Eye position of positional nystagmus in the right-ear-down and left-ear-down head positions in patients with horizontal canal type of benign paroxysmal positional vertigo. Eye position of positional nystagmus in the right-ear-down and left-ear-down head positions in patients with horizontal canal type of benign paroxysmal positional vertigo. (A) Persistent geotropic positional nystagmus in patient A and (B) persistent apogeotropic positional nystagmus in patient B. Takao Imai et al. BMJ Open 2015;5:e006607 ©2015 by British Medical Journal Publishing Group