The Functional Head Impulse Test to Assess Oscillopsia in Bilateral Vestibulopathy

Area of Science:

• Neurology
• Ophthalmology
• Vestibular System Science

Background:

• Bilateral vestibulopathy (BV) is a chronic condition characterized by severe impairment or loss of vestibular function in both ears.
• Oscillopsia, the perception of visual instability, is a primary symptom in BV patients.
• Objective quantification of oscillopsia is crucial for assessing disease impact and treatment efficacy.

Purpose of the Study:

• To compare the functional Head Impulse Test (fHIT) with Dynamic Visual Acuity on a treadmill (DVA_treadmill) and the Oscillopsia Severity Questionnaire (OSQ).
• To evaluate the fHIT's ability to objectively measure oscillopsia in patients diagnosed with BV.
• To determine the feasibility and correlation of fHIT with subjective oscillopsia experience.

Main Methods:

• Twenty-three patients with BV were included based on specific vestibular function test criteria and reported symptoms.
• The functional Head Impulse Test (fHIT) involved patients identifying a displayed optotype during passive head impulses.
• Dynamic Visual Acuity on a treadmill (DVA_treadmill) assessed visual acuity decline during walking at various speeds.
• All participants completed the Oscillopsia Severity Questionnaire (OSQ) to report their subjective oscillopsia experience.

Main Results:

• The fHIT demonstrated a moderate correlation with subjective oscillopsia scores from the OSQ (rightward head rotations: r_s = -0.559, p = 0.006).
• No significant correlation was found between OSQ scores and DVA_treadmill, nor between DVA_treadmill and fHIT.
• The fHIT was completed by all patients, while only 52% completed the DVA_treadmill across all tested speeds.

Conclusions:

• The fHIT is a feasible and effective tool for quantifying oscillopsia in patients with bilateral vestibulopathy.
• fHIT correlates with the subjective experience of oscillopsia, unlike DVA_treadmill.
• The fHIT's higher completion rate suggests it is a more practical clinical assessment for BV patients compared to DVA_treadmill.