by John J. Oró, MD
In papers published in 1891 and 1894, pathologist Dr. Hans von Chiari described a series of hindbrain malformations now known as the Chiari malformations. The traditional definitions went unchallenged for over 100 years. However, the marked advances in medicine over the past couple of decades have led to a new understanding of these malformations and proposed new definitions. We will review the pertinent neuroanatomy, pathology, clinical presentation, diagnosis, treatment, and outcome of patients with CMI with or without syringomyelia. Emphasis will be placed on new research findings, new concepts, and the current naming controversy.
Transcribed Presentation Notes
Well thank you, it’s always a great pleasure to be here annually at this meeting. We’re going to talk about the Chiari Malformation and syringomyelia. To get started we have to have a sense of the normal anatomy. Let’s start with the ventricular system here[see Figure 1].
Within the core of the brain there are fluid spaces called the ventricles and it is in these ventricles that spinal fluid is created and it has to flow a certain direction. These large two ventricles up here connect to this small little canal, into a third ventricle, down the Aqueduct of Sylvius, into the forth ventricle and then they drain out through three openings into the spaces on the outside of the brain and around the spinal canal. Here we have a cross sectional image [see Figure 2] showing the inside of the ventricles. This is the choroid plexus- it’s a tuft of vascular tissue.
With each pulsation an ultra filtrate is created of spinal fluid that again has to flow down these pathways into the forth ventricle and comes out- in particular in this foramen (opening) of Magendie, and two on the side; and here we have a cistern. This fluid filled space, is the cisterna magna, which we’ll talk some more about. It flows around the spinal canal on up and it has to find it’s way for the most part up into this area where it – through these little granulations as they’re called – gets backed into the venous system, and this happens with every heart beat, about 100,000 times a day.
The area that we’re going to talk about today, which is this posterior fossa, this compartment down low here where we see the brain stem turning into the spinal cord and we see the cerebellum in this area. The posterior fossa: there is a lot of activity in the area. The cranial nerves, the nerves that run the eye movements, the facial movements, the tongue movements, et cetera, come out of the brain through the brain stem in this area here. Regulatory mechanisms for the heart and the lungs are in this area, and of course, the cerebellum, and all the highways coming up and down the spinal cord are traveling through this area. So it’s a very busy area. From our point of view, as far as the Chiari malformation is concerned, this is some anatomy [see Figure 3] that we want to kind of put into our brains, if you will, to help understand things. This is a side view of the posterior fossa and what you’re seeing here is some bone at the base of the skull and in the back of your skull, ending at this point, called the basion. This point is called the episthion, and that’s not that important, but the bottom line is the opening at the base of the skull. A line drawn from here to here (and it happens to be called the foramen, which we know is anopening) the foramen magnum (and magnum means large) the large foramen at the base of the skull. Normally what you’re supposed to have in this area is a cistern, a fluid pocket, if you will, and it’s large and when the ancients found this they gave it the term magna, again for large, so it’s the cisterna magna.