By Dr Ananya Mandal, MD
Brain tumors may be malignant (cancerous) or non-malignant (benign). They result from an abnormal growth of brain tissues. (1)
Since the brain lies within the strong bony cages of the skull, any growth or tumor that occurs within these tissues may create pressure on sensitive brain tissues. This leads to impairment of various brain and nerve functions including problems in vision, speech, balance etc. (1)
The brain is comprised of three major areas of function. The largest part is the cerebrum. It is the brain as we know. It is the source of thinking, memory, speech, learning, reading, writing, cognition and movement by volition.
The lower back region of the brain is called the cerebellum. This controls posture, balance and movement.
The brain is connected to the spinal cord at a region called the brain stem. This controls the most vital functions like heart beats, breathing as well as muscles that control vision, auditory functions, eating and movement.
The brain is bathed in a fluid called the Cerebrospinal fluid (CSF) and is encased in membrane like sheaths called the meninges. (2)
Types of brain tumor
Brain tumors may be of two basic types: primary or secondary. The latter is also known as metastatic.
The primary tumors originate within the brain tissue. These tumors are not spread from one to another and in most cases are not preventable. Metastatic tumors often are a result of cancer that has spread from another area of origin. (1)
Primary brain tumors may originate in the brain cells or nerves, or glands or in the sheaths that cover the brain tissues called meninges. These tumors, if cancerous, may literally erode parts of the brain by causing inflammatory changes apart from creating pressure on the surrounding nerve tissues.
Cause of primary brain tumors
The exact reason for the origin of primary brain tumors is still unknown. These may occur either due to faulty genetics – e.g. in case of neurofibromatosis, Von Hippel-Lindau syndrome, Li-Fraumeni syndrome, Turcot syndrome or tuberous sclerosis etc. or result due to exposure to cancer causing toxins or radiation.
Studies show that radiation exposure to the brain, which is often used for treatment of brain cancers as well, are often responsible for raising the risk of brain tumors in 20 to 30 years.
Radiation exposure as part of occupational hazard in workers at power lines, as well as those with history of smoking, head trauma, hormone replacement therapy, have not been cited as risk factors for brain tumors.
There is a controversy whether use of cell phones and wireless devices are responsible for increased risk of brain tumors. This needs further study.
Infections with Epstein-Barr virus, that raises risk of blood cancer, like lymphoma, may begin in the brain as cancer is also recorded. (3)
Cause of secondary brain tumors
Metastatic brain cancers may spread from an advanced breast, melanoma, kidney, bladder, or lung cancer. The lesions may also spread from sarcomas, testicular or germ cell cancers.
Some cancers, however, do not usually spread to the brain readily. These include prostate and colon cancer.
Sometimes the original site of the tumor that has spread to the brain is not detected. This is called cancer of unknown primary (CUP) origin.
Around one fourth of all cancers that spread or metastasize are brain tumors. These secondary cancers are more common than primary brain tumors and are seen in 10-30% adults with cancer. These metastatic lesions often are seen in end-stage patients and are liable to be fatal. (1, 4)
Brain cancer in children
Brain cancers can occur in children as well. In fact after blood cancers, like leukemia and lymphoma, brain tumors are the third most common cancers in children.
In most of these cases the tumors are primary in nature and the exact cause is unknown.
At present both early detection and treatment of brain tumors and cancers is of paramount importance. In many cases brain cancers and tumors have a tendency to recur after remission. This is especially seen in children with primary brain tumors. (2)
Edited by April Cashin-Garbutt, BA Hons (Cantab)
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- NINDS Brain and Spinal Tumors Information Page. Available at: http://www.ninds.nih.gov/disorders/brainandspinaltumors/brainandspinaltumors.htm