A new saccadic indicator of peripheral vestibular function based on the video head impulse test

Area of Science:

• Neuroscience
• Ophthalmology
• Vestibular System Research

Background:

• The conventional head impulse test (HIMP) uses an earth-fixed target to assess vestibular loss via compensatory saccades.
• A complementary suppression head impulse paradigm (SHIMP) with a head-fixed target elicits anticompensatory saccades, indicating vestibular function.

Purpose of the Study:

• To investigate the utility of the SHIMP in identifying vestibular function and loss.
• To compare the saccade patterns elicited by HIMP and SHIMP in patients with vestibular loss and healthy controls.

Main Methods:

• Horizontal video head impulse test (vHIT) was used to measure eye movements.
• Participants included patients with unilateral vestibular loss, bilateral vestibular loss, and healthy controls.
• Both HIMP and SHIMP paradigms were employed.

Main Results:

• Vestibulo-ocular reflex (VOR) gains correlated highly between HIMP and SHIMP (R² = 0.97).
• HIMP elicited compensatory saccades in patients, while SHIMP elicited anticompensatory saccades in controls and smaller/no saccades in patients with bilateral loss.
• Cumulative saccade amplitude in both paradigms differentiated patients from controls with high sensitivity and specificity.

Conclusions:

• Anticompensatory saccades in SHIMP indicate vestibular function, complementing HIMP's assessment of vestibular loss.
• SHIMP saccades are often later and more visible than HIMP saccades, aiding VOR gain measurements.
• The SHIMP is an intuitive and effective tool for diagnosing unilateral or bilateral vestibulopathies.