FIG 8. Surgically induced enhancement: problematic case. This was one of the first patients in whom an intraoperative MR examination was performed. The tumor is above the level of these T1-weighted images. Preoperative MR image (left) (674/20/2) does not show enhancement in the head of the right caudate nucleus. Problems with hemostasis necessitated repeated electrocoagulations in this region. Intraoperative MR images (middle images, 5 and 20 minutes postcontrast) (532/15/3) partially show solid-appearing contrast enhancement of the head of the caudate nucleus with almost no time dependence during the observed time interval. A small biopsy was taken from this region, which did not show residual tumor histologically. Surgery was terminated. Early postoperative MR imaging (674/20/2) did not show persistent enhancement of the head of the caudate nucleus. The intraoperative enhancement probably represented transient blood-brain barrier disruption