CVT Gaze Stabilization & Oculomotor Assessment 1 — Questions and Answers
Question 1: Which reflex is primarily responsible for maintaining stable gaze during head movement?
- Optokinetic reflex
- Vestibulo-ocular reflex (VOR) (Correct answer)
- Cervico-ocular reflex
- Smooth pursuit reflex
Correct answer: Vestibulo-ocular reflex (VOR)
The vestibulo-ocular reflex (VOR) generates compensatory eye movements in the opposite direction of head movement to maintain stable gaze on a target.
Question 2: VOR gain is defined as:
- The ratio of eye velocity to head velocity (Correct answer)
- The ratio of head velocity to eye velocity
- The frequency of eye movements during head rotation
- The latency of eye movement response to head movement
Correct answer: The ratio of eye velocity to head velocity
VOR gain is calculated as eye velocity divided by head velocity; a normal gain is approximately 1.0, meaning eye velocity closely matches head velocity.
Question 3: Which of the following best describes the function of gaze stabilization exercises (GSE)?
- To improve smooth pursuit eye movements at rest
- To enhance VOR adaptation through repeated head movements with visual targets (Correct answer)
- To train saccadic eye movements between stationary targets
- To reduce sensitivity to optokinetic stimulation
Correct answer: To enhance VOR adaptation through repeated head movements with visual targets
Gaze stabilization exercises promote VOR adaptation by repeatedly exposing the patient to head movements while maintaining focus on a visual target, creating a retinal slip signal that drives recalibration.
Question 4: During the head impulse test (HIT), a corrective saccade following the head thrust indicates:
- Normal VOR function on the tested side
- Central vestibular pathology only
- Impaired semicircular canal function on the tested side (Correct answer)
- Intact otolith organ function
Correct answer: Impaired semicircular canal function on the tested side
A corrective saccade (catch-up saccade) after a head thrust indicates the VOR failed to maintain gaze, suggesting hypofunction of the semicircular canal on the tested side.
Question 5: The horizontal VOR arc is mediated primarily through which cranial nerve pathway?
- CN V to CN VI
- CN VI to CN IV directly
- CN VIII connecting to CN VI and CN III via the MLF (Correct answer)
- CN IV to CN III via the cerebellum
Correct answer: CN VIII connecting to CN VI and CN III via the MLF
The horizontal VOR is mediated via CN VIII (vestibulocochlear), which projects to the abducens nucleus (CN VI) and oculomotor nucleus (CN III) through the medial longitudinal fasciculus.
Question 6: The video head impulse test (vHIT) primarily assesses which aspect of vestibular function?
- Otolith organ function at low frequencies
- High-frequency semicircular canal function (Correct answer)
- Central vestibular processing in the brainstem
- Visual-vestibular interaction during slow movement
Correct answer: High-frequency semicircular canal function
The vHIT uses high-velocity, small-amplitude head impulses to assess high-frequency semicircular canal function, the range most affected by peripheral vestibular hypofunction.
Question 7: Which condition is most associated with reduced VOR gain and overt corrective saccades on vHIT testing?
- Benign paroxysmal positional vertigo (BPPV)
- Unilateral vestibular neuritis (Correct answer)
- Mal de débarquement syndrome
- Superior semicircular canal dehiscence
Correct answer: Unilateral vestibular neuritis
Vestibular neuritis causes unilateral peripheral vestibular hypofunction, resulting in reduced VOR gain and corrective saccades on the affected side during vHIT.
CVT Gaze Stabilization & Oculomotor Assessment 1
Which reflex is primarily responsible for maintaining stable gaze during head movement?