The influence of gliomas and nonglial space-occupying lesions on blood-oxygen-level-dependent contrast enhancement.

BACKGROUND AND PURPOSE Functional MR (fMR) imaging with blood-oxygen-level-dependent (BOLD) contrast enhancement is increasingly used as a noninvasive tool for presurgical mapping in patients with intracranial tumors. Most physiologic studies of task-related BOLD contrast enhancement have involved healthy volunteers. Therefore, it is not known whether BOLD contrast is evoked in the same way in or adjacent to tumor tissue. The purpose of this study was to study the influence of different intracranial tumors on BOLD contrast enhancement. METHODS fMR mapping of the sensorimotor cortex was successfully performed in 15 of 21 patients with intracranial space-occupying lesions by using a bimanual motor task. Tumors were located either within the sensorimotor area itself or in adjacent brain areas, inducing changes of signal intensity on T2-weighted images along the pre- or postcentral gyrus. Space-occupying lesions were divided into a group comprising gliomas (seven cases) and a group comprising nonglial space-occupying lesions (three metastases, two cavernomas, one abscess, one arteriovenous malformation, one meningioma). A hemispheric activation index was calculated using the volume of activation on the affected and on the contralateral hemisphere. Hemispheric activation indices of gliomas and nonglial lesions were compared statistically. RESULTS The activated volume in the hemispheres ipsilateral to the nonglial lesions was 14% larger than in the contralateral hemisphere, whereas in the hemispheres ipsilateral to gliomas, the activated volume decreased by 36% in comparison with the contralateral hemisphere. The difference between nonglial lesions and gliomas was significant (P < .05). CONCLUSION The generation of BOLD contrast enhancement is reduced near gliomas but is not affected by nonglial tumors.