Application of the video head impulse test to detect vertical semicircular canal dysfunction

Area of Science:

• Vestibular system diagnostics
• Ophthalmology
• Neurology

Background:

• The video head impulse test (vHIT) is established for assessing horizontal semicircular canal function.
• Current vHIT applications are limited, primarily focusing on horizontal canal assessment.
• Detecting vertical semicircular canal dysfunction remains a clinical challenge.

Purpose of the Study:

• To evaluate the efficacy of vHIT in detecting vertical semicircular canal dysfunction.
• To determine if vHIT can identify deficits in individual vertical semicircular canals.
• To expand the diagnostic utility of vHIT for vestibular disorders.

Main Methods:

• High-speed video recording (250 Hz) captured eye movements during passive head impulses in vertical canal planes.
• Head movements were precisely measured during unpredictable, abrupt head turns.
• Patients with confirmed vestibular loss (via scleral search coil) were tested to validate vHIT's sensitivity.

Main Results:

• vHIT successfully differentiated between healthy subjects and patients with vestibular loss.
• Patients with unilateral vestibular loss showed reduced responses to impulses stimulating affected anterior, posterior, and horizontal canals.
• A patient with isolated posterior canal loss demonstrated reduced responses specific to that canal.

Conclusions:

• vHIT is effective in detecting peripheral vestibular deficits in both vertical and horizontal semicircular canals.
• This study establishes vHIT as a novel tool for assessing individual semicircular canal function.
• vHIT offers a new diagnostic approach for vestibular patients with specific canal impairments.