Brainstem gliomas are tumors that occur in the region of the brain referred to as the brain stem, which is the area between the aqueduct of Sylvius and the fourth ventricle. Although various systems are used to classify these tumors, the authors have divided brainstem gliomas into 3 distinct anatomic locations—diffuse intrinsic pontine, tectal, and cervicomedullary. Intrinsic pontine gliomas carry a grave prognosis. Longer survival is associated with the tectal and cervicomedullary gliomas. Tumors also are characterized on the basis of site of origin, focality, direction and extent of tumor growth, degree of brainstem enlargement, degree of exophytic growth, and presence or absence of cysts, necrosis, hemorrhage, and hydrocephalus.

Pathophysiology: These tumors have a predilection to originate from the left side. Most are located in the pons; however, medulla and midbrain may be involved as well. Brainstem gliomas are highly aggressive brain tumors. Anatomic location determines the pathophysiological manifestation of the tumor. With tectal lesions, hydrocephalus may occur as a result of fourth ventricular compression. With pontine and cervicomedullary lesions, cranial nerve or long tract signs are observed commonly.

Frequency:

• In the US: Brainstem gliomas have been reported to make up 2.4% of all intracranial tumors in adults and 9.4% of intracranial tumors in children. Brainstem gliomas account for approximately 10-20% of all childhood brain tumors. The incidence in adults is lower than that in children younger than 16 years. A tendency for brainstem gliomas to follow a more indolent course in adults than in children has been noted; in adults, these tumors are more likely to be low grade and remain localized.

Mortality/Morbidity:

• Morbidity is due to the location of the space-occupying lesion and compression of surrounding structures; because these structures regulate basic body functions of blood pressure, respiration, and swallowing as well as motor and sensory functions, compression can produce substantial neurological disability.

• Sudden death can result from increased intracranial pressure and subsequent cerebral herniation. This may be a consequence either of edema induced by the tumor or of hemorrhage into the neoplasm.

Race: CNS tumors vary in incidence by age, sex, ethnic group, and country, and also over time. How much of this variation is due to artifactual influences or etiologic differences has been the subject of many debates.

Sex: Some reports have suggested a slight male preponderance, whereas others have failed to observe any sex predilection.

Age:

• Bimodal age distribution has been noted, with a peak incidence in the latter half of the first decade of life and a second peak in the fourth decade.

• Approximately three fourths of patients are younger than 20 years.

• Neoplasms of the brain stem have been identified in children younger than 1 year.

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