Patients with NMOSD, regardless of disease status, rarely develop brain lesions

Asymptomatic brain lesions were rarely observed on conventional MRI in patients with clinically stable, antibody-seropositive neuromyelitis optica spectrum disorder, according to study results of nearly 300 patients.

Additionally, researchers rarely observed brain MRI lesions typical of neuromyelitis optica spectrum disorder (NMOSD) during the relapse-free period in these patients, the study findings — which were published in Neurology — demonstrated.

“Brain MRI abnormalities are not uncommon in patients with NMOSD and encompass both symptomatic and asymptomatic brain lesions,” the researchers wrote. “The former has been incorporated in the latest diagnostic criteria for NMOSD, but data regarding the timing of occurrence of asymptomatic brain MRI abnormalities remain scarce.”

The possibility of novel, asymptomatic brain lesions during the relapse-free period in NMOSD “cannot be excluded,” according to Min Young Lee, MD, of the department of neurology at the National Cancer Center’s Research Institute and Hospital in Korea, and colleagues. As a result, the researchers examined the development of novel, asymptomatic brain lesions in patients with aquaporin-4 (AQP4) antibody-seropositive NMOSD in the relapse-free period.

Lee and colleagues examined records from 296 consecutive patients with AQP4 antibody-seropositive NMOSD in the NMSOD database of the National Cancer Center from May 2005 to November 2019. Serial brain MRI scans from an interval of at least 1 year during the relapse-free period following immunosuppressive therapy were available for 145 of these patients. The researchers performed a retrospective analysis of these scans to determine the presence of novel, subclinical brain lesions in the relapse-free period.

In total, Lee and colleagues analyzed 370 scans.

The researchers identified novel, asymptomatic brain lesions in deep white matter in five out of 145 patients (3.4%) during a total relapse-free period of 708 person-years, according to the study findings. Lee and colleagues noted that all identified lesions were smaller than 6 mm and determined to be “nonspecific.” They saw no brain lesion characteristics of NMOSD and no gadolinium-enhancing lesions.

“ ... Unlike well-described brain MRI findings characteristic of NMOSD, such as corticospinal tract, extensive hemispheric white matter, periependymal and cervico-medullary lesions, and poorly demarcated, multifocal enhancing lesions, all silent lesions detected in this study were deemed to be nonspecific in terms of their location and configuration,” the researchers wrote.

The median interval between consecutive MRIs during the relapse-free period was 24 months (range, 17-73 months), according to the study results. Lee and colleagues found that baseline characteristics of all recruited patients did not differ significantly between the groups with vs. without new asymptomatic brain lesions.

Limitations of the present study included the retrospective design and the irregular intervals of the MRI scans, Lee and colleagues noted, although they also wrote that the detection rate and accuracy of the lesions “were rather improved” due to the comprehensive scans that followed.

“Further studies examining the presence of silent lesions in the spinal cord and optic nerve, which were not investigated here, or progressive subclinical cerebral atrophy in NMOSD similar to that in [MS] may further map the diagnostic and therapeutic landscape of NMOSD,” the researchers wrote.