Zahra Janamiri^1,, Omid Sadeghpour Moradi²

Introduction: Optic Neuritis is defined as inflammation of the optic nerve, which is mostly idiopathic, while demyelinating lesions secondary to auto-immune conditions are among other causes. These lesions are demonstrated on Magnetic Resonance Imaging (MRI) as hyper intensities. In this study, authors plan to investigate the relationship between MRI pattern of patients suffering from optic neuritis, and their pain and visual loss patterns. Materials and Methods: From June 2017 to December 2017, we have enrolled 127 patients suffering from optic neuritis. These patients were referred to neurology and ophthalmology clinic of a private hospital in Tehran. Demographic data of all patients were collected and they underwent MRI for evaluation of optic nerve abnormalities and possible lesions and enhancements. Also, detailed pain score regarding their ocular pain were recorded by an expert blind neurologist, categorizing them into pain with movement, pain during rest and no pain. Also, visual field assessments were performed by an expert blinded ophthalmologist. Statistical analysis performed using SPSS version 17.00 and Student T-test and Mann-whitney test and Chi-square test. Results: There were 110 females and 17 males, with mean age of 35.2 years for females and 39.8 for males. Statistical analysis revealed no significant difference between demographic data of patients. (P value=0.12) Of these patients, 116 cases have abnormalities in their neuro-imaging, which 60 cases have pain in eye movement (group A), 37 cases experienced pain during rest (group B) and 19 cases have no pain (group C). Also, 78 patients have optic nerve enhancement in the orbital segment (39 cases of group A, 28 cases of group B, 11 cases of group C), 16 patients have canalicular segment enhancement (4 cases of group A, 9 cases of group B, 3 cases of group C) and 22 patients have intracranial segment enhancement (13 cases of group A, 6 cases of group B, 3 cases of group C). Also we have found that enhancements longer than 8 mm are consistent with more severe ocular pain, whether during movement or rest. (P value < 0.05) Visual field assessment revealed no significant correlation between type and length of optic nerve enhancement on MRI and visual field loss. (P value=0.09). Conclusion: Authors have found that most of the patients suffering from optic neuritis may demonstrate their symptoms as ocular pain during movement, which most of them have orbital segment involvement of optic nerve. Also, we have found that canalicular optic nerve enhancement were mostly associated with ocular pain at rest, opposed to other types of enhancement (orbital and intracranial). Also, we have found a specific threshold defined as 8 mm of optic nerve enhancement and severity of pain, which is less than other studies in literature.

optic neuritis, magnetic resonance imaging, enhancement, optic nerve length, visual field