Presence of asymptomatic lesions in myelin oligodendrocyte glycoprotein antibody-associated disease and neuromyelitis optica spectrum disorder: a retrospective study

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and neuromyelitis optica spectrum disorder (NMOSD) can present with asymptomatic lesions in the absence of corresponding clinical symptoms. These lesions may represent inter-attack subclinical disease activity. However, their frequency on surveillance MRI in MOGAD and NMOSD is not well established. The primary objective was to compare the frequency and anatomical locations of asymptomatic lesions detected by MRI in individuals with MOGAD and NMOSD. Secondary objectives included exploring demographic and clinical factors associated with asymptomatic lesion development. A single-centre (MS and NeMO Clinics) retrospective study was conducted. We used a natural language processing algorithm to extract structured data from clinical notes for 42 participants (22 MOGAD, 20 NMOSD) in the MuSicaL-NeMO database, containing clinical information spanning from 2006 to 2022. During a mean follow-up of 11.0 ± 10.0 years for MOGAD and 11.2 ± 7.6 years for NMOSD, asymptomatic lesions were identified on surveillance MRIs in 31.8% of MOGAD participants and 40.0% of NMOSD participants, primarily in the spinal cord in both cohorts. When symptom-triggered MRIs were additionally considered to surveillance MRIs, 54.5% of MOGAD and 75.0% of NMOSD participants had at least one asymptomatic lesion. Descriptive analyses across both MRI types indicated that most asymptomatic lesions were found in participants not receiving standard disease-modifying therapies (78.3% of lesions in MOGAD, 61.5% of lesions in NMOSD). Exploratory patient-level analyses across both MRI contexts suggested greater asymptomatic lesion burden among those with optic neuritis than those presenting with other clinical syndromes, and possibly among female participants and those with a history of smoking. However, these observations were hypothesis-generating given the modest sample size and imbalanced subgroup distributions. Asymptomatic lesions detected on surveillance MRI are relatively common in MOGAD and NMOSD, suggesting that silent inter-attack disease activity may occur more frequently than previously recognized. Findings from symptom-triggered MRI should be interpreted separately, as they may indicate a distinct biological phenomenon during acute inflammatory episodes. Prospective studies incorporating standardized MRIs are needed to confirm the frequency and clinical significance of asymptomatic lesions and to guide future MRI surveillance strategies.