About Nystagmus Transformation in a Case of Apogeotropic Lateral Semicircular Canal Benign Paroxysmal Positional Vertigo

Figure 2

When the patient in supine position rolls his/her head by 180° from the left to the right side for the third time, pushed by the endolymphatic flow (dashed arrow), some of the debris moves into the posterior arm of the canal, while another part remains in the anterior arm, both moving in an ampullofugal way (thin arrows), thus triggering a right beating geotropic nystagmus (head arrow).