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Old 05-18-2013
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Correct Answer Caloric reflex in MLF transection

Who can explain the responses obtained by eliciting the caloric reflex in a patient with bilateral transection of the medial longitudinal fasciculi?
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I'm not a 100% but I'll give ot a short.

"When the caloric test is performed in a patient with bilateral MLF lesion, the appropriate nystagmus response (towards opposite side with cold water and same side with warm water) will be observed as expected but only in the eye on the side OPPOSITE to which water has been injected."

I suspect that because the chief function of MLF as I've understood is to excite the occulomotor nucleus of it's own side (fibres in the MLF ascend and activate the occulomotor nucleus) thereby causing adduction of the corresponding eye. Hence, if MLF is lesioned bilaterally, adduction of both eyes as a part of the caloric reflex would be lost, and abduction of the contralateral eye (and subsequent nystagmus) will only be observed.
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Quote:
Originally Posted by DNA 105 View Post
I'm not a 100% but I'll give ot a short.

"When the caloric test is performed in a patient with bilateral MLF lesion, the appropriate nystagmus response (towards opposite side with cold water and same side with warm water) will be observed as expected but only in the eye on the side OPPOSITE to which water has been injected."

I suspect that because the chief function of MLF as I've understood is to excite the occulomotor nucleus of it's own side (fibres in the MLF ascend and activate the occulomotor nucleus) thereby causing adduction of the corresponding eye. Hence, if MLF is lesioned bilaterally, adduction of both eyes as a part of the caloric reflex would be lost, and abduction of the contralateral eye (and subsequent nystagmus) will only be observed.
I stand corrected. By the same logic, appropriate nystagmus would be observed in the opposite eye with warm water and same eye with cold water.

Pretty convoluted issue. You actually read that question somewhere?
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Originally Posted by DNA 105 View Post
I stand corrected. By the same logic, appropriate nystagmus would be observed in the opposite eye with warm water and same eye with cold water.

Pretty convoluted issue. You actually read that question somewhere?
Yup! HY neuroanatomy. The answer is there but I don't really understand the mechanism.
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Did the best I could. Just remember; MLF lesion causes loss of adduction in the corresponding eye during VOR or horizontal gaze.
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Yup! HY neuroanatomy. The answer is there but I don't really understand the mechanism.
Pls post the question lets see the various options and see if we can solve by question
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Old 05-20-2013
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There's a mnenonic for fast phase of nystagmus in caloric test. COWS, cold-opposite, worm-same.
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Old 05-20-2013
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DR najeeb's neuro lecture:
NORMAL SITUATION:

Cold water : 1st eyes move away from ear which wos cooled(put water)
i.e nystagmus occurs(fast comp)away from ear

Warm water:1st eyes moves toward ear where we put warm water i.e nystagmus occur (fast comp) toward side which wos warmed

in short COWS ' Cold opposite nystgmus warm same side'

now 3 comatose patients


1st patient with brainstem intact:

cold water : eye moves toward ear where we put water but it doesn show nystgmus

now
warm water: eyes moves to that ear where u put water but again no nystgmus

its called persistant congugate movement



2nd comatose patient
with NOw M.L.F problem: connection btween 6th and 3rd nerve nucleus is lost
so when one eye abducts (abducting eye) other eye cannot adduct to coordinate '

cold water: one eye abducts but other eye doesnt adduct to that side( cant coordinate)

same for warm water ': one abducts other doesnt sync(adducts)


now 3rd comatose person with Low brain stem bilateral infarct :

Dolls eye ' ---> vestibulo Occular reflax not working
Caloric test : cold or warm water : No reflex no ovemet'






if any mistake plz mention
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