Clinical and imaging characteristics of optic nerve tumors as the differencial diagnosis of optic neuritis

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Objective: To investigate the clinical and imaging features of optic nerve tumors that require differential diagnosis from optic neuritis. Methods: A retrospective case series study was conducted. Clinical data of patients diagnosed with optic nerve tumors from January 2017 to December 2021 at the Second Affiliated Hospital of Zhejiang University School of Medicine were collected. A total of 29 patients (39 eyes) with clinical and magnetic resonance imaging (MRI) findings similar to optic neuritis or optic neuropathy were included. There were 15 cases of optic nerve sheath meningioma (ONSM) (17 eyes), 4 cases of optic nerve glioma (ONG) (5 eyes), and 10 cases of infiltrative optic nerve lesions (ION) (17 eyes). All patients underwent best-corrected visual acuity (BCVA), anterior and posterior segment examinations, visual field examination, and orbital or cranial MRI examination. Patient data were observed and analyzed, treatment and follow-up information were recorded, and clinical and imaging features were summarized and compared with those of optic neuritis or optic neuropathy. Results: Among the 29 patients with optic nerve tumors, 10 were male and 19 were female, with an average age of (43.3±13.8) years and a range of 11 to 72 years. The follow-up time was 6.8 (2.0, 11.0) months, with a range of 1 to 33 months. Sixteen patients (21 eyes) with optic nerve tumors were initially misdiagnosed as having acute optic neuritis and showed poor response to steroid treatment. Of these, 9 cases (11 eyes) were ONSM, 4 cases (6 eyes) were ION, and 3 cases (4 eyes) were ONG. The diagnostic delay time was 7.1 (1.5, 12.0) months, with a range of 1 to 24 months. The main clinical symptoms of all affected eyes were acute vision loss in 23 eyes, slow vision loss in 5 eyes, transient blackouts in 4 eyes, and no obvious visual symptoms in 7 eyes. The median BCVA of all affected eyes was 0.1, ranging from light perception to 1.0. Fundus examination results showed optic disc edema in 34 eyes and normal optic disc in 5 eyes among the 39 eyes with optic nerve tumors. A total of 27 patients (33 eyes) completed visual field examinations, which revealed an enlarged physiological blind spot in 11 eyes, a concentric or tubular visual field contraction in 8 eyes, a diffuse decrease in light sensitivity in 7 eyes, an arcuate scotoma in 4 eyes, and a normal visual field in 3 eyes. All affected eyes completed orbital or cranial MRI examinations, which showed mild optic nerve thickening in 22 eyes, significant thickening in 6 eyes with distortion, and no significant thickening in 6 eyes. Contrast-enhanced T1-weighted imaging (T1WI) MRI showed optic nerve parenchymal thickening in 5 eyes, all of which were ONG, and 2 of them had optic nerve parenchymal enhancement. Optic nerve sheath thickening and enhancement without optic nerve parenchymal thickening or enhancement were observed in 28 eyes, including 17 eyes of ION and 11 eyes of ONSM. There were 6 eyes with no obvious optic nerve thickening, which were all ONSM, showing mild or significant thickening and enhancement of the optic nerve sheath without optic nerve parenchymal thickening or enhancement. Conclusions: Optic nerve tumors can present with ophthalmic clinical features similar to optic neuritis, such as optic disc edema, and demonstrate MRI findings that resemble those of optic neuritis. Therefore, differentiation between the two is crucial, based on differences in their natural course and response to steroid therapy.