By Todd E. Williams, M.D., F.A.C.R
There are many types of tumors which can arise within the skull. These can arise from the brain, the cranial nerves (those nerves which work the eyes, the ears, the facial muscles and the feelings of the face area), the coverings of the brain, the pituitary gland and the blood vessels of the brain. The most common tumors arise from the glial cells within the brain, which are the fibrous tissues of the brain, giving the brain its support. Forty percent of the malignant tumors of the brain arise from these structures. They can occur anywhere within the brain, but usually occur in the upper portions of the brain. These are the areas that control memory, motion and speech.
Each year, there are about 15,000 to 17,000 new cases of primary brain tumor diagnosed in the United States. These tumors occur twice as often in Caucasians than in African-Americans. They occur about 50 percent more often in men than they do in women. Most of these tumors occur in patients over the age of 70. There is a small incidence of such tumors occurring in children between the ages of five and 10 years old.
There is no clear cause for brain tumors, but animal research has shown that certain factors may give rise to tumors of the central nervous system. These can include genetic factors, with such diseases as von Recklinghausen disease or von Hippel-Lindau disease; environmental factors, such as various chemical exposures; viruses; and actually radiation received as a fetus.
Primary brain tumors spread invasively within the skull because there are no natural fibrous capsules to stop their growth. They can present in many ways depending on the part of the brain in which they arise. The most common tumors -- the gliomas -- tend to arise in one side of the brain. Some will extend across the midline into the other side of the brain.
Local spreading usually occurs along blood vessels and nerve pathways. These tumors tend to grow quite rapidly, especially the more malignant types of gliomas. Since the skull is a closed space, any swelling around the tumor makes the symptoms from the tumor worse than they would be otherwise.
The most common types of findings from tumors in the brain include seizure activity, headaches, confusion, a decrease in the ability to move an extremity (arm or leg), or difficulty speaking. Sometimes there is memory loss.