clar697
Forum Guru
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A 29-year-old man has a 1-week history of feeling dizzy. Warm water instilled into the left ear while the patient is supine elicits nystagmus with a quick phase to the left, warm water instilled into the right ear elicits no eye movement. Which of the following is the most likely site of a lesion?
A) Left frontal eye fields
B) Right frontal eye fields
C) Left pontine gaze center
D) Right pontine gaze center
E) Left vestibular apparatus
F) Right vestibular apparatus
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| drms
Forum Senior
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E not sure
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| dkmj13
Forum Junior
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Rem COWS,
Warm water same side so it is E
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| hitesh
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F) Right vestibular apparatus... No response means the lesion is on the side being tested.
COWS tell you the direction of nystagmus, not the lesion.
(And even if it did, the answer would still be f), since warm water is being used,, lol  )
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| dkmj13
Forum Junior
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If the water is warm (44°C) the eyes turn toward the contralateral ear, with horizontal nystagmus to the ipsilateral ear
Answer is still E, because fast phase is to the left in the left ear.
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| zwmack
Forum Junior
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No its definitely F.
Using warm water stimulates that side so that it mimicks a head movement to the left. If your head moves to the left then your eyes slowly move to the right. When your cortex realizes that the eyes are in the opposite direction you consciously move your eyes back to the center. Therefore the symptom on the left is completely normal. The right side is lesioned because there is no effect.
Now to add a twist to the question, what would happen if the patient had a slow nystagmus to the right following caloric stimulus, but there was no slow component to the left?
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| Belladona
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F...
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| Belladona
Forum Newbie
Topics: 6
Posts: 33
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F...
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| zwmack
Forum Junior
Topics: 7
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No its definitely F.
Using warm water stimulates that side so that it mimicks a head movement to the left. If your head moves to the left then your eyes slowly move to the right. When your cortex realizes that the eyes are in the opposite direction you consciously move your eyes back to the center. Therefore the symptom on the left is completely normal. The right side is lesioned because there is no effect.
Now to add a twist to the question, what would happen if the patient had a slow nystagmus to the right following caloric stimulus, but there was no slow component to the left?
No one answered the twist to the question I posted but here is the answer anyway. It would indicate no cortical function. The brain stem is functioning fine because the first portion of the nystagmus tests the vestibular nerve which is working fine. This person is brain dead because they cannot correct the nystagmus.
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| spinal shock
Forum Senior
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F
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