Clinical Assessment of Otolith Function

The two otolith organs (the saccule and utricle) are positioned perpendicular to each other and sense linear acceleration, head tilt, and gravity, with the primary role of providing input to the vestibulospinal reflex for postural stability. The vestibulospinal reflex serves to modulate posture via two descending pathways that aid in tonic contractions of the antigravity muscles in the arms and legs (lateral vestibulospinal tract) and activate neck motoneurons for the coordination of neck and eye movements (medial vestibulospinal tract). The lateral vestibulospinal tract receives the majority of its input from the otoliths and the cerebellum, whereas the medial vestibulospinal tract receives the majority of its input from the semicircular canals