Figure 1

The instance of light cupula observed in the right hSCC. The patient’s head and right hSCC were viewed from the top of the patient’s head. (A) In the supine position, a left-beating nystagmus (maximal SPV = 33°/s) was persistently observed due to an utriculofugal deflection of the cupula. (B) When the patient’s head was turned to the right while in the supine position, the right hSCC was activated because of an utriculopetal deflection of the cupula resulting in a persistent right-beating nystagmus (maximal SPV = 10°/s). (C) The cupula of the right hSCC was deflected utriculofugally when the head was turned to the left side, which caused a persistent left-beating nystagmus (maximal SPV = 53°/s). Note that the intensity of the nystagmus is stronger in left-head rolling than in right head-rolling. hSCC, horizontal semicircular canal; SPV, slow-phase velocity.