These tumors account for 10% to 20% of all CNS tumors in children. There are no predisposing factors known. Traditionally, brainstem tumors have been divided into four categories: diffuse, focal, exophytic and cervicomedullary. Tumors in the last group tend to be more similar to intramedullary spinal-cord tumors. Diffuse brainstem gliomas represent the typical brainstem tumor (Chapter 2, Fig. 20). These tumors typically arise in young children, between the ages of 5 and 10 years. The
presentation is subacute, with cranial nerve palsies and long-tract signs such as gait instability and weakness. These tumors seem to be centered in the pons and enlarge the entire brainstem.
Focal tumors of the brainstem can occur in any location and are associated with either no symptoms or slowly progressive symptoms. One type of tumor in this category is the tectal glioma. It typically appears as a localized nonenhancing mass involving the tectum of the midbrain. They often present with hydrocephalus secondary to obstruction of the aqueduct of Sylvius rather than focal neurological symptoms. Biopsy of these lesions is not required if the imaging findings are classic. Focal tumors in other locations in the brainstem can be a number of different pathologies such as low-grade astrocytomas, pilocytic astrocytomas, gangliogliomas and gangliocytomas.
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