Benign paroxysmal vertigo of the horizontal canal.

Over a period of 4 years we observed 15 cases of benign positional vertigo (BPV) probably caused by deposition of otoliths in the horizontal semicircular canal. Rapid rolling onto one side in recumbent position provokes a paroxysmal, purely horizontal and geotropic nystagmus which nearly always spontaneously inverts direction. Rolling the patient onto the other side provokes a left intense geotropic nystagmus. BPV is more violent but resolves more rapidly than that of the better known posterior canal positional vertigo. Sometimes both syndromes are present together.