense horizontal geotropic nystagmus provoked by rotation of the head in a supine position. Six patients underwent ENG and we recorded four patients' nystagmus, provoked by rotating head from extreme lateral, mid and nose-up position to extreme contralateral direction in supine position. RESULTS: All observed horizontal nystagmus beated towards the ground on both sides and were more pronounced when head was rotated to pathological side. In rotating to pathological side, nystagmus had mean latency of 2.6+/-1.8 seconds, peak velocity of slow phase of 66,8+/-19.7 degree/second and mean duration of 24.7+/-3.4 seconds. In rotating to healthy side the nystagmus had 3. 7+/- 2.9, 38.0+/-11.5 and 22.5+/-4. Secondary phase nystagmus occurred in 2 patients and fatigue was observed in 4 patients. The slow phase velocity of nystagmus was relative to the distance of head rotation. The duration of attack is 3 to 17 days(6.9+/-5.2days). Liberatory manuever had relatively a good effect. CONCLUSION: HBPPV represents the origin of horizontal semicircular canal and has a good prognosis Above findings support that mechanism of horizontal BPPV is canalolithiasis.