Preserved function in brain invaded by tumor.

OBJECTIVE: Intrinsic brain tumors can arise within regions of the cortex that are essential to language, motor, and somatosensory functions. Although it is commonly thought that such tumors can be safely resected, as long as the resection is limited to grossly abnormal cortex, functional mapping of the cerebral cortex during tumor resection does not support this contention.
METHODS: We report our experience with 14 patients (9 men, 5 women; median age, 43 yr) with intrinsic brain tumors of varying degrees of malignancy (four glioblastomas multiforme, four anaplastic astrocytomas, two anaplastic oligodendrogliomas, one anaplastic mixed glioma, three gangliogliomas). Cortical mapping was performed either intraoperatively (n = 11) or extraoperatively via intracranial electrodes (n = 3).
RESULTS: Tumors were found to grossly invade functioning cortices (frontal lobe language cortex, four tumors; temporal lobe language cortex, five tumors; motor cortex, four tumors; somatosensory cortex, one tumor). The gross invasion of functional cortex by tumor limited safe resection in all patients. Three patients experienced transient postoperative deficits caused by the proximity of the resection to functional cortex. One patient suffered a delayed postoperative hemorrhage, with resultant persistent motor aphasia.
CONCLUSION: Intrinsic brain tumors grow by infiltration of normal brain. Consequently, brain that appears to be abnormal may remain functional, thus precluding safe tumor resection.