Phonological Processing is Below Expectations and Linked to Word-Finding Difficulty in Multiple Sclerosis

BackgroundWord-finding difficulty is prevalent but poorly understood in persons with relapsing-remitting multiple sclerosis (RRMS). ObjectiveInvestigate our hypothesis that phonological processing ability is below expectations and related to word-finding difficulty in patients with RRMS. MethodData were analyzed from patients with RRMS (n=50) on patient-reported word-finding difficulty (PW-WFD) and objective performance on WIAT-4 Phonemic Proficiency (PP; analysis of phonemes within words), Word-Reading (WR, proxy of premorbid literacy and verbal ability), and Sentence Repetition (SR; auditory processing of word-level information). ResultsPerformance (mean [95% CI]) was reliably lower than normative expectations for PP (- 0.41[-0.69, -0.13]) but not for WR (0.02[-0.21, 0.25]) or SR (0.08[-0.15, 0.31]. Within-subjects performance was worse on PP than both WR (t[49]=4.00, p<0.001, d=0.47) and SR (t[49]=3.76, p<0.001, d=0.54). Worse PR-WFD was specifically related to lower PP (F2,47=6.24, p=0.004, {eta}2=0.21); worse PP performance at PR-WFD Often (n=13; -1.16[-1.49, -0.83]) than Sometimes (n=17; -0.14[-0.68, 0.41]) or Rarely (n=20; -0.16[-0.58, 0.27]. PR-WFD was unrelated to WR or SR (Ps>0.25). ConclusionPhonological processing was below expectations and specifically linked to word-finding difficulty in RRMS. Findings are consistent with early disease-related cortical changes within the posterior superior temporal / supramarginal region. Results inform our developing model of MS-related word-finding difficulty.