[Receptor function of the semicircular canals: Part 1: anatomy, physiology, diagnosis and normal findings]

Abstract

The perception and conversion of motion stimuli by the vestibular receptors, unimpaired postural control and intact visual acuity are essential for spatial orientation. Disturbances in these three sensory systems can manifest as "vertigo", "dizziness" or "imbalance". The integrity of peripheral receptor function, especially of the three semicircular canals, plays a superficial role. They are sensitive to acceleration stimuli, which they transmit via reflexes to the eye muscles. The stabilization of a visual target is via vestibulo-ocular reflexes, which have a very short latency and thus ensure a permanently stable image on the retina. Modern lateral-specific testing procedures are available to diagnose the receptor function of the peripheral vestibular system. The function of the semicircular canals can be analyzed using a head impulse test (HIT) and, more recently, by means of video-HIT as well as on the basis of a caloric test. Using these techniques, all three semicircular canals can be assessed in a side- and receptor-specific manner.