oVEMP measures the vestibulo-ocular reflex by recording from extraocular muscles. The inferior oblique muscle, located beneath the eye, is the primary muscle monitored because it reliably reflects utricular-driven vestibulo-ocular activity when stimuli such as sound or vibration are used. Electrodes are placed under the eye to capture potentials from these muscles, which distinguishes oVEMP from cVEMP that uses neck muscles like the sternocleidomastoid. So the monitored muscle for oVEMP is the inferior oblique / extraocular muscles beneath the eyes.

The vestibulo-ocular reflex (VOR) is the mechanism that keeps what you see stable when your head moves. Testing VOR asks how well this reflex stabilizes gaze, so you can detect vestibular problems. A quick bedside method, the head impulse test, probes high-frequency VOR function. You look at a fixed target and the clinician makes small, rapid, unpredictable head movements. If the VOR is working, the eyes stay on the target; if not, you’ll see a quick catch-up saccade as the eyes refocus on the target. For a quantitative readout, you measure the VOR gain—the ratio of eye velocity to head velocity. A normal gain is around 1.0, meaning the eyes move the same amount in the opposite direction as the head. Reduced gain indicates impaired VOR function. This gain is commonly obtained with video head impulse testing (vHIT), which records precise eye and head movements to give a numerical gain and identify corrective saccades. Other tests like caloric testing or rotary chair can assess different frequencies of VOR and broader semicircular canal function, but the most widely used practical approach in many clinics is combining the head impulse test with VOR gain measurement.

Canalith repositioning maneuvers aim to relocate the loose otoconia from the semicircular canals back into the utricle. Otoconia are crystals that normally reside in the utricle and saccule to sense gravity. When they drift into a semicircular canal, their presence makes the canal sensitive to head movements, causing spinning vertigo and abnormal eye movements. By guiding the head through a precise sequence of positions, gravity helps the crystals move along the canal and out into the utricle, where they no longer disrupt vestibular signaling. This directly addresses the abnormal stimulation causing vertigo, leading to symptom relief. The other options don’t fit because destroying otolithic organs would cause irreversible vestibular loss, reducing hearing isn’t the goal of these maneuvers, and widening the vestibular aqueduct would alter inner-ear fluid balance rather than correct displaced crystals.

The vestibular system provides motion information that the brain uses to coordinate gaze, balance, and bodily state. It drives eye movements through the vestibulo-ocular reflex, stabilizing vision when the head moves. It also communicates with the spinal cord via vestibulospinal pathways to influence muscle tone and reflexes that keep us upright and maintain posture. Additionally, vestibular input reaches autonomic centers in the brainstem, helping regulate heart rate, blood pressure, and visceral responses, which can also produce nausea or changes in arousal during motion. Hearing and visual perception rely on separate pathways (cochlear/auditory and cortical visual systems), so while vestibular input supports gaze stability, its main broad influences are eye movements, postural control, and autonomic regulation.