11.In upward herniation, there's a displacement of the cerebellum upward, through a notch in the tentorium cerebelli, while in tonsillar herniation, parts of the cerebellum slip down through an opening in the skull called the foramen magnum.
小脑幕切迹上疝指的是小脑经过小脑幕切迹被向上挤压;小脑扁桃体下疝指的则是小脑部分组织经过枕骨大孔向下疝出。