Non-Verbal and Verbal Fluency in Prodromal Huntington's Disease

Abstract

Background: This study examines non-verbal (design) and verbal (phonemic and semantic) fluency in prodromal Huntington's disease (HD). An accumulating body of research indicates subtle deficits in cognitive functioning among prodromal mutation carriers for HD. Methods: Performance was compared between 32 mutation carriers and 38 non-carriers in order to examine the magnitude of impairment across fluency tasks. The predicted years to onset (PYTO) in mutation carriers was calculated by a regression equation and used to divide the group according to whether onset was predicted as less than 12.75 years (HD+CLOSE; n = 16) or greater than 12.75 years (HD+DISTANT; n = 16). Results: The results indicate that both non-verbal and verbal fluency is sensitive to subtle impairment in prodromal HD. HD+CLOSE group produced fewer items in all assessed fluency tasks compared to non-carriers. HD+DISTANT produced fewer drawings than non-carriers in the non-verbal task. PYTO correlated significantly with all measures of non-verbal and verbal fluency. Conclusion: The pattern of results indicates that subtle cognitive deficits exist in prodromal HD, and that less structured tasks with high executive demands are the most sensitive in detecting divergence from the normal range of functioning. These selective impairments can be attributed to the early involvement of frontostriatal circuitry and frontal lobes.

Huntington's Disease: Premotor Phase

“…Phonemic, semantic and nonverbal fluency were assessed by Robins Wahlin et al [33] in a group of 16 distant-from-onset patients and 16 close-to-onset premotor patients and 38 controls. Statistically significant differences were found in all types of fluency when comparing HD-close patients to controls.…”

“…However, HD-distant patients and controls did not differ in the remaining tasks; this might be due to the small sample size. Also, the authors showed a correlation between predicted years to onset (based on CAG repeats) and performance on all tasks [33]. …”

“…Alternatively, an explanation could be that nonverbal fluency tasks tap visuospatial functions or that emerging motor dysfunction lowers the performance on this task. The slight rise in the number of rule violations, when comparing HD-close with controls, favors the theory of attention and executive function dysfunction being present in the premotor phase of HD [33]. Executive function is mediated by the prefrontal cortex and it is involved in planning, decision-making, problem solving, judgement, etc.…”

Visual Dysfunction in Huntington’s Disease: A Systematic Review

“…Another cautionary note concerns recent findings that FM100 performance is not purely a measure of colour discrimination but instead also reflects general nonverbal ability [42]. Given evidence that non-verbal fluency is reduced even in prodromal HD [43], the FM100 may not represent a suitable means of testing colour discrimination in this group.…”

Evaluation of language functions in Huntington's disease

“…Klinik olarak belirgin HH'da lisan fonksiyonları konuşma akıcılığı görevlerinin performansı, striatum, frontal loblar ve frontostriatal devrenin bütünlüğüne ve bir dereceye kadar temporal loblara bağlıdır [4]. Hastalık ilerledikçe bu döngülerdeki disfonksiyon artmakta ve hastanın konuşması anlaşılmaz hale gelebilmektedir [5].…”