The brain - higher

The brain can be damaged by accidents or illness. When this happens, its functions can be impaired. For example, a bang on the head can cause concussion and blurred vision.

Brain tumours

A brain tumour happens when cells in the brain grow and divide uncontrollably or when cancer cells from cancer cells from other parts of the body, such as the lung or the breast, spread to the brain. The tumour damages the brain and causes it to press against the skull. This causes symptoms such as headaches, double vision, trembling and personality changes.

Stroke

A stroke happens when a part of the brain does not get enough oxygen and is damaged. This can happen if a blood vessel in the brain bursts or gets a blood clot. Unlike most other cells, brain cells cannot re-grow and permanent damage and even death can be caused.

The symptoms depend on which part of the brain was damaged. They can include:

numbness and poor reflexes
difficulty in walking
loss of speech, memory or use of limbs - usually on one side of the body

Parkinson's disease

Parkinson's disease is caused by a reduced amount of dopamine, a chemical involved in transmitting nerve impulses from one neurone to another in the brain. It gradually gets worse and symptoms include:

trembling and stiffness
slowed movements
difficulty speaking and swallowing

Epilepsy

Epilepsy is caused by sudden bursts of unusual activity in the brain. This makes the brain stop working properly for a short time. It can cause the person to become unconscious and their body shakes repeatedly. This type of seizure is called a tonic-clonic seizure, which used to be called a grand mal seizure.