The vestibular evoked myogenic potential (VEMP or VsEP) is a neurophysiological assessment technique used to determine the function of the otolithic organs (utricle and saccule) of the inner ear. It complements the information provided by caloric testing and other forms of inner ear (vestibular apparatus) testing. There are two different types of VEMPs. One is the oVEMP and another is the cVEMP. The oVEMP measures integrity of the utricule and superior vestibular nerve and the cVemp measures the saccule and the inferior vestibular nerve.
The vestibular system helps a person maintain: balance, visual fixation, posture, and lower muscular control.
There are six receptor organs located in the inner ear: cochlea, utricle, saccule, and the lateral, anterior, and posterior semicircular canals. The cochlea is a sensory organ with the primary purpose to aid in hearing. The otolith organs (utricle and saccule) are sensors for detecting linear acceleration in their respective planes (utrical=horizontal plane (forward/backward; up/down); saccule=sagital plane (up/down)), and the three semicircular canals (anterior/superior, posterior, and horizontal) detect head rotation or angular acceleration in their respective planes of orientation (anterior/superior=pitch (nodding head), posterior=roll (moving head from one shoulder to other), and horizontal=yaw (shaking head left to right).Located within the membranous labyrinthine walls of the vestibular system are approximately 67,000 hair cells in total. This includes ~7,000 hair cells from each of the semicircular canals located within the crista ampullaris, ~30,000 hair cells from the utricle, and ~16,000 hair cells from the saccule. Each hair cell has about 70 stereocilia (short rod-like hair cells) and one kinocilium (long hair cell)