(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (AG) Baylor College of Medicine, Houston, Texas
Subject
VI/XII; Clivus; Gottfredson; Tongue
Description
Dr. Lee lectures medical students on the subject of VI/VII syndrome.
Transcript
All right today we're going to talk about a specific syndrome which is a combination of a cranial nerve 6, which causes a turning in of the eye - esotropia - and an abduction deficit with an incompetent esotropia and a 12 which causes the tongue to deviate. So as you know the tongue muscles protrude the tongue because it's balanced. So if you have a weakness of one 12th nerve the good 12th nerve function muscle will push the tongue towards the weak side. So it's like pushing a wheelbarrow: if you lose your arm on one side the wheelbarrow will go towards where your arm dropped. So the combination of a 6/12 has really only one localization from a single lesion that's right here - hypoglossal canal is at the base of the clivus which is like a slope that's what that word means clivus so you can imagine skiing down from the dorsum sellæ all the way down to the hypoglossal canal and the 6th nerve arises from the pons and exits the root exit zone and rises up the clivus. So the combination of a 6/12 skipping the in-between number seven eight nine ten eleven means you have a midline lesion at the level of the clivus. Most common lesions in that location are chordoma, chondro sarcoma, metastasis, meningioma, rarely plasma cytoma. Clival lesions-very short list for what it could be radiographically and clinically and 6/12 is the way it comes to us.So the combination of a cranial nerve 6 and a cranial nerve 12.That's tongue deviation and diplopia that localizes to clivus. Common things are common: chondroma, chondrosarcoma, meningioma - rare things in that location. And you should know that sometimes it resolves spontaneously. So even if you have a 6th nerve palsy that resolves that sometimes is still a clival chordoma because the lesion causes disruption of the blood supply and it's got cystic degeneration and other features that could make the 6 come and then remyelinate and go away. You need to think about 12 in that setting by asking the patient to protrude their tongue and if we see the tongue come out and it goes - it'll go towards the weak side. They'll also be atrophied on that side and we can see that atrophy on an MRI scan as denervation atrophy. So in the 6/12 syndromes we're going to be looking for denervation atrophy in the lateral rectus - the muscle will be smaller-and the tongue. Half the tongue muscle will be small and will be infiltrated by fat and we can see that on the MRI scan. And that finding is called denervation atrophy so in a 6/12 syndrome we're gonna be looking for denervation atrophy in the tongue even though the lesion is in the clivus. This goes by a name in the literature: Gottfredson's syndrome. Even though what Gottfredson described was not at all what this is and so I just prefer 6/12.
