Stereotactic resection and its limitations in glial neoplasms.

With imaging-based volumetric stereotactic techniques, it is possible to selectively and accurately remove any CT- or MRI-defined part or all of any intra-axial neoplasm. However, glial neoplasms are composed of two elements: tumor tissue and isolated tumor cells which infiltrate brain parenchyma. In high-grade gliomas and pilocytic astrocytomas, the tumor tissue component is most accurately defined by the volume of contrast enhancement. Tumor tissue in low-grade nonpilocytic gliomas is indistinguishable on imaging from infiltrated parenchyma. Stereotactic biopsy is presently the only method by which CT hypodense tumor tissue can be differentiated from infiltrated parenchyma, which is also hypodense. In eloquent brain areas, stereotactic resection is appropriate for the tumor tissue component only in patients harboring glial tumors.