Meerwein CM, et al. - This is the first and largest study investigating the diagnostic performance of simultaneous preoperative MRI and CT for the determination of anterior skull base (ASB) and medial orbital wall (MOW) infiltration by advanced sinonasal tumors, compared with the systematic intraoperative assessment. Participants in the study were 73 patients. According to findings, CT and MRI are precise methods for MOW infiltration evaluation. ASB evaluation is complex and both approaches share false-positive and false-negative results, stressing the need for intraoperative exploration.