Can caloric testing evaluate the function of vertical semicircular canals?

Abstract

Conclusion: Neither posterior nor superior semicircular canal receives a caloric effect; therefore, caloric testing cannot evaluate the function of vertical semicircular canals. Objective: To clarify whether caloric stimulation reaches the posterior and superior semicircular canals. Methods: The subjects were 10 healthy humans. The right ear was stimulated using ice-water. Each subject was kept in a supine position for 40 s and then repositioned to a sitting position until horizontal nystagmus stopped; afterwards, a nose-down position was adopted. Nystagmus was analyzed by three-dimensional video-oculography. Results: In the supine position, four subjects revealed a vertical component and five subjects showed a torsional component. In the sitting position, neither a vertical nor a torsional component occurred when the horizontal component stopped. Three subjects revealed a vertical component and four subjects showed a torsional component in the nose-down position.

Keywords::

• Nystagmus
• video-oculography
• hydrostatic pressure
• ossicles
• Pascal's principle
• thermal conductivity

Acknowledgment

We thank Dr Kazunori Futai for preparing some of the figures.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.