Eye Movements Induced by Stimulation to the Otolith Organs

Background: We have been performing a canalith repositioning procedure for benign paroxysmal positional vertigo. When we adopted the Epley maneuver for posterior semicircular canal type, and affected-ear-up 90° maneuver for lateral semicircular canal type, we noticed that no nystagmus occurred in the sitting position just after treatment. Despite direct excitation to the utricle by the pathological debris, none of the subjects complained of dizziness. Thus, we hypothesized that nystagmus and dizziness do not occur by stimulation of the otolith organs. Objective: The aim of the study was to observe and record the eye movements induced by the otolith organs to confirm our hypothesis. Materials and Methods: Twelve healthy humans were tested. In the sitting position, the head was tilted to the right ear by 45° and vice versa. Afterward, the head was bent forward by 90° (nose-down), and the subject’s seat was reclined to the head-hanging position. Each position was kept for five seconds. We interviewed the subjects to assess their dizziness. Results: None of the subjects showed nystagmus and complained of dizziness in every position. Conclusions: Nystagmus does not occur by the stimulation to the otolith organs; therefore, ocular counter-rolling is a semicircular canal ocular reflex.