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Mobius syndrome

Mobius syndrome is basically a maldevelopment of cranial nerve nuclei. The most commonly affected one is facial nerve Mobius syndrome. And you may remember, what the major function of the facial nerve is, it’s muscles of facial expression. So those of you who are in Los Angeles know that there was a big story not too long ago about a child that could not smile. And they had this doctor flown from Canada to come to Kaiser in Woodland Hills to do a muscle transfer and nerve transfer.

These children can present with ptosis, ophthalmoplegia, difficulty with chewing, all the cranial nerve problems and yet they are cognitively intact. The problem is limited to the cranial nerve nuclei.

Obstructive hydrocephalus can be due to a congenital problem, like aqueductal stenosis. We are referring to the aqueduct of Sylvius that connects the third ventricle to the fourth. It can also be acquired due to midline brain tumors that compress the aqueduct. It may be a congenital anomaly, such as Dandy-Walker syndrome which has atresia of the foramina of Magendie and Luschka with compensatory dilatation of the fourth ventricle and cerebellar hypoplasia. Later when we talk about ataxia I’m going to show you a picture of Dandy-Walker. Another reason kids sometimes present with obstructive hydrocephalus is they have a vein of Galen’s aneurysm. It’s often called an aneurysm but that’s a misnomer.

There are inferior fossa hematoma, like after trauma you could develop obstructive hydrocephalus. The key features of obstructive hydrocephalus, you will notice, that we are focusing on obstruction in the vicinity either due to a mass lesion or due to a congenital lesion, in such a manner that the flow from third to fourth ventricle is affected. That’s the key. What we call communicating hydrocephalus, where there still may be a problem with obstruction but it is not proximal to the fourth ventricle. This could happen partly because you have a problem with arachnoid granulations on the convexities. This could happen because the child had meningitis as a neonate and there was a lot of pus. Because the meninges got fibrosed and the absorptive surfaces are damaged. It could be post CMV or toxo, maybe a sequelae of large subarachnoid hemorrhages again.

Cranial synostosis. So here we first want to show you what the major sutures are. As you can see, here is the metopic suture, there is the coronal one going across, sagittal and the lambdoid, and there’s the anterior fontanelle. So growth occurs at right angles to any suture. So any time you have synostosis where the suture fuses prematurely, you cannot grow orthogonal to it. You will grow tangential. I’ll show you, for instance, how brachycephaly develops. Here’s someone where there is coronal synostosis. See, the yellow line is thick. So the arrows show the growth that is orthogonal to this line, that is 90 degrees perpendicular, is limited and compensatory growth occurs tangential to the suture. What happens then is the shape of the head assumes that.

Vascular malformations. Vein of Galen’s you should know. The important associations you make with vein of Galen’s is, first of all I told you it is not an aneurysm. It’s an AVM. You may get this question, not for neurology. You may get it for Neonatology. It’s very very big in the differential for high output heart failure in the newborn. Auscultation of a cephalic bruit accompanies that. A lot of times that how people know somebody has this. You should know a word or two about berry aneurysms.

Tuberous sclerosis occurs in about 1:30,000 births, dominant inheritance but many are spontaneous mutations. So if you see a baby with TS you should examine the skin of the patients family and inquire about seizure history in parents. It is certainly a dominant one but a large number of spontaneous mutations. There are two chromosomes that have been identified. One is tuberous sclerosis complex number 1 on chromosome 9 with the first linkage TSE-2, tuberous sclerosis complex 2.

So the cerebral lesions are what I am going to talk about first. They are cortical tubers, or hamartomas and this is where epilepsy comes from. Epilepsy comes from the cortex, and it’s the tubers that cause that problem. There are subependymal glial nodules that I don’t think are that big a problem, except maybe they will appear on the Board with the radiologic questions. Because they make a big issue about these things sticking into the ventricle, giving it a verrucous irregular appearance. You all remember what I am talking about? Okay, so radiologic identification of those and then they can have giant cell astrocytomas.

There are dermatologic lesions that assist in diagnosis for you clinically. A very prominent one is adenoma sebaceum, which are angiokeratomas. They can have hypopigmented macules, ash-leaf spots, shagreen patches. We saw this picture earlier, with the ash-leaf spot and several hypopigmented macules and there’s the shagreen patch. These can occur quite early in life. Later in life you may see angiofibromas or the adenoma sebaceum develop. Often you need to refer your patients to plastic surgery or dermatology for management of those. They can sometimes bleed and get messy. Periungual fibromas; all TS patients.