Intracranial tumor in children: MR imaging findings within 24 hours of craniotomy

PURPOSE: To evaluate whether very early magnetic resonance (MR) imaging enables distinction of residual tumor from benign postoperative change in children. MATERIALS AND METHODS: Forty-six postoperative MR examinations were performed in 43 children with intracranial tumors within 24 hours of the completion of surgery during a 2-year period. These examinations were categorized according to whether residual tumor could be definitely identified or excluded, or whether the diagnosis was uncertain. RESULTS: Contrast enhancement occurred in 33 of 46 MR examinations performed within 24 hours of surgery. In 18 instances, this was associated with obvious residual tumor In 15 patients, only small amounts of linear or patchy enhancement were seen. Of these, seven patients (46%) were disease-free for an average of 4.5 years. Assessment for postoperative enhancement was hampered in seven patients because of the presence of methemoglobin in the tumor bed. Contrast enhancement was not observed in two patients before surgery. CONCLUSION: Surgically induced, MR-detectable contrast enhancement and extracellular methemoglobin formation occurs within 24 hours of the completion of intracranial surgery. This can interfere with the detection of small amounts of residual tumor.