Early Language Impairment as an Integral Part of the Cognitive Phenotype in Huntington's Disease.

Objective: Huntington's disease (HD) speech/language disorders have typically been attributed to motor and executive impairment due to striatal dysfunction. In-depth study of linguistic skills and the role of extrastriatal structures in HD is scarce. This study aimed to explore the profile of language compromise in HD and identify the structural neuroimaging correlates.

Methods: Language and structural correlates were assessed using the Mini Linguistic State Examination (MLSE) in 81 participants (20 HD-ISS 0-1, 40 HD-ISS 2-3 and 21 controls). Clinical and global cognition measures were also obtained. Imaging data included computed gray matter volume (GMV) and cortical thickness (CTh) values extracted from a general linear model with the MLSE. Correlation analyses were performed with the language components of the MLSE. Multivariate regression analyses were used to explore the predictive ability of the language components on GMV and CTh loss.

Results: HD individuals showed impaired MLSE performance (84.5 ± 12.8), particularly in syntax, motor speech, and to a lesser extent, semantics and phonology. Significant associations were found between linguistic performance and the structural integrity of nodes within the temporo-parietal, fronto-parietal, and fronto-striatal lexical-semantic and syntactic networks. Correlation analyses linked motor speech and syntax with predominantly left fronto-striatal GMV and CTh clusters, while semantics had a bilateral fronto-parietal topography. Multivariate regression analyses showed language domains as independent contributing factors of GMV and CTh loss in classical language-related regions.

Interpretation: Language impairment is an integral part of the HD cognitive phenotype, with severity associated with structural disintegration in extensive cortico-subcortical territories involved in language production and processing.