Videonystagmography (VNG) and Caloric testing: Our eyes are window to our body’s balance function. Therefore, by recording the eye movement through a specialised infra-red clinical camera system-we can evaluate the balance function in the inner ear and central nervous system. That’s where the name Videonystagmography comes from-it is the video recording of an eye reflex called nystagmus that naturally occurs when your balance system is stimulated. We use different stimulation techniques involving projection of images/dots on the wall via projector, and something called caloric stimulation where the inner ear balance system is stimulated by temperature controlled air.
Video Head Impulse Test (vHIT): vHIT provides quick, lesion-specific assessment of inner ear’s vestibular system (semicircular canals) in the natural range of head movements. It is the only test that can assess all six semicircular canals. We use ICS Impulse® kit from Otometrics in our clinic, which is the world’s first vHIT device to combine gold-standard accuracy with unrivalled patient comfort.
vHIT is complementary to the caloric stimulation test. It is more comfortable to have vHIT and in some cases e.g. in people with migraine, it may be even safer to use vHIT than caloric stimulation to assess the peripheral vestibular system. Furthermore, vHIT can predict bilateral vestibular losses with more accuracy than caloric test and it can also be used to monitor the progress of vestibular rehabilitation. So, there are clear relative advantages.
We feel that vHIT should be the first line peripheral vestibular assessment tool in 21st century clinic. Although it does not replace caloric stimulation test that is hitherto considered the gold standard but if a peripheral issue is noticed on vHIT, there may only be a little point in carrying on with caloric testing as it may not affect the management.