| Identifier |
One_and_half_syndrome_1080p_Lee |
| Title |
One and Half Syndrome |
| Creator |
Andrew G. Lee, MD; Anirudh Mukhopadhy |
| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (AM) Baylor College of Medicine, Houston, Texas |
| Subject |
Pontine Syndromes; Dorsal Pontine Syndrome; Horizontal Gaze Palsy; Intranuclear Ophthalmoplegia; Dorsal Pons Lesion; Exotropia; Eight and a Half Syndrome |
| Description |
Dr. Lee lectures medical students on the subject of one and a half syndrome. |
| Transcript |
Today we're going to be talking about one-and-a-half syndrome. And these syndromes are pontine syndromes. As you know the pons is the final common pathway for horizontal gaze in the brainstem. When you have a pontine lesion, you can have a lesion that dorsal or ventral. These ocular motor problems are the dorsal pontine syndrome. You're very familiar I'm sure with the dorsal midbrain syndromes. The dorsal midbrain syndrome is also known as the Parinaud dorsal midbrain syndrome or the Sylvian aqueduct syndrome and we can see the same types of problems occurring in the pons, except in the pons as opposed to the third nerve nuclei this is the sixth nerve nucleus which is the final common pathway for horizontal gaze. It receives information from the parapontine reticular formation so these two are gonna be very difficult to separate out because they are so close together; however, you should know that they do exist as separate entities, it is just very, very rare. So, the sixth nerve nucleus provides the fascicle for the sixth nerve which then becomes the peripheral sixth nerve which of course goes to the lateral rectus muscle. And the sixth nerve provides contralateral innervation across the medial longitudinal fasciculus rising up to the third nerve nucleus. And so, the connection between the sixth and the third nerve nucleus is what we call an inter-nuclear fascicle. That inter nuclear fascicle is called the medial longitudinal fasciculus: the two nuclei, six and three. And so, you can get a lesion just in the sixth nerve nucleus, that produces a horizontal gaze palsy, and that equals the "one:" you have one horizontal gaze palsy. So, in this example if this is the left six nerve nucleus, you are not only dinging out the left six nerve innervation, you are also digging out the contralateral medial rectus, and that means you're not going to be able to look to the left because you have a left horizontal gaze palsy. That is the "one" in the one-and-a-half; however, if you also damage the other MLF because it crosses right away, you'll get half of the gaze palsy. And so you get left gaze palsy plus a half of the gaze palsy. And a half of the gaze palsy is an intranuclear ophthalmoplegia. And so, the patient will be unable to look to the left but when they look to the right the only thing they'll have is the abduction of the right eye the left eye won't be able to adduct because you have an intranuclear ophthalmoplegia from the medial longitudinal fasciculus. And so, what that means is a single lesion in the left dorsal pons can knockout not only the horizontal gaze, the "one," but also the crossing medial longitudinal fasciculus and that's going to make a "one and a half." And because the eye can still abduct on the right that's gonna cause an exotropia. And the combination of the one and a half syndrome and the exotropia we call that paralytic pontine exotropia. In addition, because we can still tell the third nerve nucleus to fire from the rostral thalamo-mesan-cephalic near convergence center we can converge. So, if someone has a one and a half syndrome they can't look to the left and they get a INO when they look to the right we can still make that person converge. And if the medial rectus can fire that tells us the lesion is in the pons and not more rostrally in the midbrain. So, you need to know a little bit about the dorsal pontine syndrome, the one and a half, because the pons also is near the seventh nerve and the seventh nerve's fascicle wraps are right around the sixth nerve nucleus, that "seven" plus "one and a half" is called an "eight and a half" |
| Date |
2021-06 |
| Language |
eng |
| Format |
video/mp4 |
| Type |
Image/MovingImage |
| Collection |
Neuro-Ophthalmology Virtual Education Library: Andrew G. Lee Collection: https://novel.utah.edu/Lee/ |
| Publisher |
North American Neuro-Ophthalmology Society |
| Holding Institution |
Spencer S. Eccles Health Sciences Library, University of Utah |
| Rights Management |
Copyright 2019. For further information regarding the rights to this collection, please visit: https://NOVEL.utah.edu/about/copyright |
| ARK |
ark:/87278/s6tf5x2d |
| Setname |
ehsl_novel_lee |
| ID |
1701577 |
| Reference URL |
https://collections.lib.utah.edu/ark:/87278/s6tf5x2d |
