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Old 07-09-2014
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Default Doubt in Neuroanatomy

Hi frns...what causes nystagmus in bilateral MLF lesion..in kaplan it is given ..'abducting eye exhibits nystagmus on attempted gaze'...pls help...thank u
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Old 07-09-2014
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Your MLF is responsible for the conjugate gaze pathway. It transmits signals from the parapontine reticular formation to the contralateral medial rectus. If your MLF is destroyed, the abducting eye (abducens nerve) will experience nystagmus since it is trying to "pull" the contralateral eye for a conjugate gaze but cannot do so. It "bounces" back to midline gaze since your contralateral eye is in midline. Hope you got my explanation.
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Old 07-09-2014
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Default thank u baiken17

thanks for ur reply..but im still confused...so for the abducting eye to bounce back to midline,its lateral rectus which is contracting shuld relax..so how exactly does that happen..in the case of vestibulo-ocular reflex,nystagmus( fast component) happens when cortex tries to correct..so does the abducens nucleus has its own mechanism of correcting itself when the other eye doesnt ADDUCT?????
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Old 07-09-2014
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I don't know the exact mechanism of how the lateral rectus relaxes. But if I remember correctly, in my Neurosurg rotation, they explained that the nystagmus is an effect of an "overcompensation" because the abducting eye is trying to "pull" the adducting eye.

In terms of vestibulo-ocular reflex, the cortex does not have any action on the muscle because it is a REFLEX (if you remember, a reflex does not need any cortical input). The circuit of vestibulo-ocular reflex is from the semicircular canal to the vestibular nucleus to the abducens nucleus.
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