The brain stem consists of the midbrain, pons and medulla located deep in the posterior part of the brain. Tumors that arise along these structures are called brain stem gliomas. Most brain stem gliomas occur in the pons ("pontine gliomas"). The pontine tumors have a poorer prognosis than the less common midbrain and medullary gliomas.
Incidence
Brain stem tumors account for 10 percent of pediatric brain tumors. The peak incidence is between ages 5 and 10.
Clinical Features and Symptoms
Pontine brain stem tumors affect the cranial nerves, causing symptoms related to the nerves that supply the muscles of the eye and face, and muscles involved in swallowing. These symptoms include double vision, inability to close the eyelids completely, dropping one side of the face, and difficulty chewing and swallowing. The tumor also affects the "long tracks" of the brain, with resultant weakness of the arms or legs and difficulty with speech and walking. Symptoms usually worsen rapidly because the tumor is rapidly growing.
Tumors arising in the midbrain usually affect only the nerves supplying the eye muscles. They also block the flow of cerebrospinal fluid in the brain, causing increased pressure with headaches and vomiting. Tumors involving the medulla usually cause swallowing problems and weakness of the arms and legs.
Survival Rates
Pontine Gliomas - The patients' symptoms often improve dramatically during or after six weeks of irradiation. Unfortunately, problems usually recur after six to nine months, and progress rapidly. Survival past 12 to 14 months is uncommon, and new approaches to treating these tumors are urgently needed.
Midbrain/Medullary Gliomas - With the use of radiation therapy, these patients often to well. Long-term survival ranges from 65 to 90 percent for brain stem tumors that arise from the midbrain or medulla.
Treatment Strategies
Surgery is not generally possible because these tumors (especially pontine gliomas) are widely spread within the brain stem and can not be removed. Surgery may be possible in the few patients where the tumor is very localized.
Radiation therapy has been the main treatment approach
Current Research
To improve the outcome of pontine gliomas, researchers are studying drugs that may enhance the effect of radiation therapy. For midbrain and medullary tumors, the new radiation techniques allow more localized therapy.
