There are two types: upward herniation and tonsillar herniation.

其中包括两种类型：小脑幕切迹上疝、小脑扁桃体疝。

The most common signs of the tonsillar herniation are headache and neck stiffness.

扁桃体疝最常见的症状是头痛与颈项强直。

On the other hand, infratentorial herniations are subdivided into upward herniation and tonsillar herniation.

另一方面，幕下脑疝也可分为：小脑幕切迹上疝与小脑扁桃体疝。

In tonsillar herniation, parts of the cerebellum, called cerebellar tonsils, slip down through an opening in the skull called the foramen magnum.

在扁桃体疝中，小脑的一部分，即小脑扁桃体，经过枕骨大孔被挤压推出颅骨。

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。