Blood-Brain Barrier: A wall of nerves and cells surrounding the brain membrane. While this barrier has a protective function, it also reduces the ability of chemotherapeutic drugs to effectively reach some brain tumors.
Brain stem: The brain stem, located at the front of the cerebellum, links the cerebrum to the spinal cord and controls various automatic as well as motor functions. It is composed of the medulla oblongata, the pons, the midbrain, and the reticular formation.
Cerebrospinal Fluid (CSF): This protective, clear fluid circulates through the brain and the spinal canal. When this flow is blocked-as may be the case with a brain tumor-hydrocephalus, or water on the brain, occurs.
Cerebrum: The brain’s largest section can be divided into two parts: the left and right cerebral hemispheres. These hemispheres are joined by the corpus callosum, which enables “messages” to be delivered between the two halves. The right side of the brain controls the left side of the body, and vice versa. Each hemisphere also has four lobes that are responsible for different functions: frontal (behavior, emotions, problem solving); temporal ( short-term memory, identification of sound and smell); parietal (touch, language comprehension), and occipital (visual processing, shape and color identification).
Clinical Trials: These studies involve patients in the testing of new treatments and therapies and are part of the drug approval process in America. A clinical trial, which typically has three stages, or phases, gauges a drug’s safety, effectiveness, dosage requirements, and side effects. Patients must meet certain criteria to be enrolled in a clinical trial (which is determined for each individual study), and participation in a study is voluntary. Clinical trials are sponsored by pharmaceutical companies, government agencies, and other healthcare-related organizations; many are based at research universities or hospitals. A set of rules, or protocol, is established for each trial.
Frameless Stereotactic Surgery: See “Stereotactic Surgery.”
Functional Image-Guided Surgery (FIGS): A technique that combines Functional MRI (fMRI) with frameless stereotactic radiosurgery to optimize the safety and efficacy of treatment for patients with tumors located in the cerebral hemispheres.
Functional MRI (fMRI): A technique that helps to pinpoint functional areas of the brain. While the MRI is scanning, the patient is asked to perform a series of activities and movements, such as reading a list or tapping fingers. The areas of the brain that correlate to these movements and activities “light up” on the scan and create an image. This information is used by surgical navigation computers in the planning of incisions, skull openings and tumor removal to minimize neurological deficits.
Gliomas: A large category of primary brain tumors that originate from nerve cells called glial cells. There are many specific types of gliomas; see Astrocytes; Glioglastoma Multiforme; Mixed Gliomas; Optic Nerve Gliomas.
Grading: Brain tumors can be categorized by grades. Grading occurs after biopsy, when a pathologist examines the brain tissue for breakdown of cell structure. While there are different systems used to assign grades, in general, they are as follows:
- Grade I tumors are slow growing; their cells are near-normal in appearance; and are not malignant.
- Grade II tumors have cells that are slightly abnormal in appearance and can spread to surrounding tissue.
- Grade III tumors grow quickly, contain abnormal cells, and spread to surrounding tissue.
- Grade IV tumors contain aggressive, abnormal cells that reproduce quickly. These are the most malignant of brain tumors.
Left Hemisphere: The half of the cerebrum sometimes referred to as the “dominant” hemisphere. It has primary responsibility for speech and language. However, in some left-handed people, the right hemisphere controls speech function.
Medulloblastomas: These malignant tumors represent more than one-fourth of all childhood brain tumors. Left untreated, medulloblastomas can spread throughout the nervous system and, sometimes, to other parts of the body
Meningiomas: Tumors that originate from the meninges, thin membranes that cover the brain and the spinal cord. These slow-growing tumors rarely become malignant or spread; malignancy occasionally does occur.
Neuroendoscopy: The use of miniaturized, optically guided instruments that can be navigated directly to the tumor site. Oligodendrogliomas: Slow-growing, rare tumors that most commonly affect young adults.
Pituitary Adenomas: These tumors are located near the pituitary gland, a small oval-shaped structure that supplies hormones. Hormones are chemical messengers that control many bodily processes, such as growth and metabolism. Secreting tumors release unusually high levels of pituitary hormones, which can result in a variety of symptoms-from impotence to abnormal body growth to hyperthyroidism-depending on the hormone involved.
Pons: This part of the brain stem is the origin of four pairs of cranial nerves: fifth (facial sensation); sixth (eye movement); seventh (taste, facial expression, eyelid closure); and eighth (hearing and balance).
Primitive Neuroectodermal Tumors: PNETs, which usually affect children and young adults, originate from primitive cells left over from early nervous system development. PNETs are usually very malignant, growing rapidly and spreading easily within the brain and spinal cord. In rare cases, they spread outside the CNS.
Schwannomas: These tumors, while usually benign, can affect balance and hearing, and may cause facial paralysis. They are also known as vestibular schwannomas or acoustic neuromas and may grow on one or both sides of the brain.
SPECT: Single Photon Emission Computed Tomography, or SPECT, is a scanner that measures a low-dose radioactive material as it circulates through the brain. SPECT can be used to differentiate between low and high grade tumors.
Stereotactic Radiosurgery: A non-invasive modality that precisely delivers focused, multiple beams of radiation to areas where they’re needed-a single point on a tumor site-while avoiding healthy tissue.
Stereotactic Surgery: A sophisticated, computer-based modality where a metal frame is attached to the patient’s skull to provide a fixed reference point. This point, combined with a three-dimensional image of the brain provided by a computer and MRI scanning, allows for precise mapping and visualization of the tumor and surrounding tissue. Precise navigation to the tumor site and optimal tumor resection is possible using a variety of surgical devices attached to the frame.
Frameless Stereotactic Surgery: provides the same precision without the need to attach a heavy metal frame to the patient’s skull. Frameless systems substitute a reference system created by “wands,” plastic guides, or infrared markers.