Current Surgical Management

For the majority of brain tumors in children, the extent of resection is the most important factor predicting long-term outcome. This has led many neurosurgeons to be as aggressive as possible during the initial surgical procedure in an effort to achieve gross total resection (GTR;(Pollack 1999)). It should be recognized that GTR is not the primary goal for tumors, where sensitivity to adjuvant therapy is high (e.g., germinoma), or where there is clear extension into eloquent regions (e.g., brainstem and thalamic glioma). Fortunately, these latter groups represent a minority of pediatric brain tumors (Pollack 1994).

The majority of pediatric tumors are primary glial neoplasms arising within the cerebellar or cerebral hemispheres. Factors affecting the extent of resection are: relation to functionally important structures, degree of infiltration, and the presence or absence of tumor dissemination at time of presentation. Although the portions of infiltrative supratentorial tumors that extend into eloquent locations (primary motor, speech cortex, basal ganglia, or major white matter tracts such as the internal capsule) are likely to defy GTR, an argument can be offered for extending resection sufficiently to allow a change to occur in the natural history of the disease (Keles et al. 2001). Earlier, the definition of eloquent cortex relied mainly on variable anatomical maps, and resective procedures were limited by the inability to predict functional anatomy in specific patients. In the posterior fossa, GTR is limited either by involvement of the brainstem or the cranial nerves. Monitoring of virtually all cranial nerves is now possible, which greatly facilitates safe dissection of the tumor from normal structures. Infiltration into the brainstem by malignant tumors is not amenable to surgical resection.