Click here to view next page of this article

 

Macrocephaly

Macrocephaly is characterized by excessive head size. Here we have again a big differential of macrocephaly, large head, macrocefaly. It can be metabolic disease, like Sturge, Tay-Sachs, Hurlerís, some of those. Leukodystrophies like Alexander and Canavan are known to create progressively large head. You can see it sometimes in neurocutaneous syndromes, or bone disease. There is a syndrome called Sotos syndrome which is truly macrencephaly. There is no hydrocephalus. The brain looks normal although itís rather large. Kids present with a big head, mildly hypotonic, and mental acuity varies and a lot of them tend to be kind of dull. They are not only cerebrally large, they are just big kids. They are kind of macrosomic. You will notice that when I talked about macrocephaly I didnít really say anything about hydrocephalus, because that will come under CSF circulation and thatís not really big encephalus.

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 Iím going to show you a picture of Dandy-Walker. Another reason kids sometimes present with obstructive hydrocephalus is they have a vein of Galenís aneurysm. Itís often called an aneurysm but thatís a misnomer.

The difference being, an aneurysm is an abnormal swelling due to weakness of the wall of an artery. AVM is really anomalous arteriovenous channels. Itís a high conductance, low resistance channel. 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. Thatís 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.

Rarely you can get communicating hydrocephalus due to excessive production of CSF, such as a choroid plexus papilloma. These tend to occur quite frequently between the second and third ventricles, near the foramen of Monroe.

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 thereís 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. Iíll show you, for instance, how brachycephaly develops. Hereís 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.

Vascular malformations. Vein of Galenís you should know. The important associations you make with vein of Galenís is, first of all I told you it is not an aneurysm. Itís an AVM. You may get this question, not for neurology. You may get it for Neonatology. Itís 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. Usually an adolescent gets into trouble, maybe 17-18-year-old, has the worst headache of their life, with a subarachnoid hemorrhage and severe neurologic morbidity. Then they realize after they do the angiography that they have a berry aneurysm. And these usually occur along the circle of Willis at the base of the head, and there is an association of berry aneurysms with aortic coarctation and polycystic renal disease. You just have to try to remember that type of strange associations.

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.