Atypical PC BPPV Variant Figures

Figure 1: Atypical posterior canal BPPV variants The labyrinth consists of the cochlea (C), two otolithic organs including utricle (U) and saccule (S), and three semicircular canals including anterior canal (AC), horizontal canal (HC), and posterior canal (PC). A. If otoconia are located within the PC superior to the short-arm and near the common crus (CC), the Dix-Hallpike maneuver can create endolymph flow in an inhibitory, ampullopetal direction (arrow) resulting in downbeat-torsional nystagmus. B. Within the short arm of the PC, otoconia can float freely (canalithiasis) or can adhere to the cupula (cupulolithiasis, as in this figure where the arrow demonstrates the associated gravito-inertial acceleration), and its specific location will dictate the symptoms and signs triggered by positional testing (see Figure 2). Figure 2: Understanding the short arm variant of posterior canal BPPV A. When upright, the orientation of the PC is such that the cupula is inferior to the utricle and short arm, making it possible for otoconia to enter and either float freely (canalithiasis) or adhere to the cupula (cupulolithiasis) within the short arm. With canalithiasis of the PC short-arm, otoconia may exit the PC with Dix-Hallpike (i.e., no vertigo, no nystagmus) and enter the PC when sitting up (i.e., vertigo, upbeat-torsional nystagmus). B. With cupulolithiasis of the PC short-arm, the Dix-Hallpike maneuver can cause the cupula to deflect in an inhibitory (ampullopetal) direction, causing downbeat-torsional nystagmus.