Cognitive issues affect nearly 1 in 3 with NMOSD, study finds
Researchers find attention, executive function particularly impaired in patients
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Nearly a third of people with neuromyelitis optica spectrum disorder (NMOSD) may have cognitive impairment, especially in the areas of attention/processing speed and executive function, according to a study in Brazil.
Processing speed refers to a person’s ability to receive, interpret, and respond to information, while executive function refers to a person’s ability to plan, solve problems, and regulate their own thoughts and feelings.
While most MRI-based measures of brain health were similar in people with and without NMOSD, researchers identified some brain structure differences associated with differences in executive function.
The study, “Cognitive impairment and multiparametric brain MRI in aquaporin-4-IgG positive neuromyelitis optica spectrum disorder,” was published in Multiple Sclerosis and Related Disorders.
NMOSD is an autoimmune disorder marked by inflammation that mainly affects the spinal cord and the optic nerve, which relays signals between the eyes and the brain. Increasing evidence also points to brain involvement, which “may present early, raising critical questions about its implications for cognitive performance, potential disease progression, and patient management,” the researchers wrote.
How to predict?
Reported rates of cognitive impairment in people with NMOSD range from 3% to 75%. This wide range is likely due to small sample sizes and methodological differences between studies, the researchers noted, including in neuropsychological evaluations, cognitive impairment definition, and limited MRI assessments.
The team set out to assess the frequency of cognitive impairment in people with NMOSD and identify potential MRI-based predictors of these problems. The study involved 57 people with NMOSD and 42 age-, sex-, and education-matched people without the disease. All were recruited at a single Brazilian center.
All participants completed a comprehensive set of cognitive tests and a brain MRI in the same week. Validated cognitive tests assessed five domains: processing speed and attention to visual input, processing speed and attention to auditory input, executive function, verbal memory, and visual memory.
Results showed that 32% of the NMOSD patients had cognitive impairment, defined as scores substantially below average for their age in at least two cognitive domains. Deficits were particularly pronounced in the domains of attention/processing speed and executive function.
Further analyses showed that rituximab, a therapy commonly used off label for NMOSD and sold as Rituxan and others, was used significantly more often among people with preserved cognitive function than among those with cognitive impairment (36% vs. 5.6%).
When the team examined participants’ MRI scans, they found that nearly all brain measurements were similar between people with and without NMOSD, and between patients with and without cognitive impairment.
The researchers did identify a few statistically significant associations between MRI measures and cognitive test scores.
For example, NMOSD patients with a lower ratio of brain tissue volume to total volume inside the skull, known as brain parenchymal fraction or BPF, tended to have worse executive function scores. Having a lower percentage of gray matter, which comprises the brain tissue that houses nerve cell bodies, was also significantly associated with worse executive function.
“While most MRI metrics were not predictive of cognitive tests performance, notable exceptions included BPF and [gray matter fraction], which were associated with executive function,” the scientists wrote.
They noted that the study was limited by the fact that patients underwent a single MRI scan, highlighting a need for further research that tracks how MRI measures and cognitive measures change over time.
Still, the study “identifies a significant CI [cognitive impairment] prevalence in NMOSD patients, with one-third meeting criteria for CI,” the team wrote. “Since CI significantly impacts the quality of life of patients, neuropsychological screening tests are crucial for identifying CI and guiding appropriate management in NMOSD.”
