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Brain tumours is the generic name for a group of about 130 different diseases [cite] that are all caused by the uncontrolled growth of cells within the brain, spinal cord, or elsewhere within the central nervous system. Different types of brain tumour can be either benign or malignant. Although benign tumours tend to stay localised at the site at which they initially arise, they can be fatal if left untreated, and can occasionally become malignant. Malignant tumours are capable of spreading to other regions of the brain and central nervous system.

Brain tumours are generally named after the type of brain or nerve cell from which they developed, or the region of the brain in which they are growing (for example, tumours arising in cells called astrocytes are named astrocytomas, wheras tumours arising in the pituitary gland are called pituitary tumours). The most common brain tumours in adults are gliomas, which develop from cells called glial cells; they account for about 70 per cent of new cases in US adults. In children, the most common form is medulloblastoma [ref].

Cancers that arise elsewhere in the body can also spread to the brain. These are called secondary brain tumours, and tend to behave and respond to similar treatments to the original (primary) cancer type from which they arose.

Brain tumours can cause a diverse range of symptoms, all of which are hard to tell apart from other more common conditions. These are divided into symptoms caused by the physical pressure inside the skull - including fits, persistent headaches and seizures - and others caused when a growing tumour the disruption of normal brain functioning - such as memory, personality and coordination problems.

The causes of brain tumours are still poorly understood. The only environmental cause recognised by the International Agency for Research on Cancer (IARC) is ionising radiation (for example, medical x-rays). The risk of developing the disease generally increases with age. However some forms are more common in children. The disease is also more common in people with certain inherited genetic conditions, such as neurofibramatosis.

Approximately 256,000 people worldwide are diagnosed with a malignant brain tumour each year.

Classification
Tumours of the brain and central nervous system are classified by a number of different systems and methods, and according to a number of different attributes.

The World Health Organisation's 'classification of tumours of the central nervous system' classifies tumours according to their location or tissue of origin within the brain or central nervous system (as determined by CT or MRI imaging, see 'Diagnosis'). While essential for proper understanding of brain tumour epidemiology, such classification is not necessarily useful in the treatment and management of the disease.

Thus, an essential step in determining the best treatment for a patient is the analysis of a tumour sample using a microscope (histopathology), to assign a brain tumour's grade. Listed using Roman numerals from I to IV, tumour grade indicates the likely speed of growth and spread, i.e. a tumour's aggressiveness. Grade I tumours are considered the slowest growing, whereas grade IV are the fastest. However, grading is not always possible due to the fact that a tumour's position in the brain may make obtaining a tissue sample impossible. Approximately xx% of tumours are ungraded and listed in statistics as 'tumours of unknown/uncertain behaviour'.

Increasingly, in keeping with the general trend towards genetic and molecular classification of diseases, brain tumours are classified according to the specific molecular defects inside tumour cells. This is leading to a new understanding of the difference between benign and malignant tumours, and on the origins and development of the disease.

Types of brain tumour

 * Main article: List of types of brain tumour [need to create?]

Gliomas
Looking at all age groups, around 45 out of 100 primary brain tumours originate in the glial cells that support nervous tissue, and are called gliomas. There are 3 main types of glioma:
 * Astrocytoma (including glioblastoma multiforme - a grade IV astrocytoma)
 * Oligodendroglioma
 * Ependymoma

Meningiomas
About 25 out of every 100 brain tumours originates in the tissues covering the nervous system (the meninges) and are termed meningiomas.

Pituitary adenomas
Tumours arising in the pituitary gland are termed pituitary adenomas, and account for about 15 per 100 brain tumours.

Nerve sheath tumour
About 8 in 100 brain and CNS tumours are nerve sheath tumours, that arise from the myelin sheath surrounding nerve tissue.

Lymphomas
About 5 in every 100 brain tumours originates in the immune cells that patrol the central nervous system (CNS) and are termed CNS lymphomas.

Other types
Other forms of brain tumour can be extremely rare overall, but more common among children (for example, medulloblastoma, which is rare in adults but accounts for nearly 15 in every hundred children diagnosed with a malignant brain tumour).

Signs & symptoms
The symptoms of brain tumours are often hard to differentiate from other more common ailments, as well as other neurological conditions. Broadly speaking, they are divided into two categories - symptoms caused by the physical presence of a mass within the brain or central nervous system; and those caused by the disruption to normal neurological function by the growing tumour.

Symptoms caused by pressure
These include:

Headaches
About 1 in 3 people with a brain tumour first go to their doctor with headaches. Typically, a headache caused by a brain tumour tends to be quite bad, although can be mild at first. They may last for a long time, starting with a severe headache receding throughout the day.

Fits (seizures)
About 1 in 4 people diagnosed with a brain tumour are diagnosed with fits. These can manifest themselves in many ways, from fits in single limbs, to whole-body fits, and momentary unconsciousness. They can often be controlled with anti-epilepsy medicines.

Nausea
As with headaches, this may be more serious in the morning.

Drowsiness
Drowsiness is often a symptom of a more advanced brain tumour, as progressive growth of the tumour increases tiredness. If untreated, this can lead to unconsciousness.

Visual problems
Problems with sight are also a symptom of raised intracranial pressure caused by a brain tumour. They can include blurred vision, floating shapes, tunnel vision, or a loss of vision that comes and goes.

Symptoms caused by disruption of brain function
These are strongly dependent on the location of the tumour in the nervous system.

Frontal lobe

 * Changes in personality
 * Swearing or loss of inhibitions
 * Apathy
 * Difficulty with planning and organising
 * Irritability or aggressiveness
 * Weakness in part of the face, or on one side of the body
 * Difficulty walking
 * Loss of sense of smell
 * Problems with sight or speech

Temporal lobe

 * Forgetting words
 * Difficulty finding the correct word
 * Short-term memory loss
 * Fits associated with strange feelings, smells or déjà vu
 * Hearing voices

Parietal lobe

 * Difficulty speaking or understanding what is said
 * Problems with reading or writing
 * Loss of feeling in part of the body

Occipital lobe

 * Sight problems or loss of vision on one side

Cerebellum (hindbrain)

 * Poor coordination
 * Uncontrolled movement of the eyes
 * Sickness
 * Neck stiffness
 * Dizziness

Brain stem

 * Poor coordination
 * Drooping eyelid or mouth on one side
 * Difficulty swallowing
 * Difficulty speaking
 * Seeing double

Spinal cord

 * Pain
 * Numbness in part of the body
 * Weakness in the legs or arms
 * Loss of control of the bladder or bowe

Pituitary gland

 * Irregular or infrequent periods
 * Infertility in men and women
 * Lack of energy
 * Weight gain
 * Mood swings
 * High blood pressure
 * Diabetes
 * Enlarged hands and feet

Nerves controlling sight

 * Failing sight

Hearing nerves

 * Failing hearing

Meninges

 * Headache
 * Sickness
 * Sight problems
 * Problems with movement

Development
Depends on region in brain, can develop from many cell types.

Diagnosis
Although there is no specific or singular clinical symptom or sign for any brain tumors, the presence of a combination of symptoms and the lack of corresponding clinical indications of infections or other causes can be an indicator to redirect diagnostic investigation towards the possibility of an intracranial neoplasm

Distribution
According to the GLOBOCAN database, in 2012, for every 100,000 people worldwide, there were 3.4 cases of  primary malignant  brain and CNS tumours. Rates were higher in men (3.9 per 100,000) than in women (3.0 per 100,000). Overall, this represented an estimated 139,608 males and 116,605 females who were diagnosed worldwide with a primary malignant brain tumour in 2012, an overall total of just over 256,000 people.