Inaugural Optic Neuritis in Morocco: A 15-Year Retrospective Study of Aetiology and Visual Prognosis

Abstract

Introduction: Optic neuritis (ON) is a frequent cause of acute visual loss in young adults and often the first manifestation of demyelinating diseases such as multiple sclerosis (MS) or neuromyelitis optica spectrum disorder (NMOSD). Data from North Africa are limited. This study aimed to characterise inaugural ON in Morocco, with a focus on aetiology and visual prognosis. Methods: We conducted a retrospective, descriptive study at the University Hospital of Rabat over 15 years (2008–2023). All patients presenting with acute-onset visual loss and diagnosed with ON were included. Clinical history, ophthalmological and neurological examinations, brain and spinal MRI, cerebrospinal fluid analysis, and serum antibody testing (AQP4 and MOG, when indicated) were reviewed. Patients were categorised by aetiology. Visual outcomes and disability scores were assessed over a follow-up period of up to 5 years. Results: Seventy patients (mean age 34.4 years; 71% female) were analysed. MS was the leading cause (61.4%, 43/70), followed by NMOSD (15.7%, 11/70), clinically isolated syndrome (7.1%, 5/70), and idiopathic ON (7.1%, 5/70). Rare causes included MOGAD, Leber’s neuropathy, Behçet’s disease, Horton’s arteritis, and infectious or toxic ON (1.4% each). Bilateral involvement occurred in 34.3% (24/70), and painful eye movements in 52.8% (37/70). Visual recovery was complete in 62.8% (44/70), though permanent blindness occurred in 45.5% (5/11) of NMOSD cases. Discussion: Inaugural ON most often revealed MS, which generally had a favourable outcome. Atypical ON, particularly NMOSD, carried a higher risk of severe visual loss. Early aetiological diagnosis remains key to optimising outcomes. The study reflects the need for better diagnostic access and interdisciplinary collaboration in resource-limited settings.