Brain involvement in neuromyelitis optia spcectrum disorder (NMOSD) is well recognized and some characteristic magnetic resonance imaging (MRI) abnormalities are incorporated into the recently proposed diagnostic criteria for NMOSD. However, little is known about clinical implication of brain attacks in NMOSD.
To analyze patterns of frequency and timing of brain attacks with regard to treatment compared to those of optic neuritis or myelitis in patients with NMOSD.
This study retrospectively reviewed 260 consecutive aquaporin-4 immunoglobulin G (AQP4-IgG) seropositive NMOSD patients who were on immunosuppressive therapies (IST) more than 6 months between October, 2005 and April, 2020 at National Cancer Center, Korea. Brain attack was defined as newly developed acute neurological symptoms lasting ≥24 hours with corresponding acute NMOSD-characteristic brain lesion(s). The following demographic and clinical variables were collected: sex, onset age, disease duration, types (optic neuritis [ON], myelitis, brain attack and area postrema syndrome [APS]) and date of each attack, and treatment history.
A total of 1738 attacks occurred in 260 patients during median 143 months (interquartile range 84-195 months) of observation period: 1377 and 361attacks before and after initiation of IST, respectively. Brain attacks were observed in 95 (37%) patients: 147 attacks in 93 (36%) patients before IST and 13 attacks in 11 (4%) patients after IST. APS was observed in 25 (9.6%) patients before IST especially at the disease onset, but no one experienced APS after IST. Before IST, ON, myelitis and brain attack were observed at 36.8, 78.7 and 14.1 per 100 patient-years, respectively, while decreased to 4.5, 12.1 and 0.6 per 100 patient-years after IST, respectively. The reduction rates of each attack frequency after IST were significantly greater in brain attack than in ON or myelitis (mean 78% vs. 95%, p=0.014). Patients with brain attacks despite IST showed higher mean annualized relapse rate (ARR) compared to those without brain attacks (p=0.029).
Impact of IST appeared to be greater on the reduction of brain attack than that of ON and myelitis in AQP4-IgG seropositive NMOSD, resulting in rare occurrence of brain attacks after IST. ARR was higher in patients with brain attack than in those without brain attack particularly after IST. These results suggest brain attack may allude high disease activity in NMOSD.