Destroying tissue with heat or cold or by other methods such as surgery, hormones, drugs and radiofrequency.


A surgical procedure for the treatment of epilepsy. It consists of the removal of the hippocampus, which has a role in memory, spatial awareness, and navigation, and the amygdala, which has a role in the processing of emotions. Read more about the procedure performed at Barnes-Jewish Hospital.

Anaplastic astrocytoma

A rare cancerous brain tumor that forms in the supportive tissue of the brain.


Not cancerous. A benign tumor may grow larger, but does not spread to other parts of the body. Also called nonmalignant.


The removal of tissue so it can be examined to determine if a disease such as cancer is present.


A treatment using powerful drugs to kill cancer cells.

Clinical trials

Studies of new medicines, equipment, or procedures that involve human volunteers. These trials help determine whether such treatments are safe and effective.


An operation in which a piece of the skull is removed. A craniotomy may be done so doctors can remove a brain tumor or abnormal brain tissue. It may also be done to remove blood or blood clots from the brain, relieve pressure in the brain after an injury or stroke, repair a brain aneurysm (a bulge in a blood vessel wall) or skull fractures, or treat other brain conditions. The piece of skull that is removed is usually put back in place after the brain problem has been treated.


DICOM (Digital Imaging and Communications in Medicine) is a standard for handling, storing, printing and transmitting information in medical imaging.


A group of disorders marked by problems in the normal functioning of the brain. These problems can produce seizures, unusual body movements, loss of consciousness, or changes in consciousness, as well as mental problems or problems with the senses.

Epileptic lesions

Damaged areas of the brain that can trigger abnormal nerve impulses and cause symptoms common to epilepsy.

Gamma knife therapy

A treatment using gamma rays, a type of high-energy radiation that can be tightly focused on small tumors or other lesions in the head or neck, so that very little normal tissue receives radiation. The gamma rays are aimed at the tumor from many different angles at once, and deliver a large dose of radiation to the tumor in one treatment session. This procedure is a type of stereotactic radiosurgery. Gamma Knife therapy is not a knife and is not surgery. Gamma Knife is a registered trademark of Elekta Instruments, Inc.

Genetic defect

An illness or disease caused by abnormal genes. If it is present at birth, it is called congenital.


A fast-growing type of central nervous system tumor that forms from glial (supportive) tissue of the brain and spinal cord. Glioblastomas usually occur in adults and affect the brain more often than the spinal cord. They are also called GBM, glioblastoma multiforme and grade IV astrocytoma.


A cancer of the brain that begins in the glial cells that surround and support nerve cells.


Loss of blood from deep inside the body or at the surface. It usually involves a large amount of bleeding in a short time.

Intraoperative MRI

The use of MRI to image the brain during an operation. Read more about the procedure performed at Barnes-Jewish Hospital.


A device that forms light into intense, narrow beams that may be used to cut or destroy tissues such as cancers.

Laser Surgery

A surgical procedure that uses the cutting power of a laser beam to make bloodless cuts in tissue or to remove a surface lesion, such as a tumor.

Laser Therapy

Treatment that uses intense, narrow beams of light to cut and destroy tissue, such as cancer tissue.


An area of abnormal tissue. A lesion may be benign (not cancerous) or malignant (cancerous).

Magnetic Resonance Imaging (MRI)

A procedure that uses radio waves and a powerful magnet linked to a computer to create detailed pictures of the inside the body. MRI makes better images of organs and soft tissue than other scanning techniques. It is especially useful for imaging the brain, the spine, the soft tissue of joints and the insides of bones.


Cancerous. Malignant cells can invade and destroy nearby tissue and spread to other parts of the body.


The spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a metastatic tumor or a metastasis.

Metastatic tumor

A tumor that contains cancer cells that have spread from a tumor in another part of the body.

Minimally invasive surgery

Surgery performed with small instruments through a small opening in the body instead of a large incision. Minimally invasive surgery may cause less pain and scarring and less damage to healthy tissue. Patients usually recover faster than from traditional surgery.


A doctor who specializes in diagnosing and treating brain tumors and other tumors of the nervous system.


A doctor who specializes in diagnosing and treating diseases of the nervous system using radiation.


A doctor who specializes in surgery on the brain, spine and other parts of the nervous system.


Not cancerous. A nonmalignant tumor may grow larger, but does not spread to other parts of the body. Also called benign.

Primary tumor

An original tumor in the body. Cancer cells from a primary tumor may spread to other parts of the body and form new, or secondary, tumors. This is called metastasis. These new tumors are the same type of cancer as the primary tumor.

Radiation necrosis

The death of healthy tissue caused by radiation therapy. Radiation necrosis is a side effect of radiation therapy given to kill cancer cells, and can occur after cancer treatment has ended.

Radiation oncologist

A doctor who specializes in using radiation to treat cancer.

Radiation therapy

The use of high-energy radiation from x-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors (also called irradiation and radiotherapy). Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance that travels in the blood to tissues throughout the body.


Resection is a form of surgery to remove tissue or part or all of an organ.

Stereotactic radiosurgery (SRS)

A type of radiation therapy that uses special equipment to position the patient and precisely give a single large dose of radiation to a tumor. It is used to treat brain tumors and other brain disorders that cannot be treated by regular surgery. It is also called radiation surgery and radiosurgery.


An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancerous), or malignant (cancerous). It may also be called a neoplasm.

For more medical terms, visit the National Cancer Institute’s Dictionary of Cancer Terms.