Question:hard
In head impulse test, following finding seen in right vestibular neuritis:
In head impulse test, following finding seen in right vestibular neuritis:
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Turning the head toward the diseased side reveals a corrective catch-up saccade in the OPPOSITE direction. Right neuritis: turn right, saccade left.
Updated On: Jun 22, 2026
- On rotating head to right, left saccade
- On rotating head to left, right saccade
- On rotating head toward right, right saccade
- On rotating to the left, left saccade
Show Solution
The Correct Option is A
Solution and Explanation
Think mechanism-first about the reflex being probed. The head impulse test checks the vestibulo-ocular reflex (VOR) of one horizontal canal at a time. Key rule: a quick head turn in a given direction stresses the horizontal canal on the SAME side as the turn. A healthy canal instantly drives the eyes the opposite way so gaze stays locked on the target.
Put the lesion in: in right vestibular neuritis the right vestibular nerve / right horizontal canal is weak.
Now run the test toward the bad side. Turn the head rapidly to the RIGHT $\rightarrow$ you are loading the failing right canal $\rightarrow$ the VOR is too weak $\rightarrow$ the eyes cannot stay on target and get carried along with the head (to the right, off the target).
What does the brain do? It detects the eyes are off-target and fires a quick catch-up (corrective) saccade to drag the eyes BACK onto the target. Since the eyes drifted rightward, the corrective saccade must go LEFTWARD. Seeing this leftward refixation saccade after a rightward thrust is the positive sign and tells you the RIGHT side is diseased.
Filter the options:
- Turning to the right and seeing a left saccade $\rightarrow$ matches (this is option A).
- Turning to the left tests the GOOD left canal $\rightarrow$ normal VOR $\rightarrow$ no saccade (rules out B and D).
- A corrective saccade can never be in the same direction as the head turn; it is always opposite $\rightarrow$ rules out C (right turn, right saccade).
Answer: A.
Put the lesion in: in right vestibular neuritis the right vestibular nerve / right horizontal canal is weak.
Now run the test toward the bad side. Turn the head rapidly to the RIGHT $\rightarrow$ you are loading the failing right canal $\rightarrow$ the VOR is too weak $\rightarrow$ the eyes cannot stay on target and get carried along with the head (to the right, off the target).
What does the brain do? It detects the eyes are off-target and fires a quick catch-up (corrective) saccade to drag the eyes BACK onto the target. Since the eyes drifted rightward, the corrective saccade must go LEFTWARD. Seeing this leftward refixation saccade after a rightward thrust is the positive sign and tells you the RIGHT side is diseased.
Filter the options:
- Turning to the right and seeing a left saccade $\rightarrow$ matches (this is option A).
- Turning to the left tests the GOOD left canal $\rightarrow$ normal VOR $\rightarrow$ no saccade (rules out B and D).
- A corrective saccade can never be in the same direction as the head turn; it is always opposite $\rightarrow$ rules out C (right turn, right saccade).
Answer: A.
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