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Explanation of correct answer
Reading File
analyse_media
Finding Sources
Searching PubMed
"vestibular neuritis" AND "head impulse"
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vestibular neuritis head impulse test direction corrective saccade affected side
Reading File
Reading File
Finding Sources
Q1: Spontaneous vertigo with hearing loss and eye movement toward the left
Correct answer: c. Right hypoactive labyrinth
“Eye movement on the left side” refers to left-beating nystagmus, meaning that the fast phase is toward the left.
At rest, both vestibular labyrinths fire equally. If the right labyrinth is hypoactive, its reduced vestibular input makes the brain interpret this as rotation toward the left. This produces:
- Slow eye drift to the right
- Corrective fast phase to the left
- Therefore, left-beating nystagmus
So:
Left-beating spontaneous nystagmus = right peripheral vestibular hypofunction.
A right hyperactive labyrinth would instead produce right-beating nystagmus. Hearing loss points more toward labyrinthitis than isolated vestibular neuritis, because labyrinthitis affects cochlear as well as vestibular function.
Q2: Left vestibular neuritis and the head impulse test
Correct answer: b. On rapidly turning the head to the left, there will be a corrective saccade to the right.
In left vestibular neuritis, the left vestibulo-ocular reflex is impaired.
When the examiner rapidly turns the head toward the affected left side:
- The impaired left vestibular system cannot keep the eyes fixed on the target.
- The eyes move along with the head, toward the left.
- The patient then makes a quick corrective, or catch-up, saccade toward the right to re-fixate on the examiner's nose.
Therefore:
| Head movement | Eye initially drifts | Corrective saccade | Finding |
|---|---|---|---|
| Toward the affected left ear | Left | Right | Positive head impulse test |
This is the expected abnormal head impulse test in a left peripheral vestibular lesion. The textbook description confirms that vestibular neuritis impairs the vestibulo-ocular reflex, so the eyes move with the head and then saccade back to fixation. Symptom to Diagnosis: An Evidence-Based Guide, lines 2019-2041. The Merck HINTS guidance likewise describes a corrective saccade when the head is turned toward the affected side.
Memory rule:
- Nystagmus fast phase beats toward the healthy ear.
- Head impulse is abnormal when the head is turned toward the affected ear.
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