| Identifier |
lateralizing_cranial_nerve_lesions_lee |
| Title |
Lateralizing Cranial Nerve Lesions |
| Creator |
Andrew G. Lee, MD; Shangyi Fu |
| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (SF) Class of 2024, Baylor College of Medicine, Houston, Texas |
| Subject |
Cranial Nerves; Lateralizing Finding |
| Description |
Summary: •Lateralizing findings: o problem on right or left side o Cranial nerves: > mostly ipsilateral > do not cross > palsy side is the same side of the lesion o Important cranial nerves that will be discussed: > Olfactory: ipsilateral-ipsilesional > Cranial nerve: prechiasmal > Cranial nerve 3 and 4 > Cranial nerve 5: ipsilesional > Cranial nerve 6: non-localizing, non-lateralizing • Lesion on other side • Increased intracranial pressure • An exception > Cranial nerve 7 > Cranial nerve 8, 9, 10, 11, 12: ipsilateral-ipsilesional • Exceptions: Cranial nerve 3, 4, 7 o Cranial nerve 3: > Ipsilateral • Third nerve on the right = third nerve palsy on the right • Exception: superior rectus muscle and subnucleus o Crossed o Nuclear third = small subnuclei o Centra caudate nucelus: controls lid > No ptosis or bilateral ptosis in patient with third nuclei palsy > Three inferior rectus muscles: medial rectus muscle, superior rectus muscle, inferior oblique muscle • Ipsilateral, except superior rectus muscle • Superior rectus muscle subnucleus: supplies contralateral superior rectus muscle o Obligatory nuclear third: > third nerve palsy on one side, contralateral superior muscle palsy > bilateral ptosis > no ptosis o Cranial Nerve 4: crossed immediately, exit dorsally in the midbrain at level of inferior colliculus > Contralateral fourth nerve nucleus lesion > Example: RAPD and contralateral fourth localize to same side dorsal midbrain at inferior colliculus level o Cranial nerve 7: depends on whether it's an upper motor neuron or lower motor neuron > Upper part of the face • Bilateral and contralateral innervation • Ipsilesional-ipsilateral only with lower motor neuron 7 > Whole face involved: right seventh = right-sided lesion > Right 7th with spared face = upper motor neuron lesion on contralateral side • Cranial nerve 6: on-localizing, non-lateralizing o Sign of increase intracranial pressure o Sixth on the right, even in pseudotumor cerebri: lesion can be on right, left, neither or both • Summary: cranial nerves lateralized o No crossed = ipsilateral-ipsilesional o Crossed = superior rectus subnucleus, nucleus of four, upper motor neuron of seven. |
| Transcript |
So you're all very familiar, I think, with the concept of a localizing finding, and today we're just going to be talking about lateralizing findings. A lateralizing finding means either the problem is on the right side or the left side and, in cranial nerves, it's usually pretty easy because most of the cranial nerves are only ipsilateral and that's because they don't cross. If you have an ipsilateral pathway and it doesn't cross, then whatever side the palsy is on is the side of the lesion. They're numbered and we can just go through these, so you can see what I'm talking about. Olfactory is ipsilateral-ipsilesional, cranial nerve prechiasmal, cranial nerve 3, we got to talk about as well as 4. Five is ipsilesional and six can be non-localizing, which means the lesion can be actually on the other side, so this is a non-localizing and non-lateralizing finding of increased intracranial pressure six and it's a little bit of an exception. Seven, we're also going to talk about. Eight, nine, ten, eleven, and twelve are all ipsilateral-ipsilesional. The exceptions that we're going to be talking about are three, four, and seven. For cranial nerve 3, it's going to be ipsilateral. If it's the third nerve on the right, it's going to be a third nerve palsy on the right. The only exception is the superior rectus muscle and subnucleus, which is crossed. And what that means is when you have a nuclear third, you actually have all these little subnuclei. The central caudate nucleus controls the lid and that means you either have no ptosis or bilateral ptosis in a patient who has a nuclear third nerve palsy. The other muscles of the three inferior rectus muscle (the medial rectus muscle, the superior rectus muscle, and the inferior oblique muscle) are all ipsilateral except the superior rectus muscle. The superior rectus muscle subnucleus actually supplies the contralateral superior rectus muscle. And we can call something an obligatory nuclear third if we have a third nerve palsy on one side and a contralateral superior rectus muscle palsy, or it has bilateral ptosis or no ptosis and associated with it. So that's a contralateral sub nucleus of the superior rectus muscle. Four is crossed but it crosses immediately and exits dorsally and so, in the midbrain at the level of the inferior colliculus in the midbrain, the fourth nerve exits dorsally and is crossed. That means you can have a contralateral fourth nerve nucleus lesion that produces a fourth on the other side. For example, if you can have an RAPD and a contralateral fourth that is localizing to that side's dorsal midbrain at the level of the inferior colliculus. Seven, as you know from the other video, depends on whether it's an upper motor neuron or a lower motor neuron. Because the upper part of the face actually receives bilateral and contralateral innervation, we can only say it's ipsilesional-ipsilateral when it's a lower motor neuron seven, so the whole face has to be involved for us to say that a right seventh is a right-sided lesion. But if you have a right seventh but you spare the face, then that's actually an upper motor neuron lesion on the contralateral side. Finally, sixth is non-localizing and therefore non-lateralizing because that can be a sign of increased intracranial pressure. When we have a sixth on the right, you cannot tell if the lesion is on the right, the left, either, neither or both. Even in things like pseudotumor cerebri, where there is no lesion, you could have a sixth on the right, the left, or either neither. And so that is non-localizing and non-lateralizing. In summary, all of the cranial nerves lateralized, the ones that don't cross, are all ipsilateral-ipsilesional. All the ones that cross are the superior rectus subnucleus, nucleus of four, and the upper motor neuron of seven. |
| Date |
2021-04 |
| 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/s6g79bb9 |
| Setname |
ehsl_novel_lee |
| ID |
1680608 |
| Reference URL |
https://collections.lib.utah.edu/ark:/87278/s6g79bb9 |
