vHIT (video Head Impulse Test)

Abstract

The video Head Impulse Test (vHIT) is a significant advancement in vestibular function testing, complementing caloric testing, which assesses only the horizontal semicircular canal. vHIT enables evaluation of all three semicircular canals and their corresponding vestibular nerves, providing a more comprehensive assessment.

Principles of vHIT: vHIT measures vestibulo-ocular reflex (VOR) gain using high-speed cameras and accelerometers. Unlike the conventional Head Impulse Test (HIT), which relies on visual detection of catch-up saccades (CUS), vHIT quantifies VOR gain and detects covert CUS, which occur during head rotation and are otherwise imperceptible.

Clinical Advantages: As compared with caloric testing, vHIT has three main advantages: 1. Assessment of Vertical Semicircular Canals – It allows evaluation of the anterior and posterior canals in addition to the horizontal semicircular canal, aiding in the diagnosis of conditions like vestibular schwannoma and superior canal dehiscence syndrome. 2. Independence from Ear Pathologies – Unlike caloric testing, the results of vHIT remain unaffected by external and middle ear conditions, making it useful in cases with conditions such as labyrinthine fistula due to cholesteatoma or otitis media. 3. Reduced Discomfort and Reproducibility – vHIT induces less nausea, allowing for repeated assessments, such as for disease monitoring and post-surgical evaluation.

Future Perspectives: CUS patterns may reflect vestibular compensation, with covert CUS associated with better postural stability. Analyzing CUS transitions could optimize vestibular rehabilitation, offering personalized therapy approaches.

While vHIT should not replace caloric testing, it serves as a valuable complementary tool. Further research into its application in vestibular compensation and rehabilitation is warranted.