Brainstem Glioma
Brainstem gliomas make up approximately 10-20% of all central nervous system tumors of childhood. They typically occur in children less than 10 years of age. Brainstem gliomas arise from glial cells within the brain stem. Glial cells are a type of support tissue cell. The behavior, treatment and prognosis of a brainstem glioma are determined by where it is located within the brainstem (midbrain, pons, medulla), how it grows within the brainstem (diffuse or focal and intrinsic or exophytic), and the type of glioma (low grade or high grade). The brainstem is composed of three main parts: midbrain, pons and medulla. Brainstem gliomas can arise in any area of the brainstem, but the pons is the most common location making up 75-85% of brainstem tumor. Brainstem gliomas typically grow in a diffuse fashion among the normal cells within the brainstem, making it impossible to remove the tumor without injuring the normal brainstem. These tumors are termed “diffuse intrinsic”, have a more aggressive pathology (high grade), and have a poor prognosis. Diffuse intrinsic brainstem tumors commonly arise within the pons and rarely within the medulla. Some brainstem gliomas develop within the brainstem (intrinsic) but grow in a focal fashion and are termed “focal intrinsic” brainstem gliomas. Focal intrinsic brainstem gliomas are typically located in the medulla or midbrain. Focal brainstem gliomas can also develop in an exophytic fashion (i.e. growing from the edge of the brainstem with the majority of the tumor protruding outside of the brainstem). Focal intrinsic and exophytic brainstem gliomas tend to have a less aggressive pathology (low grade), can often be surgically removed, are typically responsive to chemotherapy and radiation therapy, and usually have a good prognosis.