The brainstem

Although the brainstem is small and hidden away deep inside the brain, it is one of the most important structures in your brain.

It sits beneath the cerebrum and in front of the cerebellum and connects the rest of the brain to the spinal cord, which runs down your neck and back.

The brainstem is in charge of all the functions your body needs to stay alive, like breathing air, digesting food and circulating blood.

Part of the brainstem's job is to operate your involuntary muscles in the stomach or heart, the ones that work automatically without you thinking about it; for example, telling the heart to pump more blood when you are cycling.

It also sorts through all the messages that the brain and the rest of the body sends back and forth.

How will a tumour in the brainstem affect me?

Symptoms of brainstem tumours may include numbness and paralysis; sight, speech and hearing problems; difficulty breathing on your own; drowsiness; and even a coma.

The brainstem in detail

Because the brainstem joins the spinal cord to the rest of the brain, all the nerves going to and from your body pass through it. This means that it is possible for a brain tumour near the brainstem to cause numbness or paralysis in any part of your body or incontinence.

Special nerves (called cranial nerves) originate in the brainstem. They each control specific functions in your head and neck such as:

• vision and eye movements
• muscles of the face, head, and neck including your tongue and muscles in your throat used to swallow
• speech (vocalisation using your mouth and vocal cords)
• taste, hearing, and balance

These come out of your brainstem and travel to whichever part they control. If your brain tumour disrupts them anywhere along their lengths (including in the brainstem itself), it could potentially interfere and cause problems with any of the functions above. Often it will only affect one side of the face or body so you may not have complete loss of any of these functions. Symptoms include facial weakness, double vision, hoarse voice and difficulty swallowing or chewing food.

The brainstem also controls your vital functions. These are the things that your body does to keep you alive without you being aware of them. It includes breathing and making your heart pump blood around your body. It also controls alertness, consciousness, and your sleep-wake cycle. Disruption of these functions can be life threatening or cause coma.