Posterior Semicircular Canal Benign Paroxysmal Positional Vertigo Presenting with Torsional Downbeating Nystagmus: An Apogeotropic Variant
Figure 1
Paroxysmal positional nystagmus due to unilateral right posterior semicircular canal (PC) lithiasis (excitatory stimulus). (a): Black arrows indicate the direction of nystagmus slow phase in the two eyes; white arrows indicate the direction of nystagmus fast phase in the two eyes. (b): Arrows indicate the ocular muscles involved in nystagmus generation. (c): The two labyrinths; arrow indicates the endolymphatic flow within the interested canal. On the left side of the figure: the right eye and the right labyrinth; on the right side of the figure: the left eye and the left labyrinth. A: anterior semicircular canal; L: lateral semicircular canal; P: posterior semicircular canal.
