Thinning Cortical Structures Contribute to Cognitive Impairment in MS

Detriments in processing speed and verbal fluency among older patients with multiple sclerosis (MS) is likely in part explained by thinning cortical structures, according to study results presented at the Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2023, held in San Diego, California, from February 23 to 25.

Older patients with MS have been found to have greater cortical atrophy rather than early neurodegenerative thalamic changes.

For the study, researchers evaluated the global and cortex-specific changes among older patients with MS and how they relate with cognitive outcomes. To that end, researchers from the University at Buffalo in the United States recruited 74 older patients with MS. Patients underwent a single time-point cognitive and neuroimaging evaluation. Cognitive impairment was defined as scores in 2 or more cognitive domains that are -1.5 standard deviations lower than published data from healthy control individuals.

Overall, 46 patients had preserved cognition and 28 had cognitive impairment. These cohorts did not differ by age (mean, 62.5 vs 62.9 years; P =.788) or years of education obtained (mean, 14.8 vs 14.9 years; P =.769), respectively.

After adjusting for age, educational level, and whole brain volume, patients with cognitive impairment were associated with significantly thinner bilateral fusiform gyrus (both P ≤.00147) as well as left inferior temporal gyrus (P =.00097), right superior frontal gyrus (P =.00085), and right middle temporal gyrus (P =.00128) compared with those who were not cognitively impaired.

Poorer performance on the Controlled Oral Word Association Test (COWAT) was explained by older age, smaller whole brain volume, smaller thalamic volume, and thinner left fusiform cortex (β, 0.629; P <.001). Poorer Symbol Digit Modalities Test (SDMT) performance was explained by smaller whole brain volume and thinner left fusiform cortex (β, 0.497; P =.001).

The major limitations of the study were the small sample and imbalanced cohort sizes.

“[P]rocessing speed and verbal fluency performance in ewMS [elderly with MS] is additionally explained by thinning of cortical structures responsible for higher level of visual information processing, subserve language, and semantic memory processing and higher cognitive functions related to working memory,” the researchers concluded, in addition to global neurodegenerative changes.