| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (ZA) Class of 2023, Baylor College of Medicine, Houston, Texas |
| Transcript |
So today we're going to be talking about lid retraction in neuro-ophthalmology. Obviously, we're not going to be covering the things that cause lid retraction from scarring or from trauma or those mechanical things. The most common cause of lid retraction either unilateral or bilateral in adults is thyroid eye disease and it's not clear exactly what causes the lid retraction in thyroid eye disease. When I'm looking for lid retraction, I'm looking for the lid to normally just cover one to two millimeters of the top of the limbus. And so, if it's at the limbus or above, I consider that to be lid retraction. So when we see lid retraction, we're going to be thinking of thyroid eye disease first so that means doing a Hertel to look for proptosis, to be asking the patient about their thyroid history and to be looking for lid lag which is where the lid lags in downgaze, so it doesn't follow smoothly. The combination of proptosis, lid lag and lid retraction is highly suggestive of thyroid eye disease. We're going to do the thyroid function studies as well as the antibodies TSIG and TPO and you might image the patient either with ultrasound to find the big muscles or CT of the orbit, non contrast, to see the same thing, big muscles. However, there are neurogenic causes of lid retraction. The one we're worried about is called the Collier lid retraction sign. So when we see a patient with lid retraction, we're going to be looking for other features of the dorsal midbrain syndrome. The other features are conversion retraction nystagmus, light near dissociation of the pupils and upgaze paresis, but it can also be downgaze. And if we see that constellation of features, we want to make sure to image the patient, looking at the dorsal midbrain. So for any patient with lid retraction, we must look at their motility, and we must look at their pupil. And the key differentiating feature is going to be light near dissociation because thyroid eye disease doesn't cause pupil abnormalities. It could cause the upgaze paresis, it could cause the lid retraction, but what it can't cause is the pupil involvement. So light near dissociation and conversions retraction nystagmus are going to be the key features that suggest that this lid retraction might be neurogenic. Sometimes, we have lid retraction because we have aberrant regeneration. So normally, the third nerve controls the lid, the levator, and the extraocular muscles except for the lateral rectus and the superior oblique as well as the pupil. So when patients look down, they might get what looks like lid lag, the lid retracts when they look down, but really, the lid is firing when the inferior rectus muscle is firing, and that is aberrancy of the third nerve. So the nerve to the inferior rectus is going to the lid now and so the lid retracts. We can get a Von Graefe sign in thyroid eye disease, but we can get a pseudo Von Graefe sign in aberrant regeneration of the third nerve. We're going to be looking for ophthalmoplegia and the pupil involvement as well and third nerve palsies with aberrancies. Finally, you can get one eyelid retracted and the other eye could be ptosis. So if we have ptosis in one eye, we have retraction in the other eye, that is called the plus minus syndrome. The plus is the retracted eye and the minus is the ptotic eye. And where this plus minus lesion can occur is in the midbrain again. If you're in the midbrain and you've got a third nerve lesion, you could get the dorsal midbrain syndrome which is causing the Collier's lid retraction sign but because the lesion extends ventrally as in involving the third, you'll get a ptotic lid on one side and a retracted lid on the other side. So you have a dorsal midbrain syndrome producing supranuclear inhibition of the levator causing lid retraction plus. But because the other eye has a third, it'll be a ptotic lid, and that is called plus minus syndrome. So the plus minus syndrome is a sign that we should be imaging the brainstem at the level of the dorsal midbrain, but it has ventral extension to involve the third nerve fassicle and is causing a ptosis. In addition, thyroid eye disease which causes lid retraction can be associated with ptosis on the other side and that is from myasthenia gravis. As you know, both thyroid eye disease and myasthenia gravis are autoimmune disorders that can occur. Between five and fifteen percent have both conditions and so the combination of retraction one side and ptosis on the other is a plus minus from thyroid eye disease. So we have a plus minus sign, and it could be the plus minus sign (ptosis and lid retraction) from a plus minus syndrome in the dorsal midbrain, or it could be a plus minus sign from a pseudo plus minus syndrome. It's actually two disorders, the combination of thyroid eye disease causing lid retraction and ptosis in the contralateral eye caused my myasthenia gravis. So neuro-op you should know about lid retraction. Think thyroid, thyroid, thyroid. If it's not thyroid, make sure its not aberrant third or the Collier's lid retraction sign and think about plus minus in patients who have both ptosis and lid retraction. |
