Tonsils...in the Brain?!?

Sorry I haven't written in a while.  I really haven't had much to say, besides how med school manages to make even the most simple things difficult - if you think tying your shoes is easy, we should talk; I bet they could write a test on it that we would all fail.    It has been a tough semester so far.  We have had two tests every week for a while, now...and neuroanatomy is not getting any easier.  We had a lab today on the cerebellum (part of the brain - for coordination of movements), and it was like starting over from the beginning; we didn't know what anything was (because we've all been studying for our imminent exams).    During our neuro lecture this morning, our professor was talking about different kinds of lesions (damage) in the cerebellum, and what affects they have on the body (loss of coordination in arms and legs...).  She said that the tonsils can herniate through the foramen magnum (the big hole at the base of your skull that your spinal column extends through) and that this is really bad and can kill you.  I kept wondering what in the world she was talking about.  We have learned about three different kinds of tonsils, and I knew she wasn't referring to any of those...but I was at a loss.  It wasn't until later, when I was studying for lab, that I learned the cerebellum has "tonsils" too; now that I know where they are, it makes perfect sense that they can herniate and compress the brainstem.    Jen