FUNCTIONAL CORTEX AND SUBCORTICAL WHITE-MATTER LOCATED WITHIN GLIOMAS

SOME NEUROSURGEONS STATE that intra-axial tumors may be resected with a low risk of neurological deficit if the tumor removal stays within t he confines of the grossly abnormal tissue. This is thought to be so e ven when the lesion is presumably located in a functional area, provid ing that the adjacent normal-appearing cortex and subcortical white ma tter are not disturbed. This retrospective analysis presents evidence that this view is not always correct, because functioning motor, senso ry, or language tissue can be located within a grossly obvious tumor o r the surrounding infiltrated brain. Intraoperative stimulation mappin g techniques identified 28 patients, ranging in age between 22 and 73 years, who showed evidence of functional tissue within the boundaries of infiltrative gliomas, as identified by correlation with computed to mography and magnetic resonance imaging scans, intraoperative ultrasou nd, gross visualization, and histological confirmation. Direct stimula tion mapping of cortical and subcortical portions of the tumor during resections identified motor, sensory, naming, reading, or speech arres t function. Nineteen patients had new or worsened neurological deficit s immediately after the operation, but after 3 months, only 6 continue d to show new deficits whereas 18 showed no deficits and 2 improved. T hese results demonstrate that regardless of the degree of tumor infilt ration, swelling, apparent necrosis, and gross distortion by the mass, functional cortex and subcortical white matter may be located within the tumor or the adjacent infiltrated brain. Therefore, to safely maxi mize glioma resection in these functional areas, intraoperative stimul ation mapping may be used to identify functional cortical or subcortic al tissue within, as well as adjacent to, the tumor, thus avoiding per manent injury.