Information on Brain Cancer:
Types of brain tumour
Brain tumours are categorised by the type of brain cell they developed from and their position within the brain. The symptoms of a particular type of tumour can vary greatly, depending upon which part of the brain it is growing in – as different parts of the brain have different functions.
The main types of malignant and benign brain tumours are discussed below:
Tumours that develop from the supporting cells of the brain (glial cells) are known as gliomas. These are the most common type of brain tumour and account for more than 50% of all primary brain tumours.
Upon diagnosis, gliomas are given a grade (1 to 4) that describes their level of activity and level of abnormality. Low grade tumours (grades 1 and 2 – or I & II) are the least aggressive and may only grow slowly, whereas high grade tumours (grades 3 and 4 – or III & IV) are more aggressive and grow more quickly. Your doctor will adjust your treatment to suit your grade of glioma.
Types of glioma are listed below:
- Astrocytoma – Developing from cells called astrocytes, astrocytoma is the most common type of glioma. Anaplastic astrocytomas (grade 3 gliomas) and glioblastoma multiforme (grade 4 gliomas) are the most commonly occurring brain tumours in adults.
- Oligodendroglioma – This type of tumour develops from the cells that produce the fatty covering of nerve cells (the myelin sheath). These tumours grow more slowly than astrocytomas.
- Ependymoma – On rare occasions, the cells which line the blood vessels of the brain and the central canal of the spinal cord (called ependymal cells) can form tumours known as ependymomas.
- Mixed glioma – If a tumour is made up of cells from two or more types of glioma they are referred to as a mixed glioma. The most common type of mixed glioma is oligo-astrocytoma.
Acoustic neuroma (schwannoma, neurilemmoma)
Acoustic neuromas develop from schwann cells in the auditory nerve (that transmits the signals necessary for hearing). Acoustic neuromas are benign tumours and are usually found only in adults. The genetic disease neurofibromatosis type II has been linked to this type of tumour.
Central nervous system (CNS) lymphoma
CNS lymphomas are cancers of the lymphatic system that can affect the brain. This type of brain tumour is quite rare.
Haemangioblastomas are a rare type of tumour that develops from the cells of the blood vessels in the brain. Often taking several years before they cause physical symptoms, these tumours are almost always benign.
Medulloblastoma (or PNET, primitive neuroectodermal tumour)
Medulloblastomas represent more than 25% of all childhood brain tumours. They develop at the back of the brain, in the cerebellum, but can spread to other areas within the brain. Medulloblastomas are much less common in adults.
Most meningiomas are benign, very slow growing and do not tend to spread to other parts of the brain. This type of tumour arises from the meninges, the protective membranes that surround the brain. Meningiomas can develop in virtually any part of the brain or spinal cord. Malignant meningiomas are very rare but meningiomas in general can account for about 15% of all brain tumours and about 25% of all primary spinal cord tumours.
Pineal region tumours
Pineal tumours only account for about 1% of brain tumours, but account for between 3% and 8% of the intracranial tumours that occur in children. The pineal gland is a part of the brain that is situated below the central division of the two cerebral hemispheres. Types of pineal tumours include germinomas, pineoblastomas, pineocytomas and teratomas – the most common being germinomas.
Pituitary adenomas account for about 10% of brain tumours. Adenomas are benign tumours in the pituitary gland that can result in disturbances of vision or hormone levels. The pituitary gland normally secretes hormones that control the other hormone-producing glands of the body, but when a tumour is present, this process can be disrupted.
Spinal tumours often present themselves as muscle weakness and pain in the back, neck and limbs. This can even escalate to loss of bladder or bowel control. This happens because the growing tumour presses on the spinal nerves, affecting their function.
Secondary brain tumours
Cancers that have developed in other parts of the body may spread via the bloodstream or lymphatic system to the brain. When this happens, these additional growths are called secondary brain tumours or metastases.
The causes of malignant brain tumours
Scientists are currently not sure what causes malignant brain tumours, but research is being carried out to help determine the causes.
The symptoms of brain tumours
Brain tumours can lead to a whole range of different symptoms, depending upon which area of the brain is affected. A list of general symptoms has been provided for your information:
- Headaches and nausea – These are usually caused by raised pressure within the brain as the tumour grows. This is likely to be worse when you cough, sneeze, bend down or do anything strenuous.
- The onset of epilepsy – which can cause fits, muscle spasms or periods of unconsciousness.
- Unsteadiness or an uncoordinated walk.
- Difficulty in organising certain movements.
- Numbness or weakness in one side of the body.
- Neck stiffness.
- Facial weakness, such as a one-sided smile or a drooping eyelid.
- Flickering involuntary movements of the eyes.
- Double vision or a loss of vision on one side.
- Loss of sense of smell.
- Difficulty in speaking or swallowing.
- Difficulty in expressing or understanding words, and problems with reading or writing.
- Changes in personality and intellect.
- Experiencing strange sensations such as regular deja vu, strange smells, a feeling of fear, or even blackouts.
Some of the above symptoms can also be caused by other medical conditions. However, if you are experiencing any of the above it is important that you consult your doctor immediately.
Methods of diagnosis
Having taken your medical history and conducted a physical examination, your doctor may want you to undergo a series of tests to assess your nervous system. These tests may include:
- Comparing the strength of your limbs,
- An eye examination.
- A facial muscle test
- Hearing tests.
- Mental exercises.
- Checking your tongue movement, ability to swallow, etc.
- Test of your reflexes.
- Testing your ability to distinguish between hot and cold, to feel pin-pricks, etc.
If the doctor still feels that further tests are necessary to give a definitive diagnosis, the following techniques may be used:
- Angiogram or arteriogram – An angiogram uses an injection of dye (which shows up on x-ray) to make the blood vessels of your brain visible on a series of x-rays. If there is a tumour present, this will help to determine its location and blood supply.
- Chest X-ray – to look for a possible primary tumour.
- CT (CAT) Scan.
- Electroencephalogram (EEG) – An EEG measures the electrical activity within the brain using wires that are placed against your head using small disks held on by a conductive gel. The resulting print-out of brain waves from the EEG machine can be examined for abnormal patterns.
- Head X-ray.
- Magnetic resonance imaging (MRI scan).
- Positron emission tomography (PET) scan – This technique can help determine how active a tumour is and whether it is malignant or benign. Having received an injection of glucose (along with a small amount of radioactive marker) you will be scanned to provide a picture of brain activity. Tumours will show up as an abnormal area on the scan.