The effect of brain tumors on BOLD functional MR imaging activation in theadjacent motor cortex: Implications for image-guided neurosurgery

BACKGROUND AND PURPOSE: Functional MR (fMR) imaging data coregistered to a neurosurgical navigation system have been proposed as guides for the resect ion of brain tumor in or adjacent to eloquent cortices, The purpose of this study was to compare data obtained from the side of the brain affected by tumor with the contralateral side and to determine if there are physiologic al limitations of fMR imaging in accurately determining the location of the primary motor cortex. METHODS: Ten patients with tumors in or directly adjacent to the motor cort ex were studied with fMR imaging (finger-tapping paradigm). fMR imaging dat a were analyzed using multiple R values. These data were coregistered to a real-time intraoperative neurosurgical navigation system. RESULTS: Significant variability of motor cortex activation patterns was no ted among individual patients. The activation volumes on the side of the tu mor were significantly smaller compared with the contralateral side for all tumors not previously resected (0.66+/-0.47). This was most pronounced in glioblastomas (0.27+/-0.21). We propose that these differences were caused by a loss of autoregulation in the tumor vasculature of glioblastomas and v enous effects. CONCLUSION: Notwithstanding the differences noted, the motor cortex was ide ntified successfully in all patients. This was confirmed by intraoperative physiological identification of the motor cortex and a lack of postoperativ e neurologic deficit.