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.