Imaging description

A 17-year-old girl presented with progressive asymmetric left eye swelling. CT images through the left orbit demonstrated a mass centered in the left superior orbital rim, extending through the left cribriform plate and into the posterior ethmoidal air cells. The internal matrix of this mass had a ground glass appearance (Fig. 90.1a, b). The orbital apex appeared to be spared (Fig. 90.1). T2-weighted MR images through the orbit demonstrated a homogeneous hypointense signal of the mass (Fig. 90.1c, d). The mass displaced rather than invaded adjacent soft tissue structures. It displaced the frontal lobe superiorly and extended into the conus of the orbit, with mass effect on the superior and medial rectus muscles. The optic nerve did not appear to be encased. There was homogeneous enhancement of the mass on the T1-weighted MR images after intravenous administration of gadolinium (Gd)-DTPA (Fig. 90.1d). Additional CT (Figs. 90.2 and 90.3b) and plain film (Fig. 90.3a) images of two other children with fibrous dysplasia (FD), one of whom has McCune–Albright syndrome (MAS) (Fig. 90.3), demonstrate the classic ground glass bony matrix.