Which test assesses otolithic pathway function?

• A. Head impulse test
• B. VEMP
• C. Caloric testing
• D. Audiometry

Answer: (B)

The main idea is to evaluate the otolith organs, which detect linear head motion and gravity. The otoliths reside in the utricle and saccule, and they send signals through the vestibular nerve to brainstem centers that help control gaze and posture. To test these pathways directly, we use vestibular evoked myogenic potentials. By delivering sound or vibration, the otolith organs are stimulated and trigger reflex muscle responses, measured as potentials in specific muscles. Cervical VEMP taps the neck muscles and mainly reflects the saccule’s (inferior vestibular nerve) pathway, while ocular VEMP looks at the eye muscles and mainly reflects the utricle’s (superior vestibular nerve) pathway. Together, VEMP testing targets otolithic function, distinguishing it from tests that focus on the semicircular canals or hearing.

In contrast, the head impulse test measures reflexes from the semicircular canals during quick head movements, addressing angular acceleration rather than linear acceleration. Caloric testing also targets the horizontal semicircular canal by creating endolymph flow with temperature changes, again about angular movement. Audiometry evaluates hearing thresholds and does not assess vestibular pathways.