Idiopathic trigeminal neuropathy with trigeminal mass lesion on MRI: Neoplasm or not?

The objective of the present study was to investigate clinical and magnetic resonance imaging (MRI) features of idiopathic trigeminal neuropathy with transient MR abnormalities mimicking a neoplasm (ITNmn). We retrospectively evaluated clinical and MRI features in two cases of ITNmn seen in our institution in comparison with those of previously reported five cases. The most common symptom was altered facial sensation and numbness limited to one or more trigeminal nerve divisions (100%). ITNmn commonly affected not only the second and third divisions (86% and 57%, respectively) but also the first division (71%). The most common findings on MRI were enlargement and gadolinium enhancement of the trigeminal nerve, which were similar to those seen in neoplasms (100%). The abnormalities spontaneously regressed in all five evaluable cases. ITNmn should be added in the differential diagnosis of non-specific mass-like lesions in trigeminal neuropathy and be observed carefully without surgical treatment.