The functional Head Impulse Test (fHIT)

The USP of fHIT is that this is a functional test and reliably measures the functional status of the semicircular canals (by ascertaining the efficiency of the rVOR) in a quick, very simple, easy-to-perform way without much complicated, cumbersome, and costly equipment that is necessary for the other tests. It does not ascertain the VOR gain which the VHIT does, measure the percentage of canal paresis that the caloric test ENG / VNG does, or even measure the loss of visual acuity that the DVA test does, but it assesses whether the semicircular canals are being able to serve the function of gaze stabilization and, if so, how efficiently. This qualitative rather than quantitative measurement is a more practical approach and more relevant to the clinician as all that the clinical practitioner in neurotology is interested to know is whether the semicircular canals are serving their function of maintaining a stable gaze when there is a fast head movement. In fact, in the clinical practice of neurotology, the functional status of an organ is much more appropriate as a clinical parameter than mathematical values like the % of canal paresis (that is measured by caloric ENG/VNG) or the % of the VOR gain (measured by the VHIT) of the semicircular canals. Of course, the qualitative evaluation obtained by fHIT can be documented quantitively also as detailed later.