Clinical and neuroimaging investigations of language disturbance in frontotemporal dementia-motor neuron disease patients.

This study systematically investigated the neuropsychological profile of language disturbance in frontotemporal dementia-motor neuron disease (FTD-MND) using a data-driven approach. Neuroanatomical correlates of language profiles were also examined. Patients with FTD-MND (N = 26), pure motor neuron disease (N = 34), progressive non-fluent aphasia (N = 30), semantic dementia (N = 17), and controls (N = 31) underwent comprehensive language assessments. Clinical assessments were complemented with the Sydney Language Battery (SYDBAT), to assess semantic abilities, and the Test for Reception of Grammar (TROG), to assess syntactic comprehension. Two-step cluster analysis examined patterns of language impairment in FTD-MND and voxel-based morphometry investigated neuroanatomical differences between clusters. Almost all (88.5%) FTD-MND patients had language impairment, with anomia in 73.1% and impaired sentence comprehension in 56%. Cluster analysis revealed two main profiles of language impairment in FTD-MND; a mild mixed semantic and syntactic impairment (mild mixed subgroup) seen in 12 cases and a subgroup with more marked impairment particularly of syntactic comprehension (PNFA-like subgroup) seen in 7 cases. VBM revealed disproportionate atrophy of the caudate head and putamen bilaterally in the PNFA-like subgroup. In conclusion, language disturbances in FTD-MND are heterogeneous and more mixed than seen in FTD language phenotypes. Atrophy of the caudate and putamen was correlated with disproportionate impairment of syntactic comprehension. A pure semantic dementia like syndrome appears to be rare in FTD-MND.