Glioma. (a) Illustration of a large glioma (colored area) within the left cerebral hemisphere in a s

Glioma. (a) Illustration of a large glioma (colored area) within the left cerebral hemisphere in a sectioned brain. Notice how the tumor crowds out normal brain tissue. (b) A glioma may also press against the cerebellum and brain stem, causing a loss of motor function and reflexes. (c) PET scan of a glioma within the frontal lobe. The red and yellow colors indicate that metabolic activity is very high, compared to normal nervous tissue in green and purple. This type of glioma is called a glioblastoma multiforme, which is a fast-growing tumor.  Courtesy of Dr. Giovanni DiChiro and Dr. Ramesh Raman of the Neuroim- aging Branch, National Institute of Neu- rological Disorders and Stroke, National Institutes of Health.