Altered speech-related cortical network in frontotemporal dementia.
BACKGROUND
In healthy subjects (HS), transcranial magnetic stimulation (TMS) demonstrated an increase in motor-evoked potential (MEP) amplitudes during specific linguistic tasks. This finding indicates functional connections between speech-related cortical areas and the dominant primary motor cortex (M1).


OBJECTIVE
To investigate M1 function with TMS and the speech-related cortical network with neuroimaging measures in frontotemporal dementia (FTD), including the non-fluent variant of primary progressive aphasia (nfv-PPA) and the behavioral variant of FTD (bv-FTD).


METHODS
M1 excitability changes during specific linguistc tasks were examined using TMS in 24 patients (15 with nfv-PPA and 9 with bv-FTD) and in 18 age-matched HS. In the same patients neuroimaging was used to assess changes in specific white matter (WM) bundles and grey matter (GM) regions involved in language processing, with diffusion tensor imaging (DTI) and voxel-based morphometry (VBM).


RESULTS
During the linguistic task, M1 excitability increased in HS, whereas in FTD patients it did not. M1 excitability changes were comparable in nfv-PPA and bv-FTD. DTI revealed decreased fractional anisotropy in the superior and inferior longitudinal and uncinate fasciculi. Moreover, VBM disclosed GM volume loss in the left frontal operculum though not in the parietal operculum or precentral gyrus. Furthermore, WM and GM changes were comparable in nfv-PPA and bv-FTD. There was no correlation between neurophysiological and neuroimaging changes in FTD. Atrophy in the left frontal operculum correlated with linguistic dysfunction, assessed by semantic and phonemic fluency tests.


CONCLUSION
We provide converging neurophysiological and neuroimaging evidence of abnormal speech-related cortical network activation in FTD.
['Suppa|Antonio|A|', 'Fabbrini|Andrea|A|', 'Guerra|Andrea|A|', 'Petsas|Nikolaos|N|', 'Asci|Francesco|F|', 'Di Stasio|Flavio|F|', 'Trebbastoni|Alessandro|A|', 'Vasselli|Federica|F|', 'De Lena|Carlo|C|', 'Pantano|Patrizia|P|', 'Berardelli|Alfredo|A|']
D000368:Aged D000369:Aged, 80 and over D019054:Evoked Potentials, Motor D005260:Female D057180:Frontotemporal Dementia D006801:Humans D008279:Magnetic Resonance Imaging D008297:Male D008875:Middle Aged D009044:Motor Cortex D009415:Nerve Net D013060:Speech D050781:Transcranial Magnetic Stimulation
Frontotemporal dementia TMS Motor cortex Aphasia MRI