HEAD AND NECK Infraorbital nerve involvement on magnetic resonance imaging in European patients with IgG4-related ophthalmic disease: a specific sign J. Ben Soussan 1 & R. Deschamps 2 & J. C. Sadik 1 & J. Savatovsky 1 & L. Deschamps 3 & M. Puttermann 4 & M. Zmuda 5 & F. Heran 1 & O. Galatoire 5 & H. Picard 6 & A. Lecler 1 Received: 9 February 2016 /Revised: 17 May 2016 /Accepted: 21 June 2016 # European Society of Radiology 2016 Abstract Objectives To measure the frequency of infraorbital nerve en- largement (IONE) on magnetic resonance imaging (MRI) in European patients suffering from an IgG4-related ophthalmic disease (IgG4-ROD) as compared to patients suffering from non-IgG4-related ophthalmic disease (non-IgG4-ROD). Methods From January 2006 through April 2015, 132 pa- tients were admitted for non-lymphoma, non-thyroid-related orbital inflammation. Thirty-eight had both pre-therapeutic orbital MRI and histopathological IgG4 immunostaining. Fifteen patients were classified as cases of IgG4-ROD and 23 patients as cases of non-IgG4-ROD. Two readers per- formed blinded analyses of MRI images. The main criterion was the presence of an IONE, defined as the infraorbital nerve diameter being greater than the optic nerve diameter in the coronal section. Results IONE was present in 53% (8/15) of IgG4-ROD cases whereas it was never present (0/23) in cases of non-IgG4- ROD (P < 0.0001). IONE was only present in cases where, on MRI, the inflammation of the inferior quadrant was present and in direct contact with the ION canal. Conclusions In European patients suffering from orbital in- flammation, the presence of IONE on an MRI is a specific sign of IgG4-ROD. Recognition of this pattern may facilitate the accurate diagnosis for clinicians and allow for the adequate management and appropriate care of their patients. Key points • IONE on an MRI is a specific sign of IgG4-ROD. • IONE recognition allows for a quicker diagnosis and appro- priate management. • IONE appears when inflammation is in direct contact with the ION canal. Keywords IgG4-related ophthalmic disease . Orbital inflammation . MRI . Infra-orbital nerve enlargement . Diagnosis Abbreviations IgG4-ROD IgG4-related ophthalmic disease non-IgG4-ROD non-IgG4-related ophthalmic disease MRI Magnetic resonance imaging ION Infra-orbital nerve IONE Infra-orbital nerve enlargement MIONE Mild infra-orbital nerve enlargement Introduction IgG4-related disease (IgG4-RD) is a rare systemic condition that was identified relatively recently [1, 2]. The estimated prevalence of IgG4-RD in Japan ranges from 0.28 to 1.08 per 100,000 inhabitants [ 2]. IgG4-RD has been found * A. Lecler alecler@fo-rothschild.fr 1 Department of Radiology, Fondation Ophtalmologique Adolphe de Rothschild, 25 rue Manin, 75019 Paris, France 2 Department of Neurology, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France 3 Department of Pathology, Bichat Hospital, APHP, Paris, France 4 Department of Pathology, Necker-Enfants Malades Hospital, APHP, Paris, France 5 Department of Orbitopalpebral Surgery, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France 6 Clinical Research Unit, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France Eur Radiol DOI 10.1007/s00330-016-4481-5