To identify whether cortical lesions in regions known to be important for language are associated with language deficits in people with multiple sclerosis (pwMS).

Language deficits are common in pwMS, with word-finding difficulty being the most frequent language complaint in early disease, yet the mechanism for this impairment is unclear. Cortical lesions are common in MS, and recent evidence suggests that cortical lesions may frequently occur in regions implicated in language function.

45 people with relapsing-remitting MS within one year of diagnosis underwent 7T brain MRI and cognitive testing, including a validated task of lexical retrieval speed/word finding. Cortical lesions were identified manually on 0.5mm³ T1 and T2* weighted images. 7T T1 weighted images were segmented into cortical parcels according to the Human Connectome Project brain atlas, and for each participant, cortical lesions were mapped to individual parcels. Group comparisons were used to identify associations between lesion presence and language impairment. Cortical parcels of interest were chosen based on previously identified regions implicated in language processing.

The analyzed cohort included 32 women and 13 men, mean time since diagnosis 0.6 ± 0.4 years, mean age 34 ± 8 years. Cortical lesions were identified in 38/45 (84%), with 26/45 (58%) having cortical lesions in regions implicated in language function. Degree of demyelination within a superior cortical subnetwork involved in semantic processing predicted slower lexical retrieval speed after controlling for sex, age, total white matter lesion volume, total cortical lesion volume, and premorbid intelligence as measured by the Weschler Test of Adult Reading (WTAR) (log1p OLS β = 24.54, p = 0.022; permutation p = 0.010). Neither total cortical lesion volume nor total white matter lesion volume were significantly associated with performance on any language task.

In early MS, cortical lesions in language regions may be important contributors to expressive language deficits.