An anatomical abnormality affecting the lowermost part of brain, where it joins the The main nerve trunk running down the spinal canal and connecting the individual’s mind and consciousness to the rest of his or her body. It is about the size of a person’s little finger, in diameter. It cannot repair itself if damaged., at the top of the neck. Various sub-types are described – see under their individual names. The term An alternative term for a Chiari malformation. It is better than the eponymous term because it is in many ways more descriptive of the anatomical abnormality. is sometimes used to incorporate all forms.