The Functional Head Impulse Test and Vestibular Rehabilitation with V-Gym: A Diagnostic and Therapeutic System for the Semicircular Canals

Abstract

The functional status of the semicircular canals can be tested by the caloric test video nystagmography/electronystagmography (VNG/ENG), dynamic visual acuity (DVA) test, gaze stabilization test (GST), and video head impulse test (VHIT). All these tests have certain limitations, for example the caloric test ENG/VNG as well as the DVA and GST evaluates only the lateral canals, and it is only the VHIT that evaluates all the six canals with precision. However, one common disadvantage is that all these tests are pretty cumbersome and involve very costly and sophisticated instrumentation that most clinicians cannot afford at least in the private sector. This new test called the functional head impulse test (fHIT) is a new addition to the neurotologist's diagnostic armamentarium for evaluation of all the six semicircular canal that addresses many of the limitations of the other available tests. The fHIT reliably measures the functional status of all the six semicircular canals by ascertaining the efficiency of the rotational vestibulo-ocular reflex (rVOR) in a quick, very simple, easy-to-perform way and with a perfectly physiologic stimulus. The fHIT precisely assesses whether the rVOR of the semicircular canals are being able to stabilize images when there is a fast head movement in the plane of the semicircular canals. After a defective canal has been detected, the system has inbuilt rehabilitative methods that can stimulate the canal and enhance its functionality. In addition to its simplicity of design and affordable costs (without compromising reliability), the fHIT system has the unique advantage of being a compact diagnostic-cum-therapeutic device and is a boon to practioners in neurotology ([Fig. 1]).