Now, the other category of herniations are infratentorial herniations.

那么，现在我们来看幕下脑疝。

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。

Finally, another common infratentorial tumor is an ependymoma.

最后，另一种常见的脑幕下肿瘤是室管膜。

And infratentorial herniations can compress the vital area in the brain stem that controls consciousness, respiration, and heart rate.

幕上脑疝可能压迫脑的供养动脉，造成脑缺血梗死；枕骨大孔疝可能压迫脑干的生命中枢，即控制意识、呼吸和心率的部位。

So let's start with tumor types that are generally infratentorial tumors, because they make up the majority of pediatric brain tumors.

我们从通常属于脑幕下肿瘤的类型开始介绍，因为它们是儿童脑肿瘤的主要类型。

As well as an infratentorial herniation, where the cerebellum is pushed against the brain stem, both of these can be lethal.

也可能形成枕骨大孔疝，即小脑被压迫挤压脑干，这些都可能致命。

Brain tumors can be categorized by their primary site location as either supratentorial, or infratentorial tumors – though some tumors can form in either.

脑肿瘤可以根据它们的原发部位分类为脑幕上或脑幕下肿瘤，某些肿瘤可以同时位于脑幕上和脑幕下。

Supratentorial herniation refers to displacement of the cerebrum which is above the tentorium, and infratentorial herniation refers to herniation of the cerebellum which is below the tentorium.

幕上脑疝指的是小脑幕上大脑的移位，而幕下脑疝指的是小脑幕下小脑的移位。

First off, there's the cerebral cortex which is the part of the brain that's supratentorial or above the tentorium, and the cerebellum, which is infratentorial or below the tentorium.

首先是大脑皮层，在脑幕上方，然后是小脑，在脑幕下方。

Because astrocytes are found through the brain and spinal cord, astrocytomas can form throughout those locations, but juvenile pilocytic astrocytomas are mostly infratentorial tumors in the cerebellum or near the brainstem.

因为星形细胞遍布大脑和脊髓，星形细胞瘤也可以遍布在这些部位，但青少年毛细胞星形细胞瘤大多数是位于小脑内或脑干旁的脑幕下肿瘤。

These cells are found in glands, like the supratentorial pineal gland which is located just behind the third ventricle, or the infratentorial pituitary gland located near the front of the third ventricle.

这些细胞位于腺体中，例如在第三脑室后的脑幕上松果体，或是靠近第三脑室前的脑幕下垂体腺。