Visual Function Improvement after Plasma Exchange Therapy for Acute Optic Neuritis in Neuromyelitis Optica Spectrum Disorders: Case Series and Review.

Objective: Neuromyelitis optica (NMO) and neuromyelitis optica spectrum disorder (NMOSD) are autoimmune-mediated central nervous system disorders distinguished by the presence of serum aquaporine-4 IgG antibody (AQP4-Ab). The clinical panel comprises severe optic neuritis (ON) and transverse myelitis, which can result in incomplete recovery and a high risk of recurrence.

Methods: This study aimed to evaluate the visual outcomes of three patients with severe acute ON in NMOSD that was non-responsive to intravenous methylprednisolone (IVMP), who received plasma exchange therapy (PLEX). We included three patients (P1, P2 and P3) with severe acute ON who had no improvement after IVMP treatment and were admitted to the ophthalmology department at the Emergency University Hospital Bucharest from January 2022 to September 2023. All three patients with ON were diagnosed in accordance with the criteria described by the Optic Neuritis Treatment Trial. All the subjects were experiencing their first attack.

Results: The mean recruitment age was 35.3 ± 7.71. All patients were seropositive for the AQP4 antibody. All patients were tested for serum myelin oligodendrocyte glycoprotein (MOG) antibody but only one showed a positive test (P3). Lesions visible in orbital MRI indicated the involvement of retrobulbar, canalicular and/or intracranial segments. All three subjects had no response or incomplete remission after an IVMP protocol (5 days of 1000 mg intravenous methylprednisolone in sodium chloride 0.9%). The mean time from onset of optic neuritis to PLEX was 37.6 days. The PLEX treatment protocol comprised five cycles of plasma exchange treatment over 10 days, with a plasma exchange session every other day. An amount of 1 to 1.5 volumes of circulating plasma were dialyzed for 2-4 h. At 1 month after the completion of PLEX therapy, BCVA and VF parameters were improved in all three patients.

Conclusion: The treatment of ON remains subject to debate and is somewhat controversial. Plasma exchange must be considered as a rescue therapy when IVMP is insufficient for AQP4-ON patients. This study revealed that PLEX treatment effectively improves the visual outcomes of patients experiencing their first attack of severe acute isolated ON after high-dose IVMP treatment. This study suggests that PLEX may be associated with improved visual outcomes in NMOSD acute optic neuritis.