Preoperative imaging to predict orbital invasion by tumor

Background. Our purpose was to examine the accuracy of preoperative imaging in assessing tumor invasion of the orbit and nasolacrimal system. Methods. Nineteen preoperative CT and 17 preoperative MR images from patients at risk for orbital invasion were retrospectively reviewed. Invasion was corroborated by pathologic and intraoperative assessment. Results. Tumor adjacent to the periorbita was the most sensitive predictor of orbital invasion (90%) for both CT and MRI. Extraocular muscle involvement on MRI (100%) and orbital fat obliteration (80% MRI, 86% CT) had the highest positive predictive values of the criteria evaluated. Extraocular muscle displacement and enhancement were less accurate (<65%) predictors. No one criterion was >79% accurate in predicting orbital invasion. Six or more positive criteria predicted invasion with 67% sensitivity and 80% specificity (accuracy, 72%). CT was more accurate than MRI in seven of nine criteria. Invasion of the nasolacrimal system was predicted accurately (89%). Conclusions. Although preoperative imaging can aid in surgical planning, it should not replace intraoperative assessment in ambiguous cases of orbital invasion. (C) 2000 John Wiley and Sons, Inc.