Brain Tumor

Reading: Principles of Neuropsychology (PN) Chapter 10

Introduction:

Brain Tumors Tumors of the central nervous system (CNS) consist of a mass of abnormal cells that affect neurological function. Most CNS tumors involve the cells of membrane linings of the CNS (e.g. meningioma) or glial support tissue (glioma). Few tumors represent the abnormal growth of neurons. In adults, approximately 50% of all CNS tumors are gliomas.

Tumors affect neurological function largely through compression of surrounding tissue (mass effect). This causes seizures, mechanical trauma, increased Intracranial Pressure (ICP), ischemia and anoxia. Many tumors also infiltrate tissue that surrounds them. This contributes to mass effects and compromise of neural function. The figure above depicts a diffuse astrocytoma that has heavily infiltrated surrounding tissue. Notice that this tumor has displaced the surrounding tissue to the point of shifting the opposite cerebral hemisphere and compressing the ventricle on the same side as the tumor.

The most common tumors are gliomas. These tumors involve glial support cells (i.e. astrocytes and oligodendrocytes). These abnormal growths are divided into four grades based on the degree of malignancy and histological features:

Grade 1: Lowest grade of dedifferentiation, cells are similar in appearance to normal cells (See Astrocytoma micro)
Grade 2: Low grade of dedifferentiation
Grade 3: Anaplastic astrocytomas; moderate dedifferentiation, poor prognosis
Grade 4: Glioblastoma multiforme; rapidly growing; very poor prognosis; highly dedifferentiated necrotic tissue.