Objective: To characterize language dysfunction in persons with the C9orf72 repeat expansion while accounting for motor impairment. Mutations in C9orf72 cause symptoms of ALS (amyotrophic lateral sclerosis) and FTD (frontotemporal dementia) which may include motor impairment and language deficits. Method: 17 patients and asymptomatic carriers with confirmed expansion mutations in C9orf72 (C9-subjects) were enrolled in a longitudinal natural history study. All C9-subjects underwent neuropsychological testing at NIH. Measures included lexical fluency, category fluency, and noun confrontation naming. Timed syllable repetition was used to quantify maximum speed of speech, which is slowed with dysarthria. 15 healthy volunteers underwent the same lexical fluency and syllable repetition task. Results: A Mann-Whitney U test was used to find the difference between C9-subjects and healthy volunteers on a lexical fluency task. C9-subjects performed worse than healthy volunteers (p = 0.0006). Dysarthria did not correlate with decreased performance on verbal fluency tasks in C9-subjects (Pearson's r = 0.12, p = 0.56). Lexical fluency did not decline significantly over the 6-month follow-up interval (Wilcoxon signed-rank test p = 1.797). Performance on lexical fluency and category fluency tasks were highly correlated (r = 0.9, p < 0.0001). Only 2 patients made errors on the noun confrontation naming. Conclusion: Motor impairments do not account for low performance on the verbal fluency tasks. Confrontation naming was mostly spared. This suggests there is possible dysfunction in the search and initiation of exemplars. In the future, we will study response association clusters to see if search processes underlie low verbal fluency performance. Studying asymptomatic C9-subjects longitudinally will be critical in determining when in disease verbal fluency is impacted.
Verbal Fluency in C9orf72 ALS/FTD
Arch Clin Neuropsychol (2015) 30 (6): 555.
25 August 2015