To validate a clinically-feasible behavioral measurement tool sensitive to word-finding deficits in persons with multiple sclerosis (MS).

Word-finding difficulty is the most prevalent cognitive complaint by persons with MS, but there is almost no research on this expressive language deficit, which is partially due to a lack of sensitive measurement tools. Traditional neuropsychological tasks (e.g., animal naming, Boston Naming Test) are insensitive to word-finding difficulty in MS.

Persons with relapsing-remitting MS (n=165) completed a survey of word-finding difficulty and performed objective measures assessing domains of processing speed, verbal memory, word-list generation, and rapid automatized naming (two tasks per domain combined into four composites). Patients also performed two novel semantic word-retrieval tasks requiring patients to quickly read words and state their opposite aloud (antonyms task) and quickly read simple definitions and state target words aloud (definitions task). These tasks formed a semantic word-retrieval composite. Patient-reported word-finding was adjusted for age, sex, and mood (MHI-5). Composites scores were adjusted for age, sex, premorbid verbal ability (WTAR), and simple word reading speed. High resolution T2-weighted MRIs were analyzed to derive T2 lesion volumes (T2LV, log-transformed) for ten bilateral regions: frontal, temporal, limbic, parietal, occipital.  Stepwise regressions (entry p<0.05) assessed independent relationships among patient-reported word-finding, behavioral composites, and regional T2LV.  

Semantic word-retrieval was the only independent predictor of patient-reported word-finding (r=0.237, p=.002). Left temporal T2LV was the only independent predictor of semantic word-retrieval (r=.250, p<.001) and patient-reported word-finding (r=.186, p=.018). Semantic word-retrieval performance explained 58.3% of the relationship between left temporal T2LV and patient-reported word-finding (significant mediation).

Behavioral and neuroimaging results support our novel semantic word-retrieval tasks as sensitive to disease-related word-finding difficulty in MS. Validation of objective word-finding assessment tools sets the stage for further research on underlying mechanisms and potential treatments of this prevalent expressive language deficit.