Efficacy of Fampridine on Refractory Optic Neuritis in Neuromyelitis Optica Spectrum Disorders

BACKGROUND: Neuromyelitis optica spectrum disorders (NMOSD) usually occur with acute refractory optic neuritis (ON). However, there is a lack of efficacious treatments to improve recovery. Since fampridine has been found to improve the prognosis of multiple sclerosis (MS) and MS-related ON, it is necessary to explore the efficacy of fampridine on visual functions in NMOSD-ON. METHODS: Patients aged 14-80 who suffered from acute refractory AQP4-IgG positive ON within 2 weeks onset and with high-dose corticosteroid treatment were included. Patients treated with sustained-release fampridine (4-aminopyridine, 4-AP) as add-on treatment for 3 months were compared with patients without 4-AP (non-4-AP). Visual functional scores (VFS), Opticospinal Impairment Scale (OSIS), the logarithm of the minimum angle of resolution (LogMAR) of visual acuity (VA), the mean deviation (MD) value of the static visual field, and retina nerve fiber layer (RNFL) thickness were measured and followed up from baseline to 6 months. RESULTS: Patients with 4-AP add-on treatment improved VFS or OSIS greater than that with control (non-4-AP) at 3 and 6 months compared with baseline (all p < 0.05). 4-AP add-on treatment also increased the proportion of better improvement of ON (VFS ≤ 2) at 3 months (36.4% vs. 7.1% in control, p < 0.05 adjusted for plasma exchange), and 4-AP improved visual field at 6 months (p < 0.05 adjusted for plasma exchange). CONCLUSION: Fampridine as an add-on treatment has potential functional benefit on refractory NMOSD-ON and improves visual functions after the attack of ON.