(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (PW) Class of 2021, Baylor College of Medicine, Houston, Texas
Subject
Pathology, Signs and Symptoms
Description
Dr. Lee lectures medical students on plus minus syndrome.
Transcript
Today a very unusual constellation of findings called the plus minus syndrome. So, normally when we have our eyelids, the eyelid covers the superior limbus by about 1 to 2 millimeters; however, in patients who have the plus syndrome they have lid retraction and inpatients who have the minus syndrome they have ptosis. So it is the combination of lid retraction on one side that characterizes the plus and ptosis on the fellow side which constitutes the minus. The most common cause of lid retraction in adults is not the plus minus syndrome, it's a pseudo plus minus syndrome from thyroid ophthalmopathy and the ptosis is usually from concomitant myasthenia or some other cause. So when we see a combination of lid retraction and ptosis you should be thinking about thyroid and myasthenia or levator dehiscence and thyroid. But there is this neurologic version of plus minus which is from the midbrain. So as you know from previous videos in the patients dorsal midbrain you have the ocular motor structures. And here's just a representative example of the midbrain. There are descending pathways that are supplying innervation to the third nerve nucleus and the third nerve is in charge of the levator which is in charge of the lid. So normally when you have a nuclear third because the third nerve nucleus has only a single central caudate nucleus, you either get bilateral ptosis or no ptosis. However, once the third nerve leaves the nucleus you can have ipsilateral and unilateral ptosis. If we have a fascicular third on one side, the fascicle of CN3 is out and it might cause ptosis on the ipsilateral side. But because there is supranuclear input to the levator from supranuclear input at the thalamomesencephalic junctions to the third. You can get lid retraction in the dorsal midbrain syndrome. The lid retraction in the dorsal midbrain syndrome is called the Collier lid retraction sign. So in the regular dorsal midbrain syndrome we might get lid retraction as part of the parinauds dorsal midbrain syndrome but if you have the dorsal midbrain syndrome and the colliers lid retraction on one side but a fascicular third ptosis on the other side, that we call the plus minus syndrome, a combination of neurogenic disinhibition of the levator causing retraction and neurogenic fascicular third ptosis. This means the lesion is at the level of the dorsal midbrain. The plus minus syndrome.
