Brain Tumors: Primary - Introduction

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Click the icon to see an image of the meninges.

They are not technically classified as brain tumors, but they have similar symptoms and develop within the brain. So in practical terms, they are considered brain tumors. In fact, meningiomas comprise 20% of all primary brain tumors. They occur more often in women than in men. Most grow very slowly, and the majority of people who have them never know they are present. Malignant forms called anaplastic meningiomas and hemangiopericytomas are less common and are difficult to remove surgically.

Cerebral Astrocytomas. Gliomas that develop inside the brain often occur in the cerebral hemispheres (the right and left sides of the brain). In such cases, they are referred to as cerebral astrocytomas. Gliomas sometimes occur in another part of the brain, called the cerebellum. The cerebellum is responsible for balance and coordination. In such cases, the term cerebellar astrocytoma is used.

Click the icon to see an image of the function of the left cerebral hemisphere.

Click the icon to see an image of the function of the right cerebral hemisphere.

Brain Stem Gliomas. Brain stem gliomas develop in the lowest portion of the brain. The brain stem connects the cerebrum (the higher centers of the brain) to the spinal cord. The brain stem is thought to be the primitive brain because it controls the most basic functions.

Click the icon to see an image of the function of the brainstem.

The brain stem consists of three primary parts:

• The medulla regulates breathing, swallowing, blood pressure, and heart rate
• The pons links the cerebellum to the cerebrum
• The midbrain helps control vision and hearing

Click the icon to see an image of the structures of the brain.

Medulloblastomas. Medulloblastomas are always located in the cerebellum, which is at the base and toward the back of the brain. They represent about 3% of all brain tumors.

Click the icon to see an image of the function of the cerebellum.

Pituitary Tumors. Pituitary tumors comprise about 10% of primary brain tumors and are often benign, slow-growing masses in the pituitary gland.

Click the icon to see an image of the pituitary gland.

Other Brain Tumor Locations. Optic nerve gliomas occur in the optic nerve, which is located behind the eye. Acoustic neuromas make up 7.5% of brain tumors.

Click the icon to see an image of the optic nerve.

Review Date: 10/19/2006
Reviewed By: Harvey Simon, M.D., Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.