AngChop
Forum Junior
Topics: 8
Posts: 36
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Can anyone explain the differences b/w Argyll robertson pupil and Marcus Gunn. Lesion of Optic Nerver, lesion of Oculomotor effect on direct and indirect light reflexes?
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| neuroguy
Forum Newbie
Topics: 3
Posts: 29
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Argyll Robertson pupils are pupils that are unreactive to light, but constrict in the near response. Argyll Robertson pupils may be seen in patients with Tabes dorsalis (caused by neurosyphilis) or in patients with diabetes mellitus.
A Marcus Gunn pupil or relative afferent pupillary defect results from a lesion of an optic nerve, and may seen in patients with optic neuritis that commonly results from multiple sclerosis. A relative afferent pupillary defect may be confirmed in patients by the swinging flashlight test. When light is presented to the normal eye, both pupils constrict, but when the flashlight is swung to the affected eye, both pupils paradoxically dilate.
A lesion of an optic tract may result in a slight suppression of the pupillary light reflex; lesions at the level of the lateral geniculate nucleus, or in the visual radiations result in a contralateral homonymous hemianopsia with no change in the pupillary light reflex.
An efferent pupillary defect results from a lesion to the oculomotor nerve. In these patients, the pupil will be dilated on the affected side and will not constrict in response to light presented to either eye or in the near response.
(From USMLE Road Map Neuroscience)
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| JS
Forum Senior
Topics: 16
Posts: 95
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Hi AngChop,
What is teh question in this context ?
JS
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| ssrpk
Forum Fanatic
Topics: 154
Posts: 2,819
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Why does Tabes Dorsalis leads to argyl-robertson pupil....plz explain the pathophysiology.....?
___________________
life is guud
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| AngChop
Forum Junior
Topics: 8
Posts: 36
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Thanks alot neuro guy! I kept getting these questions on Qbank where I had to determine which eye would constrict/dilate in response to various lesions. No particular question.
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| niti
Forum Guru
Topics: 36
Posts: 499
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Thank Ang & neuroguy...
We messed up with this concept during our discussions too... D
Checkout this...
http//www.prep4usmle.com/community/topic16154.html
Hope to cover more NBME & QBANK Qs concepts in subject forum's as well as in support forum's groups...
Happy Studying..
niti
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