The usefulness of infraorbital nerve enlargement on MRI imaging in clinical diagnosis of IgG4-related orbital disease

Purpose: To investigate the frequency of infraorbital nerve enlargement (IONE) in orbital lymphoproliferative disorders, and to show that IONE can contribute to the clinical diagnosis of IgG4-related orbital diseases (IgG4- ROD). Subjects and methods: 71 cases in which orbital lymphoproliferative disorders were diagnosed at Okayama Medical Center and Mitoyo General Hospital from April, 2004 to March, 2011 were investigated. The male-to-female ratio was 39:32, and the age range 27-87 years old (average age 64.1 years). Whenever the coronal section of the infraorbital nerve was larger than that of the optic nerve on MRI, it was defined as IONE. Results: The breakdown of the 71 cases was: 45 cases of non-Hodgkin lymphoma, 16 cases of IgG4-ROD, 5 cases of reactive lymphoid hyperplasia, and 5 cases of idiopathic orbital inflammation. Of these, a total of 9 cases had IONE. The incidence of IONE was compared between the IgG4- ROD patient group and the non-IgG4-ROD patient group and was significantly higher in the IgG4-ROD patient group (p < 0.0001). Conclusion: If IONE is observed in a case of orbital lymphoproliferative disorders on MRI, then it is highly possible that such a case is IgG4-ROD.