Optic chiasmal neuritis: clinical features, aetiologies, MRI patterns and prognosis in a real-world cohort

Optic chiasmal neuritis (OCN) is considered atypical for multiple sclerosis (MS) and more frequently associated with neuromyelitis optica spectrum disorders (NMOSD). Yet the true aetiological spectrum of OCN in the antibody era remains poorly defined.

We conducted a retrospective single-centre study of consecutive patients with MRI-confirmed chiasmal enhancement between 2017 and 2025. Non-inflammatory, non-demyelinating aetiologies and previous optic neuritis were excluded. Clinical features, ophthalmological outcomes, MRI findings, and aetiologies were analysed.

Among 293 screened records, 43 patients (median age 32 years) were included. Eye pain was reported in 58.1% of cases, phosphenes in 14%, and visual symptoms were bilateral in 39.5%. MS emerged as the most frequent aetiology (27/43; 62.8%), followed by NMOSD (20.9%) and myelin oligodendrocyte glycoprotein antibodies-associated disease (MOGAD, 9.3%). Orbital MRI patterns differed by aetiology: unilateral hemichiasmal T2-weighted involvement was significantly more frequent in MS than in non-MS patients (74.1% vs 25%, p = 0.004). Median time to intravenous methylprednisolone was 19 days (IQR 9.8-32.3). At one year, normal visual acuity was recovered in 55.4% of patients.

To our knowledge, this is the largest real-world cohort specifically dedicated to OCN, a rare and heterogeneous inflammatory disorder of the optic pathway. Contrary to current perception, MS is the leading aetiology in real-world practice, challenging the traditional view of OCN as predominantly related to NMOSD. Orbital MRI patterns may help differentiate MS from NMOSD and MOGAD, and early recognition is essential given frequent diagnostic and treatment delays.