The human brain is a very complex organ, so much so that not even Medical Doctors really know everything about it yet, and for the everyday parent whose child has just been diagnosed with one or other form of brain cancer, the sudden influx of medical terminology can be completely intimidating and overwhelming.
We will attempt to explain the basics about various types of childhood brain tumours as simply as we can (although we will have to use the medical terminology too so that you can get used to it).
Please refer to the Brain Tumour Glossary for explanations of any terms that you do not understand.
If there are terms in this article that do not appear in the glossary, you can also make use of the NCI Dictionary of Cancer Terms (link on the right hand side of almost page every page if you ever need them again – look for Bennie Bookworm)
Brain tumours are abnormal growths, in the brain, and are the most common solid tumours in children. Brain tumours can either be malignant or benign. When a tumour is benign, it means that the tumour does not contain cancer cells.
Once a benign tumour is removed, it generally does not recur. Most benign brain tumours have clear borders, which means that they do not invade surrounding tissue. Benign tumours can, however, cause symptoms that are very similar to cancerous tumours due to their size and location in the brain.
Brain cancer is the presence of one or more malignant tumours, which contain cancer cells and generally grow very quickly and invade surrounding tissue. Malignant/cancerous brain tumours rarely spread to other parts of the body, but can sometimes recur after treatment.
Sometimes brain tumours that do not contain cancer cells are also classified as malignant due to their size and location, and the damage they can do to vital functions of the brain.
Anatomy of the Brain
The central nervous system (CNS) consists of the brain and the spinal cord. The brain is a vital organ that controls thought, emotion, vision, memory, motor skills, touch, hunger, respiration, core body-temperature, and every process that regulates our body.
The brain can be divided into the cerebrum, the brain-stem, and the cerebellum
The Cerebrum (supratentorial, or front of brain) is composed of the left and right hemispheres. The cerebrum controls:
- Coordination of movement;
- Core body temperature;
- Initiation of movement;
- Problem solving;
- Touch; and
The Brainstem (midline, or middle of brain) is made up of the midbrain, the pons, and the medulla. Functions of this area include:
- Body temperature;
- Cardiac function;
- Involuntary muscle movements;
- Movement of the eyes and mouth;
- Relaying sensory messages (i.e., hot, pain, loud);
- Swallowing; and
The Cerebellum (infratentorial, or back of brain) is located at the back of the head.
Functions of the Cerebellum include:
- Coordinating voluntary muscle movements; and
- Maintaining posture, balance, and equilibrium
What causes Brain Cancer?
In most cases, nobody knows what causes brain cancer. We do know that brain cancer is not infectious; you can’t catch a brain tumour. There are, however a few risk factors that we do know about.
Researchers have found that some of the changes that occur in normal brain cells may actually lead them to form tumours:
- Normal human cells grow and function based mainly on the information contained in each cell’s chromosomes, which are long strands of DNA in each cell.
- DNA is the chemical that makes up our genes – the instructions for how all of our cells function.
- Brain and spinal cord tumours, like other tumours, generally occur as a result of changes (mutations) in the DNA inside cells.
- Some of our genes ,called oncogenes, help the cells grow, divide, and stay alive
- Others genes, called tumor suppressor genes, slow down cell division, or cause cells to die at the right time.
The medical profession believes that cancers are possibly caused by DNA changes that turn on oncogenes or turn off tumour suppressor genes. Such gene changes can be inherited from a parent, as is sometimes the case with childhood cancers, but more often than not they occur spontaneously at any time during a person’s lifetime.
In the majority of brain tumours there are some abnormalities of the genes involved in cell cycle control, which causes uncontrolled cell growth. These abnormalities are caused by alterations directly in the genes, or by chromosome rearrangements which change the function of a gene.
Patients with certain genetic conditions (i.e. neurofibromatosis, von Hippel-Lindau disease, Li-Fraumeni syndrome, and retinoblastoma) have an increased risk to develop tumours of the central nervous system. Children who have previously received radiation therapy to the head as part of a treatment regimen for other malignancies are also at an increased risk for new brain tumours.
While researchers now understand some of the gene changes that occur in different types of brain tumours, it is still unclear exactly what causes these changes. Some gene changes might be inherited, but most paediatric brain and spinal cord tumours are not the result of known inherited syndromes. It is thought that most gene changes are in all probability just random events that sometimes happen inside a cell, without having any outside cause.