Benign paroxysmal positional vertigo (BPPV) may induce inner ear dizziness, called vertigo, when lying on your back, while turning your head, when standing up out of bed, when looking upwards and downwards and with rotation in the horizontal plane. BPPV may also affect postural efficiency while walking or cause visual disturbances or nausea.
The vestibular-ocular reflex (VOR) allows us to maintain stable vision while our head is in motion. VOR impairments may result in movement-related dizziness, blurry vision, nausea or difficult focusing with activity. Measuring the VOR status quantifies changes in visual acuity with head movement. Measuring the functional VOR status provides information on an individual’s ability to maintain stable vision during daily life activities that involve head movement.
Videonystagmography (VNG) is a vestibular assessment of peripheral vestibular systems located in the inner ear and of the central motor functions of eye movement. VNG testing uses goggles with infrared cameras to track eye movements with fixation removed during visual stimulation and positional tests. VNG tests for nystagmus, which can be present with dizziness, and can detect whether dizziness is related to peripheral vestibular impairments. The ocular motor tests, which examine the brain’s ability to move the eyes when tracking targets, are sensitive to central vestibular lesions and central nervous system impairments. Caloric testing stimulates each peripheral vestibular system independently and can be used to differentiate left from right vestibular impairments.
The video head impulse test (vHIT) is a high-frequency test of the vestibular-ocular reflex (VOR). It tests the function of all six semicircular canals in the peripheral vestibular system and offers a supplementary assessment to rotary chair and caloric testing. Compared to the traditional clinical head impulse test (cHIT) that is conducted with direct observation of the eye, the vHIT can objectively detect and record overt and covert refixation saccades. These measurements can be documented and used to identify any impairment or abnormality in the generated VOR.
Smooth pursuit eye movements allow the eyes to follow moving targets in the visual fields. If the smooth pursuit system is damaged by a central lesion, the eyes will follow behind the moving target requiring catch-up saccades to get back to the target. This may contribute to any symptoms or sensations of dizziness that a patient may report.
Balance is broadly regarded as the successful integration of three sensory systems: vision, vestibular and somatosensory. The successful integration of these systems will enhance our postural stability and mobility. Postural stability is our ability to maintain our body’s center of gravity within our base of support. Postural mobility is our ability to accelerate our body’s center of gravity in the appropriate direction at the initiation of movement.