INTRACRANIAL TUMOR IN CHILDREN - MR-IMAGING FINDINGS WITHIN 24 HOURS OF CRANIOTOMY

PURPOSE: To evaluate whether very early magnetic resonance (MR) imagin g enables distinction of residual tumor from benign postoperative chan ge in children. MATERIALS AND METHODS: Forty-six postoperative MR exam inations were performed in 43 children with intracranial tumors within 24 hours of the completion of surgery during a 2-year period. These e xaminations were categorized according to whether residual tumor could be definitely identified or excluded, or whether the diagnosis was un certain. RESULTS: Contrast enhancement occurred in 33 of 46 MR examina tions performed within 24 hours of surgery. In 18 instances, this was associated with obvious residual tumor In 15 patients, only small amou nts of linear or patchy enhancement were seen. Of these, seven patient s (46%) were disease-free for an average of 4.5 years. Assessment for postoperative enhancement was hampered in seven patients because of th e presence of methemoglobin in the tumor bed. Contrast enhancement was not observed in two patients before surgery. CONCLUSION: Surgically i nduced, MR-detectable contrast enhancement and extracellular methemogl obin formation occurs within 24 hours of the completion of intracrania l surgery. This can interfere with the detection of small amounts of r esidual tumor.