HELP! Arnold-Chiari Malformation

Matt Jones jonesmat at ohsu.edu
Fri Jul 14 12:00:35 EST 1995


In article <3u4l02$mgm at ixnews3.ix.netcom.com> Ryan Gudorf,
ryguy at ix.netcom.com writes:
>        My sister just found out she has this Arnold-Chiari

Hi Ryan,

My wife also just found out that she had Arnold-Chiari. Fortunately, my
boss is a neurologist, so we asked him about it and he was really
helpful. Knowing what all the medical jargon means can really put your
mind at ease. So here's basically what I learned:

The cerebellum (the big lobe at the back and base of the brain that plays
a role in coordinating motor activity) has smaller lobes projecting down
beneath it, called Tonsils. These projections are situated close to the
hole in the base of the skull where the spinal chord comes up and meets
the brain (the foramen magnum, i.e. the big hole). In Arnold-Chiari, the
tonsils extend down farther than normal, and can stick out into the
foramemn magnum. Most people have cerebellar tonsils of a certain average
length, that come just to the edge of the foramen magnum. What
Arnold-Chiari means is that the tonsils are longer than normal. That, as
I understand it, is *all* that Arnold-Chiari means. 

Having said that, you shouldn't think that this isn't a problem. It can
be a serious problem, but the extent depends on how much longer than
"normal" the tonsils stick out. In my wife's case, they were 5
millimeters (about half an inch) longer than average, and it turned out
that this probably makes no difference at all (thank God). However, if
they are really long, they may occlude (block) the foramen magnum, or
press against other parts of the spinal chord, cerebellum, or hindbrain.
If they occlude the foramen magnum, that may prevent the normal flow and
drainage of the cerebrospinal fluid between the brain and spinal chord,
causing a build up of fluid in either place (hydrocephaly in the brain,
and I forget what it's called in the spinal chord). This can be treated
by a "shunt", in which a catheter (tube) is inserted between where the
fluid is building up and another compartment  in the head or body where
it can drain out. This may be a temporary solution, I'm not sure. If they
press against other parts of the brain, this can also be treated with
surgery. *This DOES NOT necessarily mean BRAIN SURGERY!* Since the
problem is that there's not enough space in the foramen magnum for all
the stuff that needs to get through it (fluid, tissues, nerves, etc) the
solution is probably to make the foramen magnum bigger. This is really
bone surgery, not brain surgery. Of course, it should be taken seriously,
but it's not exactly the same thing as removing a tumor. 

Your sister should see a neurologist or neurosurgeon, and they will
probably schedule an MRI (a brain scan). This will show the exact extent
of the malformation, and also whether there is any fluid build up or
constriction of other organs. Then, they'll decide what to do about it,
if anything even needs to be done. Make sure you get them to talk you
through the whole thing, and ask a lot of questions. They get paid a lot,
they should work for it by helping you understand what's going on. If
she's not experiencing any neurological symptoms like dizzyness, blurred
vision, balance problems, etc... (anxiety about the malformation doesn't
count!) that's a good sign, as it may mean either that there's really no
problem, or that it hasn't progressed very far yet. 

I hope that this all turns out to be just a curiosity, and she gets some
nifty pictures of her brain to show her son. 

Cheers,
-Matt Jones



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