Figure 1.

Otolith position changes in the Dix-Hallpike test. (A) Image taken with the patient sitting upright, back view. The otolith is located on the short arm side or near the ampulla of the long arm side of the right posterior semicircular canal. (B) Turn the head 45° to the 0 right. Lateral view. (C,D) Images taken with the patient lying supine with the right ear down and the head tilted back 30°. The otolith is initially located near the ampulla of the long arm side of the right posterior semicircular canal, moved away from the ampulla for a long distance. (E,F) The otolith is initially far away from the ampulla and moves toward the ampulla under the action of gravity, but it cannot migrate to the previous position and keep a further distance from the ampulla.