A Study of Imaging Manifestations on Idiopathic Orbital Inflammatory Pseudotumor

Objective To observe the imaging features of idiopathic orbital inflammatory pseudotumor(IOIP).Methods Eighty IOIP cases seen between January,2000 and October,2006 in affiliated hospital were evaluated retrospectively.Results ①Myositis type:Single muscle was involved in 7 eyes and multiple muscles in 18 eyes.Both muscle and tendon were involved simultaneously in 16 eyes(66.7%).The signals were isointensity on T1WI and less hyperintense on T2WI,which could be enhanced by contrast.The other orbital structures except rectus were affected in 17 cases.Extraorbital extension were seen in 4 cases.② Mass type:Most masses in the orbit were diffuse with an ill-defined shape.Five cases showed the molding pattern and inflammatory infiltrate in the orbital apex was seen in 7 cases.The signals were simillar to that of the myositis on T1WI and T2WI.The neighboring orbital structures were affected in 18 cases.Extraorbital extension were seen in 3 cases.③Lacrimal type:Most of the lacrimal glands showed diffuse enlargement with poorly defined margins.They were homogenous and showed marked enhancement after contrast.Swollen eyelid was seen in all of the 18 cases.④Scleritis and perineuritis type:Both the optic nerve and sclera were involved in 3 cases,the other 2 cases were involved respectively.Bone change and extraorbital extension were not found.⑤Mixed type:The imaging findings were various that depend on which orbital structures were affected.Conclusion The imaging features of IOIP were complex and various,but still had the certain own characteristics.It is common many kinds of orbital tissues were affected,while some tissue is primary.