Posterior Semicircular Canal Benign Paroxysmal Positional Vertigo Presenting with Torsional Downbeating Nystagmus: An Apogeotropic Variant

Figure 4

Left PC PPV due to nonampullary arm canal lithiasis. If the clot is localized into the non ampullary arm of the PC, when the patient is brought into the head hanging positions, the otoconial mass moves towards the ampulla; this movement produces a ampullopetal endolymphatic current and generates an inhibitory discharge of the posterior ampullary nerve. Thick arrow: movement of PC movement during positioning; thin arrow: direction of endolymphatic current after positioning; dashed lines: positions gained by the clot and the cupula, after positioning.