Internuclear Ophthalmoplegia

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Identifier Internuclear_Ophthalmoplegia_INO
Title Internuclear Ophthalmoplegia
Subject Ophthalmoplegia, Nystagmus, Cranial Nerves, CN3, CN6
Creator Andrew G. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX; Professor of Ophthalmology, Weill Cornell Medicine; Meesha Khatker, Baylor College of Medicine Class of 2020
Description Dr. Lee lectures medical students on internuclear ophthalmoplegia.
Transcript Today we're going to be talking about internuclear ophthalmoplegia. This means "plegia" (weakness) of "ophtho" (the eye), and "nuclear." And the two nuclei that we're talking about are the 6th nerve - which you've heard about before if you watched the horizonal gaze palsy video. The 6th nerve nucleus talks to the contralateral 3rd nerve nucleus (the medial rectus muscle in this case) via a fascicle which is longitudinal and medial…….which we call the medial longitudinal fasciculus (MLF). The 6th nerve nucleus lives in the pons. It must talk to the contralateral 3rd nerve nucleus which lives in the midbrain. So the midbrain has 3, and the pons has 6. This connecting point between the 6th and the 3rd nerve nuclei is called the medial longitudinal fasciculus. And so if you disrupt the MLF you will be disconnecting the horizonal gaze input to the contralateral medial rectus muscle. And so what that looks like clinically is, if these are your eyes…if you attempt to look this direction (to the left), if you have an MLF lesion on the right in the longitudinal fasciculus, you won't be able to adduct very well. The adduction will be decreased on the side of the MLF lesion and that is gonna cause the abducting eye (the left eye) to get nystagumus. So there will be a dissociated, horizontal, abducting nystagmus on attempted gaze to the left in a patient who has a right medial longitudinal fasciculus lesion from a right internuclear ophthalmoplegia. So clinically, a right INO has an adduction deficit - it can be partial or complete - associated with a dissociated horizontal abducting eye nystagmus on contralateral gaze. This constellation of findings, we call, the internuclear ophthalmoplegia. Because the lesion could be in the medial longitudinal fasciculus, anywhere from the pons all the way to the midbrain, one of the ways that we can try and differentiated whether the lesion is midbrain (a rostral lesion) or pontine (a caudal lesion) is by making this medial rectus muscle fire using different stimuli. We can stimulate the 3rd nerve nucleus, and in this case the medial rectus muscle, to converge by having the convergence center, the near center, talk directly to the 3rd nerve. That convergence center lives somewhere in the thalamo-mesencephalic junction (so it is way rostral). So if someone has an INO and they cannot aDduct the right eye but they can converge, that means we can make the 3rd nerve fire, and that means that if they can converge, that the lesion is probably in the pons. And that is "caudal." If however, they can't converge, then maybe the lesion is more rostral, at the thalamo-mesencephanic junction. And so we can differentiate in an INO whether we are rostral or caudal, involvement of the MLF, by testing the near reaction. If the convergence is intact, pick pons.
Publisher Spencer S. Eccles Health Sciences Library, University of Utah
Date 2019-03
Type Image/MovingImage
Format video/mp4
Rights Management Copyright 2019. For further information regarding the rights to this collection, please visit:
Holding Institution Spencer S. Eccles Health Sciences Library, University of Utah, 10 N 1900 E, SLC, UT 84112-5890
Collection Neuro-ophthalmology Virtual Education Library: NOVEL
Language eng
ARK ark:/87278/s6101g91
Setname ehsl_novel_lee
Date Created 2019-03-05
Date Modified 2020-01-13
ID 1403720
Reference URL
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