| Identifier |
vestibulo_ocular_reflex_lee_novel |
| Title |
Vestibulo-Ocular Reflex |
| Creator |
Andrew G. Lee, MD; Nadia Ansari |
| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (NA) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Subject |
VOR; Cranial Nerve Eight; Doll's Head Maneuver |
| Description |
Summary: • The vestibulo-ocular reflex (VOR) is a component of the vestibular system involving CN VIII o Input from the semicircular canals during head movement communicates with the ocular motor nuclei in the brain stem to maintain ocular alignment on a target o Head rotation -> semicircular canals -> CN VIII -> ocular motor nuclei in the pons (CN VI) and midbrain (CN III and IV) -> eye movement • The VOR can be utilized in a test called the Doll's head maneuver to differentiate between supranuclear and infranuclear palsies o When a patient cannot look in a certain direction (either horizontally or vertically), you can rotate the head passively to initiate the VOR o If the palsy is overcome, that confirms that everything below the nucleus is intact in order to the move the eye suggesting a supranuclear palsy > This includes the nucleus, the nerve, the neuromuscular junction, and the muscles • The Doll's head maneuver is especially important in patients with an ophthalmoplegia in which the exact location of the lesion cannot be discerned o The most prominent is a down gaze palsy and progressive supranuclear palsy [Note: In PSP not only downward but upward gaze is effected] |
| Transcript |
Today we'll be talking about your vestibulo-ocular (VOR) reflex and how we use that testing to differentiate supranuclear from infranuclear palsies. So, the vestibular system is part of the vestibular-cochlear system (the VIII nerve) - but this is the balance part of the vestibular-cochlear system, and it has to talk to the ocular motor nuclei in your brain stem. And that's completely reflexive -you don't need any conscious effort to do that. The reason you need it is because every time you tilt your head, you have to have counter rolling to maintain the vertical alignment of the world. So, when you tilt your head or if you're riding on a motorcycle, you have to have counter rolling and that counter rolling is produced by input from the vestibular system in your ear. So, that counter roller is what we call the VOR - a reflex in response to head rotation to the keep the eyes aligned on the target. You don't have to think about it; it just happens by itself. So, we can take advantage of the vestibular system talking directly to the ocular motor nuclei. And so, for the pons - that's the sixth - and for the midbrain - that's the third and the fourth nuclei. And so, the eighth nerve talks to the brainstem both to mediate horizontal movements and also vertical movements in response to head rotation and the effects on these semicircular canals. And so, the vestibular system talks to the ocular system in the brainstem and that is a reflex. And the way we can use this is called the doll's head maneuver. So, when someone can't look to one direction, either horizontally or vertically, we can rotate their head passively and that will initiate the vestibular ocular reflex. And if we can overcome the movement with the dolls head maneuver, then we know that everything below the nucleus is intact. So, if the person can't look to the right and we can make them look to the right with the dolls head maneuver, then we know that the nucleus, the nerve, the neuromuscular junction, and the muscle are all able to move the eyes, but the supranuclear control telling the patient to look to the right has been destructed. If we can do the doll's head on the patient by rotating their head passively, and if their eyes move, that tells us that the problem is supranuclear. And that's really important in patients who have ophthalmoplegia where we can't tell where the lesion is. The most prominent is a down gaze palsy and progressive supranuclear palsy, where we we'd like to establish that the reason this person can't look down is a supranuclear problem. But also, in problems that are arising from the cortex, frontal lobes, parietal occipital temporal region or it's a saccade problem or a pursuit problem, and its clearly cortical and everything from the brainstem down is intact. So, you need to know a little bit about this reflex, the VOR, and how we use it with the dolls head maneuver to overcome ophthalmoplegia and define that the problem is supranuclear and not infranuclear. |
| 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/s6034p3p |
| Setname |
ehsl_novel_lee |
| ID |
1680635 |
| Reference URL |
https://collections.lib.utah.edu/ark:/87278/s6034p3p |
