(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (SR) Class of 2022, Baylor College of Medicine, Houston, Texas
Summary: • Duane Syndrome -congenital absence of 6th cranial nerve o Types 1. Problems with abduction 2. Problems with adduction 3. Problems with both abduction and adduction 4. Paradoxical adduction with attempted abduction o DDx > Sixth nerve palsy > INO > Esotropia/Exotropia o Features > Eyes are straight in primary position > Lid fissure narrows and widens with abduction and adduction.
Transcript
So we're gonna be talking about the Duane syndrome. And the Duane syndrome has been classified into three different types. And in the first type, we have a problem with A-B-duction so it can look like a sixth nerve palsy. The tip-off usually is in primary position, they look relatively straight because it's an innervational problem. The six nerve which normally innervates the lateral rectus, it's not present and so they cannot A-B-duct. But in primary position they're relatively straight because the medial rectus is not unopposed, it's just not being asked to fire because the lateral rectus is missing. And in the type 2 that is the A-D-duction problem so they cannot A-D-duct and you notice the two Ds and Duane 2 and only one D in Duane 1. And in the type three we have both an A-B-duction and an A-D-duction deficit. There's also a different type which is sometimes called the fourth type which is caused by attempted A-D-duction action leads to paradoxical A-B-duction. So instead of the eye adducting, it abducts and that's because the innervation is split between the third and the sixth, but the predominant innervation is the lateral rectus and so the eye abducts. Sometimes that's referred to as synergistic divergence, but this is a paradoxical abduction in attempted A-D-duction. The reason you need to know about the Duane syndrome is it's congenital. You're born with it. You're missing the sixth nerve nucleus or there's a split in the innervation between the 3rd and the sixth. But it can mimic a sixth nerve palsy or an INO and is on the differential of an esotropia or an exotropia or an ophthalmoplegia. Patients who have the Duane's we really have to look for the distinctive finding which is on attempted A-B-duction, the lid Fisher will change. So there's narrowing and widening of the Fisher when they move from A-B-duction into A-D-duction. There might be a Down shoot as well in A-D-duction. So the lid Fisher widening and narrowing during the attempted A-D-duction is a clue that the patient actually has a congenital mis wiring, the Duane syndrome. So you need to know about the Duane syndrome. It's congenital. There's type 1, type 2, type 3. 1 is the A-B-duction, 2 is A-D-duction, 3 is both. There's this paradoxical A-B-duction phenomenon from attempted A-D-duction because the split in the innervation is mostly to the lateral rectus. The Duane syndrome can mimic six nerve palsy or mimic an A-D-duction deficit like an INO. The lid fissure narrows and widens with A-B-duction and A-D-duction and is a distinctive feature and there may be a down shoot and attempted A-D-duction or A-B-duction depending on type 1 or 2 because of the abnormal innovation the muscle slips and down shoots and upshoots. Usually they're asymptomatic. They often are straight in primary position and you should know it and keep it in the differential diagnosis of esotropia and exotropia.
