Orbital schwannomas: findings from magnetic resonance imaging in 62 cases

To evaluate the diagnostic value of magnetic resonance imaging (MRI) and illustrate the common MRI features of orbital schwannoma.

We reviewed 62 consecutive cases of pathologically proven orbital schwannoma investigated by MRI. All cases were examined using T1- and T2-weighted images. Enhanced T1-weighted images were obtained after administration of gadopentetate dimeglumine. The images were analysed and compared.

Cone-shaped lesions were the most frequent (16, 26%), followed by dumbbell-shaped (10, 16%), oval (9, 15%) and round lesions (8, 13%). The most common site was the superior aspect of the orbit (17, 27%), followed by the medial superior (12, 19%) and the orbital apex (12, 19%). On unenhanced T1-weighted images, 53 (85%) lesions showed isointensity or small patches of hypointensity. The patterns of enhancement seen on T1-weighted images correlated with the signal characteristics of unenhanced T2-weighted images. Five patterns emerged in our series. Among these patterns, the most common sign, found in 18 (29%) cases, was peripheral (ring) enhancement on enhanced T1-weighted images, which showed peripheral isointensity with central hyperintensity on T2-weighted images. Lesions with homogeneous or heterogeneous enhancement were seen in 16 (26%) and 26 (42%) cases, respectively.ConclusionsMRI is a valuable diagnostic method for orbital schwannoma, particularly when contrast is applied. The locations and shapes of tumours can be seen distinctly. T1-weighted images are relatively nonspecific. T2-weighted and enhanced T1-weighted images provide information about the pathology of tumours. In particular, peripheral enhancement should be considered a target sign of schwannoma.Eye (2008) 22, 1034-1039; doi:10.1038/sj.eye.6702832; published online 20 April 2007.