Semantic, phonologic, and verb fluency in Huntington’s disease

Verbal fluency tasks have been identified as important indicators of executive functioning impairment in patients with frontal lobe dysfunction. Although the usual evaluation of this ability considers phonologic and semantic criteria, there is some evidence that fluency of verbs would be more sensitive in disclosing frontostriatal physiopathology since frontal regions primarily mediate retrieval of verbs. Huntington's disease usually affects these circuitries. Objective To compare three types of verbal fluency task in the assessment of frontal-striatal dysfunction in HD subjects. Methods We studied 26 Huntington's disease subjects, divided into two subgroups: mild (11) and moderate (15) along with 26 normal volunteers matched for age, gender and schooling, for three types of verbal fluency: phonologic fluency (F-A-S), semantic fluency and fluency of verbs. Results Huntington's disease subjects showed a significant reduction in the number of words correctly generated in the three tasks when compared to the normal group. Both controls and Huntington's disease subjects showed a similar pattern of decreasing task performance with the greatest number of words being generated by semantic elicitation followed by verbs and lastly phonologic criteria. We did not find greater production of verbs compared with F-A-S and semantic conditions. Moreover, the fluency of verbs distinguished only the moderate group from controls. Conclusion Our results indicated that phonologic and semantic fluency can be used to evaluate executive functioning, proving more sensitive than verb fluency. However, it is important to point out that the diverse presentations of Huntington's disease means that an extended sample is necessary for more consistent analysis of this issue.